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Telegram @neetquestionpaper, , hand book, KEY NOTES TERMS, DEFINITIONS FORMULAE, , Chemistry, Highly Useful for Class XI & XII Students, Engineering, & Medical Entrances and Other Competitions, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , Arihant Prakashan (Series), Meerut, All Rights Reserved, , © Publisher, No part of this publication may be re-produced, stored in a retrieval system or distributed, in any form or by any means, electronic, mechanical, photocopying, recording, scanning,, web or otherwise without the written permission of the publisher. Arihant has obtained, all the information in this book from the sources believed to be reliable and true. However,, Arihant or its editors or authors or illustrators don’t take any responsibility for the absolute, accuracy of any information published and the damages or loss suffered there upon., All disputes subject to Meerut (UP) jurisdiction only., , Administrative & Production Offices, Regd. Office, ‘Ramchhaya’ 4577/15, Agarwal Road, Darya Ganj, New Delhi -110002, Tele: 011- 47630600, 43518550; Fax: 011- 23280316, , Head Office, Kalindi, TP Nagar, Meerut (UP) - 250002, Tele: 0121-2401479, 2512970, 4004199; Fax: 0121-2401648, , Sales & Support Offices, Agra, Ahmedabad, Bengaluru, Bareilly, Chennai, Delhi, Guwahati,, Hyderabad, Jaipur, Jhansi, Kolkata, Lucknow, Meerut, Nagpur & Pune, ISBN : 978-93-13196-49-5, , Published by Arihant Publications (India) Ltd., For further information about the books published by Arihant, log on to www.arihantbooks.com or email to info@arihantbooks.com, , /arihantpub, , /@arihantpub, , Arihant Publications, , /arihantpub, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , PREFACE, Handbook means reference book listing brief facts on a, subject. So, to facilitate the students in this we have, released this Handbook of Chemistry this book has been, prepared to serve the special purpose of the students, to, rectify any query or any concern point of a particular, subject., This book will be of highly use whether students are, looking for a quick revision before the board exams or just, before other examinations like Engineering Entrances,, Medical Entrances or any similar examination, they will, find that this handbook will answer their needs admirably., This handbook can even be used for revision of a subject, in the time between two shift of the exams, even this, handbook can be used while travelling to Examination, Centre or whenever you have time, less sufficient or more., The format of this handbook has been developed, particularly so that it can be carried around by the, students conveniently., The objectives of publishing this handbook are :, — To support students in their revision of a subject just, , before an examination., — To provide a focus to students to clear up their doubts, , about particular concepts which were not clear to them, earlier., — To give confidence to the students just before they, , attempt important examinations., , However, we have put our best efforts in preparing this, book, but if any error or what so ever has been skipped, out, we will by heart welcome your suggestions. A part, from all those who helped in the compilation of this book, a special note of thanks goes to Ms. Shivani of Arihant, Publications., Author, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , CONTENTS, 1., , Basic Concepts of Chemistry, — Dalton's Atomic Theory, , — Matter, , — Mole Concept, , — Atoms and Molecules, , — Atomic Mass, , — Physical Quantities and, , — Molecular Mass, , —, —, —, —, , 2., , Their Measurement Units, Dimensional Analysis, Scientific Notation, Precision and Accuracy, Laws of Chemical, Combinations, , — Equivalent Mass, — Stoichiometry, — Per cent Yield, — Empirical and Molecular, , Formulae, , Atomic Structure, —, —, —, —, —, —, —, —, —, , 3., , 1-14, , — Chemistry, , Atom, Electron, Proton, Neutron, Thomson's Atomic Model, Rutherford's Nuclear, Model of Atom, Atomic Number, Mass Number, Electromagnetic Wave, Theory (Maxwell), , 15-29, —, —, —, —, —, —, —, —, , Planck's Quantum Theory, Bohr's Model, Sommerfeld Extension to, Bohr's Model, de-Broglie Principle, Heisenberg's Uncertainty, Principle, Quantum Mechanical Model, of Atom, Quantum Numbers, Electronic Configuration, , Classification of Elements and Periodicity, in Properties, , 30-42, , — Classification of Elements, , — Mendeleev's Periodic Table, , — Earlier Attempts of, , — Modern Periodic Table, , Classify Elements, , — Periodic Properties, , www.aiimsneetshortnotes.com
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4., , Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, — Chemical Bond, , — Resonance, , — Ionic Bond, , — VSEPR Theory, , — Born Haber Cycle, , — VBT Theory, , — Covalent Bond, , — Hybridisation, , — Octet Rule, , — MO Theory, , — Bond Characteristics, , — Hydrogen Bond, , — Dipole Moment, , — Metallic Bond, , 43-59, , — Fajan's Rule, , 5., , States of Matter, — Factors Deciding Physical, , State of a Substance, , 60-72, — Graham's Law Diffusion, — Dalton's Law, , — The Gaseous state, , — Kinetic Theory of Gases, , — Boyle's Law, , — Van der Waals' Equation, , — Charles' Law, , — Liquefaction of Gases and, , — Gay Lussac's Law, , Critical Points, — Liquid State, , — Avogadro's Law, — Ideal Gas Equation, , 6., , The Solid State, , — Structure of Ionic Crystals, , — Bragg's Equation, , — Imperfections Defects in Solids, , — Unit Cell, , — Point Defects, , — Seven Crystal Systems, , — Classification of Solids on the, , — Packing Fraction, , Basis of Electrical, Conductivity, — Magnetic Properties of Solids, , — Coordination Number, — Density of Unit Cell, , 7., , 73-86, , — Solids, , Thermodynamics, — Thermodynamic, —, —, —, —, —, , Properties, Thermodynamic Process, Internal Energy (E or U), Zeroth Law of, Thermodynamics, First Law of, Thermodynamics, Enthalpy (H), , 87-100, — Various forms of Enthalpy of, —, —, —, —, —, —, , Reaction, Laws of Thermochemistry, Bond Enthalpy, Entropy (S), Spontaneous Process, Second Law of, Thermodynamics, Joule Thomson Effect, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, — Carnot Cycle, , — Third Law of, , Thermodynamics, , — Gibbs Free Energy, , 8., , 9., , Chemical Equilibrium, , 101-107, , — Physical and Chemical, , — Law of Mass Action, , Processes, — Types of Chemical, Reactions, — Equilibrium State, , — Relation Between Kc and Kp, — Types of Equilibrium, — Reaction Quotient, — Le-Chatelier's Principle, , Ionic Equilibrium, , 108-120, , — Electrolytes, — Calculation of the Degree, —, —, —, —, , 10., , of Dissociation (a), Ostwald's Dilution Law, Acids and Bases, The pH Scale, Dissociation Constant of, , —, —, —, —, , Solutions, — Solubility, , 121-135, — Azeotropic Mixture, , — Henry's Law, , — Colligative Properties, , — Concentration of, , — Osmotic Properties, , Solutions, — Raoult's Law, , 11., , —, , Weak Acid and Weak Base, Buffer Solutions, Salts, Common Ion Effect, Solubility Product, Acid Base Indicator, , — Abnormal Molecular Masses, — van't Hoff Factor (i), , Redox Reactions, , 136-143, , — Oxidation Number, — Balancing of Redox, , Chemical Equations, , 12., , Electrochemistry, — Conductors, , 144-159, — Electrochemical Series, , — Electrochemical Cell and, , — Nernst Equation, , Electrolytic Cell, — Electrode Potential, — Reference Electrode, — Electromotive Force (emf), of a Cell, , — Concentration Cell, — Conductance (G), — Specific Conductivity, — Molar Conductivity, — Kohlrausch's Law, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, — Electrolysis, , — Batteries, , — Faraday's Laws of, , — Fuel Cells, , Electrolysis, , 13., , — Corrosion, , Chemical Kinetics, — Rate of Reaction, , 160-169, — Methods to Determine Order, , of Reaction, , — Rate Law Expressions, , 14., , — Rate Constant, , — Arrhenius Equation, , — Order and Molecularity of, , — Activated Complex, , a Reaction, — Zero Order Reactions, — First Order Reactions, — Pseudo First Order, Reaction, , — Role of Catalyst in a Chemical, , Surface Chemistry, , — Adsorbtion, , Reaction, — Theory of Reaction Rates, — Photochemical Reactions, , — Enzyme Catalysis, , 170-179, , — Catalysis, , 15., , 16., , Colloidal State, , 180-187, , — Classification of Colloids, — Preparation of Colloids, , —, , — Purification of Colloidal, , —, , Solutions, — Properties of Colloidal, , —, —, , Solution, Protective Colloids, Emulsion, Gels, Applications of Colloids, , Principles & Processes of Isolation, of Elements, , 188-203, , — Elements in Nature, , — Purification of Crude Metals, , — Minerals and Ores, , — Occurance and Extraction of, , — Metallurgy, , Some Metals, , — Thermodynamic Principle, , in Extraction of Metals, , 17., , Hydrogen, , 204-216, , — Position of Hydrogen in the, , — Water, , Periodic Table, — Dihydrogen, — Different Forms of, Hydrogen, , — Heavy Water, — Soft and Hard Water, — Hydrogen Peroxide, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 18., , The s-Block Elements, , 217-236, , — Alkali Metals, , — Anomalous Behaviour of Be, , — Anomalous Behaviour Li, , — Compounds of Calcium, , — Compounds of Sodium, , — Cement, , — Alkaline Earth Metals, , 19., , The p-Block Elements, — Elements of Group-13, — Anomalous Behaviour of, —, —, —, —, —, —, —, —, , 20., , 21., , Boron, Boron and Its Compounds, Compounds of, Aluminium, Elements of Group-14, Carbon and Its, Compounds, Coal Gas, Natural Gas, Oil Gas, Wood Gas, , 237-283, — LPG, — Compounds of Silicon, — Compounds of Lead, — Elements of Group-15, — Nitrogen and Its Compounds, — Phosphorus and Its, , Compounds, — Elements of Group-16, — Oxygen and Its Compounds, — Compounds of Sulphur, — Elements of Group-17, — Chlorine and Its Compounds, — Elements of Group-18, , The d-and f-Block Elements, , 284-296, , — Transition Elements, , — Silver Nitrate, , — Potassium Dichromate, , — Inner-Transition Elements, , — Potassium Permanganate, , — Lanthanides, , — Copper Sulphate, , — Actinoids, , Coordination Compounds, — Terms Related to, —, —, —, —, , Coordination Compounds, Types of Complexes, Effective Atomic Number, (EAN), IUPAC Naming of, Complex Compounds, Isomerism in, Coordination Compounds, , 297-310, — Bonding in Coordination, , Compounds, — Werner's Theory, — VBT, — CFT, — Importance and Applications, , of Coordination Compounds, — Organometallic Compounds, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 22., , Environmental Chemistry, —, —, —, —, —, —, , 23., , 24., , Environment, Environmental Pollution, Pollutants, Tropospheric Pollution, Air Pollution, Smog, Green House Effect and, , —, —, —, —, —, —, —, , Global Warming, Acid Rain, Stratospheric Pollution, Water Pollution, Soil or Land Pollution, Radioactive Pollution, Bhopal Gas Tragedy, Green Chemistry, , Purification and Characterisation of, Organic Compounds, , 324-333, , — Purification of Organic, , — Quantitative Estimation of, , Compounds, — Qualitative Analysis of, Organic Compounds, , — Determination of Empirical, , Elements, and Molecular Formula, , General Organic Chemistry, — Organic Chemistry, — Classification of Organic, , Compounds, — Classification of Carbon, —, —, —, —, , 25., , 311-323, , — Classification of, , and Hydrogen Atoms, Functional Group, Homologous Series, Representation of, Different Formulae, Nomenclature of Organic, , 334-360, Compounds, , — Fission of a Covalent Bond, — Attacking Reagents, — Reaction Intermediate, — Inductive Effect, — Electromeric Effect, — Hyperconjugation, — Resonance, — Isomerism, — Types of Organic Reactions, , Hydrocarbons, , 361-383, , — Alkanes, , — Benzene, , — Conformations of Alkanes, , — Petroleum, , — Alkenes, , — Octane Number, , — Conjugated Diene, , — Cetane Number, , — Alkynes, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 31., , 32., , Biomolecules, — Lipids, , — Amino Acids, , — Acid Value, , — Proteins, , — Blood, , — Enzymes, , — Hormones, , — Nucleic Acids, , — Vitamins, , Chemistry in Everyday Life, — Medicines or Drugs, — Chemicals in Food, , 33., , 495-509, , — Chemistry in Colouring, , Matter, , — Food Preservatives, , — Chemistry in Cosmetics, , — Cleansing Agents, , — Rocket Propellants, , Nuclear Chemistry, — Nucleons and Nuclear, —, —, —, —, , 34., , 475-494, , — Carbohydrates, , Forces, Parameter of Nucleus, Factors Affecting Stability, Nucleus, Group Displacement Law, Disintegration Series, , 510-515, — Artificial Radioactivity, — Artificial Transmutation, — Nuclear Reactions, — Nuclear Fission, — Nuclear Fusion, — Applications of Radioactivity, , Analytical Chemistry, — Qualitative Analysis of, , Inorganic Compounds, — Qualitative Analysis of, , 516-539, Organic Compounds, — Titrimetric Exercises, , Appendix, , www.aiimsneetshortnotes.com, , 540-560
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Telegram @neetquestionpaper, , 1, , Basic Concepts, of Chemistry, Chemistry, It is the branch of science which deals with the composition, structure, and properties of matter., Antoine Laurent Lavoisier is called the father of chemistry., , Branches of Chemistry, Inorganic chemistry is concerned with the study of, elements (other than carbon) and their compounds., Organic chemistry is the branch of chemistry which is, concerned with organic compounds or substances, produced by living organisms., , Chemistry, Physical chemistry is concerned with the explanation of, fundamental principles., Analytical chemistry is the branch of chemistry which is, concerned with qualitative and quantitative analysis of, chemical substances., , In addition to these, biochemistry, war chemistry, nuclear chemistry,, forensic chemistry, earth chemistry etc., are other branches of, chemistry., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 2, , Handbook of Chemistry, , Matter, Anything which occupies some space and has some mass is called, matter. It is made up of small particles which have space between, them. The matter particles attract each other and are in a state of, continuous motion., , Classification of Matter, Physical classification, , Matter, , Chemical classification, Homogeneous, , Liquid, , Gas, (For physical classification, see chapter 4), , Solid, , Pure substances, , Heterogeneous, , Elements, , Metals, , Mixtures, , Non-metals, , Compounds, , Metalloids, , Inorganic compounds, , Organic compounds, , Pure Substances, They have characteristics different from the mixtures. They have fixed, composition, whereas mixtures may contain the components in any, ratio and their composition is variable., , Elements, It is the simplest form of pure substance, which can neither be, decomposed nor be built from simpler substances by ordinary physical, and chemical methods. It contains only one kind of atoms. The number, of elements known till date is 118., An element can be a metal, a non-metal or a metalloid., Hydrogen is the most abundant element in the universe., Oxygen (46.6%), a non-metal, is the most abundant element in the, earth crust., Al is the most abundant metal in the earth crust., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Basic Concepts of Chemistry, , 3, , Compounds, It is also the form of matter which can be formed by combining two or, more elements in a definite ratio by mass. It can be decomposed into, its constituent elements by suitable chemical methods, e.g. water (H 2O), is made of hydrogen and oxygen in the ratio 1 : 8 by mass., Compounds can be of two types :, (i) Inorganic compounds Previously, it was believed that these, compounds are derived from non-living sources, like rocks and, minerals. But these are infact the compounds of all the elements, except hydrides of carbon (hydrocarbons) and their derivatives., (ii) Organic compounds According to earlier scientists, these, compounds are derived from living sources like plants and, animals, or these remain buried under the earth; (e.g., petroleum). According to modern concept, these are the hydrides, of carbon and their derivatives., , Mixtures, These are made up of two or more pure substances. They can possess, variable composition and can be separated into their components by, some physical methods., Mixtures may be homogeneous (when composition is uniform, throughout) or heterogeneous (when composition is not uniform, throughout)., , Mixture Separation Methods, Common methods for the separation of mixtures are:, (a) Filtration Filtration is the process of separating solids that, are suspended in liquids by pouring the mixture into a filter, funnel. As the liquid passes through the filter, the solid particles, are held on the filter., (b) Distillation Distillation is the process of heating a liquid to, form vapours and then cooling the vapours to get back the liquid., This is a method by which a mixture containing volatile, substances can be separated into its components., (c) Sublimation This is the process of conversion of a solid, directly into vapours on heating. Substances showing this, property are called sublimate, e.g. iodine, naphthalene, camphor., This method is used to separate a sublimate from non-sublimate, substances., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 4, , Handbook of Chemistry, , (d) Crystallisation It is a process of separating solids having, different solubilities in a particular solvent., (e) Magnetic separation This process is based upon the fact, that a magnet attracts magnetic components of a mixture of, magnetic and non-magnetic substances. The non-magnetic, substance remains unaffected. Thus, it can be used to separate, magnetic components from non-magnetic components., (f) Atmolysis This method is based upon rates of diffusion of, gases and used for their separation from a gaseous mixture., , Atoms and Molecules, Atom is the smallest particle of an element which can take part in a, chemical reaction. It may or may not be capable of independent, existence., Molecule is the simplest particle of matter that has independent, existence. It may be homoatomic, e.g. H2 , Cl2 , N2 (diatomic),, O3 (triatomic) or heteroatomic, e.g. HCl, NH3 , CH4 etc., , Physical Quantities and Their Measurements, Physical quantity is a physical property of a material that can be, quantified by measurement and their measurement does not involve, any chemical reaction., To express the measurement of any physical quantity, two things are, considered:, (i) Its unit,, (ii) The numerical value., Magnitude of a physical quantity = numerical value × unit, , Unit, It is defined as ‘‘some fixed standard against which the comparison of a, physical quantity can be done during measurement.’’, Units are of two types:, (i) Basic units, , (ii) Derived units, , (i) The basic or fundamental units are length (m), mass (kg),, time (s), electric current (A), thermodynamic temperature (K),, amount of substance (mol) and luminous intensity (Cd)., (ii) Derived units are basically derived from the fundamental units,, e.g. unit of density is derived from units of mass and volume., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Basic Concepts of Chemistry, , 5, , Different systems used for describing measurements of various, physical quantities are:, (a) CGS system It is based on centimetre, gram and second as the, units of length, mass and time respectively., (b) FPS system A British system which used foot (ft), pound (lb), and second (s) as the fundamental units of length, mass and time, respectively., (c) MKS system It is the system which uses metre (m), kilogram, (kg) and second (s) respectively for length, mass and time;, ampere (A) was added later on for electric current., (d) SI system (1960) International system of units or SI units, contains following seven basic and two supplementary units:, , Basic Physical Quantities and, Their Corresponding SI Units, Physical quantity, , Name of SI unit, , Symbol for SI unit, , Length (l ), , metre, , m, , Mass (m), , kilogram, , kg, , Time (t ), , second, , s, , Electric current (I), , ampere, , A, , Thermodynamic temperature (T ), , kelvin, , K, , Amount of substance (n), , mole, , mol, , Luminous intensity (Iv ), , candela, , Cd, , Supplementary units It includes plane angle in radian and solid, angle in steradian., , Prefixes, The SI units of some physical quantities are either too small or too, large. To change the order of magnitude, these are expressed by, using prefixes before the name of base units. The various prefixes are, listed as:, , www.aiimsneetshortnotes.com
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6, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Multiple, 24, , 10, , Prefix, , Symbol, , yotta, , Y, , Multiple, , Prefix, , Symbol, , –1, , deci, , d, , –2, , 10, , 21, , 10, , zeta, , Z, , 10, , centi, , c, , 1018, , exa, , E, , 10–3, , milli, , m, , 1015, , peta, , P, , 10–6, , micro, , µ, , 12, , 10, , tera, , T, , 10–9, , nano, , n, , 109, , giga, , G, , 10–12, , pico, , p, , –15, , 6, , 10, , mega, , M, , 10, , femto, , f, , 103, , kilo, , K, , 10−18, , atto, , a, , 102, , hecto, , h, , 10−21, , zepto, , z, , 10, , deca, , da, , 10−24, , yocto, , y, , Some Physical Quantities, (i) Mass It is the amount of matter present in a substance. It, remains constant for a substance at all the places. Its unit is kg, but in laboratories usually gram is used., (ii) Weight It is the force exerted by gravity on an object. It varies, from place to place due to change in gravity. Its unit is Newton, (N), (iii) Temperature There are three common scale to measure, temperature °C (degree celsius), °F (degree fahrenheit) and K, (kelvin). K is the SI unit. The temperature on two scales (°C and, °F) are related to each other by the following relationship:, 9, °F = ( ° C) + 32, 5, The kelvin scale is related to celsius scale as follows:, K = ° C + 273 .15, (iv) Volume The space occupied by matter (usually by liquid or a, gas) is called its volume. Its unit is m3 ., (v) Density It is defined as the amount or mass per unit volume, and has units kg m −3 or g cm −3 ., , Scientific Notation, In such notation, all measurements (how so ever large or small) are, expressed as a number between 1.000 and 9.999 multiplied or divided, by 10., In general it can be given as = N × 10n, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Basic Concepts of Chemistry, , 7, , Here, N is called digit term (1.000–9.999) and n is known as exponent., e.g. 138.42 cm can be written as 1.3842 × 102 and 0.0002 can be, written as 2.0 × 10−4., , Precision and Accuracy, Precision refers to the closeness of the set of values obtained from, identical measurements of a quantity. Precision is simply a measure of, reproducibility of an experiment., Precision = individual value – arithmetic mean value, Accuracy is a measure of the difference between the experimental, value or the mean value of a set of measurements and the true value., Accuracy = mean value – true value, In physical measurements, accurate results are generally precise but, precise results need not be accurate., , Significant Figures, Significant figures are the meaningful digits in a measured or, calculated quantity. It includes all those digits that are known with, certainty plus one more which is uncertain or estimated., Greater the number of significant figures in a measurement, smaller, the uncertainty., Rules for determining the number of significant figures are:, 1. All digits are significant except zeros in the beginning of a, number., 2. Zeros to the right of the decimal point are significant., e.g. 0.132, 0.0132 and 15.0, all have three significant figures., 3. Exact numbers have infinite significant figures., , Calculations Involving Significant Figures, 1. In addition or subtraction, the final result should be, reported to the same number of decimal places as that of the, term with the least number of decimal places,, e.g., , 2.512 (4 significant figures), , 2.2 (2 significant figures), 5.23 (3 significant figures), 9.942 ⇒ 9.9, (Reported sum should have only one decimal point.), , www.aiimsneetshortnotes.com
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8, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 2. In multiplication and division, the result is reported to the, same number of significant figures as least precise term or the, term with least number of significant figures, e.g., 15.724 ÷ 0.41 = 38.3512195121(38.35), , Rounding Off the Numerical Results, When a number is rounded off, the number of significant figures is, reduced, the last digit retained is increased by 1 only if the following, digit is ≥ 5 and is left as such if the following digit is ≤ 4, e.g., 12.696 can be written as 12.7, 18.35 can be written as 18.4, 13.93 can be written as 13.9, , Dimensional Analysis, Often while calculating, there is a need to convert units from one, system to other. The method used to accomplish this is called factor, label method or unit factor method or dimensional analysis., In this,, Information sought = Information given × Conversion factor, , Important Conversion Factors, −5, , 1dyne = 10, , 1L = 1000 mL, , N, , 1atm = 101325 Nm, , –2, , = 1000 cm3, = 10−3 m3, , = 101325 Pa (pascal), 1bar = 1 × 105 Nm–2, , = 1 dm3, , 5, , = 1 × 10 (pascal), 1 L atm = 101.325 J = 24.21 cal, 19, , 1cal = 4.184 J = 2.613 × 10 eV, 1eV = 1.602189 × 10–19 J, , 1 gallon = 3.7854 L, 1 eV/atom = 96.485 kJ mol −1, 1amu or u = 1.66 × 10−27 kg, , 1 J = 10 7 erg, −10, , 1 Å = 10, , m, , = 931.5 MeV, 1esu = 3.3356 × 10−10 C, , Laws of Chemical Combinations, The combination of elements to form compounds is governed by the, following six basic laws:, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Basic Concepts of Chemistry, , 9, , Law of conservation of mass (Lavoisier, 1789), This law states that during any physical or chemical change, the total, mass of the products is equal to the total mass of reactants. It does not, hold good for nuclear reactions., , Law of definite proportions (Proust, 1799), According to this law, a chemical compound obtained by different, sources always contains same percentage of each constituent element., , Law of multiple proportions (Dalton, 1803), According to this law, if two elements can combine to form more than, one compound, the masses of one element that combine with a fixed, mass of the other element, are in the ratio of small whole numbers,, e.g. in NH3 and N 2H 4, fixed mass of nitrogen requires hydrogen in the, ratio 3 : 2., , Law of reciprocal proportions (Richter, 1792), According to this law, when two elements (say A and B ) combine, separately with the same weight of a third element (say C), the ratio in, which they do so is the same or simple multiple of the ratio in which, they ( A and B) combine with each other. Law of definite proportions,, law of multiple proportions and law of reciprocal proportions do not, hold good when same compound is obtained by using different isotopes, of the same element, e.g. H 2O andD2O., , Gay Lussac’s law of gaseous volumes (In 1808), It states that under similar conditions of temperature and pressure,, whenever gases react together, the volumes of the reacting gases as, well as products (if gases) bear a simple whole number ratio., , Avogadro’s hypothesis, It states that equal volumes of all gases under the same conditions of, temperature and pressure contain the same number of molecules., , Dalton’s Atomic Theory (1803), This theory was based on laws of chemical combinations. It’s basic, postulates are :, 1. All substances are made up of tiny, indivisible particles, called, atoms., 2. In each element, the atoms are all alike and have the same, mass. The atoms of different elements differ in mass., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 10, , Handbook of Chemistry, , 3. Atoms can neither be created nor destroyed during any physical, or chemical change., 4. Compounds or molecules result from combination of atoms in, some simple numerical ratio., , Limitations, (i) It failed to explain how atoms combine to form molecules., (ii) It does not explain the difference in masses, sizes and valencies, of the atoms of different elements., , Atomic Mass, It is the average relative atomic mass of an atom. It indicates that how, 1, many times an atom of that element is heavier as compared with th, 12, part of the mass of one atom of carbon-12., Average atomic mass =, , average mass of an atom, 1, × mass of an atom of C12, 12, , The word average has been used in the above definition and is very, significant because elements occur in nature as mixture of several, isotopes. So, atomic mass can be computed as, RA (1) × at. mass (1) + RA (2) × at. mass (2), l Average atomic mass =, RA(1) + RA(2), Here, RA is relative abundance of different isotopes., l, , In case of volatile chlorides, the atomic weight is calculated as, , and, l, , At. wt. = Eq. wt. × valency, 2 × vapour density of chloride, valency =, eq. wt. of metal + 35.5, , According to Dulong and Petit’s rule,, Atomic weight × specific heat = 6.4, , Gram Atomic Mass (GAM), Atomic mass of an element expressed in gram is called its gram atomic, mass or gram-atom or mole-atom., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Basic Concepts of Chemistry, , 11, , Molecular Mass, It is the mass of a molecule, i.e. number of times a molecule is heavier, 1, th mass of C-12 atom. Molecular mass of a substance is an, than, 12, additive property and can be calculated by taking algebraic sum of, atomic masses of all the atoms of different elements present in one, molecule., Molecular mass =, , average relative mass of one molecule, 1, × mass of C-12 atom, 12, , Gram molecular mass or molar mass is molecular mass of a, substance expressed in gram., Molecular mass = 2 × VD (Vapour density), , Formula Mass, Some substances such as sodium chloride do not contain discrete, molecules as their constituent units. The formula such as NaCl is used, to calculate the formula mass instead of molecular mass as in the solid, state sodium chloride does not exist as a single entity. e.g. formula, mass of sodium chloride is 58.5 u., , Equivalent Mass, It is the mass of an element or a compound which would combine with, or displaces (by weight) 1 part of hydrogen or 8 parts of oxygen or, 35.5 parts of chlorine., wt. of metal, Eq. wt. of metal =, × 1.008, wt. of H 2 displaced, or, , =, , wt. of metal, ×8, wt. of oxygen combined, , or, , =, , wt. of metal, × 35.5, wt. of chlorine combined, , Eq. wt. of metal =, , wt. of metal, × 11200, volume of H 2 (in mL) displaced at STP, , In general,, Wt. of substance A Eq. wt. of substance A, =, Wt. of substance B Eq. wt. of substance B, , www.aiimsneetshortnotes.com
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12, , Telegram @neetquestionpaper, , Handbook of Chemistry, , or for a compound (I) being converted into another compound (II) of, same metal,, Wt. of compound I, Wt. of compound II, =, , eq. wt. of metal + eq. wt. of anion of compound I, eq. wt. of metal + eq. wt. of anion of compound II, , Eq. mass of a salt =, Equivalent mass =, , formula mass, total positive or negative charge, , atomic mass or molecular mass, n factor, , n factor for various compounds can be obtained as, (i) n factor for acids i.e. basicity, (Number of ionisable H + per molecule is the basicity of acid.), Acid, , HCl, , H2SO 4, , H 3 PO 3, , H 3 PO 4, , H2C 2O 4, , Basicity, , 1, , 2, , 2, , 3, , 2, , (ii) n factor for bases, i.e. acidity., (Number of ionisable OH − per molecule is the acidity of a base.), Base, , NaOH, , Mg(OH)2, , Al(OH) 3, , Acidity, , 1, , 2, , 3, , (iii) In case of ions, n factor is equal to charge of that ion., (iv) In redox titrations, n factor is equal to change in oxidation, number., Cr2O72– + 6e– + 14H + → 2Cr3 + + 2H 2O, n factor = 6, MnO–4, , + 8H + + 5e− → Mn2+ + 4H 2O, , n factor = 5, Equivalent mass of organic acid (RCOOH) is calculated by the, following formula, Eq. wt. of silver salt of acid ( RCOOAg) Wt. of silver salt, =, Eq. wt. of Ag (or 108), Wt. of silver, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Basic Concepts of Chemistry, , 13, , Mole Concept, Term mole was suggested by Ostwald (Latin word mole = heap), A mole is defined as the amount of substance which contains same, number of elementary particles (atoms, molecules or ions) as the, number of atoms present in 12 g of carbon (C-12)., 1 mol = 6.023 × 1023 atoms = one gram-atom = gram atomic mass, 1 mol = 6.023 × 1023 molecules = gram molecular mass, In gaseous state at STP (T = 273 K, p = 1 atm), Gram molecular mass = 1 mol = 22.4 L = 6.022 × 1023 molecules, Standard number 6.023 × 1023 is called Avogadro number in honour, of Avogadro (he did not give this number) and is denoted by N A ., The volume occupied by one mole molecules of a gaseous substance is, called molar volume or gram molecular volume., Number of moles =, , Amount of a, substance, (in gram), , Multipli, ed, , amount of substance (in gram), molar mass, , by, , Molar mass, , Divided by, , Number, of, entities, , D, id, , iv, 22.4 L, , ed, by, , Divided by by, d, l ie, tip, l, u, M, , Mol, , lied by, Multip, NA, 23, (6.023 × 10 ), , Volume of gas (in L) at STP, , Number of molecules = number of moles × N A, NA, Number of molecules in 1g compound =, g-molar mass, Number of molecules in 1 cm3 (1 mL) of an ideal gas at STP is called, Loschmidt number (2.69 × 1019 )., One amu or u (unified mass) is equal to exactly the, of 12C atom, i.e. 1 amu or u =, , 1, th of the mass, 12, , 1, × mass of one carbon (C12 ) atom, 12, , 1, = 1 Avogram = 1 Aston, NA, = 1 Dalton = 1.66 × 10 −24 g, One mole of electrons weighs 0.55 mg (5.5 × 10 −4 g)., 1 amu =, , www.aiimsneetshortnotes.com
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14, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Empirical and Molecular Formulae, Empirical formula is the simplest formula of a compound giving, simplest whole number ratio of atoms present in one molecule,, e.g. CH is empirical formula of benzene (C6H 6 )., Molecular formula is the actual formula of a compound showing the, total number of atoms of constituent elements present in a molecule of, compound, e.g. C6H 6 is molecular formula of benzene., Molecular formula = (Empirical formula)n, where, n is simple whole number having values 1, 2, 3, …, etc., and, can be calculated as, molecular formula mass, n=, empirical formula mass, , Stoichiometry, The relative proportions in which the reactants react and the products, are formed, is called stoichiometry (from the Greek word meaning ‘to, measure an element’.), , Limiting reagent It is the reactant which is completely consumed, during the reaction., , Excess reagent It is the reactant which is not completely consumed, and remains unreacted during the reaction., In a irreversible chemical reaction, the extent of product can be, computed on the basis of limiting reagent in the chemical reaction., , Per cent Yield, The actual yield of a product in any reaction is usually less than the, theoretical yield because of the occurrence of certain side reactions., actual yield, Per cent yield =, × 100, theoretical yield, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 2, Atomic Structure, Atom, John Dalton proposed (in 1808) that atom is the smallest indivisible, particle of matter. Atomic radii are of the order of 10−8 cm. It contains, three subatomic particles namely electrons, protons and neutrons., , Electron, Electron was discovered as a result of study of cathode rays by, JJ Thomson. It was named by Stony., It carries a unit negative charge ( −1.6 × 10−19 C)., Mass of electron is 9.11 × 10−31 kg and mass of one mole of electron is, 0.55 mg. Some of the characteristics of cathode rays are:, (i) These travel in straight line away from cathode and produce, fluorescence when strike the glass wall of discharge tube., (ii) These cause mechanical motion in a small pin wheel placed in, their path., (iii) These produce X-rays when strike with metal and are deflected, by electric and magnetic field., , Charge to Mass Ratio of Electron, In 1897, British physicist JJ Thomson measured the ratio of electrical, charge (e) to the mass of electron ( me ) by using cathode ray tube and, applying electrical and magnetic field perpendicular to each other as, well as to the path of electrons. Thomson argued that the amount of, deviation of the particles from their path in the presence of electrical or, magnetic field may vary as follows:, (i) If greater the magnitude of the charge on the particles, greater, is the deflection., (ii) The mass of the particle, lighter the particle, greater the, deflection., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 16, , Handbook of Chemistry, , (iii) The deflection of electrons from its original path increase with, the increase in the voltage. By this Thomson determined the, value e/ me as 1.758820 × 1011 C kg −1., , Proton, Rutherford discovered proton on the basis of anode ray experiment., It carries a unit positive charge (+1.6 × 10−19 C)., The mass of proton is 1.007276 u., e, e, ratio is maximum for, ratio of proton is 9.58 × 10−4 C /g. (, The, m, m, hydrogen gas.), Some of the characteristics of anode rays are:, (i) These travel in straight line and possess mass many times, heavier than the mass of an electron., (ii) These are not originated from anode but are produced in the, space between the anode and the cathode., (iii) These also cause mechanical motion and are deflected by electric, and magnetic field., e, (iv) Specific charge for these rays depends upon the nature of, m, the gas taken and is maximum for H 2., , Neutron, Neutrons are neutral particles. It was discovered by Chadwick (1932)., The mass of neutron is 1.675 × 10−24 g or 1.008665 amu or u., 9, 4 Be, , + 42He →, (α ′ − particles), , 12, 6C, , +, , 1, 0n, , ( Neutron), , Some Other Subatomic Particles, (a) Positron, , Positive electron ( +10 e), discovered by Dirac (1930), , and Anderson (1932)., (b) Neutrino and antineutrino Particles of small mass and no, charge as stated by Fermi (1934)., (c) Meson Discovered by Yukawa (1935) and Kemmer. They are, unstable particles and include pi ions [π + , π − or π 0]., (d) Anti-proton It is negative proton produced by Segre and, Weigland (1955)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Atomic Structure, , 17, , Thomson’s Atomic Model, Atom is a positive sphere with a number of electrons distributed within, the sphere. It is also known as plum pudding model. It explains the, neutrality of an atom. This model could not explain the results of, Rutherford scattering experiment., , Rutherford’s Nuclear Model of Atom, It is based upon α-particle scattering experiment. Rutherford, presented that, (i) most part of the atom is empty., (ii) atom possesses a highly dense, positively charged centre, called, nucleus of the order 10−13 cm., (iii) entire mass of the atom is concentrated inside the nucleus., (iv) electrons revolve around the nucleus in circular orbits., (v) electrons and the nucleus are held together by electrostatic, forces of attraction., , Drawbacks of Rutherford’s Model, (i) According to electromagnetic theory, when charged particles are, accelerated, they emit electromagnetic radiations, which comes, by electronic motion and thus orbit continue to shrink, so atom is, unstable. It doesn’t explain the stability of atom., (ii) It doesn’t say anything about the electronic distribution around, nucleus., , Atomic Number (Z), Atomic number of an element corresponds to the total number of, protons present in the nucleus or total number of electrons present in, the neutral atom., , Mass Number (A), The mass of the nucleus is due to protons and neutrons, thus they are, collectively called nucleons. The total number of nucleons is termed, as mass number of the atom., Mass number of an element = number of protons + number of neutrons, , Representation of an Atom, Mass number, , A, , Atomic number, , Z, , Symbol of the element, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 18, , Handbook of Chemistry, , Different Types of Atomic Species, (a) Isotopes Species with same atomic number but different mass, number are called isotopes, e.g. 1H1 , 1H 2., (b) Isobars Species with same mass number but different atomic, number are called isobars, e.g. 18 Ar40 , 19K 40., (c) Isotones Species having same number of neutrons are called, isotones, e.g. 1H3 and 2He4 are isotones., (d) Isodiaphers Species with same isotopic number are called, isodiaphers, e.g. 19K39 , 9F19., Isotopic number = mass number − [2 × atomic number], (e) Isoelectronic Species with same number of electrons are, called isoelectronic speices, e.g. Na + , Mg2+ ., (f) Isosters Species having same number of atoms and same, number of electrons, are called isosters, e.g. N 2 and CO., , Developments Leading to the Bohr’s Model of Atom, Two developments played a major role in the formulation of Bohr’s model:, (i) Dual character of the electromagnetic radiation which means, that radiation possess wave like and particle like properties., (ii) Atomic spectra explained by electronic energy level in atoms., , Electromagnetic Wave Theory (Maxwell), The energy is emitted from source continuously in the form of, radiations and magnetic fields. All electromagnetic waves travel with, the velocity of light (3 × 108 m/ s) and do not require any medium for, their propagation., An electromagnetic wave has the following characteristics:, (i) Wavelength It is the distance between two successive crests, or troughs of a wave. It is denoted by the Greek letter λ (lambda)., (ii) Frequency It represents the number of waves which pass, through a given point in one second. It is denoted by ν (nu)., (iii) Velocity (v) It is defined as the distance covered in one second, by the waves. Velocity of light is 3 × 1010 cms− 1., (iv) Wave number It is the reciprocal of wavelength and has units, cm − 1. It is denoted by ν (nu bar)., (v) Amplitude (a) It is the height of the crest or depth of the, trough of a wave., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Atomic Structure, , 19, , Wavelength ( λ ), frequency ( ν ) and velocity ( v ) of any electromagnetic, radiations are related to each other as v = νλ., Electromagnetic wave theory was successful in explaining the, properties of light such as interference, diffraction etc., but it could not, explain the, 1. Black body radiation, 2. Photoelectric effect, These phenomena could be explained only if electromagnetic waves are, supposed to have particle nature. Max Planck provided an explanation, for the behaviour of black body and photoelectric effect., , Particle Nature of Electromagnetic Radiation :, Planck’s Quantum Theory, Planck explain the distribution of intensity of the radiation from black, body as a function of frequency or wavelength at different, temperatures., hc, E = hν =, (Q c = νλ ), λ, where, h = Planck’s constant = 6.63 × 10−34 J-s, E = energy of photon or quantum, ν = frequency of emitted radiation, If n is the number of quanta of a particular frequency and ET be total, energy then, ET = nhν, , Black Body Radiation, If the substance being heated is a black body, the radiation emitted is, called black body radiation., , Photoelectric Effect, It is the phenomenon in which beam of light of certain frequency falls, on the surface of metal and electrons are ejected from it., This phenomenon is known as photoelectric effect. It was first observed, by Hertz., hν, W 0 = hν 0, 1 mv 2, hc, 2, W0 =, λ max, Metal hν0 [work function], , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 20, , Handbook of Chemistry, , Threshold frequency ( ν 0 ) = minimum frequency of the radiation, Work function (W 0 ) = required minimum energy of the radiation, E = KE + W 0, 1, ∴, mv 2 = h( ν − ν 0 ) [Kinetic energy of ejected electron = h( ν − ν 0 )], 2, where,, ν = frequency of incident radiation, ν 0 = threshold frequency, , Electromagnetic Spectrum, The different types of electromagnetic radiations differ only in their, wavelengths and hence, frequencies. When these electromagnetic, radiations are arranged in order of their increasing wavelengths or, decreasing frequencies, the complete spectrum obtained is called, electromagnetic spectrum., , Different Types of Radiations and Their Sources, Type of radiation, , Wavelength (in Å), , Generation source, , Gamma rays, , 0.01 to 0.1, , Radioactive disintegration, , X-rays, , 0.1 to 150, , From metal when an electron strikes on it, , UV-rays, , 150 to 3800, , Sun rays, , Visible rays, , 3800 to 7600, , Infrared rays, , 7600 to 6 × 10, , Micro waves, , 6 × 106 to 3 × 109, , Radio waves, , 3 × 1014, , Stars, arc lamps, 6, , Incandescent objects, Klystron tube, From an alternating current of high, frequency, , Electromagnetic spectra may be emission or absorption spectrum on, the basis of energy absorbed or emitted. An emission spectrum is, obtained when a substance emits radiation after absorbing energy. An, absorption spectra is obtained when a substance absorbs certain, wavelengths and leave dark spaces in bright continuous spectrum., A spectrum can be further classified into two categories such as, (i) Continuous or band spectrum A spectrum in which there is, no sharp boundary between two different radiations., (ii) Discontinuous or line spectrum A spectrum in which, radiations of a particular wavelength are separated from each, other through sharp boundaries., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Atomic Structure, , 21, , Bohr’s Model, Neils Bohr proposed his model in 1931. Bohr’s model is applicable only, for one electron system like H, He+ , Li2+ etc., Assumptions of Bohr’s model are, 1. Electrons keep revolving around the nucleus in certain fixed, permissible orbits where it doesn’t gain or lose energy. These, orbits are known as stationary orbits., circumference of orbit, Number of waves in an orbit =, wavelength, 2. The electrons can move only in those orbits for which the angular, h, , i.e., momentum is an integral multiple of, 2π, nh, ( n = 1, 2, 3..... ), mvr =, 2π, where, m = mass of electron; v = velocity of electron;, r = radius of orbit, n = number of orbit in which electrons are present, 3. Energy is emitted or absorbed only when an electron jumps from, higher energy level to lower energy level and vice-versa., hc, ∆E = E2 − E1 = hν =, λ, 4. The most stable state of an atom is its ground state or normal, state., From Bohr’s model, energy, velocity and radius of an electron in, nth Bohr orbit are, (i) Velocity of an electron in nth Bohr orbit, Z, m/s, ( vn ) = 2.165 × 106, n, (ii) Radius of nth Bohr orbit, n2, n2, (rn ) = 0.53 × 10−10, m = 0.53, Å, Z, Z, Z2, (iii) En = − 2.178 × 10−18 2 J/atom, n, Z2, = − 1312 2 kJ/ mol, n, Z2, = − 13.6 2 eV/atom, n, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 22, , Handbook of Chemistry, 1, 1, ∆E = − 2.178 × 10−18 2 − 2 Z 2 J/atom, n1 n 2 , where, n = number of shell; Z = atomic number, As we go away from the nucleus, the energy levels come closer,, i.e. with the increase in the value of n, the difference of energy, between successive orbits decreases., Thus,, E2 − E1 > E3 − E2 > E4 − E3 > E5 − E4, etc., , Emission Spectrum of Hydrogen, According to Bohr’s theory, when an electron jumps from ground state to, excited state, it emits a radiation of definite frequency (or wavelength)., Corresponding to the wavelength of each photon of light emitted, a, bright line appears in the spectrum., The number of spectral lines in the spectrum when the electron comes, n( n − 1), from nth level to the ground level =, 2, Hydrogen spectrum consist of line spectrum., Series, , Region, , n1, , (i) Lyman, , UV, , 1, , 2, 3, 4, …, , (ii) Balmer, , Visible, , 2, , 3, 4, 5, …, , (iii) Paschen, , IR, , 3, , 4, 5, 6, …, , (iv) Brackett, , IR, , 4, , 5, 6, 7, …, , (v) Pfund, , far IR, , 5, , 6, 7, …, , (vi) Humphery, , far IR, , 6, , 7, 8, 9, …, , n2, , Wave number ( ν ) is defined as reciprocal of the wavelength., ν=, where,, Here,, , 1, 1, 1, ⇒ ν = RZ 2 2 − 2 , λ, n1 n 2 , , n1 = 1, 2 ......, n 2 = n1 + 1, n1 + 2 ......, λ = wavelength, R = Rydberg constant = 109677.8 cm –1, , First line of a series is called line of longest wavelength (shortest, energy) and last line of a series is the line of shortest wavelength, (highest energy, n 2 = ∞)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Atomic Structure, , 23, , Sommerfeld Extension to Bohr’s Model, According to this theory, the angular momentum of revolving electron, h, in an elliptical orbit is an integral multiple of, , i.e., 2π, kh, mvr =, 2π, nh, From Bohr model,, mvr =, 2π, For K shell, n = 1, k = 1 Circular shape, L shell, n = 2, k = 1, 2 Circular, M shell, n = 3, k = 1, 2, 3 Elliptical, N shell, n = 4, k = 1, 2, 3, 4 Elliptical, , Limitations of Bohr’s Theory, (i) It is unable to explain the spectrum of atom other than hydrogen, like doublets or multielectron atoms., (ii) It could not explain the ability of atom to form molecules by, chemical bonds. Hence, it could not predict the shape of, molecules., (iii) It is not in accordance with the Heisenberg uncertainty principle, and could not explain the concept of dual character of matter., (iv) It is unable to explain the splitting of spectral lines in the, presence of magnetic field (Zeeman effect) and electric field, (Stark effect)., , Towards Quantum Mechanical Model of the Atom, Two important developments which contributed significantly in the, formulation of such a model were given below, , 1. de-Broglie Principle (Dual Nature), de-Broglie explains the dual nature of electron, i.e. both particle as well, as wave nature., h, h, or, λ=, =λ, [ p = mv (momentum)], mv, p, where, λ = wavelength; v = velocity of particle; m = mass of particle, h, λ=, 2m × K E, where, KE = kinetic energy., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 24, , Handbook of Chemistry, , 2. Heisenberg’s Uncertainty Principle, According to this principle, ‘‘it is impossible to specify at any given, instant both the momentum and the position of subatomic particles, simultaneously like electron.’’, h, ∆x ⋅ ∆p ≥, 4π, where, ∆x = uncertainty in position; ∆p = uncertainty in momentum, , Quantum Mechanical Model of Atom, It is the branch of chemistry which deals with dual behaviour of, matter. It is given by Werner Heisenberg and Erwin Schrodinger., Schrodinger wave equation is, ∂ 2ψ ∂ 2ψ ∂ 2ψ 8π 2m, +, +, +, (E − U ) ψ = 0, ∂z 2, ∂y 2, ∂x 2, h2, where, x , y , z = cartesian coordinates, m = mass of electron, E = total energy of electron, U = potential energy of electron, h = Planck’s constant, ψ (Psi) = wave function which gives the amplitude of wave, ψ 2 = probability function, For H-atom, the equation is solved as, H$ ψ = Eψ, where, H$ is the total energy operator, called Hamiltonian. If the sum, of kinetic energy operator (T ) and potential energy operator (U ) is the, total energy, E of the system,, H = T +U, (T + U )ψ = Eψ, The atomic orbitals can be represented by the product of two wave, functions (i) radial wave function (ii) angular wave function., The orbital wave function, ψ has no significance, but ψ 2 has, significance, it measures the electron probability density at a point in, an atom. ψ can be positive or negative but ψ 2 is always positive., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 25, , Atomic Structure, , Difference between Orbit and Orbital, Orbit, , Orbital, , 1., , An orbit is a well defined circular path An orbital is the three dimensional space, around the nucleus in which the around the nucleus within which the, electron revolves., probability of finding an electron is maximum., , 2., , The maximum number of electrons in The maximum number of electrons present, any orbit is given by 2 n2 where n is the in any orbital is two., number of the orbit., , Shapes of Atomic Orbitals, The shapes of the orbitals are, s-spherical, p-dumb bell, d-double-dumb-bell, f-Diffused, These orbitals combine to form subshell., (i) s-subshell will have only one spherical orbital., Y, Z, X, , (ii) p-subshell has three orbitals ( px , py , pz )., pz, z, , py, z, , px, z, , x, y, , y, , x, , x, y, , (iii) d-subshell has five orbitals ( dxy , d yz , dzx , dx 2 − y 2 and dz 2 )., dxy, z, , z, , dxz, , x, y, , x, y, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Atomic Structure, , 27, , Node, A region or space, where probability of finding an electron is, maximum, is called a peak, while zero probability space is called node., Nodes are of two types :, (a) Radial nodes, (b) Angular nodes, (i) ( n − l − 1) = radial node, (ii) ( l ) = angular node, (iii) ( n − 1) = total nodes, , Number of Peaks and Nodes for Various Orbitals, S. No., , Type of orbital, , Number of peaks, , Number of nodes, , 1., , s, , n, , n −1, , 2., , p, , n −1, , n−2, , 3., , d, , n−2, , n− 3, , 4., , f, , n− 3, , n− 4, , Quantum Numbers, Each electron in an atom is identified in terms of four quantum numbers., , Principal Quantum Number (Neils Bohr), It is denoted by n. It tells us about the main shell in which electron, resides. It also gives an idea about the energy of shell and average, distance of the electron from the nucleus. Value of n = any integer., , Azimuthal Quantum Number (Sommerfeld), It is denoted by l. It tells about the number of subshells ( s, p, d , f ) in, any main shell. It also represents the angular momentum of an, electron and shapes of subshells. The orbital angular momentum of an, h, electron = l( l + 1), 2π, Value of l = 0 to n − 1., l = 0 for s, l = 2 for d, l = 1 for p, l = 3 for f, Number of subshells in main energy level = n., , Magnetic Quantum Number (Lande), It is denoted by m. It tells about the number of orbitals and orientation, of each subshell. Value of m = − l to +l including zero., Number of orbitals in each subshell = ( 2l + 1), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 28, , Handbook of Chemistry, S. No., , Subshell, , Orbital, , 1., , s, , 1, , 2., , p, , 3, , 3., , d, , 5, , 4., , f, , 7, , Number of orbitals in main energy level = n 2., Maximum number of electrons in nth shell = 2n 2, , Spin Quantum Number (Ublenbeck and Goldsmith), It is denoted by ms or s. It indicates the direction of spinning of, electron, i.e. clockwise or anti-clockwise., Maximum number of electrons in main energy level = 2n 2, , Electronic Configuration, Arrangement of electrons in various shells, subshells and orbitals in an, atom is known as electronic configuration., , Filling of Orbitals in Atom, Aufbau Principle, According to this principle, in the ground state of an atom, the, electrons occupy the lowest energy orbitals available to them, i.e. the, orbitals are filled in order of increasing value of n + l. For the orbitals, having the same value of n + l, the orbtial having lower value of n is, filled up first., The general order of increasing energies of the orbital is, 1s < 2s < 2 p < 3s < 3 p < 4s < 3d < 4 p < 5s < 4d < 5 p < 6s < 4 f < 5d, < 6 p < 7s < 5 f < 6d < 7 p, Thus, the filling of electrons in various subshells within the atom can, be summerised through following figure., 1s, 2s, 3s, 4s, 5s, 6s, 7s, , 3d, 4d, 4f 5d, 5f 6d, , 2p, 3p, 4p, 5p, 6p, 7p, , The energy of atomic orbitals for H-atom varies as, 1s < 2s = 2 p < 3s = 3 p = 3d < 4s = 4 p = 4d = 4 f, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Atomic Structure, , 29, , Pauli Exclusion Principle, It states, no two electrons in an atom can have identical set of four, quantum numbers., The maximum number of electrons in s subshell is 2, p subshell is 6,, d subshell is 10 and f subshell is 14., , Hund’s Rule of Maximum Multiplicity, It states,, (i) In an atom no electron pairing takes place in the p, d or f-orbitals, until each orbital of the given subshell contains one electron., (ii) The unpaired electrons present in the various orbitals of the, same subshell should have parallel spins., , Methods of Writing Electronic Configuration, (i) Orbital method In this, the electrons present in respective, orbitals are denoted. e.g. Cl(17) = 1s2 , 2s2 , 2 p6 , 3s2 , 3 p5 ., (ii) Shell method In this, the number of electrons in each shell is, continuously written. e.g. Cl (17) = 1s2 , 2s2 , 2 p6 , 3s2 , 3 p5, K, , L, , M, , 2, 8, 7, (iii) Box method In this method, each orbital is denoted by a box, and electrons are represented by half-headed ( ) or full-headed, ( ↑ ) arrows. An orbital can occupy a maximum of two electrons., e.g., Cl(17) =, 1s2, , 2s2, , 2p6, , 3s2, , 3p5, , Half-filled and completely filled electronic configurations are, more stable. Hence, outer configuration of Cr is 3d5 4s1 and Cu is, 3d10 4s1., , Electronic Configuration of Ions, To write the electronic configuration of ions, first write the electronic, configuration of neutral atom and then add (for negative charge) or, remove (for positive charge) electrons in outer shell according to the, nature and magnitude of charge present on the ion. e.g., O( 8) = 1s2 , 2s2 2 p4, O2− (10) = 1s2 , 2s2 2 p6, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 3, Classification of, Elements and Periodicity, in Properties, Classification of Elements, With the discovery of a large number of elements, it became difficult to, study the elements individually, so classification of elements was done, to make the study easier., , Earlier Attempts to Classify Elements, Many attempts were made to classify the known elements from time to, time. The earlier attempts are as follows:, , Prout’s Hypothesis (1815), According to this theory, hydrogen atom was considered as the, fundamental unit from which all other atoms were made. It is also, known as unitary theory., , Dobereiner’s Triads (1829), Dobereiner classified the elements into groups of three elements with, similar properties in such a manner so that the atomic weight of the, middle element was the arithmetic mean of the other two, e.g., Element, Li, Na, K, Atomic weight, 7, 23, 39, 7 + 39, Mean of atomic masses =, = 23, 2, Similarly Cl, Br, I; Ca, Sr, Ba are two more examples of such triads., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Classification of Elements and Periodicity of Properties, , 31, , Limitations, , Dobereiner could not arrange all the elements known at that time into, triads. He could identify only three such triads that have been, mentioned., , Newland’s Octaves (1864) (Law of Octaves), Newland states that when elements are arranged in order of, increasing atomic masses, every eighth element has properties similar, to the first just like in the musical note [Every eighth musical note is, the same as the first mentioned note]. This can be illustrated as given, below, sa, re, ga, ma, pa, dha, ni, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, , Limitations, 1. This classification was successful up to the element calcium., 2. When noble gas elements were discovered at a later stage,, their inclusion in these octaves disturbed the entire, arrangement., , Lother Meyer’s Atomic Volume Curve (1869), Meyer presented the classification of elements in the form of a curve, between atomic volume and atomic masses and stated that the, properties of the elements are the periodic functions of their atomic, volumes., Molecular mass, , , Here, atomic volume =, Density, , , He concluded that the elements with similar properties occupy similar, position in the curve., , Mendeleev’s Periodic Table, Mendeleev’s periodic table is based upon Mendeleev’s periodic law, which states “The physical and chemical properties of the elements are, a periodic function of their atomic masses.”, At the time of Mendeleev, only 63 elements were known., This periodic table is divided into seven horizontal rows (periods) and, eight vertical columns (groups). Zero group was added later on in the, modified Mendeleev’s periodic table., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 32, , Handbook of Chemistry, , Importance of Mendeleev’s Periodic Table, Few important achievements of periodic table are, (i) Systematic study of the elements., (ii) Prediction of new elements and their properties, he left space for, the elements yet to be discovered, e.g. he left spaces for Ga and, Ge and named these elements as EKa-aluminium (Ga) and, EKa-silicon (Ge) respectively., (iii) Atomic mass correction of doubtful elements on the basis of their, expected positions and properties., , Modified Form of Mendeleev’s Periodic Table, Group →, Period ↓, , I, A, , II, B, , A, , III, B, , A, , IV, B, , A, , V, B, , A, , VI, B, , A, , VII, B, , A, , VIII, , 0, , B, , Zero, He, 4.003, , 1, , H, 1.008, , 2, , Li, 6.94, , Be, 9.01, , N, C, B, 10.82 12.01 14.00, 8, , 3, , Na, 22.99, , Mg, 24.32, , Al, Si, P, S, 26.98 28.09 30.975 32.06, , 4, , Cr, V, Ti, Sc, Ca, K, Co, Mn Fe, 44.96 47.90 50.95 52.01, 40.08, 39.10, 54.94 55.85 58.94, As, Ge, Zn Ga, Cu, Br, Se, 63.54 65.38 69.72 72.60 74.91, 79.91, , 5, , Rb, 85.48, , 6, , Ir, Re Os, W, Ta, Hf, La, Ba, Cs, 132.91 137.36 138.92 178.6 180.92 183.92 186.31 190.2 192.2, At, Po, Bi, Pb, Hg Tl, Au, [210], 210, 197.0 200.61 204.39 207.21 209, , 7, , Fr, 223, , O, 16, , F, 19, , Ne, 20.183, , Cl, 35.46, , Ar, 39.944, Ni, 58.69, , Kr, 83.80, , Rh, Pd, Tc Ru, Mo, Nb, Zr, Y, Sr, 99 101.1 102.91 106.7, 88.92 91.22 92.91 95.95, 87.63, I, Te, Sb, Sn, Cd In, Ag, 107.88 112.41 114.76 118.70 121.76 127.61 126.9, , Xe, 131.3, , 78.96, , Ra, 226.05, , Pt, Rn, 195.23 222, , Ac, 227, , Defects in the Mendeleev’s Periodic Table, (i) Position of hydrogen Hydrogen has been placed in group IA, (alkali metals), but it also resembles with halogens of group, VIIA. Thus, its position in the Mendeleev’s periodic table is, controversial., (ii) Position of isotopes As Mendeleev’s classification is based, on atomic weight, isotopes would have to be placed in different, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Classification of Elements and Periodicity of Properties, , 33, , positions due to their different atomic weights, e.g. 11H , 12H , 31H, would occupy different positions., (iii) Anomalous positions of some elements Without any, proper justification, in some cases the element with higher, atomic mass precedes the element with lower atomic mass., For example, Ar (atomic weight = 39.9) precedes K (atomic, weight = 39.1) and similarly Co (atomic weight = 58.9) has been, placed ahead of Ni (atomic weight = 58.7)., (iv) Position of lanthanoids and actinoids Lanthanoids and, actinoids were not placed in the main periodic table., , Modern Periodic Table (1913), Moseley modified Mendeleev’s periodic law. He stated “Physical and, chemical properties of elements are the periodic function of their, atomic numbers.” It is known as modern periodic law and considered, as the basis of Modern Periodic Table., When the elements were arranged in increasing order of atomic, numbers, it was observed that the properties of elements were, repeated after certain regular intervals of 2, 8, 8, 18, 18 and 32. These, numbers are called magic numbers and cause of periodicity in, properties due to repetition of similar electronic configuration., , Structural Features of Long Form of Periodic Table, (i) Long form of periodic table is called Bohr’s periodic table., There are 18 groups and seven periods in this periodic table., (ii) The horizontal rows are called periods., First period (1H — 2He) contains 2 elements. It is the shortest, period., Second period (3 Li —10Ne) and third period (11Na 18 Ar), contain 8 elements each. These are short periods., Fourth period (19K —36 Kr) and fifth period (37 Rb —54 Xe), contain 18 elements each. These are long periods., Sixth period ( 55 Cs — 86 Rn) consists of 32 elements and is the, longest period., Seventh period starting with 87 Fr is incomplete and consists of, 19 elements., (iii) The 18 vertical columns are known as groups., Elements of group 1 are called alkali metals., Elements of group 2 are called alkaline earth metals., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 34, , Handbook of Chemistry, , Elements of group 16 are called chalcogens [ore forming, elements]., Elements of group 17 are called halogens. [sea salt forming, elements], Elements of group 18 are called noble gases., Anomalous behaviour of the first element of a group. The, first element of a group differs considerably from its congeners, (i.e. the rest of the elements of its group)., This is due to (i) small size (ii) high electronegativity and (iii) non, availability of d-orbitals for bonding. Anomalous behaviour is, observed among the second row elements (i.e. Li to F)., (iv) The periodic table is divided into four main blocks (s, p, d and f ), depending upon the subshell to which the valence electron enters, into., (a) s-block elements Ist and IInd group elements belong to, this block and the last electron enters in s-subshell., General electronic configuration = ns1 − 2., (b) p-block elements Group 13th to 18th belong to this block, in which last electron enters in p-orbital., Their general electronic configuration is ns2np1 − 6., This is the only block which contains metal, non-metal and, metalloids. Examples of metalloids are B, Si, Ge, As, Sb, Te, and At., The elements of s-and p-block elements are collectively, called representative elements., (c) d-block elements Group 3rd to 12th belong to this block,, in which last electron enters in d-orbital., They have inner incomplete shell, so known as transition, elements., General electronic configuration is ns1 − 2 ( n − 1)d1 − 10., d-block elements are generally coloured, paramagnetic and, exhibit variable valency., (d) f-block elements They constitute two series 4f, (lanthanoids) and 5f (actinoids) in which last electron is in, 4f and 5f subshell respectively., General electronic configuration, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Classification of Elements and Periodicity of Properties, , 35, , ( n − 2) f 1 − 14 ( n − 1) d 0 − 1 ns2, The f-block elements are also called as inner-transition elements., Elements with atomic number greater than 92 (U92 ) are called the, transuranic or transuranium elements. All these elements are, man-made through artificial nuclear reactions., Very recently, on August 16, 2003, IUPAC approved the name for the, element of atomic number 110, as Darmstadtium, with symbol Ds., , Limitations of Long Form of Periodic Table, In the long form of the periodic table:, (i) The position of hydrogen still remains uncertain., (ii) The inner-transition elements do not find a place in the main, body of the table. They are placed separately., , Predicting the Position of an Element in, the Periodic Table, First of all write the complete electronic configuration. The principle, quantum number of the valence shell represents the period of the, element., The subshell in which the last electron is filled corresponds to the block, of the element., Group of the element is predicted from the electrons present in the, outermost ( n ) or penultimate ( n − 1) shell as follows :, For s-block elements,, group number = number of ns-electrons, (Number of valence electrons), For p-block elements,, group number = 10 + number of ns and np electrons, For d-block elements,, group number = the sum of the number of ( n − 1) d, and ns electrons., For f-block elements, group number is always 3., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Classification of Elements and Periodicity of Properties, , 37, , IUPAC Nomenclature of Elements With Z > 100, The names are derived directly from the atomic numbers using, numerical roots for 0 and numbers from 1-9 and adding the suffix ium., Digit, , 0, , 1, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , 9, , Root, , nil, , un, , bi, , tri, , quad, , pent, , hex, , sept, , oct, , enn, , Abbreviation, , n, , u, , b, , t, , q, , p, , h, , s, , o, , e, , The IUPAC names and symbols of elements with Z > 100 are, Z, IUPAC, name, Symbol, , 101, , 102, , 103, , 104, , 105, , 106, , 107, , 108, , 109, , 110, , Unnilu Unnilb Unniltr Unnilq Unnilp Unnilh Unnils Unnilo Unnil Ununn, nium, ium, ium uadiu entium exium eptium ctium enniu ilium, m, m, Unu, , Unb, , Unt, , Unq, , Unp, , Unh, , Uns, , Uno, , Une, , Uun, , Metals, Non-metals and Metalloids, l, , l, , l, , Metals comprise more than 78% of all known elements and, appears on the left side of the periodic table., In contrast, non-metals are located at the top right handside of, the periodic table., Within the non-metals, some elements show the properties of both, metals and non-metals, i.e. metalloids. These elements border the, zig-zag line beginning from boron and running diagonally across, the p-block., , Periodic Properties, The properties which are directly or indirectly related to their, electronic configuration and show gradual change when we move from, left to right in a period or from top to bottom in a group are called, periodic properties., , Atomic Radius, It is the distance from the centre of the nucleus to the outermost shell, containing of electrons. It is an hypothetical definition because in a, single atom, it is almost impossible to measure this distance. Hence,, practically, atomic radius is defined in the following four ways :, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 38, , Handbook of Chemistry, , Covalent radius, , If the combining atoms are non-metals (except noble gases) and the, bond between them is the single covalent bond then their radius is, called the covalent radius. It is measured as the half of their, internuclear distance, i.e. For an atom A in a molecule A2., r + rA dA − A, rA = A, =, 2, 2, [Distance A − A = Radius of A + Radius of A], For heterodiatomic molecule AB,, dA − B = rA + rB + 0.09 ( X A − X B ), Where, X A and X B are electronegativities of A and B., , van der Waals’ Radius, It is defined as one-half of the distance between the nuclei of two, non-bonded isolated atoms or two adjacent atoms belonging to two, neighbouring molecules of an element in the solid state., , Metallic Radius, It is defined as one-half of the internuclear distance between the, centres of nuclei of the two adjacent atoms in the metallic crystal., , Ionic Radius, An atom can be changed to a cation by loss of electrons and to an anion, by gain of electrons. A cation is always smaller than the parent atom, because during its formation effective nuclear charge increases and, sometimes a shell may also decrease. On the other hand, the size of an, anion is always larger than the parent atom because during its, formation effective nuclear charge decreases., In case of iso-electronic ions, the higher the nuclear charge, smaller is, the size, e.g. Al3 + < Mg2+ < Na + < F – < O2– < N3 –, The order of radii is :, covalent radius < metallic radius < van der Waals’ radius, In general, the atomic size decreases on moving from left to right in a, period due to increase in effective nuclear charge and increases on, moving from top to bottom in a group due to addition of new shells., The concept of effective nuclear charge is discussed below :, , Effective Nuclear Charge, In a multielectron atom, the electron of the inner-shell decrease, the force of attraction exerted by the nucleus on the valence electrons., This is called shielding effect. Due to this, the nuclear charge ( Z ), actually present on the nucleus, reduces and is called effective nuclear, charge ( Z eff )., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Classification of Elements and Periodicity of Properties, , 39, , It is calculated by using the formula, Z eff = Z − σ, where, σ = screening constant, The magnitude of σ is determined by Slater’s rules., , Slater Rules, (i) Write the electronic configuration in the following order and, groups., (1s) ( 2s, 2 p) ( 3s, 3 p) ( 3d ), ( 4s, 4 p) ( 4d ) ( 4 f ) ( 5s, 5 p) etc., (ii) Electrons of ( n + 1) shell (shell higher than considering electrons), do not contribute in shielding, i.e. σ = 0, (iii) All other electrons in ( ns, np) group contribute σ = 0.35 each., (iv) All electrons of ( n − 1) s and p shell contribute σ = 0.85 each., (v) All electrons of ( n − 2) s and p shell or lower shell contribute, σ = 1.00 each, (vi) All electrons of nd and nf orbital contribute σ = 0.35 and those of, ( n − 1) and f or lower orbital contribute σ = 1.00 each., e.g., Be (4) = 1s2 , 2s2, (for 2s), for 1s, σ = 0.35 + 2 × 0.85 = 2.05, Z eff = Z − σ = 4 − 2.05 = 1.95, , Ionisation Enthalpy (IE), It is the amount of energy required to remove the loosely bound, electron from the isolated gaseous atom., A( g) + IE → A+ ( g) + e−, Various factors with which IE varies are :, (i) Atomic size : varies inversely, (ii) Screening effect : varies inversely, (iii) Nuclear charge : varies directly, Generally left to right in periods, ionisation enthalpy increases; down, the group, it decreases., IE values of inert gases are exceptionally higher due to their stable, configurations. Successive ionisation enthalpies, IE3 > IE2 > IE1, IE1 of N is exceptionally greater than that of oxygen due to stable, half-filled 2 p-orbitals., Among transition elements of 3d-series, 24Cr and 29Cu have higher IE2, due to half-filled and fully-filled stable d-orbitals., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 40, , Handbook of Chemistry, , Electron Gain Enthalpy (∆e g ), It is the amount of energy released when an electron is added in an, isolated gaseous atom. First electron gain enthalpy is negative while, the other successive electron gain enthalpy will be positive due to, repulsion between the electrons already present in the anion and the, electron being added., O ( g) + e− → O− ( g) ;, ∆e g H = − 141 kJ mol−1, O− ( g) + e− → O2− ( g) ;, , ∆e g H = + 780 kJ mol−1, , Various factors with which electron gain enthalpy varies are :, (i) Atomic size : varies directly, (ii) Nuclear charge : varies directly, Along a period, electron gain enthalpy becomes more and more, negative while on moving down the group, it becomes less negative., Noble gases have positive electron gain enthalpies., Halogens have maximum value of ∆e g H within a period due to, smallest atomic size., F and O atom have small size and high charge density, therefore they, have lower values of electron gain enthalpy, than Cl and S, respectively., Cl > F; S > O, Elements having half-filled and fully-filled orbitals exhibit more, stability, therefore, electron gain enthalpy will be low for such, elements., Electron gain enthalpy can be measured by Born-Haber cycle and, elements with high ∆e g H , are good oxidising agent., , Electronegativity (EN), It is defined as the tendency of an atom to attract the shared electron, pair towards itself in a polar covalent bond. Various factors with which, electronegativity varies are :, (i) Atomic size : varies inversely, (ii) Charge on the ion : varies directly, e.g. Li < Li+ , Fe2+ < Fe3 +, (iii) Hybridisation : (Electronegativity ∝ % age s-character in the, hybrid orbital), Electronegativity of carbon atom = C2H 6 < C2H 4 < C2H 2, In periods as we move from left to right electronegativity increases,, while in the groups electronegativity decreases down the group., For noble gases, its value is taken as zero., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Classification of Elements and Periodicity of Properties, , 41, , Electronegativity helps to predict the polarity of bonds and dipole, moment of molecules., Electronegativity order of some elements (on Pauling scale) is, F > O, (4.0), , (3.5), , > N ≈ Cl > Br, (3.0), , (3.0), , (i) Mulliken scale, Electronegativity ( x ) =, , (2.8), , IE + ∆e g H, , 2, (ii) Pauling scale The difference in electronegativity of two, atoms A and B is given by the relationship, xB − xA = 0.208 ∆, where, ∆ = EA − B − EA − A × EB − B, (∆ is known as resonance energy.), EA − B , EA − A and EB − B represent bond dissociation energies of, the bonds A − B, A − A and B − B respectively., (iii) Allred and Rochow’s scale, Electronegativity = 0.744 +, Where, Z eff, , 0.359 Z eff, , r2, is the effective nuclear charge = Z − σ, , Where, σ is screening constant. It’s value can be determined by, Slater’s rule., , Valency, It is defined as the combining capacity of the element. The valency of, an element is related to the electronic configuration of its atom and, usually determined by electrons present in the valence shell., On moving along a period from left to right, valency increases from 1 to, 4 and then decreases to zero (for noble gases) while on moving down a, group the valency remains the same., Transition metals exhibit variable valency because they can use, electron from outer as well as penultimate shell., , Chemical Reactivity, Reactivity of metal increases with decrease in IE, electronegativity and, increase in atomic size as well as electropositive character., Reactivity of non-metals increases with increase in electronegativity as, well as electron gain enthalpy and decrease in atomic radii., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 42, , Handbook of Chemistry, , Melting and Boiling Points, On moving down the group, the melting point and boiling point for, metallic elements go on decreasing due to the decreasing forces of, attraction. However, for non-metals, melting point and boiling point, generally increase down the group., Along a period from left to right, melting point and boiling point, increases and reaches a maximum value in the middle of the period, and then start decreasing., Tungsten (W) has highest melting point (3683 K) among metals,, carbon (diamond) has the highest melting point among non-metals., Helium has lowest melting point ( −270° C) among all elements,, , Electropositivity or Metallic Character, The tendency of an atom of the element to lose valence electrons and, form positive ion is called electropositivity., Greater the electropositive character, greater is the metallic character., Electropositive character decreases on moving across the period and, increases on moving down the group., Alkali metals are the most electropositive and halogens are the least, electropositive element in their respective period., Basic nature of oxides ∝ metallic character, i.e. it also decreases along, a period and increases down the group., , Density, Li metal has minimum density while osmium (Os) metal has, maximum density., , Diagonal Relationship, Certain elements of 2nd period show similarity in properties with their, diagonal elements in the 3rd period as shown below :, 2nd period, 3rd period, , Group 1, Li, Na, , Group 2, Be, Mg, , Group 13, B, Al, , Group 14, C, Si, , Thus, Li resembles Mg, Be resembles Al and B resembles Si. This is, called diagonal relationship and this is due to the reason that these, pairs of elements have almost identical ionic radii and polarizing, power (i.e. charge/size ratio). Elements of third period, i.e. Mg, Al and, Si are known as bridge elements., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 4, , Chemical Bonding, and Molecular, Structure, Chemical Bond, It is defined as the attractive force which hold the various chemical, constituents (atoms, ions, etc.) together in different chemical species., Bond forms to get the stability, with a release of energy., , Kossel-Lewis Approach to Chemical Bonding, According to this theory, atoms take part in the bond formation to, complete their octet or to acquire the electronic configuration of the, nearest inert gas atoms (octet rule). This can be achieved by gaining,, losing or sharing the electrons., , Lewis Symbols, Valence electrons are reported by dots around the chemical symbol of, element, e.g., •, , Li, , •, , •B•, , •, , •C •, •, , ••, • •, •F •, •, , ••, •, •, • Ne •, ••, , Octet Rule, According to Octet rule during the formation of a covalent bond, the, atoms attain an inert gas electronic configuration (valence shell, contains 8e− or shell is completely filled). An atom may attain this, configuration by gaining, losing or sharing electrons with other atoms., , www.aiimsneetshortnotes.com
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44, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Exceptions to the Octet Rule, (i) Incomplete octet of the central atom, e.g. LiCl, BeH 2 and BCl3, Cl, Li, , •, •, , Cl ; H, , •, •, , Be, , •, •, , H ; Cl, , •, •, , •, •, , B, , •, •, , Cl, , (ii) Odd-electron molecules, ••, , ••, , ••, , •, , ••, , ••, , •+, , •• −, , N == O ; O == N O •• ; ClO−2 , He+2, ••, , (iii) Expanded octet of central atoms, PCl5, , [10 electrons, around the, P atom], , SF6, , [12 electrons, around the, S atom], , H 2SO4, , [12 electrons around, the S atom], , Ionic Bond, A chemical bond formed by complete transference of electrons from one, atom (metal) to another (non-metal) and hence, each atom acquires the, stable nearest noble gas configuration, is called ionic bond or, electrovalent bond, e.g. formation of sodium chloride, Na • +, ( 2,8,1), , ••, • Cl••, ••, , ( 2, 8, 7), , ••, , → [Na + •• Cl•• − ], ••, , ( 2, 8) ( 2, 8, 8), , Favourable factors for the formation of ionic bonds, (i) Metal should have low ionisation enthalpy., (ii) Non-metal must have high electron gain enthalpy., (iii) The energy released during the formation of 1 mole of crystal, lattice, i.e. lattice enthalpy must be high., Some elements exhibit variable electrovalency. The reason for this is, unstable configuration of penultimate orbit and inert pair effect., , Ions, Species carrying either positive or negative charge are termed as ions., Species carrying positive charge are called cations and those carrying, negative charge are called anions. Metals usually form cation while, non-metals (except H) usually form anions., , General Characteristics of Ionic Compounds, (i) Ionic compounds are usually solid in nature., (ii) Ionic compounds have high melting and boiling points., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, , 45, , (iii) Ionic compounds are soluble in polar solvents like water but, insoluble in non-polar solvents like benzene, CCl4 etc., (iv) Ionic compounds are good conductor in molten state and in, aqueous solution., (v) Ionic compounds have crystal structure., , Method of Writing Formula of Ionic Compound, (i) Write the symbol of cation at the left and anion at the right., (ii) Write their electrovalencies in figures on the top of each symbol, as Ax B y ., (iii) Divide their valencies by HCF., x, y, (iv) Now apply criss-cross rule as, , i.e. formula is Ay Bx ., A B, 3+ 2−, is Al2(SO4 )3 ., e.g. formula of aluminium sulphate, Al SO4, , Born Haber Cycle, This cycle is based upon the fact that the formation of an ionic, compound may occur either by direct combination of the elements or by, an alternate process in which :, (i) The reactants (metal) are vaporised to convert into gaseous state., (ii) The gaseous atoms are converted into ion., (iii) The gaseous ions are combined to form ionic lattice of molecules., e.g. formation of NaCl can be shown as, Na( s) +, , Q, 1, Cl2( g) → Na +Cl−, 2, 1, D, 2, , S, , Na( g), , Cl, −E, , I, , Na, Thus,, where, S, D, U, Q, , +, , +, , Cl−, , −U, , 1, D − E −U, 2, = enthalpy of sublimation, I = ionisation enthalpy, = enthalpy of dissociation, E = electron gain enthalpy, = lattice enthalpy, = total enthalpy change., Q =S + I +, , www.aiimsneetshortnotes.com
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46, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Covalent Bond, A chemical bond formed between two atoms by mutual sharing of, electrons between them so as to complete their octets or duplets, is, known as covalent bond and the number of electrons contributed by, each atom is known as covalency, e.g. formation of Cl2., Cl + Cl, 2,8,7, , 2,8,7, , Cl, , Cl, , or, Cl—Cl, , In covalent bonding, the shared pairs of electrons present between the, atoms are called bond pairs while unshared or non-bonding electron, pairs are known as lone pairs., , Types of Covalent Bonds, (a) Non-polar Covalent Bond, If the covalent bond is formed between two homonuclear atoms,, i.e. between atoms of exactly equal electronegativity, e.g. H 2 , Cl2 etc., , (b) Polar Covalent Bond, If a covalent bond is formed between the different atoms, the shared, pair is displaced towards the more electronegative atom causing, greater concentration of electron density around the more, electronegative atom. Such a covalent bond develops some ionic, character and is called polar covalent bond, (e.g. H—Cl)., , Properties of Covalent Compounds, (i) In general, covalent compounds exist in the liquid or gaseous, state at room temperature due to magnitude of intermolecular, forces., (ii) Covalent compounds have low melting and boiling points., (iii) Covalent compounds are generally poor conductors of electricity, because they do not contain free electrons or ions to conduct, electricity., (iv) They are soluble in non-polar solvents like benzene but usually, insoluble in water., , Formal Charge on an Atom in a Molecule/Ion, Formal charge (F.C.) on an atom in a Lewis structure, = [total number of valence electrons in the free atom], – [total number of non-bonding (lone pair) electrons], , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, –, , 47, , 1, [total number of bonding (shared) electrons], 2, O, O, , O, , 1, ( 6) = + 1, 2, 1, , , F.C. on O2 = 6 − 4 + × 4 = 6 − 6 = 0, 2, , , 1, , , F.C. on O3 = 6 − 6 + × 2 = 6 − 7 = − 1, 2, , , F.C. on O2 = 6 − 2 −, , Hence, O3 along with the formal charges can be represented as follows:, δ+, O, O, , δ–, O, , Bond Characteristics, Bond Length, In a covalently bonded molecule, distance between the nuclei of the two, atoms is known as bond length. Bond length increases with increase in, the size of bonded atoms and decreases with an increase in the number, of bonds between bonded atoms., Bond type, , Covalent bond length (in pm), , C—H, , 107 pm, , C—C, , 154 pm, , C== C, , 133 pm, , C≡≡ C, , 120 pm, , Bond length is determined by X-ray diffraction or electron diffraction, methods., , Bond Angle, In a covalently bonded molecule having more than two atoms, the bonds, form an angle with each other, which is known as bond angle. In, general an increase in the size of central atom decreases the bond angle., Factors affecting bond angle (i) Lone pair repulsion (ii) hybridisation of, central atom. It is determined by X-rays diffraction method., , www.aiimsneetshortnotes.com
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48, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Bond Order, It is defined as the number of covalent bonds present in a molecule., 1, Bond order = [Number of electrons in bonding orbitals, 2, – Number of electrons in anti-bonding orbitals], 1, Bond order ∝, bond length, If bond order comes out to be zero, the molecule does not exist., , Bond Enthalpy, It is the amount of energy released when one mole of covalent bonds is, formed while the bond dissociation enthalpy is the amount of energy, required to break one mole of bonds of the same kind so as to separate, the bonded atoms in the gaseous state., The bond enthalpy and bond dissociation enthalpy are equal in, magnitude and opposite in sign., Bond dissociation enthalpy is determined by thermal or spectroscopic, methods., As the bond order increases, bond enthalpy also increases and bond, length decreases., Factors affecting bond enthalpy, (i) atomic size, (ii) electronegativity, (iii) extent of overlapping, (iv) bond order, , Fajan’s Rule, The partial covalent character of ionic bonds was discussed by Fajan’s, in terms of following rules:, The smaller the size of cation and the larger the size of the anion, the, greater the covalent character of an ionic bond., The greater the charge on the cation or anion, the greater the covalent, character of the ionic bond., , Resonance, According to the concept of resonance, a single Lewis structure cannot, explain all the properties of the molecules. The molecule is then, supposed to have many structures, each of which can explain most of, the properties., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, , 49, , The actual structure lies in between of all these contributing structures, and is called resonance hybrid and the different individual structures, are called resonating structures or canonical structures. This, phenomenon is known as resonance., O, O, , O, O, , O, , O, , (I), , O, O, , O, , (II), , (III), , Resonance in ozone molecule, , Resonance stabilises the molecule as the energy of the resonance, hybrid is less than the energy of any single canonical structure., Resonance averages the bond characteristics as a whole., The difference in the energy of the resonance hybrid and the most, stable contributing structure (having least energy) is called resonance, energy. Greater the resonance energy, greater is the stability of the, molecule., Calculation of bond order for molecules showing resonance :, Bond order, total number of bonds between two atoms in all the structures, =, total number of resonating structures, , Dipole Moment (µ), It is defined as the product of the magnitude of the charge and the, distance between the centres of positive and negative charges., µ = charge (Q ) × distance of separation (r ), Dipole moment is expressed in Debye (D)., 1 D = 1 × 10−18 esu-cm = 3.33564 × 10−30 C-m, where, C is coulomb and m is meter., (The shift in electron density is symbolised by broken arrow), In chemistry, presence of dipole moment is represented by the crossed, arrow ( →, | ) put on Lewis structure of molecule. The cross is on, positive end and arrow head is on negative end., NH3 has higher dipole moment than NF3 ., , N, H, , N, H, , H, , F, , F, , F, , Resultant dipole moment,, , www.aiimsneetshortnotes.com
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50, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 2, , 2, , µ = µ 1 + µ 2 + 2 µ 1µ 2 cos θ, , Applications of Dipole Moment, 1. Dipole moment is helpful in predicting the geometry of the, molecule., 2. Dipole moment helps in determining the polarity., Hannay-Smith equation, Per cent ionic character = 16 [X A − X B ] + 3.5 [X A − X B ]2, where, X A and X B are the electronegativities of atoms., Per cent ionic character can also be calculated by dipole moment as, observed dipole moment, Per cent ionic character =, × 100, calculated dipole moment, 3. Non-polar molecule has zero dipole moment like BF3 , CCl4, etc., F, B, F, , µ=0, , O, F, , C, , O, , µ=0, , 4. cis and trans isomers can be distinguished by dipole moments, usually cis isomer have higher dipole moment and hence, higher, polarity., 5. Dipole moment is greatest for ortho isomer; zero for para isomer;, and less than that of ortho, for meta isomer., , The Valence Shell Electron Pair Repulsion, (VSEPR) Theory, According to this theory,, 1. The geometry of a molecule or ion depends on the number of, electron pairs in the valence shell of its central atom., 2. To attain minimum repulsive state, electron pairs try to stay as, far away as possible., 3. If the central atom is surrounded by only bonded electron pairs of, similar atoms, the repulsive interactions are similar and the, molecular geometry is regular., 4. If the central atom is surrounded by only bonded electron pairs of, dissimilar atoms, the repulsive interactions are not equivalent, and hence, the geometry of molecule will not be regular., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, , 51, , 5. If the central atom is surrounded by both bonded pairs (bp) as, well as lone pairs (lp) of electrons, repulsive interactions are not, equivalent and hence, geometry of the molecule will be irregular., The repulsive interactions decrease in the order, lp – lp > lp – bp > bp – bp, , Shapes (Geometry) of Molecules Containing Bond Pairs Only, or Bond Pairs and Lone Pairs, Total number Number Number, Geometry (shape) of the, of electron of bond of Lone, molecule, pairs, pairs, pairs, 2, , 2, , 0, , B—A—B, , Illustrative, examples, BeF2 , CO2 , BeCl2, , Linear, , 3, , 3, , 0, , B, , B, , BF3, AlCl 3, SO 3, , A, B, Triangular planar, , 2, , 1, , SO2 , O 3, NO2, , A, B, , B, , Bent (V-shape), , 4, , 4, , 0, , CH 4 , SiF4 , NH 4+, , B, , A, B, , B, B, , Tetrahedral, , 3, , 1, , NH 3, PCl 3, NCl 3,, PH 3, , A, B, , B, B, , Trigonal pyramidal, , 2, , 2, , H2O, H2S, A, B, B, Bent, , Contd.…, , www.aiimsneetshortnotes.com
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52, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Total number Number Number, Geometry (shape) of the, of electron of bond of Lone, molecule, pairs, pairs, pairs, 5, , 5, , 0, , Illustrative, examples, PCl 5, , B, B, A, , B, , B, B, Trigonal bipyramidal, , 4, , 1, , SF4, , B, B, A, B, B, See saw, , 3, , 2, , ClF3, BrF3, , B, B, , B, , B, T-shaped, , 2, , 3, , XeF2 , I−3 , ICl2−, , B, A, B, Linear, , 6, , 6, , 0, , SF6, , B, B, , B, A, , B, , B, B, , Octahedral, , 5, , 1, , BrF5, ClF5, , B, B, , B, A, B, , B, , Square pyramidal, , Contd.…, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, Total number Number Number, Geometry (shape) of the, of electron of bond of Lone, molecule, pairs, pairs, pairs, 4, , 53, , Illustrative, examples, , 2, , XeF4, , B, , B, A, , B, , B, , Square planar, , Valence Bond Theory of Covalent Bond, According to this theory, a covalent bond is formed by the overlapping, of two half-filled atomic orbitals having electrons with opposite spins., It is based on wave nature of electron., , (i) Sigma Bond (σ bond), This type of covalent bond is formed by head-on overlap, i.e. end to end, overlap along the internuclear axis. Sigma bond can be formed by any, one of the following types of combinations of atomic orbitals :, (a) s-s overlapping (b) s-p overlapping (c) p-p overlapping (axial), The strength of σ bond depends upon the extent of overlapping, between atomic orbitals. The greater the extent of overlapping, the, stronger is the σ bond., , (ii) Pi Bond (π bond), It is formed by the sidewise or lateral overlapping between p-atomic, orbitals [p-p side by side or lateral overlapping], π bond is a weaker bond than σ bond., , Comparison of Sigma and Pi Bonds, Sigma bond, , Pi bond, , 1. This bond is formed by overlapping of orbitals This bond is formed by sideway, along their internuclear axis., overlapping of atomic orbitals., s-p, or, s-s, p-p, , p-orbital p-orbital, , p-p, , 2. Free rotation along a σ bond is possible., , Free rotation about a π bond is not, possible., 3. Sigma bond consist of only one electron cloud Pi ( π) bond consists of two electron, clouds, one above the plane of atomic, symmetrical about the internuclear axis., nuclei and the other below it., , www.aiimsneetshortnotes.com
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54, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Limitations of VBT, It fails to explain, 1. The magnetic properties of some molecules., 2. Bonding in electron deficient compounds., , Hybridisation, It is defined as the mixing of the atomic orbitals belonging to the same, atom but having slightly different energies so that a redistribution of, energy takes place between them resulting in the formation of new, orbitals of equal energies and identical shapes. The new orbitals thus, formed are known as hybrid orbitals and are more stable., , Method for Finding the Hybridisation, Apply the following formula to find the hybridisation of central atom., number of valence electrons of central atom, , 1, , Z = + number of monovalent atoms attached to it, , 2, , + negative charge if any − positive charge if any, Value of Z, Hybridisation, , 2, sp, , 3, sp2, , 4, sp3, , 5, sp3 d, , 6, sp3 d 2, , 7, sp3 d3, , Examples, 1, [5 + 3 + 0 − 0] = 4 ⇒ sp3, 2, 1, = [6 + 0 + 2 − 0] = 4 ⇒ sp3, 2, , Hybridisation of N in NH3 =, Hybridisation of S in SO2−, 4, , Some Common Types of Hybridisation, with Shapes and Examples, Types of, Atomic orbitals, hybridisation, involved, sp, , one s + one p, , sp2, , one s + two p, , Representing directions of, hybrid orbitals formed, alongwith bond angles, , Examples, , 180°, , BeCl2 , BeH2 , C 2H2, , Linear, , BF3, BCl 3, C 2H 4 , CO2−, 3, 120°, Triangular planar, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, Types of, Atomic orbitals, hybridisation, involved, sp 3, , Representing directions of, hybrid orbitals formed, alongwith bond angles, , 55, , Examples, CH 4 , CCl 4 , SnCl 4 , NH 4+, , one s + three p, 109°28′, , Tetrahedral, , dsp2, , one d + one s +, two p, , XeF 4, , 90°, , Square planar, 3, , sp d, , one s + three p, + one d, , PCl 5, PF5, , 90°, 120°, , Trigonal bipyramidal, , sp 3d2, , one s + three p, + two d, , 90°, , SF6, [CrF6] 3–, , Octahedral, , Coordinate or Dative Bond, It is a type of covalent bond in which the electron pair (lone pair) is, donated by one atom but shared by both the atoms so as to complete, their octets, e.g., (i) NH3 →, donor, , ••, , BF3, , acceptor, , ••, , ••, , (ii) •• O == O → O ••, ••, , Molecular Orbital Theory, According to this theory, the atomic orbitals combine to form the, molecular orbitals. The number of molecular orbitals formed is equal to, the number of atomic orbitals involved. Molecular orbital of lower, energy is known as bonding molecular orbital and that of higher, energy is known as anti-bonding molecular orbital. Aufbau rule,, Pauli’s exclusion principle and Hund’s rule are all applicable for, molecular orbitals., , www.aiimsneetshortnotes.com
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58, , Telegram @neetquestionpaper, , Handbook of Chemistry, , A positive bond order, (i.e. N b > N a* ) means a stable molecule while a, negative (i.e. N b < N a* ) or zero, (i.e. N b = N a* ) bond order means, unstable molecule., Molecular species having unpaired electrons are paramagnetic, while, if all the electrons in the orbitals are paired then the molecule is, diamagnetic., , Hydrogen Bond, It is defined as the force of attraction existing between hydrogen atom, covalently bonded to highly electronegative atom (N, O or F) and the, electronegative atom belonging to another molecule of the same or, different substance. It is represented by dotted lines. The chains, possess a zig-zag structure., δ, , δ, , δ, , H, , F, , δ, , δ, , H, , δ, , F, , H, , F, , δ, , H, , δ, , F, , Hydrogen bond is purely electrostatic and a weak bond. The strength, of the strongest hydrogen bond is about 5-10 kcal per mol. The more, the electronegativity of atom involved in H-bonding, the more is the, bond strength, e.g., H- - -F >, H- - - O > H- - -N, 10 kcal/mol > 7 kcal/mol > 2.0 kcal/mol, Types of hydrogen bonds are:, , Intermolecular H-bonding, H-bonding involving two or more different molecules. e.g. o-nitrophenol., , Intramolecular H-bonding, H-bonding within a same molecule. e.g., p-nitrophenol, , Applications of Intermolecular H-bonding, (i) Melting point and boiling point of water Water has the, lowest molecular weight among the hydrides of group 16, elements yet it has the highest melting and boiling points. It is, due to intermolecular H-bonding in H 2O., (ii) Ice has less density than water In crystal structure of ice,, every water molecule is associated with four other water, molecules by H-bonding in a cage like tetrahedral structure. On, melting the ice, H-bonds are broken and space between water, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Bonding and Molecular Structure, , 59, , molecules decreases and density of water increases up to 4°C., Above 4°C, more H-bonds are broken, the water molecules get, apart from each other and the density again decreases. Thus,, water has maximum density at 4°C., (iii) Melting point and boiling point of alcohols The marked, difference between the melting and boiling points of alcohols is, also due to H-bonding., , Applications of Intramolecular H-bonding, Volatile character of nitrophenols o-nitrophenol is more volatile, (b.p. 214°C) as compared to meta (b.p. 290°C) and para (b.p. 279°C). It, is due to chelation (ring like structure)., δ, , O, N, , Hδ, Oδ, , O, , In meta and para isomer, chelation is not possible due to the formation, of desired size of ring., , Metallic Bond, The attractive force that binds the metal ions to the mobile electrons is, called metallic bond. The positive metal ions are called positive cores or, kernels and mobile electrons are electron pool or electron gas., Electron-sea theory of metallic bond explains number of the, properties of the metal., Strength of bonds, Ionic bond > covalent bond > metallic bond > H-bond, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 5, States of Matter, Five states of matter are known, viz, solid, liquid, gas, plasma and, Bose-Einstein condensate. Out of these, solid, liquid and gas are, commonly found while remaining two are found only under specific, conditions., , Interconversion of States of Matter, These states are interconvertible., (i) Melting point This is the temperature at which a matter, converts from its solid state to liquid state. It decreases in the, presence of impurity., (ii) Boiling point This is the temperature at which the, vapour pressure of a liquid becomes equal to the atmospheric, pressure., It increases in the presence of impurity and with rise in pressure., Boiling point of water is 100°C., (iii) Freezing point At this temperature, a matter converts from, its liquid state into solid state., Freezing point of water is 0°C., (iv) Evaporation It is the process of conversion of a liquid into, vapours at any temperature., Due to evaporation,, (a) water droplets appear on the outer surface of a glass, containing ice-cold water., (b) water kept in earthen pot becomes cool during summer., (c) desert cooler cool better on a hot dry day., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, States of Matter, , 61, , In short,, Liquid, n, si o, n, Fu, tio, i ca, f, i, d, i, l, So, , Solid, , Va, p, , Co, , nd, , ori, , en, , sa, , sa, ti, , Sublimation, , tio, n, , on, , Gas, , Deposition or Desublimation, , The temperature and pressure at which all the three states of a, substance can exist together in equilibrium is called triple point,, e.g. ice, liquid water and water vapours can coexist, i.e. ice, water, vapour at 0.0098°C and 4.58 mm of Hg., , º, , º, , Plasma, It is a state of matter similar to gas in which a certain portion of, gaseous particles are ionised. Because of the average strength of, electrical forces, the plasma is neutral. It is commonly found in, universe., On earth, plasma is naturally occurring in flames, lightnings and, auroras., , the, the, the, the, , Bose-Einstein Condensate, A Bose-Einstein condensate is a gaseous superfluid phase formed by, atoms cooled to temperature very near to absolute zero., This state was first predicted by Satyendra Nath Bose and Albert, Einstein in 1924-25. Such first condensate was produced by Eric, Cornell and Carl Wiemann in 1995. It can be thought of as the, opposite of a plasma., , Intermolecular Forces, The forces of attraction existing among the molecules of a substance, (gaseous, liquid or solid) are called intermolecular forces., Greater the intermolecular forces, higher is the melting and boiling, point. Attractive intermolecular forces are known as van der Waals’, forces., The different types of intermolecular forces are briefly explained below:, (i) Dispersion forces or London forces Dispersion forces or, London forces are present among non-polar atoms and, molecules, e.g. among the atoms or chlorine molecules. These are, the weakest intermolecular forces., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 62, , Handbook of Chemistry, These forces increases with, (i) increase in number of electrons in molecules,, (ii) increase in molecular size., , (ii) Dipole-dipole interactions Dipole-dipole forces act, between the molecules possessing permanent dipoles., δ+, , H, , δ–, , Cl, , δ+, , H, , δ–, , Cl, , The interaction is stronger than London forces and weaker than, ion-ion interaction. The intensity of these forces is generally, hampered by increase in temperature., (iii) Dipole-induced dipole forces Dipole-induced dipole forces, act between the polar molecules having permanent dipole and, the molecules lacking permanent dipole., δ+, , A, , δ–, , δ+, , non-polar, , B, , Polar molecule, , A, , δ–, , δ+, , δ–, , B, , Permanent dipole, (A polar molecule), , Induced dipole in a, non-polar molecule, , (iv) Hydrogen bond It is a special case of dipole-dipole, interaction. This is found in the molecules in which highly polar, N—H, O—H or H—F bonds are present. The strength of H-bond, is determined by the coulombic interaction between the lone-pair, electrons of the electronegative atom of one molecule and H-atom, of other molecule., , Thermal Energy, Thermal energy is the energy of a body arising from motion of its atom, or molecules., So, Thermal energy ∝ Temperature of the substances, , Factors Deciding Physical State of a Substance, For gaseous state,, Forces of attraction << Thermal energy, For liquid state,, Forces of attraction > Thermal energy, For solid state,, Forces of attraction >> Thermal energy, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, States of Matter, , 63, , The Gaseous State, It is the most disordered state of matter. Characteristics of this state of, matter are:, (i) In gases, the intermolecular forces are weakest., (ii) Gases are highly compressible., (iii) Gases exert pressure equally in all directions., (iv) Gases have much lower density than the solids and liquids., (v) The volume and the shape of gases are not fixed., (vi) Gases mix evenly and completely in all proportions without any, mechanical aid., , Measurable Properties of Gases, (i) Mass It is expressed in gram or kg., (ii) Volume It is equal to the volume of the container and is, expressed in terms of litre (L), millilitre (mL), cubic centimetre, ( cm ), cubic metre ( m ) or cubic decimetre (dm )., 1 L = 1000 mL = 1000 cm = 1 dm, 1 m = 10 dm = 10 cm = 10 mL = 10 L, (iii) Pressure Gas pressure is measured with manometer and, atmospheric pressure is measured by barometer., 1 atm = 76 cm of Hg = 760 mm of Hg = 760 torr, 1 atm = 101.325 kPa = 101325 Pa = 101.325 Nm −, = 1.01325 bar, 1 bar = 10 Pa = 0.987 atm, , Measurement of pressure of gas, (a) Open end manometer, p, (b) Closed end manometer, p, , = p, , −h, , =h, , where h is difference in the mercury levels in the two, columns of density ( d ) (of a gas)., (iv) Temperature It is measured in celsius scale (°C) or in, Kelvin scale (K). SI unit of temperature is kelvin (K)., T (K) = t ° (C) + 273, , Standard temperature and pressure (STP or NTP) means 273.15, K (0°C) temperature and 1 bar (i.e. exactly 10 pascal) pressure. At, STP, molar volume of an ideal gas is 22.71098 L mol− ., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 64, , Handbook of Chemistry, , Gas Laws, Boyle’s Law (1662), The volume of a given mass of a gas is inversely proportional to its, pressure at constant temperature., V ∝, , 1, or Vp = K, p, , K is a constant and its value depends on mass, temperature and, nature of gas., ∴, , pV = p V, , Graphical Representation of Boyle’s Law, Graphs of p vs V or p vs, , 1, or pV vs p at constant temperature are, V, , known as isotherms., T2, p, , p, , V, , pV, , 1/V, , T1, , p, , Air is dense at the sea level because it is compressed by the mass of air, above it., , Charles’ Law (1787), 1, of, 273, its volume for each degree rise or fall of temperature respectively at, constant pressure., t , , V t = V 1 +, at constant p, , 273, The volume of the given mass of a gas increases or decreases by, , Or, The volume of a given mass of a gas is directly proportional to the, absolute temperature at constant pressure., V, V, V, =, = constant or, V ∝ T (at constant p),, T, T, T, Absolute zero is the theoretically possible temperature at which the, volume of the gas becomes zero. It is equal to 0°C or 273.15 K., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, States of Matter, , 65, , Graphical Representation of Charles’ Law, A graph of V vs T at constant pressure is known as isobar., , V, , V, , T (K), , –273, , 0, , t (°C), , Charles’ law explains that gases expand on heating, so hot air is less, dense than cold air., , Gay Lussac’s Law (1802), 1, of its, 273, pressure for each degree rise or fall of temperature respectively at, constant volume., t , , pt = p 1 +, at constant V and n, , 273, The pressure of a given mass of gas increases or decreases by, , Or, The pressure of a given mass of a gas at constant volume is directly, proportional to absolute temperature., p, p, p, p ∝ T or p = KT or, = K at constant V and n or, =, T, T, T, , Graphical Representation of Gay Lussac’s Law, A graph of p vs T at constant volume is known as isochore., V1, V2 > V1, V2, , p, , T, , Avogadro’s Law, It states that equal volumes of all gases under the same conditions of, temperature and pressure contain equal number of molecules., Mathematically, (at constant T and p), V ∝n, m, V, , or, =K, n = number of moles, n = M , n, , , , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 66, , Handbook of Chemistry, , Molar gas volume The volume of one mole of a gas, i.e. 22.4 L at STP (0°C, 1 atm), is known as molar gas volume., , Ideal Gas Equation, V ∝, , ⇒, , 1, , T and n constant, p, , V ∝ T , p and n constant, V ∝ n , p and T constant, nT, V ∝, p, , (Boyle’s law), (Charles’ law), (Avogadro’s law), , or, pV ∝ nT, or, pV = nRT ., This is known as ideal gas equation. R is known as universal gas, constant., From the ideal gas equation, density,, pM, (where, M = molecular mass), d=, RT, , Numerical Values of R, (i) R = 0.0821 L atm mol− K −, (ii) R = 0.083 L bar mol− K −, (iii) R = 8.314 JK − mol−, (iv) R = 8.314 × 10 erg K − mol−, (v) R = 1.987 or 2 cal K − mol−, Ideal gas The gas which obeys the equation pV = nRT at every temperature and, pressure range strictly is known as ideal gas., Real gases Since none of the gases present in universe strictly obey the equation, pV = nRT , hence they are known as real or non-ideal gases. Real gases behave, ideally at low p and high T ., , Graham’s Law of Diffusion, Under similar conditions of temperature and pressure, the rates of, diffusion of gases are inversely proportional to the square root of their, densities., r, d, M, Mathematically,, =, =, r, d, M, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, States of Matter, , 67, , Diffusion is the tendency of gases to distribute itself uniformly, throughout the available space while effusion is the movement of gas, through a small hole when it is subjected to pressure., , Dalton’s Law of Partial Pressure, At constant temperature, the total pressure exerted by a mixture of, non-reacting gases is the sum of partial pressures of different gases, present in the mixture., p= p + p + p + …, Partial pressure of a gas = mole fraction of the gas × total pressure., If n , n and n are moles of non-reacting gases filled in a vessel of, volume V at temperature T , the total pressure, p is given by, p = ( n + n + n )RT / V, This is the equation of state of a gaseous mixture., Pressure of a dry gas can be determined by Dalton’s law. When a gas is, collected over water, its observed pressure is equal to the sum of the, pressure of dry gas and the pressure of water vapour (aqueous tension), then pressure of moist gas = pressure of dry gas + aqueous tension., Aqueous tension It is the pressure exerted by water vapours at a, particular temperature. It depends upon temperature., , Kinetic Theory of Gases, Main assumptions of this theory are:, 1. A gas consists of large number of small particles, called, molecules., 2. Volume occupied by gas molecules is negligible as compared to, the total volume of the gas., 3. There is continuous rapid random motion of gas molecules. The, molecules collide with each other and with the walls of container., 4. The molecules are perfect elastic bodies and there is no loss of, kinetic energy during collisions., 5. There are no attractive forces between the gaseous molecules., 6. The pressure exerted by a gas is due to the bombardment of gas, molecules against the walls of the container., 7. The different molecules possess different velocities and hence,, different energies. The avearge KE is directly proportional to, absolute temperature., 3, KE = RT, 2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 68, , Handbook of Chemistry, 3, kT, 2, Here, k is Boltzmann constant, it is gas constant per molecule., R, k=, = 1.38 × 10− JK mol−, NA, , ∴ Average kinetic energy per molecule =, , From the above postulates, the kinetic gas equation derived is, 1, pV = mnU, 3, 3RT, where, U = root mean square velocity =, M, , Velocities of Gas Molecules, The different velocities possessed by gas molecules are :, (i) Most probable velocity (α) It is the velocity possessed by, maximum fraction of gas molecules at a particular temperature., α=, , 2RT, M, , (ii) Average velocity (ν) This is the average of the different, velocities of all the molecules., ν=, , 8RT, πM, , (iii) Root mean square velocity (U, ) It is the square root of, the mean of the square of the different velocities of the molecules., U, , =, , Mathematically, U =, , n c + n c + n c +…, n + n + n +…, 3RT, =, M, , 3 pV, =, M, , 3p, d, , 3p, =, , d, , α : v : U = 1 : 1.128 : 1.224, , www.aiimsneetshortnotes.com, , 3RT , , M
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Telegram @neetquestionpaper, States of Matter, , 69, , Deviation from Ideal Behaviour, At high pressure and low temperature, the gases deviate considerably, from the ideal behaviour. Deviation can be expressed in terms of, compressibility factor (Z), expressed as, pV, Z=, nRT, In case of ideal gas, pV = nRT , Z = 1, In case of real gas,, pV ≠ nRT , Z ≠ 1, CO, , CH4, Real gas, , H2, , Ideal gas, , pV, , ideal gas, , 0, , p, , Plot of pV vs p for real gas and, ideal gas., , Pressure, , He, , 0, Volume, Plot of pressure vs volume for, real gas and ideal gas., , It can be seen easily that at constant temperature, pV vs p plot for, real gas is not a straight line., , Negative deviation In such case, Z < 1, gas is more compressible., Positive deviation In such case, Z > 1, gas is less compressible., The factors affecting the deviation are:, (i) Nature of the gas In general, the most easily liquefiable and, highly soluble gases show larger deviation., (ii) Pressure The deviation is more at high pressure. CO and N, show negative deviation at low pressure and positive deviation at, high pressure., (iii) Temperature The deviation is more at low temperature. H, and He always show positive deviations at 0°C., , Cause of deviation from the ideal behaviour It is due to two, faulty assumptions of kinetic theory of gases, particularly not valid at, high pressure and low temperature., 1. Volume occupied by the gas molecules is negligible as compared, to the total volume of the gas., 2. There are no attractive forces between the gas molecules., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 70, , Handbook of Chemistry, , van der Waals’ Equation, After volume and pressure correction, van der Waals’ obtained the, following equation for n moles of a gas., , n a, (V − nb) = nRT, p+, V , , a , , p+, (V − b) = RT ,, , V , , (for one mole), , where,, b = excluded volume or co-volume = 4 × actual volume of gas molecules, a = magnitude of attractive forces between gas molecules., The greater the value of ‘a’, the greater the strength of van der Waals’, forces and greater is the ease with which a gas can be liquefied., , Units for van der Waals’ constant, Pressure correction,, p=, , n a, V, , or a =, , pV, n, , = atm L mol −, , Volume correction,, V = nb, , or b =, , V, = L mol −, n, , Limitation of van der Waals’ Equation, There is specific range of temperature and pressure, to apply the, equation. It deviates at very high pressure and very low temperature., , Liquefaction of Gases and Critical Points, The phenomenon of conversion of a gas into liquid is known as, liquefaction. The liquefaction of a gas takes place when the, intermolecular forces of attraction becomes so high that it exist in the, liquid. A gas can be liquefied by, (i) increasing pressure, (ii) decreasing temperature., The critical points are as follows, (i) Critical temperature (TC ) It may be defined as the, temperature above which no gas can be liquefied. Critical, temperature of CO is 30.98°C., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, States of Matter, , 71, , Critical temperature (TC ) of some gases are He (5.4), H ( 33.2),, N (126.0), CO(134.4), O (154.3), CO (304.1), NH (405.5),, 8a, TC =, 27Rb, (ii) Critical pressure ( pC ) At critical temperature, the pressure, needed to liquefy a gas is known as critical pressure., a, pC =, 27b, (iii) Critical volume (VC ) The volume occupied by one mole of a, gas at critical temperature and critical pressure is known as, critical volume., VC = 3b, (iv) Boyle’s temperature (Tb ) Temperature at which a real gas, exhibits ideal behaviour for considerable range of pressure is, called Boyle’s temperature., a, Tb =, bR, , Liquid State, If a substance is having melting point below room temperature and, boiling point above room temperature, the substance is known as, liquid. In liquid state, matter has definite shape and molecular motion, is in between solids and gases., , Properties of Liquids, (i) Vapour pressure The pressure exerted by the vapours above, the liquid surface when these are in equilibrium with the liquid, at a given temperature is known as vapour pressure of liquid., The vapour pressure of a liquid depends on :, (i) Nature of liquid, (ii) Temperature : Vapour pressure increases with increasing, temperature., (ii) Boiling point The temperature at which vapour pressure of, liquids becomes equal to the atmospheric pressure, is called, boiling point., At 1 atm pressure, boiling point is known as normal boiling point., At 1 bar pressure, boiling point is known as standard boiling point., Boiling point varies linearly with external pressure., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 72, , Handbook of Chemistry, , (iii) Surface tension It is the force acting per unit length, perpendicular to the imaginary line drawn on the surface of, liquid. It is denoted by γ (gamma)., Force ( F ), SI unit : Nm −, γ=, Length ( L ), Dimensions : kgs−, The magnitude of surface tension of a liquid depends on the, attractive forces between the molecules. It is measured with the, help of an apparatus, called stalgmometer., Surface tension decreases as the temperature increases., Rise or fall of liquid in a capillary tube is due to surface tension., (iv) Viscosity Viscosity is a measure of resistance to flow which, arises due to internal friction between layers of fluid as they slip, past one another while liquid flows., When there is a regular gradation of velocity, in passing from one, layer to the next, it is called laminar flow., Adv, F=η, dz, where, F = forces required to maintain the flow of layers., A = area of contact, dv/ dz = velocity gradient; (the change in velocity with, distance.), ‘η’ is proportionality constant and is called coefficient of viscosity., Viscosity coefficient is the force when velocity gradiant is unity and, the area of contact is unit area. CGS unit of coefficient of viscosity is, poise. S.I. unit of coefficient of viscosity is Nsm − ., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 6, The Solid State, Solids are the chemical substances which are characterised by, definite shape and volume, rigidity, high density, low compressibility., The constituent particles (atoms, molecules or ions) are closely packed, and held together by strong interparticle forces., , Types of Solids, The solids are of two types : Crystalline solids and amorphous solids., , Distinction Between Crystalline and Amorphous Solids, S.No., , Crystalline solids, , Amorphous solids, , 1., , These have definite and regular, arrangement of the constituent, particles in space., , These doesn’t have any regular, arrangement of the constituent, particles in space., , 2., , These are true solids., , These are super cooled liquids or, pseudo solids., , 3., , These have long order in arrangement, of the particles., , These have short order in arrangement, of particles., , 4., , These are anisotropic in nature, i.e., their physical properties are different, in different directions., , These are isotropic in nature i.e. their, physical properties are same in all the, directions., , 5., , They have sharp melting points., , They melt over a certain range of, temperature., , 6., , They undergo a clean cleavage when, cut., , They undergo irregular cleavage when, cut., , 7., , They have a definite and characteristic They do not have definite heat of, heat of fusion., fusion., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 74, , Handbook of Chemistry, , Types of Crystalline Solids, Character, , Ionic, solids, , Covalent or, network, solids, , Molecular, solids, , Metallic solids, , Constituent, particles, , Positive and, negative ions, , Atoms, , Molecules, , Positive metal, ions (kernels) and, free electrons, , Bonding forces, , Electrostatic or, coulombic, attraction, , Covalent, , van der, Metallic bonding, Waals’, Dipole-dipole, , Melting point, , High melting, point, , Very high, melting point, , Low melting Moderate to high, point, melting point, , Physical nature, , Hard and brittle, , Very hard, , Very soft, , Hard but, malleable and, ductile, , Conductance, , Conductors in, Non-conductor, aqueous solution, or in molten state, but insulators in, solid state, , Insulator, , Good conductor, , Examples, , NaCl, CaF2 , MgO, Diamond,, ZnS, Silica, SiC, , H2O, CO2 ,, CCl 4 , HCl,, SO2, , Cu, Fe, Ag, Mg., , Molecular solids are further subdivided into non-polar molecular solids,, polar molecular solids and hydrogen bonded molecular solids., , Structure Determination by, X-ray Diffraction (Bragg’s Equation), When a beam of X-rays falls on a crystal, plane composed of regularly arranged, atoms or ions, the X-rays are diffracted., If the waves are in phase after reflection,, the difference in distance travelled by the, two rays (i.e. path difference) must be, equal to an integral number of, wavelength,, for, constructive, nλ, interference., Thus, path difference = WY + YZ, = XY sin θ + XY sin θ, = 2 XY sin θ = 2d sin θ, ∴, nλ = 2d sin θ, , θ, W, , X θ, θ θ, Y, , www.aiimsneetshortnotes.com, , Z, , d
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Telegram @neetquestionpaper, The Solid State, , 75, , This equation is called Bragg’s equation., where, n = 1, 2, 3 K (diffraction order),, λ = wavelength of X-rays incident on crystal and, d = distance between atomic planes, θ = angle at which interference occurs., , Crystal Lattices, In three dimensional space, a regular arrangement and repeating, pattern of the constituent particles of a crystal in which each particle is, depicted as a point is known as crystal lattice or space lattice., , Unit Cell, The smallest geometrical portion of the crystal lattice which can be, used as repetitive unit to build up the whole crystal is called unit cell., , Types of Unit Cell, 1. Simple or primitive unit cell In which the particles are, present at the corners of unit cell only., , 2. Face centred unit cell In which the particles are present at, the corners as well as at the centre of each of six faces of unit cell., , 3. Body centred unit cell In which the particles are present at, the corners as well as at the centre of unit cell., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 76, , Handbook of Chemistry, , 4. End centred unit cell In which the particles are present at, the corners and at the centre of two opposite faces of unit cell., , Number of Particles Per Unit Cell, No. of particles and their contribution, Unit cell, , Total, Corner, , Simple cubic, , 8×, , 1, 8, , Face centred, , 8×, , 1, 8, , Body centred, , 8×, , 1, 8, , End centred, , 8×, , 1, 8, , Face, , Centre, , —, , —, , 1, , —, , 4, , 1, , 2, , —, , 2, , 6×, , 1, 2, , —, 2×, , 1, 2, , Seven Crystal Systems and Possible Variations, There are about 230 crystal forms, which have been grouped into 14, types of space lattices, called Bravais Lattices, on the basis of their, symmetry and seven different crystal systems on the basis of, interfacial angles and axial distances., , Seven Crystal Systems, Parameters of unit cell, Crystal, system, , Axial distances, or edge, lengths, , Possible variation, Angles, , 1., , Cubic, , a=b=c, , α = β = γ = 90°, , Primitive, body, centred, face centred., , 2., , Tetragonal, , a=b≠c, , α = β = γ = 90°, , Primitive, body, centred, , 3., , Rhombohedral, or trigonal, , a=b=c, , α = β = γ ≠ 90°, , Primitive, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Solid State, , 77, , Parameters of unit cell, Crystal, system, , Axial distances, or edge, lengths, , Possible variation, Angles, , 1., , Cubic, , a=b=c, , α = β = γ = 90°, , Primitive, body, centred, face centred., , 4., , Orthorhombic, , a≠b≠c, , α = β = γ = 90°, , Primitive, body, face, and end centred., , 5., , Monoclinic, , a≠b≠c, , α = γ = 90° , β ≠ 90°, , Primitive and end, centred., , 6., , Triclinic, , a≠b≠c, , α ≠ β ≠ γ ≠ 90°, , Primitive, , 7., , Hexagonal, , a=b≠c, , α = β = 90°, γ = 120° Primitive, , Coordination Number (CN), It is defined as the number of particles immediately adjacent to each, particle in the crystal lattice. In simple cubic lattice, CN is 6, in body, centred lattice, CN is 8 and in face centred cubic lattice, CN is 12., High pressure increases CN and high temperature decreases the CN., , Close Packing in Crystals, Packing in solids may be divided into the following categories :, , One Dimensional packing of constituent particles, In one dimensional close packing arrangement, the coordination, number is 2., , Two Dimensional Packing of Constituent Particles, (i) Square Close Packing When atoms arranged in a row is, stacked with atoms arranged in another row exactly one over, another is known as square close packing. Coordination number, in square close packing is 4. This is also known as AAA...type, arrangement space occupied by spheres is 52.4%., Voids, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 78, , Handbook of Chemistry, , (ii) Hexagonal Close Packing This is generated by placing, spheres of the second row in the depressions of first row., Coordination number in hexagonal closed packing is 6. This is, also known as ABAB…type arrangement space occupied by, spheres is 60.4%. Hence, it is more efficient., , Three Dimensional Packing of Constituent Particles, (a) Three dimensional closed packing from two dimensional, square close packed layers When two dimensional square, close packed layers are arranged exactly one over the other they, constitute a three dimensional close packing. The arrangement, is known as AAA arrangement., , (b) Three dimensional close packing from two dimensional, hexagonal close packed layers When hexagonal close packed, layers are stacked kone over another, they form three, dimensional close packing., (i) Hexagonal close packing When third layer is placed over, second layer in such a way that they constitute tetrahedral, void. The arrangement is called ABAB pattern., (ii) Cubic close packing When the third layer is placed over, second layer in such a way that sphere covers octahedral, voids. The arrangement is called ABABC pattern., In both these arrangements 74% space is occupied., Coordination number in hcp and ccp arrangement is 12 while in bcc, arrangement, it is 8., Close packing of atoms in cubic structure = fcc > bcc > scc, All noble gases have ccp structure except He (hcp structure)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Solid State, , 79, , Void or Space or Holes, Empty or vacant space present between spheres of a unit cell, is called, void or space or hole or interstitial void. When particles are close, packed resulting in either ccp or hcp structure, three types of voids are, generated:, Trigonal voids exist in two dimensional arrangement., , Trigonal voids, , Tetrahedral voids are holes or voids surrounded by four spheres, present at the corner of a tetrahedron. Coordination number of a, tetrahedral void is 4., , Tetrahedral void, , rvoid = 0.225 × rsphere, , (for tetrahedral voids), , Octahedral voids are holes surrounded by six spheres located on a, regular tetrahedron. Coordination number of octahedral void is 6., , Octahedral void, , rvoid = 0.414 × rsphere, , (for octahedral voids), , The number of octahedral voids present in a lattice is equal to the, number of close packed particles., The number of tetrahedral voids present in a lattice is twice to the, number of close packed particles., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 80, , Handbook of Chemistry, , Packing Efficiency or Packing Fraction, The percentage of total space filled by the particles., (i) Primitive cubic unit cell Atoms touch each other along, edges., a, Hence, d = a or r =, (r = radius of atom and a = edge length), 2, Therefore,, 4 3, πr, Volume of one atom, PF =, = 3 3 = 0.524 or 52.4%, Volume of cubic unit cell ( 2r ), G, H, , B, A, , F, E, , C, D, , Simple cubic unit cell, the spheres are in contact with each, other along the edge of the cube, (ii) Face centred cubic unit cell Atoms touch each other along, the face diagonal., G, , B, A, A, , H, , r, 2r, , F, , F, , E, , r, , C, , D, , Cubic close packing, or face centred cubic unit cell other, sides are not provided with spheres for sake of clarity, d = a/ 2, r = 2a/ 4, , Hence,, or, Therefore,, , PF =, , (Q Length of face diagonal = 2a), , 4 3, πr, 3, = 0.74 or 74%, 3, 4r , , 2, , 4×, , The packing efficiency of hcp and ccp structures is also 74%., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Solid State, , 81, , (iii) Body centred cubic unit cell Atoms touch each other, along the body diagonal., B, , G, H, , A, c, F, , a, C, , b, , a, E, , a, , D, , Body-centred cubic unit cell (sphere along the body, diagonal are shown with solid boundaries), Hence,, , d = 3a/ 2, , or, , r = 3a/ 4, , Therefore,, , PF =, , (Q Length of body diagonal = 3a), , 4 3, πr, 3, = 0.68 or 68%, 3, 4r , , 3, , 2×, , The packing efficiency of hcp and ccp structure is also 74%., , Density of Unit Cell (d), Density of unit cell =, d=, , mass of unit cell, volume of unit cell, Z⋅m, a3, , =, , ZM, a3 × N A, , kg/cm3, , , M , Mass of an atom ( m ) = N , , A, (The density of the unit cell is same as the density of the substance.), where, d = density of unit cell, M = molecular weight, Z = number of atoms per unit cell, N A = Avogadro number, a = edge length of unit cell., , The Structure of Ionic Crystals, The ionic radius ratio of cation and anion play a very important role, in giving a clue to the nature of the crystal structure of ionic substance., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 82, , Handbook of Chemistry, , The ratio r+ to r− is called radius ratio., radius of positive ion r+, Radius ratio =, =, radius of negative ion r−, , Radius Ratio and Crystal Structure, S. Radius ratio, No., ( r+ / r− ), , Coordination, number, , 1., , < 0.225, , 2 or 3, , 2., , 0.225–0.414, , 4, , 3., , 0.414–0.732, , 4 or 6, , 4., , 0.732 or more, , 8, , Shape, Linear or, triangular, , Crystal, structure, Linear or, triangular, , Example, B2O 3, , Tetrahedral ZnS type, CuCl, CuBr, HgS, BaS, (sphalerite), Squar, planar or, octahedral, , NaCl type, , MgO, NaBr, CaS, KBr,, CaO, AgCl, , Cube, , CsCl type, , CsI, CsBr, NH 4Br, TlBr, , Ionic crystals may be of two types:, (i) AB type and, (ii) A2B or AB2, , Structure of Ionic Crystals, Ionic crystal type, , Cation occupy, , Anion form, , Coordination, number, , NaCl (Rock salt, structure) type, , All octahedral voids, , fcc unit cell, , 6:6, , CsCl type, , Body centre, , simple cubic unit cell, , 8:8, , ZnS (Sphalerite, structure) type, , Alternate tetrahedral, voids, , fcc unit cell, , 4:4, , CaF2 (Fluorite, structure) type, , Alternate body centre, , simple cubic unit cell, , 8:4, , Na2O (Antifluorite, structure) type, , All tetrahedral sites, , fcc unit cell, , 4:8, , On applying pressure, NaCl structure (6 : 6 coordination) changes into, CsCl structure (8 : 8 coordination) and reverse of this occur at high, temperature (760 K)., , Imperfections Defects in Solids, In a crystalline solid, the atoms, ions and molecules are arranged in a, definite repeating pattern, but some defects may occur in the pattern., Deviations from perfect arrangement may occur due to rapid cooling or, presence of additional particles., The defects are of two types, namely point defects and line defects., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Solid State, , 83, , The irregularities or deviations from ideal arrangement in entire rows, of lattice points is called line defects., Point defects are the irregularities or deviations from ideal, arrangement around a point or an atom in a crystalline substance., Point defects can be classified into three types :, (1) stoichiometric defects, (2) impurity defects, (3) non-stoichiometric defects., , 1. Stoichiometric Defect, These are point defects that do not disturb the stoichiometry of the, solid. They are also called intrinsic or thermodynamic defects., (a) In non ionic solids, two types of defects are present:, , Vacancy Defect When some of the lattice sites are vacant, crystal is, said to have vacancy defect and results in decrease in density of, substance., Interstitial Defect When some constituent particles occupy an, interstitial site, the crystal is said to have interstitial defect and results, in increase in density of substances., (b) In ionic solids, basically these are of two types, Frenkel defect and, Schottky defect., Schottky defect, , Frenkel defect, , 1., , It is due to equal number of cations It is due to the dislocation of ions, and anions missing from the lattice (usually cations) from the lattice, sites., sites to occupy the interstitial sites., , 2., , This results in the decrease in, density of crystal., , It has no effect on the density of, crystal., , 3., , This type of defect is found in highly, ionic compounds with high, coordination number, e.g. NaCl,, CsCl, etc., , This type of defect is found in, crystal where the difference in the, size of cations and anions is very, large, e.g. AgCl, ZnS, etc., , AgBr has both Schottky and Frenkel defects. Frenkel defects are not, found in pure alkali metal halides because cations are of large size., , 2. Impurity Defect, It arises when foreign atoms or ions are present in the lattice. In case, of ionic compounds, the impurity is also ionic in nature. When the, impurity has the same charge as the host ion, it just substitutes some, of the host ions. Impurity defects can also be introduced by adding, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 84, , Handbook of Chemistry, , impurity ions having different charge than host ions, e.g. molten NaCl, containing a little amount of SrCl2 is crystallised. In such cases,, cationic vacancies produced = [number of cations of higher valence ×, difference in valence of the host cation and cation of higher valence], , 3. Non-Stoichiometric Defect, Non-stoichiometric crystals are those which do not obey the law of, constant proportions. The number of positive and negative ions present, in such compounds are different from those expected from their ideal, chemical formulae. However, the crystal as a whole is neutral., Types of non-stoichiometric defects are as follows:, (i) Metal excess defect due to anionic vacancies Alkali, halides like NaCl and KCl show this type of defect. F-centres are, the sites from where anions are missing and the vacant sites are, occupied by electrons. F-centres contribute colour and, paramagnetic nature of the crystal [F stands for German word, Farbe meaning colour]., Metal excess defect due to presence of extra cations at, interstitial sites, e.g. zinc oxide is white in colour at room, temperature. On heating, it loses oxygen and turns yellow., Heating, , ZnO → Zn2+ +, , 1, O2 + 2e−, 2, , (ii) Metal deficiency defect due to cation vacancy It is due, to the absence of a metal ion from its lattice site and charge is, balanced by ion having higher positive charge. Transition metals, exhibit this defect, e.g. FeO, which is found in the composition, range from Fe0.93O to Fe0.96O., In crystal of FeO, some Fe2+ cations are missing and the loss of, positive charge is made up by the presence of required number of, Fe3 + ions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The Solid State, , 85, , Electrical Properties of Solids, Solids can be classified into three types on the basis of their, conductivities., , Classification of Solids on the Basis of Electrical, Conductivity, Type of, solid, Conductors, Insulators, , Conductivity, (ohm −1 m −1 ), , Reason of, conductivity, , 104 − 107 (Very high), −20, , 10, , −10, , to10, , (Very low), , Energy, , Semiconductors 10−6 − 104 (Moderate), , Partially, filled band, , Conduction, band, Overlapping, band, Valence, band, , Conductors, , Examples, , Motion of electrons, , Metals like Ag, Al, , Do not permit electricity Wood, rubber, bakelite, to pass, Motion of interstitial Si, Ge, etc., electrons or holes or, both, , Conduction, band, , Conduction, band, , Forbidden zone, (Large energy gap), Valence band, , Insulator, , Small energy, gap, Valence band, , Semiconductor, , The electricity produced on heating a polar crystal is called, . When mechanical stress is applied on polar crystals,, electricity produced due to displacement of ions is called, ., , Semiconductors, Electronic conductors having electrical conductivity in the range of, 104 − 10−6 Ω −1 m −1 are known as semiconductors, e.g. Si, Ge, Sn (grey),, Cu2O, SiC and GaAs., , Intrinsic Semiconductors, Pure substances that are semiconductors are known as intrinsic, (undoped) semiconductors, e.g. Si, Ge., , Extrinsic Semiconductors, Their conductivity is due to the presence of impurities. They are, formed by doping. It is defined as addition of impurities to a, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 86, , Handbook of Chemistry, , semiconductor to increase the conductivity. Doping of Si or Ge is, carried out with P, As, Sb, B, Al or Ga., (i) n-type semiconductors Silicon or germanium doped with 15, group elements like phosphorus is called n-type semiconductor., The conductivity is due to the presence of negative charge, (electrons)., (ii) p-type semiconductors Silicon or germanium doped with 13, group element like gallium is called p-type semiconductor. The, conductivity is due to the presence of positive holes., Some typical 13-15 compounds are InSb, AlP and GaAs and some, typical 12-16 compounds are ZnS, CdS, CdSe and HgTe., These exhibit electrical and optical properties of great use in electronic, industry., , Magnetic Properties of Solids, Solids can be divided into different classes depending on their response, to magnetic field., , Paramagnetic Substances, These are attracted by the magnetic field and have unpaired electrons., These lose magnetism in the absence of magnetic field,, e.g. O2 , Cu2+ , Fe3 + , etc., , Diamagnetic Substances, These are weakly repelled by the magnetic field and do not have any, unpaired electron, e.g. TiO2 , V2O5 , C6H 6 , NaCl, etc., , Ferromagnetic Substances, These are attracted by the magnetic field and show permanent, magnetism even in the absence of magnetic field, e.g. Fe, Co, CrO 2 and, Ni., , Anti-ferromagnetic Substances, These substances have net magnetic moment zero due to compensatory, alignment of magnetic moments, e.g. MnO, MnO2, FeO, NiO, Cr2O3 etc., , Ferrimagnetic Substances, These substances have a net dipole moment due to unequal parallel, and anti-parallel alignment of magnetic moments, e.g. Fe3O4, ferrites, ( M 2+Fe2O4 ), where M = Mg, Cu, Zn etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 7, Thermodynamics, The branch of science which deals with the quantitative relationship, between heat and other forms of energies is called thermodynamics., , Thermodynamic Terms, (i) System It refers to the part of universe in which observations, are carried out., (ii) Surroundings The part of universe other than the system is, known as surroundings., (iii) Boundary The wall that separates the system from the, surroundings is called boundary., (iv) Thermodynamic equilibrium A system in which the, macroscopic properties do not undergo any change with time is, called thermodynamic equilibrium., (v) Thermal equilibrium If there is no flow of heat from one, portion of the system to another, the system is said to be in, thermal equilibrium., (vi) Mechanical equilibrium If no mechanical work is done by, one part of the system on another part of the system, it is said to, be in mechanical equilibrium. Such a condition exists when, pressure remains constant., , Types of Systems, (i) Open system The system in which energy and matter both, can be exchanged with the surroundings., (ii) Closed system The system in which only energy can be, exchanged with the surroundings., (iii) Isolated system The system in which neither energy nor, matter can be exchanged with the surroundings., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 88, , Handbook of Chemistry, , State of System, When microscopic properties have definite value, the conditions of, existence of the system is known as state of system., , State functions (State variables) When values of a system are, independent of path followed and depend only on initial and final, state, it is known as state function, e.g. ∆U , ∆H , ∆G etc., , Path functions These depend upon the path followed, e.g. work,, heat, etc., , Thermodynamic Properties, Intensive Properties, Properties of the system which depend only on the nature of matter, but not on the quantity of matter are called intensive properties, e.g., pressure, temperature, specific heat, etc., , Extensive Properties, Properties of the system which are dependent on the quantity of, matter are called extensive properties, e.g. internal energy, volume,, enthalpy, etc., , Thermodynamic Process, It is the operation which brings change in the state of the system., Thermodynamic processes are, (i) Isothermal process In which temperature remains, constant, i.e. ( dT = 0, ∆U = 0)., (ii) Isochoric process In which volume remains constant,, i.e. ( ∆V = 0)., (iii) Isobaric process In which pressure remains constant,, i.e. ( ∆p = 0)., (iv) Adiabatic process In which heat is not exchanged by system, with the surroundings, i.e. ( ∆q = 0)., (v) Cyclic process It is a process in which system returns to, its original state after undergoing a series of change,, i.e. ∆U cyclic = 0 ; ∆H cyclic = 0., (iv ) Reversible process A process that follows the reversible, path, i.e. the process which occurs in infinite number of steps in a, way that the equilibrium conditions are maintained at each step,, and the process can be reversed by infinitesimal change in the, state of functions., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Thermodynamics, , 89, , (vii) Irreversible process The process which cannot be reversed, and amount of energy increases. All natural processes are, irreversible., , Internal Energy (E or U), It is the total energy within the substance. It is the sum of many types, of energies like vibrational energy, translational energy, etc. It is an, extensive property and state function., Its absolute value cannot be determined but experimentally change in, internal energy ( ∆U ) can be determined by, ∆U = U 2 − U 1 or ΣU P − ΣU R, For exothermic process, ∆U = − ve, whereas for endothermic process, ∆U = +ve., U depends on temperature, pressure, volume and quantity of matter, and is independent of the method by which state has been attained., , Zeroth Law of Thermodynamics or Law of, Thermal Equilibrium, The law states that if the two systems are in thermal equilibrium with, a third system then they are also in thermal equilibrium with each, other. Temperature is used here to know whether the system is in, thermal equilibrium or not., , First Law of Thermodynamics, Energy can neither be created nor destroyed although it can be, converted from one form to the other., Mathematically,, ∆U = q + W, where, ∆U = internal energy change, q = heat added to system, W = work added to system, Sign convention, (i) q is + ve = heat is supplied to the system, (ii) q is – ve = heat is lost by the system, (iii) W is +ve = work done on the system, (iv) W is –ve = work done by the system, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 90, , Handbook of Chemistry, , Modes of Transference of Energy, Work (W ), If the system involves gaseous substances and there is a difference of, pressure between system and surroundings, work is referred as, pressure-volume work (W pV )., , Expression for Pressure-Volume Work, (i) Work done in irreversible expansion against constant pressure, p under isothermal conditions, q = − W pV = pext ∆V, (ii) Work done in reversible expansion under isothermal conditions, V , q = − W rev = 2.303 nRT log 2 , V1 , q = − W rev = 2.303 nRT log, , or, , p1, p2, , (iii) Work done in reversible expansion under adiabatic conditions, nR, W rev =, (T2 − T1 ), γ −1, where, γ = Poisson’s ratio, (Under adiabatic conditions T V γ, , −1, , = constant), , (iv) Work done in irreversible expansion under adiabatic conditions, p T − p2T1 , W irrev = − pext × nR 1 2, , p1 p2, , , (v) When an ideal gas expands in vacuum then, pext = 0, Work done is maximum in reversible conditions., , Units CGS system – erg, SI system – joule, Work and heat both appear only at the boundary of the system, during a change in state., , Heat (q), It occurs when there is a difference of temperature between system, and surroundings. It is a random form of energy and path dependent., Its units are joule or calorie., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Thermodynamics, , 91, , Heat Capacity of a System, Heat capacity (C) of a system is defined as the amount of heat required, to raise the temperature of a system by 1°C., , Molar Heat Capacity, It is the heat capacity of 1 mole of substance of the system., , Specific Heat Capacity, It is the heat capacity of 1 g of substance of the system., q = mc ∆T ,, where, m = mass of substance, c = specific heat or specific heat capacity, Molar heat capacity, at constant pressure, C p = c p × M, Molar heat capacity, at constant volume, CV = cV × M, (c p and cV are specific heats at constant pressure and constant volume, respectively and M is molecular weight of gas), (R = Molar gas constant), c p − cV = R, R, C p − CV =, M, 3, The molar heat capacity at constant volume, CV = R, 2, The molar heat capacity at constant pressure,, 5, 3, Cp = R + R = R, 2, 2, C p 5, Poisson’s ratio,, γ=, = = 1.66, CV 3, γ = 1.66 for monoatomic gas, γ = 1.40 for diatomic gas, γ = 1.33 for triatomic gas, , Measurement of ∆H and ∆U : Calorimetry, (a) For gaseous reactions Reactions involving gases are carried, out in a bomb calorimeter at constant volume., ∆U = − (Heat absorbed by bomb calorimeter), (b) For reaction in solution Reactions involving solution are, carried out at constant pressure inside a coffee-cup calorimeter., ∆ r H = ( mc ∆T )calorimeter + ( mc ∆T )solution ., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 92, , Handbook of Chemistry, , Enthalpy (H ), It is the sum of internal energy and pV -energy of the system. It is a, state function and extensive property. Mathematically,, H = U + pV, Like U , absolute value of H also cannot be known, ∆H is determined, experimentally., ∆H = H 2 − H 1 or ∆H = ΣH P − ΣH R, For exothermic reaction (the reaction in which heat is evolved),, ∆H = −ve, whereas for endothermic reaction (the reaction in which, heat is absorbed), ∆H = +ve., Relationship between ∆H and ∆U, ∆H = ∆U + p ∆V or ∆H = ∆U + ∆n ( g ) RT, Here, ∆n g = change in the number of gas moles., , Enthalpy Change or Reaction Enthalpy ( ∆r H), It is the change in enthalpy that accompanies a chemical reaction, represented by a balanced chemical equation., ∆ r H = ΣH ( P ) − ΣH ( R ), Enthalpy of reaction expressed at the standard state conditions is, called standard enthalpy of reaction ( ∆H s )., Factors affecting enthalpy of reaction are, (i) Physical state of reactants and products., (ii) Allotropic forms of elements involved., (iii) Chemical composition of reactants and products., (iv) Amount of reactants., (v) Temperature., , Various Forms of Enthalpy of Reaction, Enthalpy of Formation (∆ f H° ), It is the heat change when one mole of compound is obtained from its, constituent elements. Enthalpy of formation at standard state is, known as standard enthalpy of formation ( ∆ f H ° ) and is taken as, zero by convention., , Enthalpy of Combustion (∆ CH° ), It is the enthalpy change taking place when one mole of a compound, undergoes complete combustion in the presence of oxygen (∆C H )., ∆C H is always negative, because process of combustion is exothermic., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Thermodynamics, , 93, , Enthalpy of Solution (∆ sol H° ), It is the enthalpy change when one mole of a substance is dissolved in, large excess of solvent, so that on further dilution no appreciable heat, change occur., So,, ∆sol H ° = ∆ lattice H ° + ∆ hyd H °, , Enthalpy of Hydration ( ∆ hyd H° ), It is the enthalpy change when one mole of anhydrous or partially, hydrated salt combines with required number of moles of water to form, a specific hydrate undergoes complete combustion. It is an exothermic, process., , Enthalpy of Fusion ( ∆ fus H° ), It is the enthalpy change that accompanies melting of one mole of solid, substance., , Enthalpy of Vaporisation ( ∆ vap H° ), It is the enthalpy change that accompanies conversion of one mole of, liquid substance completely into vapours., , Enthalpy of Neutralisation ( ∆ n H° ), It is the enthalpy change that takes place when 1 g-equivalent of an, acid (or base) is neutralised by 1 g-equivalent of a base (or acid) in, dilute solution., Enthalpy of neutralisation of strong acid and strong base is always, constant, i.e. 57.1 kJ., Enthalpy of neutralisation of strong acid and weak base or weak acid, and strong base is not constant and numerically less than 57.1 kJ due, to the fact that here the heat is used up in ionisation of weak acid or, weak base. This is known as enthalpy of ionisation of weak acid/or, base., , Enthalpy of Transition ( ∆ t H° ), It is the enthalpy change when one mole of the substance undergoes, transition from one allotropic form to another., , Enthalpy of Atomisation ( ∆ a H° ), It is the enthalpy change occurring when one mole of the molecule, breaks into its atoms., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 94, , Handbook of Chemistry, , Enthalpy of Dilution, It is the enthalpy change, when one mole of a substance is diluted from, one concentration to another., , Enthalpy of Sublimation ( ∆ sub H° ), It is the enthalpy change, when one mole of a solid substance sublimes., , Lattice Enthalpy, It is the enthalpy change, when one mole of an ionic compound, dissociates into its ions in gaseous state., , Bond Enthalpy ( ∆ bond H° ), Enthalpy is required to break a bond and energy is released when, bond is formed. For this, two different terms are used in, thermodynamics., (a) Bond dissociation enthalpy The enthalpy change is the, change in enthalpy when one mole of covalent bonds of a gaseous, covalent compound is broken to form product in the gas phase., (b) Mean bond enthalpy The average value of dissociation, energies of polyatomic molecule., Some factors affecting the bond enthalpy:, (i) Size of atoms, (ii) Electronegativity, (iii) Bond length, (iv) Number of bonding electrons, , Joule-Thomson Effect, The phenomenon of cooling of a gas when it is made to expand, adiabatically from a region of high pressure to a region of extremely, low pressure is known as Joule-Thomson effect. This effect is zero, when an ideal gas expands in vacuum., When an ideal gas undergoes expansion under adiabatic condition in, ∂E , vacuum, no change takes place in its internal energy, i.e. = 0, ∂V T, ∂E , where, is called the internal pressure., ∂V T, , Joule-Thomson Coefficient, The number of degrees of temperature change produced per, atmospheric drop in pressure at constant enthalpy when a gas is, allowed to expand through a porous plug is called Joule-Thomson, coefficient. It is given as, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Thermodynamics, µ=, , 95, , dT, dp, , where, µ = Joule-Thomson coefficient, dT = change in temperature, dp = change in pressure., , Inversion Temperature, The temperature below which a gas becomes cooler on expansion is, known as the inversion temperature. It is given as, 2a, Ti =, Rb, where, a and b = van der Waals’ constant., At inversion temperature Ti , the Joule Thomson coefficient µ = 0, i.e., the gas is neither heated nor cooled., , Laws of Thermochemistry, Lavoisier Laplace Law, The enthalpy change during a reaction is equal in magnitude to the, enthalpy change in the reverse process but it is opposite in sign., , Hess’s Law of Constant Heat Summation, The standard enthalpy of a reaction, which takes place in several steps,, is the sum of the standard enthalpies of the intermediate reactions into, which the overall reactions may be divided at the same temperature., According to Hess’s law, ∆H = ∆H 1 + ∆H 2 + ∆H 3, Applications of Hess’s law are, (a) In determination of heat of formation., (b) In determination of heat of transition., (c) In determination of heat of hydration., (d) To calculate bond energies., , Trouton’s Rule, According to this rule, “The ratio of enthalpy of vaporisation and, normal boiling point of a liquid is approximately equal to 88 J per mol, per kelvin, i.e., ∆H vap, ≈ 88 J/mol/K, T
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Telegram @neetquestionpaper, , 10, Solutions, Solution is a homogeneous mixture of two or more substances in same, or different physical phases. The substances forming the solution are, called components of the solution. On the basis of number of, components a solution of two components is called binary solution., , Solute and Solvent, In a binary solution, solvent is the component which is present in large, quantity while the other component present in small quantity is, known as solute., , Classification of Solutions, (A) Following types of solutions are seen on the basis of physical state, of solute and solvent., S.No., , Solute, , Solvent, , Examples, , Solid solutions, 1., , Solid, , Solid, , Alloys (Copper dissolved in gold), , 2., , Liquid, , Solid, , Hydrated salts, Amalgam of Hg with Na, , 3., , Gas, , Solid, , Solution of hydrogen in palladium, , Liquid solutions, 4., , Solid, , Liquid, , Salt/sugar solution in water, , 5., , Liquid, , Liquid, , Alcohol in water, , 6., , Gas, , Liquid, , Aerated drinks, O2 in water, , Gaseous solutions, 7., , Solid, , Gas, , Iodine vapour in air, , 8., , Liquid, , Gas, , Water vapour in air, , 9., , Gas, , Gas, , Air (O2 + N2 ), , If water is used as a solvent, the solution is called aqueous solution, and if not, the solution is called non-aqueous solution., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 122, , Handbook of Chemistry, , (B) Depending upon the amount of solute dissolved in a solvent we, have the following types of solutions:, (i) Unsaturated solution A solution in which more solute, can be dissolved without raising temperature is called an, unsaturated solution., (ii) Saturated solution A solution in which no more solute can, be dissolved further at a given temperature is called a saturated, solution., (iii) Supersaturated solution A solution which contains more, solute than that would be necessary to saturate it at a given, temperature is called a supersaturated solution., , Concentration of Solutions, The concentration of a solution is defined as the relative amount of, solute present in a solution. On the basis of concentration of solution,, there are two types of solutions:, (i) Dilute solution Solution containing relatively very small, quantity of solute., (ii) Concentrated solution Solution containing relatively very, large quantity of solute., , Methods of Expressing Concentration of Solutions, Various expression for the concentrations of solutions can be, summarised as, (i) Percentage by weight (w/w %) It is defined as the amount, of solute present in 100 g of solution., w, weight of solute, %=, × 100, w, weight of solution, (ii) Percentage by volume ( v/ V %) It is defined as the volume of, solute present in 100 mL of solution,, volume of solute, v, %=, × 100, volume of solution, V, (iii) Percentage of mass by volume ( w/ V %) It is defined as the, weight of solute present in 100 mL of solution., weight of solute, w, %=, × 100, volume of solution, V, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 123, (iii) Mole fraction (χ) It is defined as the ratio of the number of, moles of a component to the total number of moles of all the, components in solution. For a binary solution, if the number of, moles of A and B are n and n respectively, the mole fraction of, A will be, n, χ =, n +n, n, [ χ + χ = 1], Similarly,, χ =, n +n, (iv) Parts per million (ppm) It is defined as the parts of a, component per million parts (10 ) of the solution. It is widely used, when a solute is present in trace quantities., number of parts of the component, ppm =, × 10, total number of parts of all the components, of the solution, (v) Molarity (M) It is the number of moles of solute present in 1L, (dm ) of the solution., number of moles of solute, M=, volume of solution (L), mass of solute (in gram) × 1000, M=, mol. wt. of solute × volume of solution (in mL), Molarity varies with temperature due to change in volume of, solution. Its unit is g-mol/L., When molarity of a solution is 1 M, it is called a molar solution., 0.1 M solution is called a decimolar solution while 0.5 M solution is, known as semimolar solution., per cent by mass × density × 10, Molarity =, molecular weight, l, , l, , l, , Dilution law, M V = M V (for dilution from volume V to V ), MV, MV, For reaction between two reactants,, =, n, n, where, n and n are stoichiometric coefficients of reactants in, balanced equation., If two solutions of the same solute are mixed ten molarity of, the existing solution., MV +MV, M=, V +V, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 124, , Handbook of Chemistry, l, , Volume of water to be added to set a solution of molarity M, from V mL of molarity M is, M − M , V −V = , V, M, , , (vi) Molality (m) It is the number of moles of solute per kilogram of, the solvent., mass of solute in gram × 1000, Molality =, mol. wt. of solute × mass of solvent (in g), Molality is independent of temperature. Its unit is g-mol/kg., When solvent used is water, a molar (1 M) solution is more, concentrated than a molal (1 M) solution., (vii) Normality (N ) The number of gram equivalents of solute, present in 1 L of solution., number of gram − equivalents of solute, Normality =, volume of solution (in L), mass of solute in gram, Number of gram-equivalents of solute =, equivalent weight, Relationship between normality and molarity, N × eq. weight = M × mol. weight, If two solutions of the same solute having volumes and molarities, V , M and V , M are mixed, the molarity of the resulting, solution is, V M +V M, M=, V +V, NV +N V, Similarly, Normality (N) =, V +V, To dilute V mL of a solution having molarity M to molarity M, up to the final volume V mL, the volume of water added is, M − M , V −V = , V., M, , N − N , Similarly, V − V = , V, N, , (viii) Formality (F) It is the number of formula weights of solute, present per litre of the solution., moles of substance added to solution, Formality =, volume of solution (in L), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 125, (ix) Mass fraction Mass fraction of any component in the solution is, the mass of that component divided by the total mass of the solution., Mass % of a component = mass of the component, in the solution, × 100, total mass of the solution, Molality, mole fraction and mass fraction are preferred over, molarity, normality, etc., because former involve weights which, do not change with temperature., (x) Demal (D) It represents one mole of solute present in 1L of, solution at 0°C., , Solubility, The maximum amount of a solute that can be dissolved in a given, amount of solvent (generally 100 g) at a given temperature is termed, as its solubility at that temperature., The solute can be either solid or gas. Likewise, solubility is defined as, the one of solid in liquid or the solubility of gas in liquid., The solubility of a solute in a liquid depends upon the following factors:, , Solubility of gases in liquids, All gases are soluble in water as well as in other liquids to a greater or, smaller extent., , Factors affecting solubility of gases, (i) Nature of the gas The gases which can be easily liquified, are, more soluble in common solvents., (ii) Nature of the solvent The gases which are capable of forming, ions in aqueous solutions are much more soluble in water than, in other solvents., (iii) Temperature The solubility of most gases in liquids decreases, with increase of temperature., (iv) Pressure The solubility of a gases increase with increase in, pressure., , Henry’s Law, The most commonly used form of Henry’s law states “the partial, pressure (p) of the gas in vapour phase is proportional to the mole, fraction ( x ) of the gas in the solution’’ and is expressed as, p= K ⋅x, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 126, , Handbook of Chemistry, , Higher the value of K at given pressure, the lower is the solubility of, the gas in the liquid. The value of K decreases with increase in the, temperature. Thus, aquatic species are more confortable in cold water, [more dissolved O ] rather than warm water., Partial, pressure, of solute, , Mole fraction of component in its solution, , Applications, 1. In manufacture of soft drinks and soda water, CO is passed at, high pressure to increase its solubility., 2. To minimise the painful effects (bends) accompanying the, decompression of deep sea divers, O diluted with less soluble, He gas is used as breathing gas., 3. At high altitudes, the partial pressure of O is less than that at, the ground level. This leads to low concentrations of O in the, blood of climbers which causes ‘anoxia’., , Vapour Pressure, The pressure exerted by the vapour molecules above the liquid surface, in equilibrium with the liquid at a given temperature is called vapour, pressure., , Factors affecting vapour pressure, Vapour pressure gets affected by following factors., (i) Purity of the liquid Pure liquid always has a vapour pressure, higher than its solution., (ii) Nature of the liquid Liquids which have weak intermolecular, forces are volatile and have greater vapour pressure., (iii) Temperature The vapour pressure of a liquid increases with, increase in temperature., (iv) Effect of adding solute When a liquid contains a solute, some, of the solvent molecules are replaced by the solute particles on, the liquid surface and therefore, the available surface area for, the escape of solvent molecule decreases. Therefore, rate of, evaporation as well as rate of condensation both decrease., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 127, Raoult’s Law, The Raoult’s law states “For a solution of two volatile liquids, the, vapour pressure of each liquid in the solution is less than the, respective vapour pressure of the pure liquids and the equilibrium, partial vapour pressure of the liquid is directly proportional to its mole, fraction., For a solution containing two liquids A and B, the partial vapour, pressure of liquid A is, p ∝χ, or, p = kχ, n, where,, χ =, (n + n ), = mole fraction of liquid A, The proportionality constant is obtained by considering the pure liquid, when, χ = 1 then k = p ° , the vapour pressure of pure liquid, hence,, p = p° χ, Similarly,, , p = p° χ, , The total vapour pressure of the solution,, p = p + p, = p° χ + p° χ, = p° + ( p° − p° ) χ, , Rault’s Law as a Special Case of Henry’s Law, According to Raoult’s law, the vapour pressure of a volatile component, in a given solution is given by p = x p . In the solution of a gas in a, liquid, one of the components is so volatile that it exists a a gas and we, have already seen that its solubility is given by Henry’s law which, states that, p = K x., If we compare the equations for Raoult’s law and Henry’s law and, Henry’s law, it can be seen that the partial pressure of the volatile, component of gas is directly proportional to its mole fraction in, solution. Only the proportionality constant K differs from p . Thus,, law becomes a special case of Henry’s law in which K becomes equal, to p ., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 128, , Handbook of Chemistry, , Those solutions in which solute-solute, (B—B) and solvent-solvent (A—A), interactions are almost similar to, solvent- solute (A—B) interactions are, called ideal solutions. These solutions, satisfy the following conditions :, (i) Solution must obey Raoult’s law, i.e.,, , Vapour pressure, , Ideal Solutions, p°B, , pt, pB, , p°A, , pA, χA = 1, χB = 0, , p = p° χ , p = p° χ, , χA = 0, χB = 1, , Mole fraction, , (ii) ∆H, = 0 (No energy evolved or absorbed), (iii) ∆V, = 0 (No expansion or contraction on mixing), Some solutions behave like nearly ideal solutions, e.g., benzene +, toluene, n-hexane + n-heptane, ethyl iodide + ethyl bromide,, chlorobenzene + bromobenzene., , Non-ideal Solutions, Those solutions which shows deviation from Raoult’s law are called, non-ideal solutions., For such solutions,, ∆H, ≠0, ∆V, ≠0, (a) Non-ideal solutions showing positive deviation In such, a case, the A − B interactions are weaker than A − A or B − B, interactions and the observed vapour pressure of each, component and the total vapour pressure are greater than that, predicted by Raoult’s law., p > p° χ ; p > p° χ, > p° χ, , p, , + p° χ, , For such solutions, , Vapour pressure, , ∆H, p>, pA°, , χA = 1, χB = 0, , > 0, ∆V, Max, pB, pA +, n, o, ti, lu, o, Ideal s, pB, pA, , Mole fraction, , >0, pB°, , χA = 0, χB = 1, , Non-ideal solution showing positive deviation, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 129, Examples : Ethanol + water, CS + acetone, CCl + C H ,, CCl + C H CH , ethanol + cyclohexane, CCl + CHCl ., (b) Non-ideal solution showing negative deviation In such, a case, the A − B interactions are stronger than A − A or B − B, interactions and the observed vapour pressure of each, component and the total vapour pressure are lesser than that, predicted by Raoult’s law., p < p° χ , p < p° χ, p, , < p° χ, , + p° χ, , Vapour pressure, , For such solutions,, ∆H, < 0, ∆V, , pA°, , <0, lution, Ideal so, +, pB, p < pA, MIN, pB, , pB°, , pA, χA = 1, χB = 0, , Mole fraction, , χA = 0, χB = 1, , Non-ideal solution showng negative deviation, , Examples : CHCl + CH COCH , CHCl + C H , H O + HCl,, H O + HNO , methanol + acetic acid., , Azeotropic Mixture, A mixture of two liquids which boils at a particular temperature like a, pure liquid and distils over in the same composition is known as, constant boiling mixtures. These are formed by non-ideal solutions., (i) Minimum boiling azeotropes are formed by those liquid, pairs which show positive deviation from ideal behaviour. Such, azeotropes have boiling points lower than either of the, components, e.g. C H OH (95.57%) + H O (4.43%) (by mass)., (ii) Maximum boiling azeotropes are formed by those liquid, pairs which show negative deviation from ideal behaviour. Such, azeotropes have boiling points higher than either of the, components, e.g. H O(20.22%) + HCl [79.78%] by mass., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 130, , Handbook of Chemistry, , Colligative Properties, [Colligative : from Latin = Co means ‘together’; ligate means ‘to bind’], Colligative properties are those properties which depend only upon the, number of solute particles in a solution irrespective of their nature., , Relative Lowering of Vapour Pressure, When a non-volatile solute is added to a solvent, to vapour pressure is, solvent. Relative lowering in vapour pressure is the ratio of lowering in, vapour pressure to vapour pressure of pure solvent. The relative lowering, in vapour pressure of solution containing a non-volatile solute is equal to, the mole fraction of solute in the solution., p° − p, =χ, p°, where,, , p° − p, p°, , = relative lowering of vapour pressure of pure solvent, p° − p, , p°, for dilute solutions, n << n ., Hence,, p° − p, p°, or, , p° − p, p°, , =, , n, n +n, , =, , n, n, , =, , W ×M, M ×W, , M =, , W, W, , ×M, , ×, , p, ( p° − p ), , Above expression is used to find the molecular weight of an unknown, solute dissolved in a given solvent. where, W and W = mass of solute, and solvent respectively, M and M = molecular weight of solute and, solvent respectively., Ostwald and Walker method is used to determine the relative lowering, of vapour pressure., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 131, Elevation in Boiling Point ( ∆Tb ), Boiling point of a liquid is the, temperature at which its vapour, pressure becomes equal to the, atmospheric pressure. As the vapour, pressure of a solution containing a, non-volatile solute is lower than that, of the pure solvent, then it’s boiling, point will be higher than that of the, pure solvent as shown in figure. The, increase in boiling point is known as, elevation in boiling point, ∆T, , Boiling point, of solution, , Boiling point, of solvent, , t, tio, , n, , ve, n, lu, , So, l, , So, , Vapour pressure, , 1 atm, , ∆Tb, , Temperature, (K), , Tb°, , Tb, , ∆T = T − T °, (where, m = molality), ∆T = K m, K is molal elevation constant or ebullioscopic constant. Molecular, mass of solute can be calculated as, K ⋅ W × 1000, ∆T =, M ×W, M =K ⋅, , W, W, , ×, , 1000, ∆T, , where, W and W = mass of solute and solvent respectively., K has units of K/m or K kg mol− , for water, K = 0.52 K kg mol− ., , Solu, , ∆Tf, , Tf, , Tf°, , Temperature, (K), , Depression in freezing point ( ∆T ) = T ° − T, ∆T = K ⋅ m = K, , W, M, , ×, , e liq, , Pur, , Vapour pressure, Fr, oz, en, so, lv, e, , nt, , Depression in Freezing Point ( ∆Tf ), Freezing point of a liquid is the, temperature at which vapour pressure of, the solvent in its liquid and solid phase, become equal. As we know that vapour, pressure, of, solution, containing, non-volatile solute is lower than that of, pure solvent, solid form gets separated out, at a lower temperature as shown in the, figure., This decrease in freezing point of a liquid, is known as depression in freezing point., , 1000, W, , www.aiimsneetshortnotes.com, , uid, , tion
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Telegram @neetquestionpaper, 132, , Handbook of Chemistry, , To find molecular mass of solute,, K ⋅ W × 1000, M =, ∆T ⋅ W, where, K is molal depression constant or cryoscopic constant., K has units of K/m or K kg mol− ., Ethylene glycol is usually added to water in the radiator to lower its, freezing point. It is called antifreeze solution., Common salt (NaCl) and anhydrous CaCl2 are used to clear snow on, the roads because they depress the freezing point of water. The, freezing point depression is determined by Beckmann method or Rast, method., Calculations of molal elevation constant (K b ) and molal, depression constant (K f ), M R(T ° ), K =, 1000 × ∆H, K =, , M ⋅ R(T ° ), ∆H × 1000, , T ° = boiling point of solvent, T ° = freezing point of solvent, ∆H = molar enthalpy of fusion, where, M, , ∆H = molar enthalpy of vaporisation, is molar mass of solvent in kg mol− , R = gas constant., K, ∆T, =, K, ∆T, , Osmosis and Osmotic Pressure, Osmosis is the phenomenon of spontaneous flow of the solvent, molecules through a semipermeable membrane from pure solvent to, solution or from a dilute solution to concentrated solution. It was first, observed by Abbe Nollet., Some natural semipermeable membranes are animal bladder, cell, membrane etc., Cu [Fe(CN) ] is an artificial semipermeable membrane which does not, work in non-aqueous solutions as it dissolves in them., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 133, Osmosis may be, (i) Exosmosis It is outward flow of water or solvent from a cell, through semipermeable membrane., (ii) Endosmosis It is inward flow of water or solvent from a cell, through a semipermeable membrane., The hydrostatic pressure developed on the solution which just prevents, the osmosis of pure solvent into the solution through a semipermeable, membrane is called osmotic pressure., , n, W , Osmotic pressure (π) = RCT ;, =, C =, , V, M V, , ⇒, , W RT, πV, dRT, π=, ;, M, , M =, , W , , , d =, , V , , where, d = density, R = solution contant,, T = temperature, M = molar mass of solute, Osmotic pressure can be determined by any one of the method listed below, (i) Pfeffer’s method, (ii) Berkeley and Hartley’s method (very good method), (iii) Morse and Frazer’s method, On the basis of osmotic pressure, the solution can be, (i) Hypertonic solution A solution is called hypertonic if its, osmotic pressure is higher than that of the solution from which it, is separated by a semipermeable membrane., When a plant cell is placed in a hypertonic solution, the fluid, from the plant cell comes out and cell shrinks, this phenomenon, is called plasmolysis., (ii) Hypotonic solution A solution is called hypotonic if its, osmotic pressure is lower than that of the solution from which it, is separated by a semipermeable membrane., (iii) Isotonic solution Two solutions are called isotonic if they, exert the same osmotic pressure. These solutions have same, molar concentration. 0.91% solution of pure NaCl is isotonic with, human RBC’s., Two solutions are isotonic if they have the same molar, concentration, e.g. if x % solution of X is isotonic with y %, solution of Y , this means molar concentration of X = Molar, concentration of Y, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 134, , Handbook of Chemistry, 1000, x, y × 1000, ×, =, 100 M, 100 × M, , ⇒, , x, y, =, M, M, , Osmotic pressure method is the best method for determining the, molecular masses of polymers since observed value of any other, colligative property is too small to be measured with reasonable, accuracy., Reverse osmosis When the external pressure applied on the solution is more than, osmotic pressure, the solvent flows from the solution to the pure solvent, which is, called reverse osmosis. Desalination of sea water is done by reverse osmosis., , Abnormal Molecular Masses, In some cases, observed colligative properties deviate from their, normal calculated values due to association or dissociation of, molecules. As we know,, 1, Colligative property ∝, M, Hence, higher and lower values of molar mass is observed in case of, association and dissociation respectively, e.g. in benzene, acetic acid, gets associated, so, its observed molecular mass is 120. Similarly KCl, undergoes dissociation in aqueous solution, so its observed molecular, mass is 37.25., These observed values are corrected by multiplying with van’t Hoff, factor (i)., , van’t Hoff Factor (i), It is the ratio of observed value of colligative property to the calculated, value of colligative property., observed value of colligative property, i=, calculated value of colligative property, or, or, , normal molecular mass, observed molecular mass, number of particles after association or dissociation, i=, number of particles initially, i=, , So to correct the observed value of molar mass, van’t Hoff factor, (i) must be included in different expressions for colligative properties., ∆T = i K ⋅ m, ∆T = iK ⋅ m, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Solutions 135, π = i CRT, ∆p, = ix, p°, i for several strong electrolytes (Complete dissociation), For KCl, NaCl and MgSO , i approaches 2 as the solution becomes, very dilute. As expected, the value of i gets close to 3 for K SO ., , Degree of Dissociation (α) and van’t Hoff Factor (i), If one molecule of a substance gets dissociated into n particles or, molecules and α is the degree of dissociation then, A → nP, Initially, , 1 mol, , 0, , At eq., , 1− α, , nα, , Total number of moles at equilibrium, , ∴, ⇒, , = 1 − α + nα, 1 − α + nα, i=, 1, i−1, α=, n −1, , Degree of Association (α) and van’t Hoff Factor (i ), If n molecules of a substance A associate to form A and α is the degree, of association then, nA → A, Initially, , 1 mol, , At equilibrium, , 1− α, , 0, α, n, , Total number of moles at equilibrium, α, =1−α +, n, α, 1−α +, n, i=, 1, i−1, ⇒, α=, 1, −1, n, van’t Hoff factor ( i ) > 1 for solutes undergoing dissociation and it is < 1, for solutes undergoing association., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 11, Redox Reactions, Chemical reactions which involves both oxidation as well as reduction, process simultaneously, are known as redox reactions (‘red’ from, reduction and ‘ox’ from oxidation). All these reactions are always, accompanied by energy change in the form of heat, light or electricity., , Oxidation and Reduction, Oxidation, It involves, (i) Addition of oxygen to an element or, compound, or the removal of hydrogen, from a compound. e.g., 2Mg + O2 → 2MgO, 2H2S + O2 → 2H2O + 2S, (ii) Addition of electronegative element or, removal of any other electropositive, element., Zn + S → ZnS, 2KI + Cl2 → 2 KCl + I2, (iii) Oxidation is the loss of electrons by an, atom, ion or molecule. It is also known, as de-electronation., Zn → Zn2 + + 2 e −, , Reduction, It involves, Addition of hydrogen to an element or, compound, or the removal of oxygen, from a compound. e.g., H2S + Cl2 → 2HCl + S, Fe2O 3 + 3CO → 2Fe + 3CO2, Addition of electropositive element or, removal of any other electronegative, element., 2HgCl2 + SnCl 4 → Hg 2Cl2 + SnCl 4, SiCl 4 + 4Na → Si + 4NaCl, Reduction is the gain of electrons by an, atom, ion or molecule. This process is, known as electronation., Cu2 + + 2 e − → Cu, , (iv) Oxidation involves increase in oxidation, number., , Reduction involves decrease in oxidation, number., , (v), , Reduction is caused by a reducing agent., , Oxidation is caused by an oxidising agent., , Reductants and Oxidants, Oxidant or oxidising agent is a chemical substance which can, accept one or more electrons and causes oxidation of some other, species. In other words, the oxidation number of oxidant decreases in a, redox reaction., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Redox Reactions 137, Important Oxidants, Molecules of most electronegative elements such as O , O , halogens., Compounds having element in its highest oxidation state,, e.g. K Cr O , KMnO , HClO , H SO , KClO , Ce(SO ) ., Oxides of metals and non-metals such as MgO, CrO , CO , etc., , Reductant or reducing agent is a chemical substance which can, give one or more electrons and causes reduction of some other species., In other words, the oxidation number of reductant increases in a redox, reaction., , Important Reductants, All metals such as Na, Al, Zn, etc., and some non-metals, e.g. C, S, P,, H , etc., Metallic hydrides like NaH, LiH, KH, CaH , etc., The compounds having an element in its lowest oxidation state such as, H C O , FeSO , Hg Cl SnCl , H S, SO , Na S O , etc., SO , HNO and H O can act both as oxidant as well as reductant., molar mass, Eq. wt. of oxidant/reductant =, change in oxidation number, For disproportionation reaction,, Eq. wt. of oxidant/reductant = sum of eq. wt. of two half reactions, e.g., , 4H PO, , → 3H PO + PH, , Eq. wt. of H PO =, , M M 2M, +, =, 2, 6, 3, , Oxidation Number, The oxidation number is defined as the charge which an atom appears, to have when all other atoms are removed from it as ions. It may have, + or – sign., An element may have different values of oxidation number depending, upon the nature of compound in which it is present., Oxidation number of an element may be a whole number (Positive or, negative) or fractional or zero., , Important Points for Determining Oxidation Number, (i) The algebraic sum of the oxidation numbers of all the atoms in, an uncharged (neutral) compound is zero. In an ion, the, algebraic sum is equal to the charge on the ion., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 138, , Handbook of Chemistry, , (ii) All elements in the elementary state have oxidation number, zero, e.g. He, Cl , S , P , etc., (iii) As fluorine is the most electronegative element, it always has, an oxidation number of – 1 in all of its compounds., (iv) In compounds containing oxygen, the oxidation number of, oxygen is – 2 except in peroxides (–1) such as Na O , in OF and, in O F ( +2 and + 1 respectively)., (v) In all compounds, except ionic metallic hydrides, the oxidation, number of hydrogen is +1. In metal hydrides like NaH, MgH ,, CaH , LiH, etc., the oxidation number of hydrogen is –1., (vi) Oxidation number for alkali metals is +1 and for alkaline earth, metals is + 2., (vii) Oxidation number of metal in amalgams is zero., (viii) In case of coordinate bond, it gives +2 value of oxidation number, to less electronegative atom and –2 value to more, electronegative atom when coordinate bond is directed from less, electronegative atom to more electronegative atom., (ix) If coordinate bond is directed from more electronegative to less, electronegative atom then its contribution be zero for both the, atoms., (x) For p-block elements [Except F and O], the highest oxidation, number is equal to their group number and lowest oxidation, number is equal to the group number minus eight., (xi) In transition elements the lowest oxidation number is equal to, the number of ns electrons and highest oxidation number is, equal to number of ‘ns’ and ( n − 1)d unpaired electrons., , Determination of Oxidation Number of, Underlined Element, (i) K Cr O, , Solution, , K, , Cr, , O, , ( 2 × 1) ( 2 × x ) ( − 2 × 7), , 2 + 2x − 14 = 0 ; x = + 6, (ii) [ Fe(CN) ], , Solution, , [Fe (CN) ], ↓, x, , −, , ↓, −, , x− 6= − 4, , ⇒, , x=2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Redox Reactions 139, (iii) Na S O, , Solution, O, O, ↑, ↑, Na O S S S S ONa, ↓, ↓, O, O, Oxidation number of Na = + 1, Oxidation number of O = − 2, ∴, 2 (1) + 4x + 6 × − 2 = 0, x = 5 / 2 , this is average oxidation number, because the, compound has two types of sulphur atom., ON of sulphur bonded with coordinate bond = 5, ON of sulphur which have S—S bond = 0, 5+ 5+ 0+ 0 5, =, ∴ Average oxidation number =, 4, 2, (iv) Caro’s acid (H S O ), O−, ↑ −, −, −, H O S O O H, +, +, ↓, O−, 2+ x− 6− 2= 0, , ⇒, , x=6, , (v) Cr O, –2, –1 O, –1, , O, , O, Cr, , O –1, O–1, , x + 4 ( − 1) + ( − 2) (1) = 0 ⇒ x = 6, (vi) C O (carbon suboxide), −, , +, , +, , −, , O== C ==C== C ==O, (vii) NH NO, There are two types of nitrogen atoms. Therefore, evaluation, should be made separately as, Oxidation number of N in NH +, x + 4 ( + 1) = + 1 ⇒ x = − 3, Oxidation number of N in NO−, y + 3 × ( − 2) = − 1 ⇒ y = 5, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 140, , Handbook of Chemistry, , Stock Notations, The oxidation states of elements exhibiting variable oxidation states, are specified by Roman numerals such as I, II, III, IV, etc., within, parenthesis after the symbol or name of the element. This system was, introduced for the first time by German chemist, Alfred Stock and is, known as Stock notation. This may be illustrated as, Formula of the compound, , Chemical name, , Stock notation, , Cu2O, , Cuprous oxide, , Copper (I) oxide; Cu2 (I)O, , Fe2O 3, , Ferric oxide, , Iron (III) oxide; Fe2 (III)O 3, , HgCl2, , Mercuric chloride, , Mercury (II) chloride; Hg(II) Cl2, , SnCl2, , Stannous chloride, , Stannous (II) chloride, Sn(II) Cl2, , Types of Redox Reactions, (i) Combination reactions The reactions in which two atoms or, molecules combine together to form a third molecule are, , combination reactions., , +, , −, , e.g. 2 Mg( s) + O ( g) → 2 Mg O( s), (ii) Decomposition reactions The reactions in which molecule, breaks down to form two or more components are called, , decomposition reactions., ∆, , e.g. 2KClO ( s) → 2KCl( s) + 3O ( g), (iii) Displacement reactions The reactions in which an atom, (or ion) of a compound is replaced by another ion (or atom) of, same nature are called displacement reactions., These are of the following two types :, (a) Metal displacement reactions When a metal in the, compound is displaced by some other metal in the elemental, state., e.g. CuSO ( aq. ) + Zn( s) → Cu( s) + ZnSO ( aq. ), (b) Non-metal displacement reactions In these reactions,, a metal or a non-metal displaces another non-metal from its, compound., e.g. Mg( s) + 2H O( g) → Mg(OH ) ( aq. ) + H ( g), (iv) Intermolecular redox reactions In such reactions,, oxidation and reduction take place separately in two compounds., e.g., SnCl + 2FeCl → SnCl + 2FeCl, (oxidation), Sn + → Sn +, Fe, , +, , → Fe, , +, , www.aiimsneetshortnotes.com, , (reduction)
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Telegram @neetquestionpaper, Redox Reactions 141, (v) Intramolecular redox reactions In these reactions,, oxidation and reduction take place in a single compound. e.g., −, , 2KClO, , −, , → 2KCl + 3 O, , (vi) Disproportionation reactions These reactions involve, reduction and oxidation of same element of a compound. e.g., +, , Cl + 2 OH, , → ClO + Cl + H O, , This reaction is also known as autoredox reaction., −, , +, , −, , 2H O ( aq ) → 2 H O( l ) + O ( g), , Classification of Redox Reactions, Direct Redox Reactions, Chemical reaction in which oxidation as well as reduction is carried, out simultaneously in the same container, is known as direct redox, reaction. In such reactions, energy is generally liberated in the form of, heat energy., , Indirect Redox Reactions, A reaction in which oxidation and reduction are carried out separately, in two separate half-cells, is known as indirect redox reaction. In such, reactions, energy is generally liberated in the form of electrical energy., , Balancing of Redox Chemical Equations, Every chemical equation must be balanced according to law of, conservation of mass. In a balanced chemical equation, the atoms of, various species involved in the reactants and products must be equal, in number. Redox reaction can be balanced through, (i) Ion electron method, (ii) Oxidation number method., , Ion Electron Method (Half Reaction Method), This method of balancing was developed by Jette and Lamer in 1927., For example, balance the equation, Cu + HNO → Cu(NO ) + NO + H O, It involves the following steps., , Step I Write the redox reaction in ionic form., Cu + H + NO, , → Cu, , + NO + H O, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 142, , Handbook of Chemistry, , Step II Split the redox reaction into its oxidation-half and reduction, half-reaction., oxidation, , Cu → Cu, and, , NO, , +, , Reduction, , → NO, (Removal of O), , Step III Balance atoms of each half-reaction (except H and O) by, using simple multiples., and NO− → NO, Cu → Cu, (Except H and O, all atoms are balanced), , Step IV Balance H and O as, (i) For acidic and neutral solutions Add H O molecule to, the side deficient in oxygen and H + to the side deficient in, hydrogen., and 4H + + NO− → NO + 2H O, Cu → Cu, ↑, ↑, to balance H, , to balance O, , (ii) For alkaline solutions For each excess of oxygen, add one, water molecule to the same side and OH − ion to the other side to, balance H., , Step V Add electrons to the side deficient in electrons., + 2e−, , Cu → Cu, , 3e− + 4H + + NO− → NO + 2H O, , Step VI Equalise the number of electrons in both the reactions by, multiplying a suitable number., [Cu → Cu + + 2e− ] × 3, [NO− + 4H + + 3e− → NO + 2H O] × 2, , Step VII Add the two balanced half reactions and cancel common, terms of opposite sides., 3Cu → 3Cu, , +, , + 6e−, , 2NO− + 8H + + 6e− → 2NO + 4H O, 3Cu + 2NO− + 8H + → 3Cu, , +, , + 2NO + 4H O, , Step VIII Convert the ionic reaction into molecular form by adding, spectator ions., 3Cu + 2NO + 8H + 6NO → 3Cu + 2NO + 6NO, + 4H O, spectator ion, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Redox Reactions 143, or, , 3Cu + 8HNO, , → 3Cu(NO ) + 2NO + 4H O, , (Ions which are present in solution but do not take part in the redox, reaction, are omitted while writing the net ionic equation of a reaction, and are known as spectator ions.), , Oxidation Number Method, For example, balance the equation, Mg + HNO → Mg(NO ) + N O + H O, It involves the following steps., , Step I Write the skeleton equation (if not given), Step II Assign oxidation number of each atom, Reduction, , + 2, , 0, + + −, , Mg, , →, , + HN O, , Mg, , + 5 − 2 + 1− 2, , (NO ) + N O,, , oxidation, , Step III Balance atoms other than H and O in two processes., change in OS = 10 – 2 = 8, , Mg + 2HNO → Mg(NO ) + N O, change in OS = 2 – (0) = 2, , Step IV Equalize the total increase or decrease in oxidation number., 4Mg + 2HNO, , → 4Mg(NO ) + N O, , Step V Balance H and O, 8H + + 4Mg + 2HNO + 8NO− → 4Mg(NO ) + N O + 5H O, 4Mg + 10HNO, , → 4Mg(NO ) + N O + 5H O, , Redox Reactions in Daily Life, Oxidation processes, , It involves in, Corrosion, Bleaching, Antiseptics, Combustion of fuel, , Reduction processes, , It involves in, Photography, Antioxidants, Photosynthesis, Metallurgy, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 12, Electrochemistry, Electrochemistry is that branch of chemistry which deals with the, study of production of electricity from energy released during, spontaneous chemical reactions and the use of electrical energy to, bring about non-spontaneous chemical transformations., , Conductors, Substances that allow electric current to pass through them are known, as conductors. Certain materials called superconductors by definition, have zero resistivity or infinite conductivity. e.g. ceramic materials and, mixed oxides also show superconductivity at temperature as high as, 150 K., , Metallic Conductors or Electronic Conductors, Substances which allow the electric current to pass through them by, the movement of electrons are called metallic conductors, e.g. metals., , Electrolytic Conductors or Electrolytes, Substances which allow the passage of electricity through their fused, state or aqueous solution and undergo chemical decomposition are, called electrolytic conductors, e.g. aqueous solution of acids, bases and, salts., Electrolytes are of two types:, (i) Strong electrolytes The electrolytes which dissociate, completely into ions., (ii) Weak electrolytes The electrolytes which do not ionise, completely in aqueous as well as in molten state., , Cell, Cells are the devices in which interconversion of electrical energy and, chemical energy takes place., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Electrochemistry 145, A cell is made up of various components i.e. electrolytic solution, (already discussed), salt-bridge and electrodes., , Salt-bridge, It is a U-shaped glass tube which contains agar-agar paste with, NH4NO3 , KNO3 or KCl as conducting electrolytes. KCl is not used, when electrode is made of Ag. This salt-bridge is only used in, electrochemical cell., , Electrodes, These are the materials that conduct electricity to or from the cell due, to movement of electrons. It may be taken in any form like wire, rod,, sheet etc., , Types of cell, Cells are of two basic types as discussed below, (i) Electrochemical cell In this cell chemical reaction (redox, reactions) are carried out that result in production of electricity., It is also called voltaic or galvanic cell. One of the important, example of this type of cells is Daniell cell., (ii) Electrolytic cell In this cell electricity is used to produce, non-spontaneous chemical changes. As there occurs, breaking, down of a molecule with the help of electricity, the process is, called electrolysis., , Electrochemical Cell and Electrolytic Cell, Characteristics, , Electrochemical cell, (Galvanic cell), , Electrolytic cell, +–, , V, , –, , +, , +, Salt bridge, , Anode M, Cathode Mn+ +, , 1. Definition, , –, –, –, –, –, , +, +, +, +, , –, , Mn+ + ne–, ne–, , M, , A device used to convert, chemical energy into electrical, energy., , A device used to carry out, non-spontaneous chemical, reactions by electrical energy., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 146, , Handbook of Chemistry, , Characteristics, , Electrochemical cell, (Galvanic cell), , Electrolytic cell, , 2. Assembly, , It is combination of two, half-cells, containing the same, or different electrodes in the, same or different electrolytes., , It is a single cell containing the, same electrodes present in the, same electrolyte., , 3. Nature of, electrodes, , Anode is negative, cathode is, positive., , Anode is positive, cathode is, negative., , 4. Movement of, electrons, , From anode to cathode in, external circuit., , Electrons enter through cathode, and leave by anode., , 5. Spontaneity, , Cell reaction is spontaneous, , Cell reaction is nonspontaneous., , 6. Salt bridge, , Salt bridge is required, , Salt bridge is not required., , A cell of almost constant emf is called standard cell. The most, common is Weston standard cell., General Representation of an Electrochemical Cell, M1( s)| M1n + ( aq ), ||, M 2n + ( aq ) | M 2( s), Anode, oxidation, half-cell, , Salt, bridge, , Cathode, reduction, half-cell, , Cathode, , Anode, , Sign, , Positive due to consumption of Negative due to release of, electrons, electrons, , Reaction, , Reduction, , Oxidation, , Movement of electrons, , Into the cell, , Out of cell, , Other features of the electrochemical cell are, 1. There is no evolution of heat., 2. The solution remains neutral on both sides., 3. The reaction and flow of electrons stops after sometime., , Daniell Cell, An electrochemical cell of zinc and copper metals is known as Daniell, cell. This cell converts the chemical energy liberated during the redox, reaction to electrical energy and has an electrical potential equal to 1.1, V., Zn( s) + Cu2+ ( aq ) → Zn2+ ( aq ) + Cu( s), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Electrochemistry 147, When concentration of Zn2+ and Cu2+ ion has unity (1 mol dm −3 ) such, a device is called galvanic or voltaic cell., It is represented as :, Electron flow, –, Zn anode, , Current, +, , Voltmeter, , ~~ ~~~, , ~~ ~~~, , ~ ~ ~ ~ ~ ~~, , ZnSO4, , Salt, bridge, , Cu cathode, , CuSO4, , Cell representation,, Zn( s)|Zn2+ ( aq )||Cu2+ ( aq )|Cu( s), Zn → Zn2+ + 2e−, , LHS oxidation,, RHS reduction,, , Cu2+ + 2e− → Cu, , Overall reaction, Zn + Cu2+ ( aq ) → Zn2+ ( aq ) + Cu, By convention cathode is represented on the RHS and anode on the, LHS., , Function of salt bridge, 1. It completes the circuit and allows the flow of current., 2. It maintains the electrical neutrality on both sides. Salt-bridge, generally contains solution of strong electrolyte such as, KNO3 , KCl, etc. KCl is preferred because the transport numbers, of K + and Cl− are almost same., , Transport number or transference number The current, flowing through an electrolytic solution is carried by the ions. The, fraction of the current carried by an ion is called its transport number, or transference number. Thus,, current carried by cation, Transport number of cation, n c =, total current, current carried by anion, Transport number of anion, n a =, total current, Evidently n c + n a = 1, , Electrode Potential, When an electrode is in contact with the solution of its ions in a, half-cell, it has a tendency to lose or gain electrons which is known as, electrode potential. It is expressed in volts. It is an intensive property,, i.e. independent of the amount of species in the reaction., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 148, , Handbook of Chemistry, , Oxidation potential The tendency to lose electrons in the above, case is known as oxidation potential. Oxidation potential of a half-cell, is inversely proportional to the concentration of ions in the solution., , Reduction potential The tendency to gain electrons in the above, case is known as reduction potential. According to IUPAC convention,, the reduction potential alone be called as the electrode potential unless, it is specifically mentioned., ° = − Eoxidation, °, Ered, It is not possible to determine the absolute value of electrode potential. For this a, reference electrode [NHE or SHE] is required. The electrode potential is only the, difference of potentials between two electrodes that we can measure by, combining them to give a complete cell., , Standard electrode potential The potential difference developed, between metal electrode and solution of ions of unit molarity (1M) at, 1 atm pressure and 25°C (298 K) temperature is called standard, electrode potential. It is denoted by E°., , Reference Electrode, The electrode of known potential is called reference electrode. It may, be primary reference electrode like hydrogen electrode or secondary, reference electrode like calomel electrode., , Standard hydrogen electrode (SHE), Standard hydrogen electrode (SHE), also, known as normal hydrogen electrode, H2 gas at, 1 bar pressure, (NHE), consists of platinum wire, carrying, Connecting wire, platinum foil coated with finely divided, 1 M HCl solution, platinum black. The wire is sealed into a, Platinum foil, glass tube, placed in beaker containing 1, coated with Pt, M HCl. The hydrogen gas at 1 atm, black, pressure is bubbled through the solution, +, at 298K. Half-cell is Pt H 2 (1 atm)|H (1 M), In SHE, at the surface of plantinum, either of the following reaction, can take place, (Reduction), 2H + ( aq ) + 2e− → H 2( g), H 2( g) → 2H + ( aq ) + 2e−, , (Oxidation), , The electrode potential of SHE has been fixed as zero at all, temperatures., Its main drawbacks are, 1. It is difficult to maintain 1 atm pressure of H 2 gas., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Electrochemistry 149, 2. It is difficult to maintain H + ion concentration 1 M., 3. The platinum electrode is easily poisoned by traces of, impurities., Hence, calomel electrodes are conveniently used as reference, electrodes. It consists of mercury in contact with Hg2Cl2 (calomel) paste, in a solution of KCl., , Electromotive Force (emf) of a Cell, It is the difference between the electrode potentials of two half-cells, and cause flow of current from electrode at higher potential to, electrode at lower potential. It is also the measure of free energy, change. Standard emf of a cell,, ° = Ecathode, °, °, ° − Eleft, ° = Ered, ° + Eoxi, °, Ecell, − Eanode, = Eright, , Emf and Cell Potential, S.No., , Emf, , Cell potential, , 1., , Potential difference between two, electrodes when no current is flowing, in the circuit is called emf., , The potential difference of the two halfcells when electric current flows, through the cells is called cell potential., , 2., , Emf is the maximum voltage which can It is always less than the maximum, be obtained from the cell., voltage obtainable from the cell., , 3., , Emf is measured by a potentiometer., , It is measured by a voltmeter., , Electrochemical Series, It is the arrangement of electrodes in the increasing order of their, standard reduction potentials., , Standard Electrode Potential at 298 K, Reaction (Oxidised form) + ne –, F2 ( g) + 2 e, Co, , 3+, , + e, , −, , −, , H2O2 + 2H + 2e, +, , −, , + 8H + 5e, , Au, , 3+, , + 3e, , Reduced form, , E °/V, , →, , 2F −, , 2.87, , →, , +, , MnO −4, , →, , −, , −, −, , Co, , →, →, →, , 2+, , 2H2O, 2+, , Mn, , + 4H2O, , Au(s), −, , 1.81, 1.78, 1.51, 1.40, , →, , 2Cl, , Cr2O72− + 14H + + 6e −, , →, , 2Cr 3 + + 7H2O, , 1.33, , O2 ( g) + 4H + + 4e −, , →, , 2H2O, , 1.23, , Cl2 ( g) + 2 e, , www.aiimsneetshortnotes.com, , 1.36
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Telegram @neetquestionpaper, Electrochemistry 151, 2. Metals placed below hydrogen in ECS replace hydrogen from dil, acids but metals placed above hydrogen cannot replace, hydrogen from dil acids., Ca + dil. H 2SO4 → CaSO4 + H 2 ↑, possible,, (Ca + 2H + → Ca 2+ + H 2 ), Cu + dil. H 2SO4 → CuSO4 + H 2 ↑, not possible,, (Cu + 2H + → Cu2+ + H 2 ), 3. Oxides of metals placed below hydrogen are not reduced, by H 2 but oxides of iron and metals placed above iron are, reduced by H 2., (a) SnO, PbO, CuO are reduced by H 2., (b) CaO, K 2O are not reduced by H 2., 4. Reducing character increases down the series., 5. Reactivity increases down the series., 6. Determination of emf; emf is the difference of reduction, potentials of two half-cells., Eemf = ERHS − ELHS, If the value of emf is positive, the reaction takes place, spontaneously, otherwise not., 7. Greater the reduction potential of a substance, higher is its, oxidising power. (e.g. F2 > Cl2 > Br2 > I2 ), 8. A negative value of standard reduction potential shows that it, is the site of oxidation., ° ≥ 0.79 will be decomposed by, 9. Oxides of metals having Ered, heating to form O2 and metal., HgO ( s) → Hg ( l ) +, (E°, , Hg 2+ / Hg, , = 0.79 V ), , 1, O2 ( g ), 2, , Nernst Equation, The relationship between the concentration of ions and electrode, potential is given by Nernst equation., M n + + ne− → M, E M n+ / M = E °M n+ / M −, , 2.303 RT, 1, log, nF, [M n + ], , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 152, or, , Handbook of Chemistry, E M n+ / M = E °M n+ / M −, , 0.0591, 1 , log n + (at 298 K), n, M , , For a electrochemical cell,, aA + bB → cC + dD, c, d, ° − 2.303RT log [C ] [D ], Ecell = Ecell, a, nF, [ A] [B]b, Concentration of pure solids and liquids is taken as unity., , Nernst equation and K c, At equilibrium, Ecell = 0, ° = 0.0591 log K c at 298K, Ecell, n, °, ∆G ° = − nFEcell, Here, ∆G ° is the standard Gibbs free energy change., ∆G°, , °, E cell, , Spontaneous, , –ve, , +ve, , Galvanic, , Non-spontaneous, , +ve, , –ve, , Electrolytic, , 0, , 0, , Type of reaction, , Equilibrium, , Type of cell, , Dead battery, , Relationship between free energy change and equilibrium, constant, ∆G ° = − 2.303RT log K c, , Concentration Cells, The cells in which both the electrodes are of the same type but the, electrolytic solution have different concentration, are called, concentration cells., (i) Electrode concentration cells Two hydrogen electrodes of, different pressures are dipped in the same solution of electrolyte,, e.g., Pt, H 2( p1 )|H +|H 2( p2 )Pt, p1 > p2, Ecell =, , 2.303RT, p, log 2, nF, p1, , (ii) Electrolyte concentration cells Electrodes are the same, but electrolyte solutions have different concentrations, e.g., Zn|Zn2+ (C1 )||Zn2+ (C2 )|Zn, C2 > C1, Ecell =, , 2.303RT, 0.0591, C, C, log 2 =, log 2, nF, C1, n, C1, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Electrochemistry 153, Conductance G, It is the ease of flow of electric current through the conductor. It is, reciprocal of resistance (R)., 1, G = , Units ohm −1, mhos or Ω −1, R, , Specific Conductivity (κ), It is the reciprocal of specific resistance., l, 1, l, l, , κ= =, = G × = G × cell constant (G*) = cell constant, a, , a, ρ R. a, Units of κ = Ω −1cm −1 = S cm −1(Ω −1 = S i.e. Siemens), Unit of cell constant is cm −1 or m −1., Specific conductivity decreases on dilution. This is because, concentration of ions per cc decreases upon dilution., , Molar Conductivity Λm, The conductivity of all the ions produced when 1 mole of an electrolyte, is dissolved in V mL of solution is known as molar conductivity., It is related to specific conductance as, κ × 1000, Λm =, M, , where, M = molarity., , Its units are Ω −1cm 2mol−1 or S cm 2 mol−1., , Equivalent Conductivity Λ eq, The conducting power of all the ions produced when 1 g-equivalent of, an electrolyte is dissolved in V mL of solution, is called equivalent, conductivity. It is related to specific conductance as, κ × 1000, Λ eq =, N, where, N = normality., Its units are ohm −1 cm 2 (equiv −1) or mho cm 2 (equiv −1) or S cm 2, (g-equiv −1)., , Debye-Huckel Onsagar equation It gives a relation between, molar conductivity, Λ m at a particular concentration and molar, conductivity, Λ m at infinite dilution., Λ m = Λ0m − A C, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 154, , Handbook of Chemistry, , where, A is a constant. It depends upon the nature of solvent,, temperature and on the type of electrolyte, i.e. the charge on the cation, and anion produced on the dissociation of the electrolyte in the, solution. Thus, NaCl, CaCl2 , MgSO4 are known as 1-1, 2-1 and 2-2, electrolytes respectively. All electrolytes of a particular type have the, same value for A., , Factors Affecting Conductivity, (i) Nature of electrolyte The strong electrolytes like, KNO3 , KCl, NaOH, etc. are completely ionised in aqueous, solution and have high values of conductivity (molar as well as, equivalent). The weak electrolytes are ionised to a lesser extent, in aqueous solution and have lower values of conductivity (molar, as well as equivalent)., (ii) Concentration of the solution The concentrated solutions, of strong electrolytes have significant interionic attractions,, which reduce the speed of ions and lower the value of Λ m and Λ eq ., The dilution decreases such attractions and increases the value, of Λ m and Λ eq . The limiting value, Λ0m or Λ∞m (the molar, conductivity, at, zero, Λ°m, concentration or at infinite, dilution) can be obtained by, KCl (Strong electrolyte), extrapolating the graph., Λm, In case of weak, CH3COOH (Weak electrolyte), electrolytes, the degree of, ionisation increases on, C, dilution which increases, the value of Λ m and Λ eq . The limiting value Λ0m cannot be, obtained by extrapolating the graph. The limiting value, Λ0m,, for weak electrolytes is obtained by Kohlrausch law., (iii) Temperature The increase of temperature decreases, inter-ionic attractions and increases kinetic energy of ions and, their speed. Thus, Λ m and Λ eq increase with temperature., , Kohlrausch’s Law, At infinite dilution, the molar conductivity of an electrolyte is the sum, of the ionic conductivities of the cations and anions, e.g. for Ax By ., Λ0m ( Ax By ) = xΛ0A + + yΛ0B − or Λ0eq = Λ0A + + Λ0B −, (where, Λ0A + and Λ0B − are the limiting molar conductivity of the cation, and anion respectively)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Electrochemistry 155, Applications, (i) Determination of equivalent/molar conductivities of weak, electrolytes at infinite dilution, e.g., Λ∞CH3 COOH = Λ∞CH3 COONa + Λ∞HCl − Λ∞NaCl, Λ∞NH 4 OH = Λ∞NH 4Cl + Λ∞NaOH − Λ∞NaCl, (ii) Determination of degree of dissociation (α ) of an electrolyte at a, given dilution,, molar conductance at concentration ‘ C ’ ΛCm, = ∞, α=, molar conductance at infinite dilution, Λm, The dissociation constant (K) of the weak electrolyte at, concentration C of the solution can be calculated by using the, formula, Cα 2, Kc =, 1−α, where, α is the degree of dissociation of the electrolyte., (iii) Salts like BaSO4 , PbSO4 , AgCl, AgBr and AgI which do not, dissolve to a large extent in water are called sparingly, , soluble salts., The solubility of a sparingly soluble salt can be calculated as, κ × 1000, Λ°m =, solubility ( in mol L–1 ), Solubility (in mol L−1 ) =, , κ × 1000, Λ°m, , Electrolysis, It is the process of decomposition of an electrolyte when electric current, is passed through either its aqueous solution or molten state., (i) In electrolytic cell both oxidation and reduction takes place in, the same cell., (ii) Anode is positively charged and cathode is negatively charged,, in electrolytic cell., (iii) During electrolysis of molten electrolyte, cations are liberated, at cathode, while anions at the anode., (iv) When two or more ions compete at the electrodes, the ion with, higher reduction potential gets liberated at the cathode while, the ion with lower reduction potential at the anode., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 156, , Handbook of Chemistry, For metals to be deposited on the cathode during electrolysis,, the voltage required is almost the same as the standard, electrode potential. However for liberation of gases, some extra, voltage is required than the theoretical value of the standard, electrode potential. The extra voltage thus required is called, over voltage or bubble voltage., , How to Predict the Products of Electrolysis?, When an aqueous solution of an electrolyte is electrolysed, if the cation has higher, reduction potential than water (–0.83 V), cation is liberated at the cathode (e.g. in, the electrolysis of copper and silver salts) otherwise H2 gas is liberated due to, reduction of water (e.g. in the electrolysis of K, Na, Ca salts, etc.) Similarly if anion, has higher oxidation potential than water (– 1.23 V), anion is liberated at anode, (e.g.Br − ) otherwise O2 gas is liberated due to oxidation of water (e.g. in case ofF− ,, aqueous solution of Na2SO 4 as oxidation potential of SO2−, 4 is – 0.2 V)., Discharge potential is defined as the minimum potential that must be applied, across the electrodes to bring about the electrolysis and subsequent discharge of, the ion on the electrode., , Faraday’s Laws of Electrolysis, 1. First law, The amount of the substance deposited or liberated at cathode is, directly proportional to the quantity of electricity passed through an, electrolyte., W ∝I × t= I × t× Z =Q × Z, I = current in amp, t = time in sec,, Q = quantity of charge (coulomb), Z is a constant known as electrochemical equivalent., When I = 1 amp, t = 1 sec and then Q = 1 coulomb, then w = Z ., Thus, electrochemical equivalent is the amount of the substance, deposited or liberated by passing 1A current for 1 sec (i.e. 1 coulomb,, I × t = Q), , 2. Second law, When the same quantity of electricity is passed through different, electrolytes, the amounts of the substance deposited or liberated at the, electrodes are directly proportional to their equivalent weights. Thus,, Mass of A eq. wt. of A, ω1 E1, ZQ E, or, =, =, ⇒ 1 = 1, Mass of B eq. wt. of B, ω 2 E2, Z 2Q E2, Hence, electrochemical equivalent ∝ equivalent weight., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Electrochemistry 157, Batteries, These are source of electrical energy which may have one or more cells, connected in series. For a good quality battery, it should be reasonably, light, compact and its voltage should not vary appreciably during its, use., , Primary Batteries, In the primary batteries, the reaction occurs only once and after use, over a period of time, battery becomes dead and cannot be reused again., (i) Dry cell or Leclanche cell, Anode-Zinc container, Cathode-Graphite rod surrounded by MnO2 powder, Electrolyte-Paste of NH 4Cl + ZnCl2, Cathode reaction,, 2MnO2 ( s) + 2 NH +4 ( aq ) + 2e− → Mn2O3 ( s) + 2NH3 ( g) + H 2O( l ), Anode reaction, Zn( s) → Zn2+ ( aq ) + 2e−, Cell potential 1.25 V to 1.5 V, (ii) Mercury cell, Anode-Zn-Hg amalgam, Cathode-Paste of (HgO + C), Electrolyte-Moist paste of KOH-ZnO, Cathode reaction, HgO( s) + H 2O( l ) + 2e− → Hg( l ) + 2 OH −, Anode reaction,, , Zn (Hg) + 2OH − aq → ZnO( s) + H 2O( l ) + 2e−, , Net reaction,, Zn(Hg) + HgO( s) → ZnO( s) + Hg( l ), Cell potential 1.35 V and remains constant during its life as the net, reaction does not involve any ion in solution whose concentration can, change during its life time., , Secondary Batteries, These cells can be recharged and can be used again and again, e.g., (i) Lead Storage battery, Anode-Spongy lead, Cathode-Grid of lead packed with PbO2, Electrolyte-38% H 2SO4 by mass, Anode reaction,, Pb( s) + SO24− ( aq ) → PbSO4 ( s) + 2e−, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 13, Chemical, Kinetics, The branch of chemistry, which deals with the rate of chemical, reactions, the factors affecting the rate of reactions and the mechanism, of the reaction, is called chemical kinetics., , Chemical Reactions on the Basis of, Rate of Reaction, (i) Fast/Instantaneous reactions Chemical reactions which, complete in less than 1ps (10−12 s) time, are known as fast, reaction. It is practically impossible to measure the speed of such, reactions, e.g. ionic reactions, organic substitution reactions., (ii) Slow reactions Chemical reactions which completes in a long, time from some minutes to some years are called slow reactions., e.g. rusting of iron, transformation of diamond etc., (iii) Moderately slow reactions Chemical reactions which are, intermediate between slow and fast reactions are called, moderately slow reactions., , Rate of Reaction, Rate of a chemical reaction is the change in the concentration of any, one of the reactants or products per unit time. It is expressed in, mol L−1 s −1 or Ms −1 or atm time −1 units., Rate of reaction, decrease / increase in the concentration of reactant / product, =, time taken, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Kinetics 161, This rate of reaction is known as average rate of reaction (rav ). (rav, can be calculated by dividing the concentration difference by the time, interval)., For a chemical reaction,, aA + bB → cC + dD, 1 ∆ [ A], 1 ∆ [B], Average rate of reaction (rav ) = −, =−, a ∆t, b ∆t, 1 ∆ [C ] 1 ∆ [D ], =, =, c ∆t, d ∆t, ∆ [ A], Rate of disappearance of A = −, ∆t, ∆ [B], Rate of disappearance of B = −, ∆t, ∆ [C ], Rate of appearance of C =, ∆t, ∆ [D ], Rate of appearance of D =, ∆t, , Instantaneous Rate of Reaction, Rate of a chemical reaction at a particular moment of time, is known, as instantaneous rate of reaction., For reaction,, R → P, ∆ [R ], ∆ [P ], or, as ∆ → d, rinst = −, ∆t, ∆t, d [R ] d [P ], ⇒, rinst = −, =, dt, dt, , Methods for measuring reaction rate (i) pH measurement,, (ii) change in optical activity, (iii) change in pressure, (iv) change in, conductance., Slowest step of a reaction was called rate determining step by van’t Hoff., , Factors Affecting Rate of Reaction, (i), (ii), (iii), (iv), (v), , Nature and concentration of reactant, Temperature, Surface area of reactant, Radiations and catalyst, Pressure of gas, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 162, , Handbook of Chemistry, , Rate Law Expressions, It is defined as a mathematical expression in which reaction rate is, given in terms of molar concentration of reactants with each term, raised to some power., For a chemical reaction,, aA + bB → Products, According to the law of mass action,, Rate ∝ [ A]a [B]b = k[ A]a [B]b, But experimentally, it is observed that the rate of reaction is found to, depend upon ‘α’ concentration terms of A and ‘β’ concentration terms of, B. Then,, Rate ∝ [ A]α [B]β = k [ A]α [B]β, where, [ A] and [B] molar concentrations of A and B respectively and, k is the velocity constant or rate constant. The above expression is, known as rate law., , Rate Constant or Specific Reaction Rate, In the above expression, k is called rate constant or velocity constant., Rate constant may be defined as the specific rate of reaction when the, molar concentrations of the reactants is taken to be unity, i.e., Rate = k, if [ A] = [B] = 1, Units of rate constant or specific reaction rate for a nth order reaction, is given as, 1, 1, k=, ×, Time [Conc. ]n − 1, , Characteristics of rate constant, (i) Greater the value of rate constant, faster is the reaction., (2) Each reaction has a particular value of rate constant at a, particular temperature., (iii) The value of rate constant for the same reaction changes with, temperature., (iv) The value of rate constant for a reaction doesn’t depend upon, the concentration of the reactants., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Kinetics 163, Order and Molecularity of a Reaction, Find of plain order and molecularity separately given comparison, differences, Order of reaction, 1. Order of reaction is the sum of the, concentration terms on which rate of, reaction actually depends., Or, , Molecularity of reaction, Molecularity of a reaction is the number of, atoms, ions or molecules that must collide, with one another to form products in a, chemical reaction., , It is also defined as sum of the, exponents of the molar concentrations in, the rate law equation., 2. It can be fractional as well as zero., , It cannot be zero or fractional., , 3. It is an experimentally determined term., , It is theoretically determined term., , 4. Order of reaction is applicable to, Molecularity is applicable only to, elementary as well as complex reactions. elementary reactions., 5. Negative order reaction is also possible,, e.g. 2O 3 → 3O2 Rate = k[O 3]2 [O2 ] –1, , Molecularity can never be negative., , Order w.r.t O2 is –1., 6. Types of reactions depending upon, orders, , Types of reactions depending upon, molecularity, (i) Unimolecular reaction,, , (i) Zero order reaction, hv, (I) H2 ( g) + Cl2 ( g) → 2HCl, , N2O 4 ( g) → 2NO2 ( g), , Pt, (II) 2NH 3 → N2 + 3H2, (ii) First order reaction, (I) H2O2 → H2O +, , (ii) Bimolecular reactions,, 1, O2, 2, , (II) Radioactive disintegration, , 2HI( g) → H2 ( g) + I2 ( g), (iii) Trimolecular reactions,, 2NO ( g) + O2 ( g), , → 2NO2 ( g), , (III) Inversion of cane sugar., (iii) Second order reaction, (I) 2HI → H2 + I2, (II) Alkaline hydrolysis of ester, (saponification), (iv) Third order reaction, 2NO + O2 → 2NO2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 164, , Handbook of Chemistry, , Integrated Rate Equation for, Zero Order Reactions, Zero order reaction means that the rate of the reaction is proportional, to zero power of the concentration of reactants., 1, k0 = {[ A]0 − [ A]}, t, [where, [ A]0 is initial concentration and [ A] is final concentration], [ A]0, t = t1/ 2 when [ A] =, 2, [ A]0, Half-life period, t1/ 2 =, 2k0, Units of rate constant, k0 = mol L −1s −1 = unit of rate, For zero order gaseous reactions,, 1, k0 = [ p0 − p] and, t, , t1/ 2 =, , p0, 2k0, , Integrated Rate Equation for, First Order Reactions, First order reaction means that the rate of the reaction is proportional, to the first power of the concentration of the reactnat., 2.303, [ A]0, −k t, ⇒ [ A] = [ A]0 e 1, k1 =, log, [ A], t, Half-life period (t1/2 ) It is concentration independent term., [ A]0, t = t1/ 2 , [ A] =, 2, [ A], 0.693, Amount of a substance after n half-lives = n 0 ⇒ t1/ 2 =, k1, 2, For such reactions, t75% = 2 × t50% ⇒ t99.9% = 10 × t1/ 2, All radioactive changes follow the first order kinetics., Integrated rate equation for first order gaseous reactions,, A( g) → B ( g) + C( g), Initial pressure (t = 0), Pressure at t, , p 0 atm, [ p0 − p ] atm, , k1 =, , 0, 0, p atm p atm, , p0, 2.303, log, t, ( 2 p0 − pt ), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Kinetics 165, For first order chemical reactions,, H+, , CH3COOC2H5 + H 2O → CH3COOH + C2H5OH, k1 =, , V − V0 , 2.303, log ∞, , t, V∞ − Vt , , (V 0 , V t and V ∞ are the volumes of NaOH solution used for the titration, of same volume of the reaction mixture after times 0, t and ∞, respectively.), , Pseudo First Order Reaction, Chemical reactions which appear to be of higher order but actually are, of the lower order are called pseudo first order reactions. In case of, pseudo first order reaction, chemical reaction between two substances, takes place and one of the reactant is present in excess, e.g. hydrolysis, of ester., CH3COOC2H5 + H 2O → CH3COOH + C2H5OH, So, in this reaction,, Rate = k [CH3COOC2H5 ], For chemical reaction,, H+, , C12H 22O11 + H 2O → C6H12O6 + C6H12O6, glucose, , k=, , fructose, , r − r , 2.303, log 0 ∞ , t, rt − r∞ , , [r0 , rt and r∞ are the polarimetric readings at t = 0, t and ∞, respectively.], , Methods to Determine Order of Reaction, (i) Graphical method In this method, rate of reaction is plotted, against the concentration., , Rate, , Rate, , [A], Zero order, , Rate, , [A], First order, , [A]2, Second order, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 166, , Handbook of Chemistry, , (ii) Initial rate method In this method, the order of a reaction, is determined by varying the concentration of one of the, reactants while others are kept constant., (iii) Integrated rate law method In this method out of, different integrated rate equation which gives the most, constant value for the rate constant corresponds to a specific, order of reaction., (iv) Half-life period ( t1/ 2 ) method In general half-life period, ( t1/ 2 ) of a reaction of nth order is related to initial concentration, of the reactant as, 1, t1/ 2 ∝, [ A]n0 − 1, , t1/2, , t1/2, , [A]0, Zero order, , t1/2, , [A]0, First order, , 1/[A]0, Second order, , This method is employed only when the rate law involved only, one concentration term., (v) Ostwald’s isolation method This method is employed in, determining the order of complicated reactions by isolating one, of the reactants so far as its influence on the reaction rate is, concerned., , Temperature Dependence of Rate of a Reaction, For every 10°C rise in temperature, the rate of reaction becomes, double, but only 16% collisions increases. It can be explained by, Arrhenius equation., Temperature coefficient is the ratio of rate constant of a reaction at two, temperature differing by 10. Temperature selected are usually 298 K, and 308 K., kt + 10, Temperature coefficient =, ≈ 2 to 3, kt, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Kinetics 167, Arrhenius Equation, Arrhenius equation is a mathematical expression to give a quantitative, relationship between rate constant and temperature, and the, expression is, Intercept = log10 A, k = Ae− E a / RT, Ea, E, Slope = –, or, ln k = ln A − a, 2.303R, RT, log10 k, Ea, or, log10 k = log10 A −, 2.303RT, 1/T, , where, A = frequency or Arrhenius factor. It is also called, pre-exponential factor, R = gas constant, Ea = activation energy, , Activated Complex (or Transition State), Activated complex, , ET, Energy, , Activated complex is the highest, energy unstable intermediate between, the reactants and products and gets, decomposed immediately (having very, short life), to give the products. In this, state, bonds of reactant are not, completely broken while the bonds of, products are not completely formed., , Ea, ER, EP, Reaction coordinates, , Threshold energy ( ET ), , The minimum amount of energy which, the reactant must possess in order to convert into products is known as, threshold energy., , Activation energy ( Ea ) The additional amount of energy, required, by the reactant so that their energy becomes equal to the threshold, value is known as activation energy., ⇒, Ea = ET − ER, Lower the activation energy, faster is the reaction., Different reactions have different rates because their activation, energies are different. Larger the value of Ea , smaller the value of rate, constant and greater is the effect of a given temperature rise on K., , Important points about Arrhenius equation, (i) If k2 and k1 are rate constant at temperature T2 and T1 then, T2 − T1 , k, Ea, log 2 =, , , k1 2.303 R T1T2 , , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 168, , Handbook of Chemistry, , (ii) Fraction of molecules with energy equal to or greater than the, activation energy is called Boltzmann factor and is given by, − Ea, n, = e− E a / RT and loge x =, x=, 2.303 RT, N, (iii) Ea is constant for a particular reaction., (iv) Ea doesn’t depend on temperature, volume, pressure, etc., but, gets affected by catalyst., In the Arrhenius equation, when T → ∞ then k = A e0 = A when, Ea = 0, k = A and the rate of reaction becomes independent of, temperature., , Role of Catalyst in a Chemical Reaction, , Potential energy, , A catalyst is a chemical substance which alters the rate of a reaction, without itself undergoing any permanent chemical change., In the chemical reactions, catalyst provides an alternate pathway or, reaction mechanism by reducing the activation energy between, reactants and products and hence, lowering the potential energy, barrier as shown., , Reaction, path with, catalyst, , Reaction path without catalyst, Energy of activation, without catalyst, Energy of activation, with catalyst, Products, , Reaction coordinate, , In the presence of catalyst, activation energy decreases and hence,, kP, = e(E a − EP )/ RT = e∆E/RT, ka, where, P denotes presence of catalyst and a denotes absence of catalyst., , Theory of Reaction Rates, Collision Theory, According to this theory, the reactant molecules are assumed to be, hard spheres and the reaction is postulated to occur, when molecules, collide with each other., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemical Kinetics 169, The number of collisions between the reacting molecules taking place, per second per unit volume is known as collision frequency ( Z AB )., But only those collisions in which the colliding species are associated, with certain minimum amount of energy and collide in proper, orientation result in the product formation, such collisions are called, fruitful collisions or effective collision., dv, Here, rate = −, = collision frequency × fraction of effective collision, dt, = Z AB × f = Z AB × e− E a / RT, where, Z AB represents the collision frequency of reactants, A and B, e− E a / RT represents the fraction of molecules with energies equal to or, greater than Ea ., So, to account for effective collisions, another factor, P called the, probability or steric factor is introduced., rate = PZ AB e− E a / RT, , So,, , The Activated Complex Theory or, Transition State Theory, Reactants, , º, , Activated complex → Products, , This theory is based on the fact that bond cleavage and bond, formation, involved in a chemical reaction, must occur simultaneously., Hence, the reactants are not converted directly into the products., There is an energy barrier or activated complex [intermediate product, with partially formed bond] between the reactants and products. The, reactants must cross this energy barrier before converting into, products. The height of the barrier determines the threshold energy., , Photochemical Reactions, Chemical reactions, that occur on exposure to visible radiation are, called photochemical reactions., (i) The rate of a photochemical reactions is affected by the, intensity of light., (ii) Temperature has little effect on photochemical reactions., Quantum yield or quantum efficiency of a photochemical reaction,, number of reactant molecules reacting in a given time, φ=, number of photons (quanta) of light absorbed in the same time, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 14, Surface, Chemistry, Surface chemistry is the branch of chemistry which deals with the, phenomenon that occurs on the surfaces or interfaces, such, phenomenon includes corrosion, catalysis, crystallisation, etc., , Adsorption, The phenomena of accumulation of a substance at the surface of other, substance rather than in its bulk is called adsorption., Due to unbalanced attractive forces, accumulation of molecular species, at the surface rather than in the bulk of a solid or liquid takes place., The molecular species accumulates at the surface is termed as, adsorbate and the material on the surface of which the adsorption, takes place is called adsorbent, e.g., (i) O2 , H 2 , Cl2 , NH3 gases are adsorbed on the surface of charcoal., (ii) Silica gels adsorb water molecules from air., Charcoal, silica gel, metals such as Ni, Cu, Ag, Pt and colloids are some, adsorbents., , Causes of Adsorption, In case of solids or liquids the particles present in their bulk are, surrounded by same kind of species (atoms, molecules etc.) from all the, sides. Thus, all are surrounded by the same environment. But this fact, is not true for the particles present at their surface. These particles are, not surrounded by species (atoms, molecules etc.) of same kind from all, the sides and hence, they possess some unbalanced or residual, attractive forces. These forces are responsible for attracting particles of, another substance at its surface of solids or liquids., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Surface Chemistry 171, Important Characteristics of Adsorption, 1. It is specific and selective in nature., 2. Adsorption is spontaneous process, therefore change in free, energy ( ∆G ) is negative., ∆G = ∆H − T∆S,, For the negative value of ∆G, in a system, in which randomness, decreases, ∆H must be negative. Hence, adsorption is always, exothermic., Adsorption of gases over the surface of metal is called, occlusion., , Desorption, It is a process of removing an adsorbed substance from a surface on, which it is adsorbed, is known as desorption., , Distinction between Adsorption and Absorption, Adsorption, , Absorption, , 1. It involves unequal distribution of the, molecular species in bulk and at the, surface., , It involves uniform distribution of the, molecular species throughout the bulk., , 2. It is a surface phenomenon., , It occurs throughout the body of, material., , 3. It is rapid in the beginning., , It occurs at a uniform rate., , Sorption, It is a process in which both adsorption and absorption take place, simultaneously., , Positive and Negative Adsorption, When the concentration of the adsorbate is more on the surface of the, adsorbent than in the bulk, it is called positive adsorption., On the other hand, if the concentration of the adsorbate is less relative, to its concentration in the bulk, it is called negative adsorption, e.g., when a dilute solution of KCl is shaken with blood charcoal, it shows, negative adsorption., Find define Physisorption and Chemisorption then diffrences are to be, given, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 172, , Handbook of Chemistry, , Distinction between Physisorption and Chemisorption, Physisorption, , Chemisorption, , 1., , It arises when the adsorbate molecules It arises when the adsorbate molecules, accumulate on the surface of adsorbent on accumulate on the surface of adsorbent on, account of weak van der Waals’ forces. account of strong chemical bonds., , 2., , It occurs at low temperature., , 3., , Heat of adsorption is low and it is in the Heat of adsorption is high and it is in the, range of 20-40 kJ/mol., range of 80-240 kJ/mol., , 4., , It is reversible process., , 5., , Multilayer adsorption and thus, adsorbed Monolayer adsorption. Thus, adsorbed, layer is several molecules thick., layer is only unimolecular in thickness., , It occurs at high temperature., , It is an irreversible process., , Factors Affecting Adsorption, (a) Nature of adsorbent Same gas may be adsorbed to different, extents on different adsorbents., (b) Surface area of the adsorbent Greater the surface area,, greater is the extent of adsorption., (c) Nature of the gas being adsorbed Greater is the critical, temperature of a gas, greater are the van der Waals’ forces of, attraction and thus, greater is the adsorption., Gas, , H2, , N2, , CO, , CH 4, , CO2, , HCl, , NH 3, , SO2, , Critical temp. (K), , 33, , 126, , 134, , 190, , 304, , 324, , 406, , 430, , (d) Temperature Adsorption is an exothermic process involving, the equilibrium :, Gas (adsorbate) + Solid (adsorbent), Gas adsorbed on solid +, Heat, Applying Le-Chatelier principle, increase of temperature, decreases the adsorption and vice-versa., (e) Pressure Adsorption increases with pressure at constant, temperature. The effect is large if temperature is kept constant, at low value., (f) Activation of the solid adsorbent Activation means, increasing the adsorbing power of the solid adsorbent. This can, be done by subdividing the solid adsorbent or by removing the, gases already adsorbed by passing superheated steam., , º, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Surface Chemistry 173, Adsorption Isotherms, It is the plot of the mass of gas adsorbed per gram of adsorbent ( x / m ), versus equilibrium pressure at constant temperature., , Freundlich Adsorption Isotherm, It gave an empirical relationship between the quantity of gas adsorbed, by unit mass of solid adsorbent and pressure at a particular, temperature. It can be expressed by the equation,, x, …(i), = kp1/ n ( n > 1), m, Where, x is the mass of the gas adsorbed on, mass m of the adsorbent at pressure p, k and, n are constants which depend on the nature, of the adsorbent and the gas at a particular, temperature., x, At low pressure, n = 1, i.e., = kp, m, x, At high pressure, n > 1, i.e., =k, m, (independent of p), At moderate pressure,, x, = kp1/ n, m, 1, where, = 0 to 1., n, , 195 K, 244 K, x, m, , 273 K, , p, , Taking logarithm of Eq. (i), log, Plot of log, , 1, x, = log k + log p, m, n, , x, vs log p is a straight line with, m, , 1, and intercept on y-axis = log k., n, 1, can have values between 0, The factor, n, and 1 (Probable range 0.1 to 00.5)., slope, , log, , 1, Slope = n, , x, m, , log k (intercept), , www.aiimsneetshortnotes.com, , log p
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Telegram @neetquestionpaper, 174, , Handbook of Chemistry, , Freundlich Adsorption Equation for Solutions, x, = kC1/ n, m, where, C is the equilibrium concentration. On taking logarithm of the, above equation, we have, 1, x, = log k + log C, log, m, n, , Langmuir Adsorption Isotherm, According to Langmuir, the degree of adsoprtion is directly, proportional to θ, i.e. the fraction of surface area occupied., x, α θ = k′ θ, m, kp, As,, θ=, 1 + kp, x, k′⋅ kp, =, m 1 + kp, , ∴, , 1, 1 + kp, =, x/ m kk′ . p, Multiply by P on both sides, p, 1, p, =, +, x / m kk′ k′, p, is plotted against p, it will give a straight line, If, x/ m, B, p, (x/m), A, , θ, , p, , At very high pressure,, , 1 + kp ≈ kp, x, k′⋅kp, =, = constant ( k′ ), m, kp, , At low pressure,, , 1 + kp ≈ 1, x, = k′⋅ kp, m, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Surface Chemistry 175, Adsorption Isobars, x, vs temperature t at constant pressure. For, m, physical and chemical adsorption, they are shown below., , These are plots of, , x, m, , x, m, , p = constant, , t, (a) Physical adsorption, , p = constant, , t, (b) Chemical adsorption, , Adsorption Isostere, These are the plot of temperature versus pressure for a given amount, of adsorption., , T, , p, , Applications of Adsorption, (i) For production of high vacuum., (ii) Gas masks containing activated charcoal are used for breathing, in coalmines. They adsorb poisonous gases., (iii) Silica and aluminium gels are used as adsorbents for, controlling humidity., (iv) Removal of colouring matter from solutions., (v) It is used in heterogeneous catalysis., (vi) In separation of inert gas., (vii) As adsorption indicators., (viii) In chromatographic analysis., (ix) Qualitative analysis, e.g. lake test for Al3 + ., (x) In curing diseses, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 176, , Handbook of Chemistry, , Catalysis, Catalyst is a chemical substance which can change the rate of reaction, without being used up in that reaction and this process is known as, catalysis., Some examples of catalysis are given below, S.No., , Process, , Catalyst, , 1., , Haber’s process of NH 3, , Finely divided Fe (Mo acts as, promoter), , 2., , Ostwald’s process for manufacture of, nitric acid, , Platinised asbestos, , 3., , Contact process for H2SO 4, , Platinised asbestos or V2O 5, , 4., , Lead chamber process for H2SO 4, , Nitric oxide, , 5., , Decon’s process, , CuCl2, , A catalyst may be positive (i.e. increases rate of reaction) or negative, (i.e. decreases rate of reaction)., , Characteristics of Catalysts, 1. The catalyst remains unchanged in mass and chemical composition., 2. In case of reversible reactions, the catalyst does not influence, the composition of reaction mixture at equilibrium. It only helps, to attain the equilibrium quickly., 3. A catalyst does not alter Gibb’s energy (∆G) of a reaction., 4. A catalyst catalyses the spontaneous reactions but does not, catalyse non-spontaneous reactions., , Promoters and Poisons, Promoters are chemical substances that enhance the activity of a, catalyst while poisons decreases the activity of a catalyst., , Types of Catalysis, (a) Homogeneous catalysis In this catalysis, the catalyst and, reactants are in the same physical state [phase], e.g., NO ( g ), , 2 SO2( g) + O2( g) → 2 SO3 ( g), (b) Heterogeneous catalysis In heterogeneous catalysis, the, catalyst is present in a different phase than that of reactants, e.g., Fe ( s), , N 2( g) + 3H 2( g) → 2NH3 ( g), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Surface Chemistry 177, (c) Autocatalysis When one of the product of a reaction acts as, catalyst, the process is called autocatalysis., , Adsorption Theory of Heterogeneous Catalysis, The mechanism involves five steps :, (i) Diffusion of reactants to the surface of the catalyst., (ii) Adsorption of reactant molecules on the surface of the catalyst., (iii) Occurrence of chemical reaction on the catalyst’s surface, through formation of an intermediate., (iv) Desorption of reaction products from the catalyst surface., (v) Diffusion of reaction products away from the catalyst’s surface., O, , O, , O, +A+B, , O, , O, , O, , Reactant, molecules, , Adsorption of, , O, , O, , O, , A, , reacting molecules, , O, , O, , O, , B, , Catalyst, , O, , O, , Intermediate, formation, , O, + A–B, , O, , O, , O, , product, , Desorption of, , O, , O, , O, , A, , product molecules, , O, , O, , O, , B, , Catalyst, , Important Features of Solid Catalysts, (i) Activity The activity of a catalyst depends upon the strength, of chemisorption to a large extent. The adsorption should be, reasonably strong but not so strong that they become immobile, and no space is available for other reactants to get adsorbed., (ii) Selectivity The selectivity of a catalyst is its ability to direct a, reaction to yield a particular product, e.g. starting with H 2 and, CO using different catalysts, we get different products., Ni, , CO ( g) + 3H 2( g) → CH 4( g) + H 2O ( g), Cu, ZnO- Cr2O3, , CO ( g) + 2H 2( g) → CH3OH ( g), Cu, , CO ( g) + H 2( g) → HCHO ( g), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 178, , Handbook of Chemistry, , Shape-selective catalysis The catalytic reaction that depends upon the, pore structure of the catalyst and the size of the reactant and product molecules is, called shape-selective catalysis. Cracking/isomerisation of hydrocarbons in the, presence of zeolites is an example of shape-selective catalysis., An important zeolite catalyst used in the petroleum industry is ZSM-5. It converts, alcohols directly into gasoline., , Enzyme Catalysis, Enzymes are complex nitrogenous organic compounds which are, produced by living plants and animals. They are actually protein, molecules of high molecular mass and form colloidal solutions in water., The enzymes are also known as biochemical catalysts and the, phenomenon is known as biochemical catalysis., , Mechanism of Enzyme Catalysis, E + S → ES, , Step I, , ES → E + P, , Step II, Active site, , E, , +, , S, , Enzyme, (catalyst), , Substrate, (reactants), , S, , E, , E, , Enzyme substrate, complex, , +, , Enzyme, , Products, , Mechanism of enzyme catalysed reaction, , Some examples of enzyme catalysed reactions are:, Invertase, , (i) C12H 22O11 + H 2O → C6H12O6 + C6H12O6, Sucrose, , Glucose, , Fructose, , Zymase, , (ii) C6H12O6 → 2C2H5OH + 2CO2, Glucose, , Ethanol, Diastase, , Maltase, , (iii) n(C6H10O5 )n + nH 2O → nC12H 22O11 → Glucose, Starch, , Maltose, , + H 2O, , Urease, , (iv) NH 2CONH 2 + H 2O → 2NH3 + CO2, Urea, , (Source of invertase, zymase and maltase is yeast and that of, diastase is malt. Soyabean is the source of urease.), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Surface Chemistry 179, (v) In stomach, the pepsin enzyme converts proteins into peptides, while in intestine, the pancreatic trypsin converts proteins into, amino acids by hydrolysis., (vi) Lactobacilli is used to convert milk into curd., , Characteristics of Enzyme Catalysis, (i) High efficiency One molecule of an enzyme may transform, one million molecules of reactant per minute., (ii) Highly specific nature Each enzyme catalyst cannot, catalyse more than one reaction., (iii) Optimum temperature Enzyme catalyst gives higher, yield at optimum temperature, i.e. at 298-310 K. Human body, temperature, i.e. at being 310 K is suited for enzyme catalysed, reactions., (iv) Optimum pH The rate of an enzyme catalysed reaction is, maximum at optimum pH range 5 to 7., (v) Activators Activators like ions such as Na + , Ca 2+ , Mn2+ help, in the activation of enzymes which cannot act on their own, strength., (vi) Co-enzyme Co-enzymes are the substances having nature, similar to the enzyme and their presence increases the enzyme, activity. Mostly vitamins act as co-enzymes., (vii) Effect of inhibitors Inhibitors slow down the rate of, enzymatic reaction. The use of many drugs is based on enzyme, inhibition action of those drugs in the body., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 15, Colloidal State, A colloid is a heterogeneous system in which one substance is, dispersed (dispersed phase) as very fine particles in another substance, called dispersion medium. The study of the colloidal state of matter, was started by Thomas Graham (1861)., , Comparison of True Solution, Colloidal, Solution and Suspension, True solution, (i) Particle size < 10 Å, (1 nm), , Colloidal solution, 10 Å – 1000 Å, (1 nm – 100 nm), , Suspension, > 1000 Å (100 nm), , (ii) Pass through filter paper as Pass through filter paper, well as animal membrane. but not through animal, membrane., , Pass through neither of the, two., , (iii) Do not settle., , Do not settle., , Settle on standing., , (iv) Particles are invisible., , Particles scatter light., , Particles are visible., , (v) Diffuse quickly., , Diffuse slowly., , Do not diffuse., , (vi) Clear and transparent., , Translucent., , Opaque., , Classification of Colloids, (A) Types of colloids based on physical state of dispersed, , phase and dispersion medium, Dispersed, phase, , Dispersion, medium, , Type of, colloid, , Solid, , Solid, , Solid sol, , Coloured glasses and gem stones., , Solid, , Liquid, , Sol, , Paints, cell fluids, ink, gold sol, proteins., , Solid, , Gas, , Aerosol, , Smoke, dust, , Liquid, , Solid, , Gel, , Cheese, butter, jellies, boot polish., , Examples, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Colloidal State 181, Dispersed, phase, , Dispersion, medium, , Type of, colloid, , Liquid, , Liquid, , Emulsion, , Milk, hair cream., , Liquid, , Gas, , Aerosol, , Fog, mist, cloud, insecticide sprays., , Gas, , Solid, , Solid sol, , Pumice stone, foam rubber., , Gas, , Liquid, , Foam, , Froth, whipped cream, soap-suds., , Examples, , Depending on the nature of dispersion medium, the colloids can be, named as hydrosols or aquasols (for water), alcosols (for alcohols),, benzosols (for benzene) and aerosols (for gases)., (B) Types of colloids based on nature of interaction between, , dispersed phase and dispersion medium, S., No., (i), , Lyophilic, colloid, , Property, Formation, , Formed easily by direct mixing, the two phases., , Lyophobic, colloid, Special chemical methods are, required., , (ii) Affinity for the Have affinity for the dispersion, medium, medium., , Do not have any affinity for the, dispersion medium., , (iii) Stability, , Highly stable due to the layers, of dispersion medium., , Less stable and are easily, coagulated due to the presence, of charge., , (iv) Reversibility, , Reversible., , Irreversible., , (v) Electrophoresis May or may not show., , Show., , (vi) Coagulation, , Small amounts of electrolyte, have no effect., , Small amounts of electrolyte, may coagulate the sol., , (vii) Examples, , Sol of gum, gelatin, starch,, rubber, etc., , Sol of metals and their, sulphides., , (C) Types of colloids based on type of particles of the, , dispersed phase, Macromolecular colloids, , Multimolecular colloids, , Associated colloids, , The colloids in which the, dispersed phase particles are, large molecules (usually, polymer) having dimensions, comparable to those of, colloidal particles are called, macromolecular colloids, e.g., starch, protein in water,, synthetic rubber, polystyrene., , A colloid in which large, number of atoms or smaller, molecules of a substance, aggregate together to form, species having size in the, colloidal range (1-1000 nm), is called multimolecular, colloid, e.g. sulphur sol, consists of particles containing, a thousand or more of S 8, sulphur molecules., , These are the chemical, substances which behave as, normal strong electrolytes at, low concentration but as, colloids at higher, concentration and are called, micelles. Micelles may, contain as many as 100 or, more particles. These, colloids have both lyophobic, and lyophilic parts., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 182, , Handbook of Chemistry, , Kraft temperature (Tk ) It is the minimum temperature of the, colloidal system above which the formation of micelles takes place., Critical micelle concentration (CMC) The minimum concentration, of the surfactant at which the formation of a micelle takes place is, called critical micelle concentration, e.g. CMC for soaps is ~ 10−4 to 10−3, mol L −1., , Preparation of Colloids, Lyophilic sols can be easily prepared by shaking the lyophilic, material with the dispersion medium, e.g. preparation of starch sol., Lyophobic sols can be prepared by following methods., , Condensation/Aggregation Method, These methods involve the joining of a large number of small particles, to form particles of colloidal size. Some methods are, (i) Oxidation, Br2 + H 2S → 2 HBr +, S, Colloidal sol, , SO2 + 2 H 2S → 3 S( sol) + 2H 2O, (ii) Reduction, 2AuCl3 + 3 SnCl2 → 2Au( sol) + 3 SnCl4, Gold sol or purple, of cassius, , (iii) Hydrolysis, FeCl3 + 3H 2O → Fe(OH)3 + 3HCl, Sol, , (iv) Double decomposition, As2O3 + 3H 2S → As2S3 + 3H 2O, Sol, , Dispersion/Disintegration Method, In this method, bigger particles are broken down to colloidal size. Some, methods are, (i) Mechanical disintegration In this method, suspension is, grind well in a colloid mill consisting of two steel discs which, rotate in opposite directions at very high speed. The materials to, be converted into colloidal sol is fed in between the two discs in, the form of a wet slurry. The particles get broken to colloidal, dimensions by the operating shearing force., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Colloidal State 183, (ii) Electrical disintegration/Bredig’s Arc method This process, involves dispersion as well as condensation. In this method,, electric arc is struck between electrodes of the metal (gold, silver,, platinum, etc) immersed in the dispersion medium. The intense, heat produced vapourises the metal which then condenses to, form particles of colloidal size., (iii) Peptization This method is used to convert fresh precipitate, into colloidal state by shaking with dispersion medium in the, presence of small amount of electrolyte. The electrolyte used, (having an ion in common with the material to be dispersed) this, purpose is called peptizing agent., , Purification of Colloidal Solutions, The process used for reducing the amount of impurities to a requisite, minimum of a colloid, is known as purification of colloidal solutions., (i) Dialysis It is based upon the principle that impurities of true, solutions can pass through the parchment paper or cellophane, membrane while, colloidal particles cannot., In this process, dissolved substances are removed from the, colloidal solution by means of diffusion through a suitable, membrane., Dialysing membrane, Water + crystalloid, Sol particle, , Water, Crystalloid, , (ii) Electrodialysis The process of dialysis is quite slow. So, if the, dissolved substance in the impure colloidal solution is only the, electrolyte, then electric field is applied. The colloidal solution is, placed in a bag of suitable membrane, while pure water is taken, outside., (iii) Ultrafiltration Ultrafiltration is the process of separation of, colloidal particles from the solvent and soluble solutes present in, the colloidal solution by specially prepared filters, called, ultrafilters., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 184, , Handbook of Chemistry, , Properties of Colloidal Solution, General Properties, (i) Colligative property Due to high average molecular masses, of colloidal particles, mole fraction of the dispersed phase is very, low. So, the values of colligative properties are very small., (ii) Colour The colour of colloidal solution depends on the, wavelength of light scattered by the dispersed particles. The, wavelength of light further depends on the size and nature of the, particles. The colour of colloidal particles also depends on the, manner in which the observer receives the light., (iii) Visibility The particles of colloidal solution are not visible to, naked eye or under ordinary microscope., (iv) Filterability Colloidal particles can pass through ordinary, filter paper, but can’t pass through parchment paper or animal, membrane., , Optical and Mechanical Properties, (i) Brownian movement Sol particles move in a random, zig-zag manner due to the unequal impacts of the particles of, dispersion medium on the particles of colloidal sol. It is called, Brownian motion. Smaller the size of the particle and lesser the, viscosity of the solution, faster is the motion., (ii) Tyndall effect If a colloidal solution is placed in dark and a, beam of light is passed through the sol, the path of light becomes, visible with a bluish light. This phenomenon is called Tyndall, effect. The scattering of light illuminates the path of beam in the, colloidal dispersion., Tyndall effect is observed only when the following two conditions are, satisfied :, (i) The diameter of the dispersed particles is not much smaller, than the wavelength of the light used., (ii) The refractive indices of the dispersed phase and the dispersion, medium differ greatly in magnitude., Tyndall effect is also observed when sunlight enters in a dark room, through a slit or when light is thrown from a light projector in a, cinema hall. Tale of comets is seen as a Tyndall cone due to, scattering of light by the tiny solid particles, left by the comet in its, path., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Colloidal State 185, Electrical Properties, (i) Charge on colloidal particles Colloidal particles always, carry an electric charge. The nature of this charge is the same on, all the particles in a given colloidal solution and may be either, + ve or –ve. The charge on the particles is due to either of the, given reasons:, (a) Due to preferential adsorption of either + ve or – ve ion which, is common and present in excess, e.g. when AgNO3 and KI, solutions are mixed, the particles of AgI are precipitated., These particles can adsorb Ag+ or I− ions. If KI is in excess, I−, ions would be adsorbed giving [AgI] I− negative sol but if, AgNO3 is in excess, a positive sol [AgI] Ag+ is obtained., SnO2 can act as positively charged as well as negatively, charged colloid depending upon the nature of medium., (b) Due to electron capture by sol particles during electro, dispersion method., (c) By frictional electrification., (d) By the dissociation of molecules followed by aggregation of, ions. Two layers are developed on the particle, one is fixed, layer and the other is diffused layer. Potential difference, across this electric double layer is called zeta potential or, electrokinetic potential., Positively charged colloids are metal hydroxides, basic dyes, like methylene blue sol, protein in acidic medium, oxides like, TiO2 sol. Examples of negatively charged colloids are metals, (like Cu, Ag, Au, etc.), metal sulphide, acid dyes like eosin and, sols of starch, gum, gelatin, clay, charcoal, etc., (ii) Electrophoresis The phenomenon of movement of colloidal, particles towards the oppositely charged electrodes under the, influence of applied electric field is called electrophoresis., (iii) Coagulation/flocculation The process of conversion of sol, into a suspension is called flocculation or coagulation or, precipitation., It can be brought about by :, (a) addition of suitable electrolyte solution, (b) continuous electrophoresis, (c) prolonged dialysis, (d) mixing two oppositely charged colloidal solution, (e) heating or cooling, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 186, , Handbook of Chemistry, , Coagulating value is the minimum amount of electrolyte (in millimoles/litres), needed to coagulate the colloidal solution. Smaller the coagulating or flocculating, value of an electrolyte, greater is its coagulating power., 1, Coagulating power ∝, Flocculating value, Hardy-Schulze rule Greater the valency of the oppositely charged ions of the, electrolyte, more will be its coagulating power, i.e. coagulating power ∝ charge of, ion, e.g. for As2 O3 sol the order is, Sn4 + > Al3 + > Ca2 + > Na+, Similarly for TiO2 sol, the order is, [Fe (CN) 6 ] 4 − > PO34− > SO24 − > Cl−, , Protective Colloids, In the presence of a lyophilic colloid lyophobic sol gets protected, towards the action of electrolyte. This phenomenon is called, protection and the lyophilic colloid is termed as protective colloid., , Gold Number, The protective power of protective colloid is measured in terms of gold, number which is defined as the number of mg of the protective colloid, which just prevents the coagulation of 10 mL of standard gold sol when, 1 mL of 10% solution of NaCl is added to it. Smaller the gold number, of a protective colloid, greater is its protective power. Gold number of, gelatin is 0.005-0.01 and of starch is 20-25., , Emulsion, It is a colloidal dispersion in which both dispersed phase and, dispersion medium are liquid., , Types of Emulsions, (i) Oil in water [oil is dispersed phase and water is dispersion, medium], e.g. milk., (ii) Water in oil [water is dispersed phase and oil is dispersion, medium], e.g. cod liver oil., Dye test and dilution test must be used to distinguish between, the two types of emulsions., , Characteristics of emulsion, Emulsions show all the properties of sols. Their important, characteristics are as follows, (i) They can be diluted with liquid forming the dispersion medium, in the emulsion., (ii) Their particles size is larger than those of other size. It ranges, from 1000 Å to 10 000 Å., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Colloidal State 187, (iii) They scatter light and thus, exhibit Tyndall effect., (iv) Brownian motion is also observed in emulsions where size of the, particle is too near to the limit of 10–6m., , Emulsifiers, Emulsifying agents or emulsifiers are the substances added in small, quantity to stabilize the emulsions of fairly high concentration., , Demulsification The separation of an emulsion into its consituent, liquids is called demulsification. It can be carried out by freezing,, boiling, centrifugation, etc., , Gels, Gel is a liquid-solid colloidal system in which a liquid is dispersed in a, solid. Gels are of two types : elastic gels (e.g. gelatin, agar-agar, starch), and non-elastic gels (e.g. silica, alumina and ferric oxide)., When gels are allowed to stand, they give out small quantity of, trapped liquid and the gel shrinks in volume. This phenomenon is, called syneresis or weeping of gel., , Colloids Around Us, Most of the substances we come across in our daily life are colloids., Following are the examples of colloids., (i) Blue colour of the sky., (ii) For, mist and rain., (iii) Food articles like milk, butter, ice-creams, etc., (iv) Blood which is a colloidal solution of an albuminoid substance., (v) Fertile soils are colloidal in nature in which humus acts as a, protective colloid., (vi) Formation of delta., , Applications of Colloids, (i), (ii), (iii), (iv), (v), (vi), (vii), (viii), (ix), , In medicine, e.g. argyrol (a silver sol used as eye lotion)., In chrome tanning., In sewage disposal., In purification of drinking water., In the preparation of nano-materials often use as catalyst., In photography., In producing artificial rain., Blood clotting by ferric chloride or potash alum., In smoke precipitation (cottrell precipitator), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 16, Principles & Processes, of Isolation of, Elements, Elements in Nature, Earth crust is the source of many elements. Out of these elements, 70%, are metals. Aluminium is the most abundant metal of earth crust, and iron comes second. The percentage of different elements in earth, crust are O-49%, Si-26%, Al-7.5%, Fe-4.2%, Ca-3.2%, Na-2.4%, K-2.3%,, Mg-2.3%, H-1%, Metals occur in two forms in nature (i) in native state (ii) in combined, state, depending upon their chemical reactivities., , Native State, Elements which have low chemical reactivity or noble metals having, least electropositive character are not attacked by oxygen, moisture, and CO2 of the air. These elements, therefore, occur in the free state or, in the native state, e.g. Au, Ag, Pt, S, O, N, noble gases, etc., , Combined State, Highly reactive elements which are readily attacked by moisture,, oxygen and carbon dioxide of the air, such as F, Cl, Na, K, etc., occur in, nature in combined form as their compounds such as oxides,, carbonates, sulphides, halides, etc., Hydrogen is the only non-metal which exists in oxidised form only., , Minerals and Ores, The naturally occurring substances in the form of which the metals, occur in the earth crust along with impurities are called minerals., Every mineral is not suitable for the extraction of the metal. The, mineral from which the metal is economically and conveniently, extracted is called an ore., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 190, , Handbook of Chemistry, , Terms Related to Extraction of Elements, (i) Flux The substance added to convert infusible mass, (impurities) into some fusible mass is called flux., Infusible mass + flux → fusible mass (slag), Depending upon the nature of impurity, it may be acidic or, basic., l, Acidic flux It is used to remove basic impurities. e.g.,, Silica (SiO2 ), boron trioxide ( B2O3 ), phosphorus pentaoxide, (P2O5 ) etc., are acidic flux., e.g., FeO + SiO2 → FeSiO3, Basic, impurity, (infusible), , l, , Acidic flux, , Fusible slag, , Basic flux It is used to remove acidic impurities e.g., lime, (CaO), lime stone (CaCO3 ), magnesia (MgO) etc., are basic, flux., e.g., SiO2, + MgO → MgSiO3, Acidic impurity, , Basic flux, , Fusible slag, , (ii) Slag The fusible mass obtained by the reaction of flux and, infusible mass is called slag and this process is called slagging, operation., (iii) Gangue or Matrix Impurities associated with ores are called, gangue or matrix., , Metallurgy, The entire scientific and technological process used for isolation of the, metal from its ores is known as metallurgy., , Types of Metallurgical Processes, (i) Pyrometallurgy In this type of metallurgy is used to extract the, element. Cu, Fe, Zn, Sn, etc., are extracted by this method., (ii) Hydrometallurgical process In this method, metals are, extracted by the use of their aqueous solution. Ag and Au are, extracted by this method., (iii) Electrometallurgical process In this method process of electrolysis, is used in the extraction of metals. Na, K, Li, Ca, etc., are extracted, from their molten salt solution through electrolytic method., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles & Processes of Isolation of Elements 191, Steps Involved in Metallurgy, Following steps are involved in the metallurgy :, Powdered ore, Removal of, gangue, , Ore, , Hydraulic washing (for carbonates and oxides), Froth floatation (for sulphides), Electromagnetic separation (for magnetic substance), Electrostatic separation (for PbS and ZnS), Leaching (for Ag, Al, Au), , Concentrated ore, Calcination (for carbonates and hydroxides), Roasting (for sulphide), , Metal, oxide, , Liquation, Poling, Electrorefining, Zone refining, Vapour phase refining, Chromatography, , Extraction of, metal, , Refining, , Smelting, Reduction with Mg, Al, Reduction with H2, water gas, Crude metal, , Pure metal, , Crushing of the Ore, The big lumps of ore are crushed into smaller pieces with the help of, jaw-crushers. The process of grinding the crushed ore into fine powder, with the help of the stamp mills is called pulverisation., , Concentration of Ores, Removal of unwanted materials (e.g. sand, clays, etc.) from the ore is, known as ore concentration, ore dressing or ore benefaction. It can, be carried out by various ways depending upon the nature of the ore., , Hydraulic Washing/Gravity Separation/Levigation, The process by which lighter earthy impurities are removed from the, heavier ore particles by washing with water is called levigation. The, lighter impurities are washed away. Thus, this method is based on the, difference in the densities (specific gravities) of ore and gangue., This method is commonly used for oxide ores such as haematite, tin, stone and native ores of Au, Ag, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 192, , Handbook of Chemistry, , Froth Flotation, This method is used for the concentration of sulphide ores. The method, is based on the preferential wetting of ore particles by oil and that of, gangue by water. As a result, the ore particles become light and rise to, the top in the form of froth while the gangue particles become heavy, and settle down. Thus, adsorption is involved in this method., The froth can be stabilised by the addition of stabilisers (aniline or, cresols)., , Rotating paddle, Air, , Mineral froth, , Pulp of ore + oil, Paddle draws in air, and stirs the pulp, Enlarged view of an air bubble showing mineral, particles attached to it, , Froth flotation process (schematic), , Activator They activate the floating property of one of the component of the ore, and help in the separation of different minerals present in the same ore. CuSO 4 is, used as activator., Depressants These are used to prevent certain types of particles from forming, the froth with air bubbled, e.g. NaCN can be used as a depressant in the separation, of ZnS and PbS ores. KCN is an another depressant., Collectors It increases the non-wettability of ore particles by water, e.g. pine oils,, xanthates and fatty acids., , Electromagnetic Separation, This method of concentration is employed when either the ore or the, impurities associated with it are magnetic in nature, e.g. chromite,, FeCr2O4, containing magnetic silicious gangue and wolframite, FeWO4,, containing cassiterite, SnO2 (non-magnetic impurities) can be, separated by this method., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles & Processes of Isolation of Elements 193, Electrostatic Separation, This method is used for the separation of lead sulphide (good conductor, of electricity) which is charged immediately in an electrostatic field and, is thrown away from the roller from zinc sulphide (poor conductor of, electricity) which is not charged and hence, drops vertically from the, roller., , Chemical Method-Leaching, Leaching is the process in which the ore is concentrated by chemical, reaction with a suitable reagent which dissolves the ore but not the, impurities, e.g. bauxite is leached with a hot concentrated solution of, NaOH, which, dissolves, aluminium, while, other, oxides, (Fe2O3 , TiO2 , SiO2 ), remain undissolved and noble metals (Ag and Au), are leached with a dilute aqueous solution of NaCN or KCN in the, presence of air., Al2O3 ⋅ 2H 2O + 2 NaOH →, bauxite, , and, , 2 NaAlO2, , + 3H 2O, , sod. meta aluminate, , Ag2S + 4NaCN → 2 Na [Ag(CN )2 ] + Na 2S, sod. argento, cyanide, , argentite, , Leaching of Ag or Au with NaCN is called cyanide process., , Extraction of Crude Metals from Concentrated Ore, The concentrated ore is usually converted to oxide before reduction, as, oxides are easier to reduce. Thus, isolation of crude metal from, concentrated ore involves two major steps:, (i) Conversion to oxide., (ii) Reduction of the oxides to metal., , Conversion to Oxides, (i) Calcination It is the process of converting an ore into its, oxides by heating it strongly, below its melting point in a limited, supply of air or in absence of air., During calcination, volatile impurities as well as organic matter, and moisture are removed., Heat, , Al2O3 ⋅ 2H 2O →, Bauxite, , CaCO3, , Al2O3 + 2H 2O, alumina, , Heat, , → CaO + CO2, , limestone, Heat, , CaCO3 ⋅ MgCO3 → CaO + MgO + 2CO2, dolomite, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 194, , Handbook of Chemistry, Calcination is used for metal carbonates and hydroxides and is, carried out in reverberatory furnace., , (ii) Roasting It is the process of converting an ore into its metallic, oxide by heating it strongly, below its melting point in excess of, air. This process is commonly used for sulphide ores and is, carried out in blast furnace or reverberatory furnace. Roasting, helps to remove the non-metallic impurities and moisture., 2ZnS + 3O2 → 2ZnO + 2SO2 ↑, 2PbS + 3O2 → 2PbO + 2SO2 ↑, The furnaces used in calcination and roasting employ refractory, materials which resist high temperature and do not become soft. The, SO2 produced is utilised for manufacturing of H 2SO4., Acidic refractories, : SiO2 and SiO2 + Al2O3, Basic refractories, : CaO and MgO, Neutral refractories, : Graphite, chromites, etc., Heavy metals like Cu, Zn, Fe, Sn, etc., are obtained by roasting and, smelting., , Reduction of the Oxides to Metal, The roasted or the calcined ore is then converted to the free metal by, reduction. Reduction method depends upon the activity of metal., Metals which are low in the activity series (like Cu, Hg, Au) are, obtained by heating their compounds in air; metals which are in the, middle of the activity series (like Fe, Zn, Ni, Sn) are obtained by, heating their oxides with carbon while metals which are very high in, the activity series, (e.g. Na, K, Ca, Mg, Al) are obtained by electrolytic, reduction method., (i) Smelting (reduction with carbon) The process of extracting, the metal by fusion of its oxide ore with carbon (C) or CO is called, smelting. It is carried out in a reverberatory furnace., e.g., ZnO + C → Zn + CO ↑, 823 K, , Fe2O3 + CO → 2FeO + CO2, Fe2O3 + 3C → 2Fe + 3CO ↑, During smelting a substance, called flux is added which removes, the non-fusible impurities as fusible slag. This slag is insoluble in, the molten metal and is lighter than the molten metal. So, it, floats over the molten metal and is skimmed off., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles & Processes of Isolation of Elements 195, Acidic flux, e.g., , For basic impurities, acidic flux is added., CaO + SiO2 → CaSiO3, , FeO +, , →, , SiO2, acidic flux, , FeSiO3, fusible slag, , Basic flux For acidic impurities, basic flux is added., e.g., SiO2 + CaCO3 → CaSiO3 + CO2↑, SiO2 + MgCO3, , →, , basic flux, , MgSiO3 + CO2 ↑, fusible slag, , In the extraction of Cu and Fe, the slag obtained are respectively, FeSiO3 and CaSiO3 ., The obtained slag is used in road making as well as in the, manufacturing of cement and fertilizers., (ii) Reduction by hydrogen, , It is done for W or Mo oxide., , Heat, , WO3 + 3H 2 → W + 3H 2O, (iii) Reduction by aluminium It is known as alumino thermic, reduction or Gold Schmidt thermite process. Aluminium powder, is used for this purpose., e.g., Cr2O3 + 2Al → Al2O3 + 2Cr, Mixture of the oxide and Al in the ratio of 3 : 1 is known as, thermite and mixture of BaO2 + Mg powder acts as ignition, powder., (iv) Auto reduction This is used for reduction of sulphide ores of, Pb, Hg, Cu, etc. The sulphide ore is heated in a supply of air at, 770-970 K when the metal sulphide is partially oxidised to form, its oxide or sulphate which then reacts with the remaining, sulphide to give the metal., e.g., 2Cu2S + 3O2 → 2Cu2O + 2 SO2, Cu2S + 2Cu2O → 6Cu + SO2, (v) Reduction by Mg, TiCl4 + 2Mg → 2MgCl2 + Ti (Kroll’s process), (vi) Electrolytic reduction or electrometallurgy It is the, process of extracting highly electropositive (active) metals such, as Na, K, Ca, Mg, Al, etc by electrolysis of their oxides,, hydroxides or chlorides in fused state, e.g. Mg is prepared by the, electrolysis of fused salt of MgCl2 (Dow’s process)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 196, , Handbook of Chemistry, , Thermodynamic Principle in Extraction of Metals, The free energy change ( ∆G ) occurring during the reduction processes, help in deciding the suitable method for reduction., For the spontaneous reduction of an oxide, halide or sulphide by an, element, the essential condition is that there is a decrease in the free, energy of the system (i.e., –ve value of ∆G)., More the negative value of ∆G, the higher is the reducing power of an, element. ∆G can be given as, ∆ G = ∆ H − T∆ S, where, ∆H = enthalpy change; ∆G = Gibbs free energy, T = temperature;, ∆S = entropy change, For the reduction of a metal oxide with a reducing agent, the plot of, ∆G ° against temperature is studied, which is called Ellingham, diagram., 0, –100, , 2Cu2O, 4Cu +O2, , ∆G0/kJ mol–1 of O2, , –200, , 2Fe +, , –300, –400, –500, , +, 2CO, , O2, , O2, , 2FeO, , 2CO 2, , C+O2 CO2, , 2C +, , O2, , 2CO, , –600, –700, –800, –900, , 4/3A, , –1000, , l + O2, O2, , 2 Mg +, , –1100, , A, l O3, 2 /3 A 2, 2 Mg O, , –1200, 0°C, 273 K, , 400°C, 673 K, , 800°C, 1073 K, , 1200°C, 1473 K, , 1600°C, 1873 K, , 2000°C, 2273 K, , Temperature, , Plot of Gibbs energy (∆G ° ) vs T (Ellingham diagram), , Characteristics of Ellingham Diagram, 1. All the plots slope upwards since ∆G ° becomes more positive, when temperature increases, i.e. stability of oxides decreases., 2. A metal will reduce the oxide of other metals which lie above it, in Ellingham diagram, i.e. the metals for which the free energy, of formation ( ∆G f° ) of their oxides is more negative can reduce, those metal oxides which has less negative ∆G °f ., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles & Processes of Isolation of Elements 197, 3. The decreasing order of the negative values of ∆G f° of metal, oxides is Ca > Mg (below 1773 K) > Al > Ti > Cr > C > Fe, > Ni > Hg > Ag, Thus, Al reduces FeO, CrO and NiO in thermite reduction but it, will not reduce MgO at temperature below 1773 K., Mg can reduce Al2O3 below 162 K but above 1023 K, Al can, reduce MgO., 4. CO is more effective reducing agent below 1073 K and above, 1073 K, coke is more effective reducing agent, e.g. CO reduces, Fe2O3 below 1073 K but above it, coke reduces Fe2O3 . Coke, reduces ZnO above 1270 K., , Electrochemical Principle of Metallurgy, In the reduction of molten metal salt, electrolysis is done. It is based on, the electrochemical principle., ∆G ° = − nFE °, where, n = no. of electrons, E° = electrode potential of redox couple formed in the system. Since,, more reactive metals have large negative values of the electrode, potential, hence their reduction is difficult. If the difference in two, values of E° of redox couple is positive, then ∆G° will be negative and, less reactive metal can be obtained from its salt by more reactive metal., , Refining or Purification of Crude Metals, Physical Methods, (i) Liquation This method is used for refining the metals having, low melting points (such as Sn, Pb, Hg, Bi) than the impurities., The impure metal is placed on the sloping hearth and is gently, heated. The metal melts and flows down leaving behind the, non-fusible impurities., (ii) Distillation This is useful for low boiling metals such as Zn,, Hg. The impure liquid metal is evaporated to obtain the pure, metal as distillate., (iii) Cupellation This method is used when impure metal, contains impurities of other metals which form volatile oxides,, e.g. traces of lead ore removed from silver (as volatile PbO) by, this process., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 198, , Handbook of Chemistry, , Chemical Methods, (i) Poling This method is used when the impure metal contains, impurities of its own oxide, e.g. Cu2O in blister copper and SnO2, in impure Sn. The molten impure metal is stirred with green, wood poles. At the high temperature, wood liberates gases such, as CH 4 which reduces any oxides present in the metal., (ii) Electro-refining In this method, impure metal forms the, anode while the cathode is a rod or sheet of pure metal. The, electrolytic solution consists of a soluble salt of the metal., , Anode r, (impure Cu metal), , Cathode s, (pure Cu metal), CuSO4, , Cu → Cu2+ + 2e−, , Anode,, Cathode,, , Cu2+ + 2e− → Cu( s), , On passing electricity, the pure metal gets deposited on the, cathode while the insoluble impurities settle down below the, anode as anode mud or anode sludge. Metals like Cu, Ag, Au, Cr,, Zn, Ni, etc are purified by this method., (iii) Zone-refining This method is based upon the principle of, fractional crystallisation, i.e. difference in solubilities of, impurities in molten and solid state of metal. Semiconductors, like silicon, germanium, gallium arsenide and indium, antimonide are purified by this method. Elements of very high, purity are obtained by this method., , Noble-gas atmosphere, Metal rod, Molten zone, , Induction-coil, heaters moving, as shown, , Zone refining process, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles & Processes of Isolation of Elements 199, (iv) Vapour phase refining In this method, crude metal is made, free from impurities by first converting it into its volatile, compound by heating with a chemical reagent at low, temperature. After this, the volatile compound is decomposed by, heating to some higher temperature to give pure metal., (a) van Arkel method This method is used for preparing, ultra-pure metal used in space technology (e.g. Ti, Zr, etc.), 1700 K, , 523 K, , Ti( s) + 2 I2( s) → TiI4( g) → Ti( s) + 2 I2( g), pure, , impure, 1800 K, , 870 K, , Zr( s) + 2 I2 → ZrI4( g) → Zr( s) + 2 I2( g), pure, , impure, , (b) Mond’s process It is used for refining of nickel., Ni, , 330− 350 K, , impure, , + 4CO → Ni(CO)4, 450− 470 K, , Ni(CO)4 →, , Ni + 4CO, , pure, , (v) Chromatographic method This method is based on the, principle that different components of a mixture are differently, adsorbed on an adsorbent. Adsorption chromatography is, generally used. The impure metal is dissolved in a suitable, solvent and the solution is allowed to run slowly into an, adsorbent column packed with alumina ( Al2O3 ). The metal and, the impurities present are adsorbed at different rates. These are, then eluted with suitable eluent (solvent). In this method,, weakly adsorbed component is eluted first and the strongly, adsorbed component is eluted afterwards., , Occurrence, Extraction and Uses of Some Metals, 1. Aluminium (Al), Occurrence, (i) Bauxite — Al2O3 ⋅ xH 2O, , (ii) Cryolite — Na3 AlF6, , Common method of extraction Electrolysis of Al2O3, dissolved in molten Na3 AlF6 (neutral flux)., Neutral flux is the neutral compound added to the ore to decrease, its melting point and to make it conducting, e.g. CaF2, cryolite, (Na3 AlF6 ) etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 200, , Handbook of Chemistry, , NaOH solution, , Bauxite, , DIGESTER, The bauxite dissolves in, NaOH solution under pressure, SETTLING TANK, Undissolved solids, removed from the solution, , Al, , Al2O3 fed into, electrolytic cell, , ppt. of Al(OH3), , PRECIPITATORS, Al(OH)3 added to encourage, precipitation of the solution, , KILN, Al(OH)3, ppt. roasted, at high temperature, Na2CO3 + CO2 +, bauxite, , Uses Making electric wires, silver paint, kitchen utensils, food, packing, extraction of Mo, Cr, etc., , 2. Iron (Fe), Occurrence, (i) Haematite — Fe2O3, , (ii) Magnetite — Fe3O4, , Common method of extraction Reduction of the oxide, with CO and coke in blast furnace. The iron obtained from blast, furnace contains about 4% carbon and many impurities in, smaller amount (e.g. S, P, Si, Mn) and is known as pig iron., Cast iron is different from pig iron and is made by melting pig, iron with scrap iron and coke using hot air blast., It has slightly lower carbon content (about 3%) and is extremely, hard and brittle., Wrought iron or malleable iron is the purest form of, commercial iron and is prepared from cast iron by oxidising, impurities in a reverberatory furnace lined with haematite. This, haematite oxidises carbon to carbon monoxide., Fe2O3 + 3C → 2Fe + 3CO, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Principles & Processes of Isolation of Elements 201, Ore, , Concentration of ore, done by gravity separation, and negative separator, , Fe2O3 .3H2O, , ∆, , Puddling process, [In reverberatory, lined with haematite,, cast iron is fused.], , decomposes carbonate, ore to oxide, , Fe2O3 .2H2O, , FeO + CO2, , Smelting is done in, blast furnance in, , Roasted mass, , Cast iron 93-94-1% Fe, (iron) with 3% carbon,, 0.5% impurities P, Si, Mn etc, , Calcied ore, , ∆, , FeCO3, , Roasting, with coal, , Wrought iron, Is the purest, form of iron, , Calcination, (to remove moisture), , Concentrated, ore, , presence of coke, and lime stone, , After pouring, into shapes, of moulds, , Molten iron in the lowest, zone is called pig iron [92-93% Fe,, 3-4% carbon and Si, P, S etc impurities], , In reductive zone, 3Fe2O3 + CO, , 2Fe3O4 + CO2, , Fe3O4 + CO, FeO + CO, , ∆, , CaCO3, , 3FeO + CO2, FeCO2, CO2 + CaO, , In central zone, FeO + CO, , CO2 + Cu + Fe, , CaO + SiO2, , CaSiO3, Slag, , In fusion zone, ∆, , 2CO ∆H = + ve, In combustion zone, ∆, C + O2, CO2 ∆H = − ve, CO2 + C, , Uses : Making wrought iron and different varieties of steel., , 3. Copper (Cu), Occurrence, (i) Copper pyrites — CuFeS2, (ii) Copper glance — Cu2S, , Common method of extraction Roasting of sulphide, partially and reduction., Cu2S + FeS is called matte. Blister copper contains 96-98% copper, with small amounts of Ag and Au as impurity., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 17, , Hydrogen, Chemical symbol-H (Atomic number = 1), Electronic configuration –1s1, Hydrogen is the lightest and most abundant element in the universe [70% of, the total mass of universe]., , It was discovered by Henry Cavendish in 1766 by the action of dilute, H 2SO4 on iron. It was named ‘inflammable air’. Lavoisier gave it the, name hydrogen [Greek : Hydra = water, gennas = producer]. It occurs, in free state as well as in combined state., , Position of Hydrogen in the Periodic Table, Hydrogen resembles with alkali metals (group 1) as well as halogens, (group 17). At the same time, it differs from both in certain, characteristics. That is why hydrogen is called “rogue element”., However, it has been placed in group 1 on the basis of its configuration, 1s1, which is the basis of modern classification of elements., , Isotopes of Hydrogen, Hydrogen exists in the form of three isotopes:, Name, , Symbol, , Atomic, number, , Relative, atomic, mass, , Density, , Relative, abundance, , Nature, , Protium, , 1, 1H, , or H, , 1, , 1.0078, , 0.09, , 99.98%, , Non-radioactive, , Deuterium, , 2, 1H, , or D, , 1, , 2.0141, , 0.18, , 0.0156%, , Non-radioactive, , Tritium, , 3, 1H, , or T, , 1, , 3.016, , 0.27, , 10−15%, , Radioactive, (emits β-rays,, t1 /2 = 12.33, year), , www.aiimsneetshortnotes.com
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206, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iv) Highly pure (> 99.95%) dihydrogen is obtained by electrolysing, warm aqueous barium hydroxide solution between nickel, electrodes., (v) From hydrocarbons by partial oxidation, CH 4, , Ni-Cr catalyst, , natural gas, , + H 2O → CO + 3H 2, steam, , 1270 K, , (vi) It is also obtained as a by-product in the manufacture of NaOH, and chlorine by the electrolysis of brine solution., During electrolysis, the reactions that take place are, At anode,, 2Cl( aq ) → Cl2( g) + 2e−, At cathode, 2H 2O( l ) + 2e− → H 2( g) + 2OH – ( aq ), The overall reactions by adding spectator Na + ions,, 2Na + ( aq ) + 2Cl( aq ) + 2H 2O( l ) →, –, , Cl2( g) + H 2( g) + 2 Na + + 2OH( aq ), , Physical Properties of Dihydrogen, Dihydrogen is a colourless, odourless, tasteless, combustible gas. It is, lighter than air and insoluble in water. It is neutral to litmus., , Chemical Properties of Dihydrogen, (i) Reactivity The relative inertness of dihydrogen at room, temperature is because of its high enthalpy of H—H bond i.e., high bond dissociation energy. So its reactions take place under, specific conditions only (at high temperature)., (ii) Action with non-metals, 970 K, , 2H 2( g)+O2( g) → 2H 2O( l ); ∆H °= − 285.9 kJ mol −1, or Electric discharge, 673 K/200 atm, , N 2( g) + 3H 2( g) → 2NH3 ( g); ∆H ° = − 92.6 kJ mol −1, Fe (Mo), , Dark, , H 2( g) + X 2( g) → 2HX ( g) (where, X represents halogens), Order of reactivity of halogens:, F2 > Cl2 > Br2 > I2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrogen 207, (iii) Reaction with metals, , Here H 2 acts as oxidising agent., ∆, , 2Na + H 2 → 2NaH, ∆, , Ca + H 2 → CaH 2 (Hydrolith), (iv) Reducing action of dihydrogen, ∆, , CuO + H 2 → Cu + H 2O, (v) Reactions with metal ions and metal oxides, H 2( g) + Pd 2+ ( aq ) → Pd( s) + 2H + ( aq ), yH 2( g) + M x O y ( s) → xM ( s) + yH 2O( l ), (vi) Reaction with organic compounds, Ni/400K, , (a) Veg. oil + H 2 → Veg. ghee, [Co(CO) 4 ]2, , (b) R CH == CH 2 + H 2 + CO → RCH 2CH 2CHO, Ni, , RCH 2CH 2CHO + H 2 → RCH 2CH 2CH 2OH, ∆, , Uses of Dihydrogen, 1. It is used in the manufacture of CH3OH., Co, , CO( g) + 2H 2( g) → CH3OH( l ), 2. It produces temperature of 2850°C and oxy-atomic hydrogen, flame produces a temperature of 4000°C, so it is used in, oxy-hydrogen flame., 3. The largest single use of H 2 is in the synthesis of NH3 which is, used in the manufacture of HNO3 and fertilizers., 4. Liquid hydrogen mixed with liquid oxygen is used as rocket fuel, in space research., 5. H 2 is used as a reducing agent in extraction of metals., 6. H 2 is used in fuel cell for generating electrical energy., 7. Hydrogen is used in the manufacture of synthetic petrol., (By heating H 2 with coal and heavy oils under very high, pressure in the presence of catalyst.), 8. It is use for the preparation of metal hydrides, hydrogen chloride., , www.aiimsneetshortnotes.com
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208, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 9. It is used in metallurgical processes to reduce heavy metal, oxides to metals., 10. Atomic hydrogen and oxy hydrogen torches find use for cutting, and welding purposes., , Different Forms of Hydrogen, Atomic Hydrogen, It is obtained from thermal decomposition of molecular hydrogen at, high temperature and low pressure., Electric arc, , H 2 → 2H;, , ∆H = 105.4 kcal mol−1, , It is very reactive and its half-life period is 0.33 s., , Nascent Hydrogen, Freshly prepared hydrogen is known as nascent hydrogen and is more, reactive than ordinary hydrogen. It causes the reduction of certain, compounds which is not possible with ordinary hydrogen. It can never, be isolated., Zn + H 2SO4 → ZnSO4 + 2[H], Activity of nascent H depends upon the reaction by which it is, obtained., , Adsorbed Hydrogen, Adsorption of hydrogen at the metal surface is called occlusion., This hydrogen brings out many chemical changes such as reduction, and hydrogenation. Occlusion decreases with rise in temperature., , Ortho and Para Hydrogen, When in hydrogen molecule, the nuclear spins are in the same, direction, it is known as ortho hydrogen. On the other hand when the, nuclear spins are in the opposite direction, it is known as para, hydrogen. At room temperature hydrogen consists of 75% ortho and, 25% para hydrogen., , Ortho hydrogen, , Para hydrogen, , Hydrides, The compounds of hydrogen with metals and non-metals (except noble, gases) are called hydrides., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrogen 209, Ionic or Saline Hydrides, These are formed by elements of group I, II, (except Be and Mg) by, heating them in hydrogen. These are white colourless solids, (crystalline) having high m.p. and b.p. easily decomposed by water,, CO2 or SO2., CaH 2 + 2H 2O → Ca(OH)2 + 2H 2, CaH 2 + 2CO2 → (HCOO)2Ca, They are strong reducing agents. Alkali metal hydrides are used for, making LiAlH 4, NaBH 4, etc and for removing last traces of water from, organic compounds., , Molecular or Covalent Hydrides, These are formed by elements of p-block having higher electronegativity, than hydrogen., (i) Electron deficient hydrides These are the hydrides which, do not have sufficient number of electrons needed to form, normal covalent bonds, e.g. hydrides of group 13 (BH3 , AlH3 ,, etc.), (ii) Electron precise hydrides These are the hydrides which, have exact number of electrons needed to form normal covalent, bonds, e.g. hydrides of group 14 (CH 4 , SiH 4, etc.), (iii) Electron rich hydrides These are the hydrides which have, greater number of electrons than required to form normal, covalent bonds, e.g. hydrides of group 15, 16, 17, (NH3 , PH3 , H 2S,, HF, HCl, etc). The excess electrons in these hydrides are present, as lone pairs of electrons., , Metallic or Interstitial or Non-stoichiometric Hydrides, The transition metals and rare earth metals combine with hydrogen to, form interstitial hydrides. They exhibit metallic properties and are, powerful reducing agents. They are non-stoichiometric hydrides and, their composition varies with temperature and pressure for, e.g. LaH 2.76 , TiH1.73 . Metals of group 7, 8 and 9 do not form hydrides, and this region of the Periodic Table is called hydride gap., , Polymeric Hydrides and Complex Hydrides, Polymeric hydrides are formed by elements having electronegativity in, the range 1.4 to 2.0, e.g. ( BeH 2 )n , (AlH3 )n , etc. In complex hydrides, H −, acts as ligand and is attached to central metal atom, e.g. LiAlH 4,, LiBH 4, etc., , www.aiimsneetshortnotes.com
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210, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Water, Water is the most abundant and widely distributed on the earth., Human body has about 65% and some plants have as much as 95%, H 2O. It occurs in all the three physical states. H 2O is a covalent, molecule in which oxygen is sp3 -hybridised. It has bent structure., 2δ–, , O, δ+, , H, , 9, , δ+, , pm, 5.7 104.5°, , H, , µ = 1.85 D, , The crystalline form of water is ice. It has a highly ordered three, dimensional hydrogen bonded structure. Examination of ice crystals, with X-rays shows that each oxygen atom is surrounded tetrahedrally, by four oxygen atom., , Physical Properties of Water, 1. Water is a colourless, odourless, tasteless liquid. It has, abnormally high b.p., f.p., heat of vaporisation due to hydrogen, bonding., 2. Pure water is not a good conductor so it is made conductor by, adding small amount of acid or alkali., 3. Density of ice (which is mass per unit volume) is lesser than, that of water and it floats over water., 4. Water has maximum density at 4°C. This property of maximum, density at 277 K helps aquatic animals to survive during, winter months., 5. Water is a highly polar solvent with high dielectric constant, 78.39. It interacts with polar or ionic substances effectively, with the release of considerable amount of energy due to ion, dipole interaction. The dissolution of covalent compounds like, urea, glucose and C2H5OH, etc is due to the tendency of these, molecules to form hydrogen bond with water., , Chemical Properties of Water, 1. Water is amphoteric in nature., H 2O( l ) + HCl( aq ), , −, , º H O (aq ) + Cl (aq ), H O( l ) + NH ( aq ) º NH ( aq ) + OH ( aq ), base, , 2, , acid, , +, , 3, , acid, , acid, , 3, , +, 4, , base, , acid, , base, −, , base, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrogen 211, 2. In redox reactions, water reacts with metals and non-metals both., 2Na( s) + 2H 2O( l ) → 2NaOH( aq ) + H 2( g), 2F2( g) + 2H 2O( l ) → 4H + ( aq ) + 4 F − ( aq ) + O2( g), 3. In hydrated salts, water may remain in five types such as, coordinated water, hydrogen bonded water, lattice water,, clathrate water and zeolite water., 4. A number of compounds such as calcium hydride, calcium, phosphide, etc., undergo hydrolysis with water., , Purification of Water, It involves two processes, (i) Removal of suspended impurities, (ii) Destroying the bacteria., Suspended particles are removed by coagulation with alum followed by, filtration. Exposure to sunlight, boiling, chlorination (treatment with, liquid Cl2 or bleaching powder), ozonisation and addition of CuSO4 are, some processes which are employed to destroy bacteria., , Soft and Hard Water, The water which produces large amount of lather with soap is known as, soft water and which forms a scum with soap is known as hard water., , Types of Hardness of Water, (i) Temporary hardness It is due to the presence of, bicarbonates of calcium and magnesium., (ii) Permanent hardness It is due to the presence of chlorides, and sulphates of calcium and magnesium., , Removal of Temporary Hardness, It can be achieved :, (i) By boiling The soluble bicarbonates are converted into, insoluble carbonates., Heating, , Ca(HCO3 )2 → CaCO3 ↓ + H 2O + CO2 ↑, Heating, , Mg(HCO3 )2 → Mg(OH)2 ↓ + 2CO2 ↑, (ii) By Clark’s process By adding lime water or milk of lime., M (HCO3 )2 + 2Ca(OH)2 → MCO3 ↓ + 2H 2O + 2CaCO3, , www.aiimsneetshortnotes.com
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214, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Physical Properties, (i) In the pure state, H 2O2 is almost colurless (very pale blue) liquid., (ii) it is miscible with water in all proportions and forms a hydrate, H 2O2 ⋅ H 2O., , Strength of Hydrogen Peroxide, The most common method to express the strength of H 2O2 is in terms, of the volume (in mL) of oxygen liberated at NTP by decomposition of, 1 mL of that sample of H 2O2. A solution of H 2O2 labelled as ‘10 volume’, actually means ‘‘1 mL of 3% of a solution of H 2O2 on decomposition by, heat produces 10 mL of oxygen at NTP’’. Similarly, 1 mL of 20 volume,, 30 volume and 100 volume H 2O2 solution produce 20 mL, 30 mL and, 100 mL of oxygen at N.T.P. respectively., (i) Strength of H 2O2 in terms of normality, 68 × X, = 17 × N ⇒ X = 5.6 × N, 22.4, where, X is volume strength of H 2O2., (ii) % strength = 17/ 56 × volume strength, (iii) X = 11.2 × molarity., , Structure, , H, , H, 95.0 pm, 147.8 pm, , 111.5°, , 94.8°, , 98.8 pm, 145.8 pm, , 90.2°, , 101.9°, H, , H, , In liquid/gas phase, , In solid phase, , Chemical Properties of H 2O 2, (i) Acidic nature It is weakly acidic in nature and pure, hydrogen peroxide turns blue litmus red., (ii) Oxidising agent It acts as a strong oxidising agent in acidic, as well as in basic medium., H 2O2 + 2H + + 2e− → 2 H 2O, H 2O2 + OH – + 2e− → 3 OH −, , www.aiimsneetshortnotes.com
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216, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Chemical Reactions of Heavy Water, Na, , NaOD, , +, , 1, D, 2 2, , sodium deuteroxide, SO3, , D2O, , CaC2, Al4C3, Ca3P2, , D2SO4, deuterosulphuric acid, , Ca(OD)2 + C2D2, 4Al(OD)3 + CD4, 3Ca(OD)2 + 2PD3, , Uses of Heavy Water, It is used, 1. in nuclear reactors to slow down the speed of neutrons and is, called moderator., 2. as a tracer compound to study the mechanisms of many, reactions., , Hydrogen Economy, Hydrogen economy is the use of liquid hydrogen as an alternate source, of energy. The technology involves the production, transportation and, storage of energy in the form of liquid or gaseous hydrogen. Large scale, production of hydrogen can be done by electrolysis of water or by, thermochemical reaction cycle. Storage of hydrogen in liquid form can, be done in vacuum insulated cryogenic tanks or in a metal or in an, alloy like iron-titanium alloy as interstitial hydride. Hydrogen fuel has, many advantages over conventional fuels in that it is non-polluting, and it liberates large amount of energy on combustion., Photohydrogen is used to obtain renewable energy from sunlight by, using microscopic organism such as bacteria or algae., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 18, The s-Block, Elements, In the s-block elements, the last electron enters in the s-orbital., As the s-orbital can accommodate only two electrons, two groups, (1 and 2) belong to the s-block., The general electronic configuration of s-block elements is ns1 or 2, , Alkali Metals [Group-I], Group-I elements have one electron in their valence shell. They do not, occur in the native or free state. These elements are collectively known, as alkali metals because their oxides and hydroxides form strong, alkalies like NaOH, KOH, etc. Lithium is known as bridge element., , General Characteristics of Alkali Metals, (i) Electronic configuration [noble gas] ns1, Element, , At. no., , Electronic configuration, , Li, , 3, , [He] 2 s1, , Na, , 11, , [Ne] 3s1, , K, , 19, , [Ar] 4s1, , Rb, , 37, , [Kr] 5s1, , Cs, , 55, , [Xe] 6 s1, , Fr, , 87, , [Rn] 7 s1 (Radioactive), , (ii) Atomic radii The alkali metals have the biggest atomic radii in, their respective periods., Atomic radii increases as we go down the group due to the addition, of a new shell in each subsequent step., All of these have bcc lattice with coordination number 8., , www.aiimsneetshortnotes.com
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218, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Ionic radii Ionic radii of the alkali metals are much smaller, than their corresponding metals due to lesser number of shells, and contractive effect of the increased nuclear charge., The ionic radii of all these alkali metal ions go on increasing on, moving down the group., (iv) Density These are light metals with low densities. Lithium is, the lightest known metal. On moving down the group, density, increases from Li to Cs., This is because, down the group, both the atomic size and, atomic mass increases but the effect of increase in atomic mass, is more as compared to increase in atomic size., The density of potassium is lesser than that of sodium because of the, abnormal increase in size on moving down from Na to K., (v) Melting and boiling points, (i) The melting and boiling points of alkali metals are quite low, and decrease down the group due to weakning of metallic, bond., (ii) Fr is a liquid at room temperature., (vi) Softness These are soft, malleable and ductile solids which, can be cut with knife. They possess metallic lustre when freshly, cut due to oscillation of electrons., (vii) Atomic volume Atomic volume of alkali metals is the, highest in each period and goes on increasing down the group, from top to bottom [Li to Cs]., (viii) Ionisation enthalpy The first ionisation enthalpy of alkali, metals is the lowest amongst the elements in their respective, periods and decreases on moving down the group., The second ionisation enthalpies of all the alkali metals are very, high because, by releasing an electron, ions acquire stable noble, gas configuration, so removal of second electron is difficult., (ix) Electropositive character Due to low ionisation, enthalpies, alkali metals are strongly electropositive or, metallic in nature and electropositive nature increases from Li, to Cs due to decrease in ionization enthalpy., (x) Oxidation state The alkali metal atoms show only +1, oxidation state, because their unipositive ions attain the stable, noble gas configuration., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 219, The alkali metal ions attain noble gas configuration with no, unpaired electrons so, they are diamagnetic in nature. Alkali, metals however have paramagnetic nature due to one unpaired, electron., (xi) Hydration of ions The degree of hydration depends upon, the size of the cation. Smaller the size of a cation, greater is its, hydration enthalpy. Relative degree of hydration,, Li+ > Na + > K + > Rb+ > Cs+, (xii) Flame colouration Alkali metals and their salts impart, characteristic colours to the flame because the outer electrons, get excited to higher energy levels. When the electron return to, the original state, it releases visible light of characteristic, wavelength which provides a colour to the flame., Li, , Na, , K, , Rb, , Cs, , Crimson Red, , Yellow, , Violet, , Red violet, , Blue, , (xiii) Photoelectric effect Due to very low ionisation enthalpy,, alkali metals specially ‘Cs’ exhibit photoelectric effect, (i.e., eject electrons when exposed to light) so it is used in, photoelectric cells., (xiv) Electrical conductivity Due to the presence of loosely held, valence electrons which are free to move throughout the metal, structure, the alkali metals are good conductors of heat and, electricity. Electrical conductivity increases from top to bottom, in the order, Li+ < Na + < K + < Rb+ < Cs+, (xv) Reducing character All the alkali metals are good, reducing agents due to their low ionisation energies. Their, reducing character, follows the order, Na < K < Rb < Cs < Li, Note : Lithium (Li), exceptionally has highest reducing character in aqueous, solution., , Chemical Properties of Alkali Metals, (i) Action of air On exposure to moist air, their surface get tarnished, due to the formation of their oxides, hydroxides and carbonates., 4Na( s) + O2( g) → 2Na 2O( s), Na 2O( g) + H 2O( l ) → 2NaOH( s), 2NaOH( s) + CO2( g) → Na 2CO3 ( s) + H 2O( l ), , www.aiimsneetshortnotes.com
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220, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Hence, they are kept under inert liquid like kerosene oil but, lithium is kept wrapped in paraffin wax because it floats on the, surface of kerosene oil due to its low density., Note Fire due to alkali metals is extinguished by CCl 4 ., , (ii) Action of oxygen, (a) All the alkali metals when heated with oxygen form different, types of oxides. e.g. lithium forms lithium oxide (Li2O), sodium, forms sodium peroxide (Na 2O2 ), while K, Rb and Cs form, superoxides MO2 (where, M = K, Rb or Cs), along with normal, oxides., The stability of peroxides and superoxides increases as the size of, alkali metal increases., (b) Superoxides are coloured and paramagnetic as these possess, −, × • •• • • •• , •, three electron bond • O O• where one unpaired electron is, •, •, , present., (c) All oxides, peroxides and superoxides are basic in nature., Basic strength of oxides increases in the order, Li2O < Na 2O < K 2O < Cs2O, Na 2O2 acquires yellow colour due to the presence of, superoxides as an impurity., KO2 (potassium superoxide) is used as a source of oxygen in, submarines, space shuttles and in emergency breathing, apparatus such as oxygen masks., (iii) Action of water or compounds containing acidic, , hydrogen, 2M + 2H 2O → 2MOH + H 2, (where, M = Li, Na, K, Rb, and Cs), The reactivity order with water is, Li < Na < K < Rb < Cs, This is due to increase in electropositive character in the same, order. KOH is stronger base than NaOH., LiOH is used to remove carbon dioxide from exhaled air in, confined quarters like submarines and space vehicles., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 221, (iv) Action of hydrogen All the alkali metals react with hydrogen at, 673 K to form crystalline ionic hydrides of the general formula, M +H − ., (where, M = Li, Na, K, Rb, Cs), 2M + H 2 → 2MH, The reactivity of alkali metals towards hydrogen is, Li > Na > K > Rb > Cs., (v) Reaction with halogens Alkali metals combine readily with, halogens to form ionic halides M + X − (with the exception of some, lithium halides)., 2M + X 2 → 2M + X −, (where, M = Li, Na, K etc., and X = F, Cl, Br, I), The reactivity of alkali metals towards a particular halogen, increases in the order, Li < Na < K < Rb < Cs, For a given halide, ionic character increases as the size of metal ion, increases., LiX > NaX < KX < RbX < CsX, All alkali metal halides except LiF, are freely soluble in water (LiF, is soluble in non-polar solvents because it has strong covalent bond)., LiCl is more covalent than KCl due to smaller size of Li., Bigger the anion, larger is its polarisability. Hence, the covalent, character follows the order, LiI > LiBr > LiCl > LiF, (vi) Solubility in liquid ammonia All alkali metals dissolve in, liquid ammonia giving deep blue solution due to formation of, ammoniated metal cations and ammoniated electrons in the, solution., M + ( x + y ) NH3 →, , [M (NH3 )x ]+, , ammoniated cation, , +, , [e(NH3 ) y ]−, , ammoniated electron, , The blue colour is due to the excitation of ammoniated electron to, higher energy levels and the absorption of photons occurs in the, red region of the spectrum. This solution is highly conducting and, paramagnetic because of the presence of ammoniated electrons, and ammoniated cations., (vii) Nature of carbonates and bicarbonates Li2CO3 is unstable, towards heat., ∆, , Li2CO3 → Li2O + CO2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 223, 3. Absence of d-orbitals in its valence shell., As a result, it differs from the other alkali metals in the following, properties :, (i) Lithium is harder than other alkali metals, due to strong, metallic bond., (ii) Lithium combines with O2 to form lithium monoxide, Li2O, whereas other alkali metals form peroxides ( M 2O2 ) and, superoxides ( MO2 )., (iii) Lithium, unlike the other alkali metals, reacts with nitrogen to, form the nitride., 6 Li + N 2 →, , 2Li3N, , Lithium nitride, , (iv) Li2CO3 , LiF and lithium phosphate are insoluble in water while, the corresponding salts of other alkali metals are soluble in, water., (v) Li2CO3 decomposes on heating to evolve CO2, whereas other, alkali metal carbonates do not., (vi) Lithium nitrate on heating evolves O2 and NO2 and forms Li2O, while other alkali metal nitrates on heating form their, respective nitrites., , Diagonal Relationship, Lithium shows diagonal resemblance with magnesium [the element of, group 2] and this resemblance is due to similar polarising power, i.e., ionic charge, ionic radius of both these elements., 2nd period, 3rd period, , Group 1, Li, Na, , Group 2, Be, Mg, , Group 13, B, Al, , Group 14, C, Si, , Lithium resembles magnesium in the following respects :, 1. The atomic radius of lithium is 1.31 Å while that of magnesium, is 1.34 Å., 2. The ionic radius of Li+ ion is 0.60 Å, which is very close to that of, Mg2+ ion (0.65 Å)., 3. Lithium (1.0) and magnesium (1.2) have almost similar, electronegativities., 4. Both Li and Mg are hard metals., 5. LiF is partially soluble in water like MgF2., , www.aiimsneetshortnotes.com
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224, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 6. Both combine with O2 to form monoxides, e.g. Li2O and MgO., 7. Both LiOH and Mg(OH)2 are weak bases., 8. Both LiCl and MgCl2 are predominantly covalent., 9. Both Li and Mg combine with N 2 to form their respective, nitrides, Li3N and Mg3N 2., 10. Both lithium and magnesium nitrates on heating evolve NO2, and O2 leaving behind their oxides., , Compounds of Sodium, 1. Sodium Chloride, Common Salt or Table Salt [NaCl], Sea water contains 2.7 to 2.9% by mass of the salt. Sodium chloride is, obtained by evaporation of sea water but due to the presence of, impurities like CaCl2 and MgCl2, it has deliquescent nature. It is, purified by passing HCl gas through the impure saturated solution of, NaCl and due to common ion effect, pure NaCl gets precipitated. 28%, NaCl solution is called brine., , Uses of Sodium Chloride (NaCl), (i) As enhance of flavour and as preservative for food., (ii) In preparation of many compounds like Na 2CO3 , NaOH, Na 2O2,, NaHCO3 etc., (iii) To clear the ice on high-ways, which blocks the roads during, winter., (iv) As physiological solution (0.9% NaCl in water), as it is, iso-osmotic with blood-plasma., , 2. Sodium Hydroxide or Caustic Soda [NaOH], Methods of Preparation, (i) A 10% solution of Na 2CO3 is treated with milk of lime, (Causticizing process)., Na 2CO3 + Ca(OH)2 → CaCO3 ↓ + 2NaOH, (ii) Electrolytic process involves Nelson cell and Castner-Kellner cell., A brine solution is electrolysed using a mercury cathode and a carbon, anode. Sodium metal discharged at the cathode combines with Hg to, form Na-amalgam. Chlorine gas is evolved at the anode., The amalgam is treated with water to give sodium hydroxide and, hydrogen gas., 2Na-Hg + 2H 2O → 2 NaOH + 2Hg + H 2, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 227, Uses, 1. It is used as a constituent of baking powder which is a mixture, of sodium bicarbonate, starch and potassium bitartrate or, cream of tartar and in medicine to remove acidity of the, stomach (as antacid)., 2. NaHCO3 is a mild antiseptic for skin infections., 3. It is used in fire extinguisher., , 5. Microcosmic Salts (Na(NH4 )HPO 4 ⋅ 4H2O), Preparation, It is prepared by dissolving Na 2HPO4 and NH 4Cl in the molecular, proportions in hot water followed by crystallisation., Na 2HPO4 + NH 4Cl → Na(NH 4 )HPO4 + NaCl, disodium hydrogen, phosphate, , Properties, On heating, it forms a transparent glassy bead of metaphosphate, which, gives coloured beads of orthophosphates when heated with coloured, salts like that of transition metal ions(Cu2+ , Fe2+ , Mn2+ , Ni2+ , Co2+ )., This test is called microcosmic bead test., Na(NH 4 )HPO4 → NH3 + H 2O + NaPO3, sodium metaphosphate, , CuSO4 → CuO + SO3, CuO + NaPO3 → CuNaPO4, (blue bead), , It is especially used to detect silica which being insoluble in NaPO3 and, gives a cloudy bead., , Alkaline Earth Metals [Group-II], Group-II elements are Be, Mg, Ca, Sr, Ba and Ra, which have two, electrons in their valence shell. These are commonly called alkaline, earth metals because their oxides are alkaline in nature and are found, in earth’s crust., Mg is present in chlorophyll and Ca is present in bones as calcium, phosphate., , www.aiimsneetshortnotes.com
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228, , Telegram @neetquestionpaper, , Handbook of Chemistry, , General Characteristics of Alkaline Earth Metals, (i) Electronic configuration [noble gas] ns 2, Element, , At. no., , Be, Mg, Ca, Sr, Ba, Ra, , 4, 12, 20, 38, 56, 88, , Electronic configuration, [He] 2 s2, [Ne] 3s2, [Ar] 4s2, [Kr] 5s2, [Xe] 6 s2, [Rn] 7 s2 (Radioactive), , (ii) Atomic radii and ionic radii The atomic radii and ionic, radii of these elements are quite large but smaller than those of, the corresponding alkali metals, due to increased nuclear charge, of these elements. The atomic as well as ionic radii goes on, increasing down the group due to the gradual addition of extra, energy levels., (iii) Density These are much denser than alkali metals because of, their smaller size and greater nuclear charge and mass. The, density, however, first decreases from Be to Ca and then steadily, increases from Ca to Ra due to difference in type of crystal structure., (iv) Melting and boiling points These metals have higher, melting and boiling points than those of alkali metals because of, greater number of bonding electrons., The melting and boiling points decrease on moving down the, group with the exception of magnesium., (v) Metallic properties These are silvery white metals, soft in, nature but harder than alkali metals due to stronger metallic, bonding., (vi) Ionization enthalpy The first ionisation enthalpy of alkaline, earth metals are higher than those of the corresponding alkali, metals due to smaller size and ns2 configuration., The second ionisation enthalpy values are higher than their first, ionisation enthalpy values but much lower than the second, ionisation enthalpy values of alkali metals., On moving down the group, due to increase in atomic size, the, magnitude of ionisation enthalpy decreases., (vii) Electropositive character These are strong electropositive, elements due to their large size and comparatively low ionisation, enthalpy., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 229, On moving down the group, the electropositive character increases, due to increase in atomic radii and decrease in ionisation enthalpy., (viii) Oxidation state Alkaline earth metals uniformly show an, oxidation state of +2., In the solid state, the dipositive ions (M 2+ ) form strong lattices due, to their small size and high charge (i.e. high lattice enthalpy)., In the aqueous solution, the M 2+ cations are strongly hydrated due to, their small size and high charge. The hydration energy released by, the M 2+ cation is very high., (ix) Flame colouration Alkaline earth metal salts impart, characteristic colours to the flame., As we move down the group from Ca to Ba, the ionisation enthalpy, decreases, hence the energy or the frequency of the emitted light, increases. Thus,, Ca, brick red, , Sr, crimson red, , Ba, apple green, , Ra, crimson, , Be and Mg because of their high ionisation energies, do not impart, any characteristic colour to the flame., (x) Crystal lattice Be and Mg crystallises in hcp, Ca and Sr in ccp, and Ba in bcc lattice., , Chemical Properties of Alkaline Earth Metals, Alkaline earth metals are quite reactive due to their low ionisation, energies but less reactive than alkali metals. Reactivity of the group-2, elements increases on moving down the group because their ionisation, enthalpy decreases., (i) Reaction with water Group-2 elements are less reactive with, water as compared to alkali metals., M + 2H 2O → M (OH)2 + H 2 (where, M = Mg, Ca, Sr or Ba), Be does not react even with boiling water and Ba react vigorously, even with cold water. Thus, increasing order of reactivity with, water is, Mg < Ca < Sr < Ba, A suspension of Mg(OH)2 in water is called milk of magnesia., Ca(OH) 2 solution (lime water) and Ba(OH) 2 solution (baryta) are used, for the detection of CO 2., , www.aiimsneetshortnotes.com
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230, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (ii) Reaction with oxygen The affinity towards oxygen increases, down the group. Thus, Be, Mg and Ca when heated with O2 form, monoxides while Sr, Ba and Ra form peroxides., ∆, , 2M + O2 →, ∆, , M + O2 →, , 2MO, , metal oxide, , (M = Be, Mg, Ca), , MO2, , (M = Ba, Sr), , metal peroxide, , (iii) Reaction with acids Alkaline earth metals except Be, displace, H 2 from acids., M + H 2SO4 → M SO4 + H 2 ↑, (where, M = Mg, Ca, Sr, Ba), Reactivity increases on moving down the group from Mg to Ba. Only, Mg displaces H 2 from a very dilute HNO3 ., (iv) Reaction with hydrogen Except Be, all other elements of, group−2 combine with hydrogen on heating to form hydride ( MH 2 )., M + H 2 → MH 2, BeH 2 and MgH 2 are covalent and polymeric whereas the hydrides, of Ca, Sr and Ba are ionic in nature., (v) Reaction with halogens All the elements of group−2 combine, with halogens at high temperature, forming their corresponding, halides ( MX 2 )., ∆, , M + X 2 → MX 2, Beryllium halides ( BeF2 , BeCl2, etc) are covalent, hygroscopic and, fume in air due to hydrolysis, BeCl2 exists as a dimer. The halides of, other alkaline earth metals are fairly ionic and this character, increases as the size of the metal increases., The halides are soluble in water and their solubility decreases in, the order, MgX 2 > CaX 2 > SrX 2 > BaX 2, (vi) Reaction with nitrogen These metals react with nitrogen to, form nitrides of the types M3N 2 which are hydrolysed with water, to evolve NH3 ., 3M + N 2 → M3N 2, M3N 2 + 6H 2O → 3M (OH)2 + 2 NH3, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 231, (vii) Reaction with carbon These metals when heated with, carbon, form their respective carbides of the general formula MC2, (except Be)., ∆, , M + 2C → MC2, (where, M = Mg, Ca, Sr or Ba), All these carbides are ionic in nature and react with H 2O to form, acetylene (except Be2C which gives methane)., CaC2 + 2H 2O → Ca(OH)2 + HC ≡≡ CH, (viii) Reducing character All the alkaline earth metals are strong, reducing agents because of their lower electrode potentials but, these are weaker than the corresponding alkali metals., As we move down the group from Be to Ra, the reducing, character increases due to decrease in ionisation enthalpy., (ix) Solubility in liquid ammonia Like alkali metals, these, metals also dissolve in liquid ammonia by giving coloured, solutions., M + ( x + y ) NH3 → [M (NH3 )x ]2+ + 2[e(NH3 ) y ]−, The tendency to form ammoniates decreases with increase in size, of the metal atom (i.e. on moving down the group)., (x) Complex formation It is favoured in case of alkaline earth, metals because of their small sizes as compared to the alkali, metals. Both Mg2+ and Ca 2+ form six membered coordinate, complexes with EDTA (ethylenediamminetetracetic acid) which, are used to determine the hardness of water., (xi) Basic strength of oxides and hydroxides BeO and, Be(OH)2 are amphoteric while the oxides and hydroxides of other, alkaline earth metals are basic. The basic strength, however,, increases from Be to Ba., The basic character of hydroxides of group−2 elements is lesser than, those of group-1 hydroxides because of the larger size of later than, former group., (xii) Thermal, , stability and nature of bicarbonates and, carbonates Bicarbonates of these metals do not exist in solid state, but are known in solution only. When these solutions are heated,, these get decomposed to evolve CO2., ∆, , M (HCO3 )2 → MCO3 + CO2 ↑ + H 2O, , www.aiimsneetshortnotes.com
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232, , Telegram @neetquestionpaper, , Handbook of Chemistry, , The carbonates of alkaline earth metals can be regarded as salts of, weak carbonic acid (H 2CO3 ) and metal hydroxide, M(OH )2. The, carbonates decompose on heating forming metal oxide and CO2., ∆, , MCO3 → MO + CO2 ↑, , Anomalous Behaviour of Beryllium, Beryllium, differs from the rest of the members of its group due to the, following reasons:, (i) Beryllium has a small atomic and ionic size., (ii) It has no vacant d-orbitals., (iii) It has a high charge density., The points of difference are:, (i) Hardness Beryllium is denser and harder than other members of, the family., (ii) Melting point Beryllium has high melting point i.e. 1551 K, while that of magnesium is 924 K., (iii) Ionisation potential It has higher ionisation potential as, compared to the rest of the members of this group., (iv) Reaction with acids Due to lower oxidation potential of Be, it, does not liberate hydrogen from acids readily., (v) Reaction with water Beryllium does not react with water even, at higher temperature while other members of the family liberates, hydrogen by reacting with water at room temperature., (vi) Amphoteric in character Oxide (BeO) and hydroxide, [Be(OH)2 ] of beryllium are amphoteric in character and dissolve in, acids to form salt and beryllate in alkali., (vii) Formation of carbides Beryllium when heated with carbon, form Be2C which on reaction with water gives methane. While other, members of the group form ionic carbide MC2 (acetylide) which on, reaction with water evolve acetylene., , Diagonal Relationship Between Be and Al, The main identical physical and chemical properties of Be with, aluminium are given below, 2nd period, 3rd period, , Group 1, Li, Na, , Group 2, Be, Mg, , Group 13, B, Al, , Group 14, C, Si, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 233, (i) Action of air Both the metals are stable in air., (ii) Action with water Be and Al do not decompose water even at, 373 K. It is due to their less electropositive character., (iii) Electropositive character Beryllium like aluminium is less, electropositive due to their small ionic radii., (iv) Complex formation Beryllium and aluminium form a number, of complexes. Both form fluoro complex anions like BeF42− and AlF63 −, in solution., (v) Reaction with alkali Beryllium and aluminium react with, sodium hydroxide liberating hydrogen., Be + 2NaOH → Na 2BeO2, + H2 ↑, sodium beryllate, , Al + 2NaOH + 2H 2O →, , 2NaAlO2, , sodium metaaluminate, , + 3H 2 ↑, , (vi) Passive nature Both these metals are rendered passive on, reaction with concentrated nitric acid due to the formation of oxide, layer on their surfaces., (vii) Amphoteric character of oxides Oxides of both Be and Al are, amphoteric in nature. So, they get dissolve in both, acids as well as, in alkalies., , Uses of Alkaline Earth Metals and, Their Compounds, 1. Beryllium (Be) is used in corrosion resistant alloys., 2. Alloy of Mg with aluminium is used as structural material, because of its high strength, low density and ease in machining., 3. Strontium carbonate is used for the manufacture of glass for, colour TV picture tubes., 4. Hydrated calcium chloride, CaCl2 ⋅ 6H 2O is widely used for, melting ice on roads, particularly in very cold countries, because, a 30% eutectic mixture of CaCl2/H 2O freezes at –55°C as, compared with NaCl/ H 2O at –18°C., 5. Barium sulphate being insoluble in water and opaque to X-rays,, is used under the name barium meal to scan the X-ray of the, human digestive system., 6. Magnesium is present in chlorophyll, a green pigment in plant,, essential for photosynthesis., , www.aiimsneetshortnotes.com
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234, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 7. Anhydrous CaCl2 because of its hygroscopic nature is a good, drying agent but it cannot be used to dry alcohols/ammonia/, amines., 8. Magnesium perchlorate Mg(ClO4 )2 is used as a drying agent, under the name anhydrone., Note Kidney stones generally consist of calcium oxalate, CaC2O4 ⋅ H2O which, dissolves in dilute strong acids but remains insoluble in bases., , Compounds of Calcium, 1. Calcium Oxide or Quick Lime or Lime [CaO], Preparation, By the thermal decomposition of calcium carbonate., 10701270, K, , CaCO3 → CaO + CO2 ↑, , Properties, 1. It is a basic oxide., 2. Its aqueous suspension is known as slaked lime., CaO, , burnt lime, , hissing sound, , + H 2 → Ca(OH)2 + Heat, slaked lime, , 3. On heating with ammonium salts, it gives ammonia., ∆, , CaO + 2NH 4Cl → CaCl2 + 2NH3 + H 2O, 4. It reacts with carbon to form calcium carbide., CaO + 3C →, , CaC2, , + CO, , calcium carbide, , 5. It is used as basic flux, for removing hardness of water, for, preparing mortar (CaO + sand + water)., , 2. Calcium Hydroxide or Slaked Lime or, Lime Water [Ca(OH) 2 ], Preparation, By dissolving quicklime in water., CaO + H 2O → Ca(OH)2;, , ∆H = − 63 kJ, , Properties, (i) Its suspension in water is known as milk of lime., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The s-Block Elements 235, (ii) It gives CaCO3 (milky) and then Ca(HCO3 )2 with CO2., Ca(OH)2 + CO2 → CaCO3 + H 2O, , lime water, , milkiness, , CaCO3 + H 2O + CO2 → Ca(HCO3 )2, excess, , soluble, , (iii) It reacts with Cl2 to give bleaching powder, CaOCl2., Ca(OH)2 + Cl2 → CaOCl2 + H 2O, , 3. Calcium Carbonate or Limestone or, Marble or Chalk [CaCO 3 ], Preparation By passing CO2 through lime water., Ca(OH)2 + CO2 → CaCO3↓ + H 2O, , Properties It is insoluble in H 2O but dissolves in the presence of, CO2, due to the formation of calcium bicarbonate., CaCO3 + H 2O + CO2 → Ca(HCO3 )2, insoluble, , soluble, , 4. Gypsum, Calcium Sulphate Dihydrate, (CaSO4 ⋅2H 2 O), It is also known as alabaster., On heating at 390 K, it gives plaster of Paris., It is added to cement to slow down its rate of setting., , 5. Plaster of Paris or Calcium Sulphate, 1, Hemihydrate (CaSO 4 ⋅ 2 H2O), When it is mixed with water, it forms first a plastic mass which sets, into a solid mass with slight expansion due to dehydration and its, reconversion into gypsum. It is obtained when gypsum is heated at, 393 K., 1, 3, CaSO4 ⋅ 2 H 2O → CaSO4 ⋅ H 2O + H 2O, 2, 2, Above 393 K, no water of crystallization is left and anhydrous calcium, sulphate is obtained. It is known as dead burnt plaster., , 6. Bleaching Powder (CaOCl 2 ), It is also called calcium chloro hypochlorite or chloride of lime., , Preparation, Ca(OH)2 + Cl2 → CaOCl2 + H 2O, , www.aiimsneetshortnotes.com
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236, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Properties, , (i) Its aqueous solution gives Ca 2+ , Cl− and OCl− ions., , (ii) With limited quantity of dil H 2SO4, it gives nascent oxygen, which is responsible for its oxidising and bleaching action., 2CaOCl2 + H 2SO4 → CaCl2 + CaSO4 + 2HClO, HClO → HCl + [O], (iii) With excess of dil H 2SO4 (or CO2 ), it forms Cl2, which is known as, available chlorine., CaOCl2 + H 2SO4 → CaSO4 + H 2O + Cl2 ↑, CaOCl2 + CO2 → CaCO3 + Cl2, The average percentage of available chlorine is 35-40%., Theoretically it should be 49%, which diminishes on keeping the, powder due to following change, 6CaOCl2 → 5CaCl2 + Ca(ClO3 )2, , Uses It is used for bleaching, as disinfectant and germicide in, , sterlisation of water, for making wool unshrinkable and in the, manufacture of chloroform., , 7. Cement, Cement is an important building material. It is a product obtained by, combining materials such as limestone (provides lime and clay, provides alumina and silica, SiO2 along with the oxides of iron and, magnesium.) The average composition of portland cement is, CaO, 50-60%; SiO2, 20-25%; Al2O3 , 5-10%; MgO, 2-3%; Fe2O3 , 1-2% and, SO3 , 1-2%., A mixture of lime (CaO) and sand in the ratio 1 : 3 with enough water, to make a thick paste is called mortar., By ash, a waste product of steel industry, has properties similar to, cement and can be added to cement to reduce its cost without affecting, its quality., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 19, The p-Block, Elements, In p-block elements, the last electron enters in the outermost, p-orbital. There are six groups of p-block elements in the Periodic, Table, numbering from 13 to 18. Their valence shell electronic, configuration is ns2np1 - 6 (except for He)., , Group 13, It is also called boron family. It includes B, Al, Ga, In, Tl, Al is the, most abundant metal and third most abundant element in the earth’s, crust., , General Physical Properties of Group 13 Elements, (i) Electronic configuration Their valence shell electronic, configuration is ns2np1., Element, , Atomic number, , Electronic configuration, , Boron (B), , 5, , [He] 2 s2 , 2 p1, , Aluminium (Al), , 13, , [Ne] 3s2 , 3p1, , Gallium(Ga), , 31, , [Ar] 3d10 , 4s2 4p1, , Indium (In), , 49, , [Kr] 4d10 , 5s2 5p1, , Thallium (Tl), , 81, , [Xe] 4f 14 , 5d10 , 6 s2 6 p1, , (ii) Atomic radii and ionic radii Group 13 elements have, smaller size than those of alkaline earth metals due to greater, effective nuclear charge, Z eff ., Atomic radii increases on moving down the group with an, anomaly at gallium (Ga). Unexpected decrease in the atomic, size of Ga is due to the presence of electrons in d-orbitals which, do not screen the attraction of nucleus effectively., In general, the ionic radii regularly increases from B3 + to Tl3 + ., , www.aiimsneetshortnotes.com
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238, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Density It increases regularly on moving down the group, from B to Tl., (iv) Melting and boiling points Melting point and boiling, point of group 13 elements are much higher than those of group, 2 elements. The melting point decreases from B to Ga and then, increases, due to structural changes in the elements., Boron has a very high melting point (2180°C) because of its three, dimensional structure in which B atoms are held together by strong, covalent bonds., Low melting point (303 K) of Ga is due to the fact that it, consists of Ga 2 molecules, and Ga remains liquid upto 2276 K., Hence, it is used in high temperature thermometer., (v) Ionisation enthalpy (IE) The first ionisation enthalpy, values of group 13 elements are lower than the corresponding, alkaline earth metals, due to the fact that removal of electron is, easy. [ns2 np1 configuration]. The ionisation energy increases as, expected IE1 < IE2 < IE3 . The sum of Ist three ionisation, energies for each of the element is very high., On moving down the group, IE decreases from B to Al, but the, next element Ga has slightly higher ionisation enthalpy than, Al due to the poor shielding of intervening d-electrons. It again, decreases in In and then increases in the last element Tl., (vi) Oxidation states B and Al show an oxidation state of +3, only while Ga, In and Tl exhibit oxidation states of both +1 and +3., As we move down in the group 13, due to inert pair effect, the, tendency to exhibit +3 oxidation state decreases and the, tendency to attain +1 oxidation state increases., Stability of +1 oxidation state follows the order (Al < Ga < In < Tl)., Inert pair effect is reluctance of the s-electrons of the valence shell to take part in, bonding. It occurs due to poor shielding of the ns2 -electrons by the intervening, d and f -electrons. It increases down the group and thus, the lower elements of the, group exhibit lower oxidation states., , (vii) Electropositive (metallic) character These elements are, less electropositive than the alkaline earth metals due to their, smaller size and higher ionisation enthalpies., On moving down the group, the electropositive character first, increases from B to Al and then decreases from Ga to Tl, due to, the presence of d and f-orbitals which causes poor shielding., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 239, (viii) Reducing character It decreases down the group from Al, to Tl because of the increase in electrode potential value for, M 3 + / M . Therefore, it follows the order, Al > Ga > In > Tl, (ix) Complex formation Due to their smaller size and greater, charge, these elements have greater tendency to form, complexes than the s-block elements., (x) Nature of compounds The tendency of the formation of, ionic compounds increases from B to Tl. Boron forms only, covalent compounds whereas Al can form both covalent as well, as ionic compounds. Gallium forms mainly ionic compounds,, although anhydrous GaCl3 is covalent., , Chemical Properties of 13 Group Elements, (i) Action of air Crystalline boron is unreactive whereas, amorphous boron is reactive. It reacts with air at 700°C as, follows, D, 4B + 3O2 ¾®, 2B2O3 (At high temperature), , Al is stable in air due to the formation of protective oxide film., 4Al + 3O2 ¾® 2Al2O3, Thallium is more reactive than Ga and In due to the formation, of unipositive ion, Tl+ ., 4Tl + O2 ¾® 2Tl2O, (ii) Reaction with nitrogen, D, , 2B + N 2 ¾®, D, , 2Al + N 2 ¾®, , 2BN, , Boron nitride, , 2AlN, , Aluminium nitride, , (iii) Action of water Both B and Al do not react with water but, amalgamated aluminium reacts with H 2O evolving H 2., 2Al(Hg) + 6H 2O ¾® 2Al(OH)3 + 3H 2 + 2 Hg, Ga and In do not react with pure cold or hot water but Tl forms, an oxide layer on the surface., (iv) Reaction with alkalies and acids, alkalies and gives sodium borates., , Boron dissolves in, , Fusion, , 2B + 6NaOH ¾¾® 2Na3 BO3 + 3H 2, Sodium borates, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 241, (vii) Oxides Except, Tl all the elements of group 13 form oxides, of general formula M 2O3 on heating with oxygen., D, , 4M + 3O2 ¾® 2M 2O3, Tl forms thallium (I) oxide, Tl2O which is more stable than, thallium (III) oxide Tl2O3 , due to inert pair effect., (viii) Nature of oxides and hydroxides B(OH)3 or H3 BO3 is, soluble in water, while other hydroxides are insoluble in, water., On moving down the group, there is a change from acidic to, amphoteric and then to basic character of oxides and, hydroxides of group 13 elements., (ix) Halides All the elements of boron family (except Tl) form, trihalides of type MX3 ., 2B + 3X 2 ¾® 2BX3, D, , B2O3 + 3C + 3Cl2 ¾® 2BCl3 + 3CO, D, , Al2O3 + 3C + 3Cl2 ¾® 2AlCl3 + 3CO, All the boron trihalides [BX3 ] and aluminium trihalides AlX3, (except AlF3 which is ionic) are covalent compounds. AlX3, exists as dimer while BX3 is monomer because boron atom is, too small to coordinate with four large halide ions. The energy, released during the formation of the bridge structure is not, sufficient for the cleavage of the typical pp - pp bond in BF3 ., Cl, , Cl, Al, , Cl, , Cl, Al, , Cl, , Cl, , [Al2Cl6], , BF3 is a colourless gas, BCl3 and BBr3 are colourless fuming, liquids and BI3 is a white solid at room temperature., Trihalides of group 13 elements behave as Lewis acids because, of their strong tendency to accept a pair of electrons. The, relative strength of Lewis acids of boron trihalides is, BF3 < BCl3 < BBr3 < BI3, This is due to pp- pp backbonding in BF3 which makes it less, electron deficient., The halides of group 13 elements behave as Lewis acids and, decreasing order of the acidic character is, BX3 > AlX3 > GaX3 > InX3 (where, X = Cl, Br or I), , www.aiimsneetshortnotes.com
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242, , Telegram @neetquestionpaper, , Handbook of Chemistry, , TlCl3 decomposes to TlCl and Cl2 and hence, acts as an, oxidising agent., D, , TlCl3 ¾® TlCl + Cl2, , Anomalous Behaviour of Boron, Boron shows anomalous behaviour with the other members of the, group, due to the following reasons:, (i) Smallest size in the group., (ii) High ionisation energy., (iii) Highest electronegativity in the group., (iv) Absence of vacant d-orbital., A few points of difference are:, 1. It is a non-metal while other members of the group are metallic., 2. It shows allotropy while other members do not., 3. It has the highest melting point and boiling point in group 13., 4. It forms only covalent compounds while other members form, both ionic and covalent compounds., 5. The halides of boron exist as monomers while AlCl3 exists as a, dimer., 6. The oxides and hydroxides of boron are weakly acidic while, those of aluminium are amphoteric and those of other elements, are basic., 7. It can be oxidised by concentrated HNO3 while aluminium, becomes passive due to the formation of oxide layer on the, surface., 2B + 6HNO3 ¾® 2H3 BO3 +, 6NO2, Boric acid, , Nitrogen dioxide, , Diagonal Relationship between Boron and Silicon, Boron exhibit resemblance with its diagonal element silicon of, group 14., 1. Both B and Si are non-metals., 2. Both are semi-conductors., 3. Both B and Si form covalent hydrides, i.e. boranes and silanes, respectively., 4. Both form covalent, and volatile halides which fume in moist air, due to release of HCl gas., BCl3 + 3H 2O ¾® H3 BO3 + 3HCl , SiCl4 + 4H 2O ¾® Si(OH)4 + 4HCl , , www.aiimsneetshortnotes.com
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246, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (ii) By heating a mixture of alumina and carbon in a current of dry, chlorine., D, , Al2O3 + 3C + 3Cl2 ¾® 2AlCl3 + 3CO, , Properties, 1. AlCl3 fumes in moist air due to hydrolysis., AlCl3 + 3H 2O ¾® Al(OH)3 + 3HCl, 2. It behaves as Lewis acid., , Uses, It is used as a catalyst in Friedel-Craft reaction and as a mordant, dye., , 2. Aluminium Oxide or Alumina [Al 2 O 3 ], It is the most stable compound of aluminium and occurs in nature as, colourless corundum and several coloured oxides, (it is present in, combination with different metal oxides) like ruby (red), topaz, (yellow), sapphire (blue), and emerald (green), which are used as, precious stones (gems)., , Alum, The term alum is given to double sulphates of the type, X 2SO4 × Y 2(SO4 )3 × 24H 2O where, X represents a monovalent cation, such as Na + , K + and NH +4 , while Y is a trivalent cation such a, Al3 + , Cr3 + , Fe3 + and Co3 + (Li+ does not form alum)., , Some important alums are:, (i) Potash alum, (ii) Sodium alum, , K 2SO4 ×Al2(SO4 )3 × 24H 2O, Na 2SO4 × Al2(SO4 )3 × 24H 2O, , (iii) Ammonium alum, , (NH 4 )2SO4 × Al2(SO4 )3 × 24H 2O, , (iv) Ferric alum, , (NH 4 )2SO4 × Fe2(SO4 )3 × 24H 2O, , Potash alum is prepared in the laboratory by mixing hot equimolar, quantities of K 2 SO4 and Al2(SO4 )3 . The resulting solution on, concentration and crystallisation gives potash alum., Note 1. A mixture of Al powder with NH4 NO3 is called ammonol and is used, in bombs., 2. Al is the chief constituent of silvery paints., 3. Al 2 (SO4 )3 is used for making fire proof clothes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 247, Group 14, General Physical Properties of Group 14 Elements, (i) Electronic configuration Their valence shell electronic, configuration is ns2 np2, Element, , Atomic number, , Electronic configuration, , Carbon (C), , 6, , [He ] 2 s2 2 p2, , Silicon (Si), , 14, , [Ne] 3s2 3p2, , Germanium (Ge), , 32, , [Ar] 3d10 , 4s2 4p2, , Tin (Sn), , 50, , [Kr] 4d10 , 5s2 5p2, , Lead (Pb), , 82, , [Xe] 4f 14 , 5d10 , 6 s2 6 p2, , (ii) Metallic character C and Si are non-metals, Ge is a, metalloid and Sn and Pb are metals., (iii) Appearance C is black, Si is light-brown, Ge is greyish, Sn, and Pb are silvery white., (iv) Density Density increases with increase in atomic number, due to increase in mass per unit volume down the group., (v) Melting points and boiling points The melting points, and boiling points decrease from carbon to lead but carbon and, silicon have very high melting and boiling points due to their, giant structure., (vi) Oxidation state They exhibit +2 and +4 oxidation state., The compounds of Pb in +4 oxidation state are powerful, oxidising agents since, +2 oxidation state of Pb is more stable, due to inert pair effect., The compounds in +2 oxidation state are ionic in nature and in, +4 oxidation state are covalent in nature (According to Fajan’s, rule)., (vii) Ionisation enthalpy It decreases from C to Sn. For Pb, it, is slightly higher than Sn., (viii) Electronegativity values The value decreases from C to, Pb but not in a regular manner probably due to filling of, d-orbitals in Ge and Sn and f-orbitals in Pb., (ix) Catenation The greater the strength of element-element, bond, the greater is the strength of catenation., C > > Si > Ge » Sn > Pb (catenation)., (x) Allotropy, allotropy., , All the elements of this group except Pb exhibit, , www.aiimsneetshortnotes.com
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248, , Telegram @neetquestionpaper, , Handbook of Chemistry, , In cold countries, white tin changes to grey tin and results in, decrease in density. This is called tin disease or tin plague., (xi) Valency All elements exhibit tetravalency. In case of carbon,, 406 kJ mol-1 of energy is required for promotion of 2s-electron, to 2 p. Formation of two extra bonds provide this energy., (xii) Atomic and ionic radii, , Both increase from C to Pb., , (xiii) Multiple bonding Carbon forms pp - pp bonds with itself, and with S, N and O. Other elements show negligible tendency, of this type due to their large size. Others form dp - pp, multiple bonds., , Chemical Properties of Group 14 Elements, (i) Hydrides All members of the group form covalent hydrides., Their number and ease of formation decreases down the group., Hydrides of carbon are called hydrocarbons (alkanes, alkenes or, alkynes)., Hydrides of Si and Ge are known as silanes and germanes., The only hydrides of Sn and Pb are SnH 4 (stannane) and PbH 4, (plumbane)., Their thermal stability decrease down the group., Their reducing character increases down the group., (ii) Halides All the elements give tetrahedral and covalent, halides of the type MX 4 except PbBr4 and PbI4., Thermal stability, CX 4 > SiX 4 > GeX 4 > SnX 4 > PbX 4, Order of thermal stability with common metals, MF4 > MCl4 > MBr4 > MI4, Except CX 4 other tetrahalides can hydrolysed due to the, presence of vacant d-orbitals., SiX 4 + 2H 2O ¾® SiO2 + 4HX, Ease of hydrolysis: SiX 4 > GeX 4 > SnX 4 > PbX 4, Except C, other elements form dihalides of the type MX 2 which, are more ionic and have higher melting points and boiling, points, e.g. SnCl2 is a solid whereas SnCl4 is a liquid at room, temperature., SnCl2 × 5H 2O is called bitter of tin and is used as a mordant in, dyeing., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 249, (iii) Oxides They form two types of oxides, mono-oxides of the, type MO, e.g., CO (neutral) and SiO, GeO, SnO, PbO(all basic) and dioxides of, the type MO2, CO2 , SiO2, GeO2 , SnO2 and PbO2, 14243, 1444424444, 3, Acidic, , Amphoteric, , CO2 is linear gas at ordinary temperature. Solid CO2 is known, as dryice or drikold., SiO2 is a solid with three dimensional network in which Si is, bonded to four oxygen atoms tetrahedrally and covalently. A, mass of hydrated silica (SiO2 ) formed from skeletons of minute, plants, known as diatoms, is called Kieselguhr. It is a highly, parous material and is used in the manufacture of dynamite., , Carbon, Free states (diamond, graphite, coal etc.) and combined states, (oxides, carbonates, hydrocarbons etc.), , Allotropic Forms of Carbon, The crystalline forms include, (i) Diamond It is the hardest and has three dimensional, polymeric structure in which hybridisation of C is sp3 . It is, covalent solid, melting point 3650°C, density 3.51 g/cm3 and, bad conductor of heat and electricity., (ii) Graphite It is dark grey, having hexagonal plates,, hybridisation of each C is sp2. It is good conductor of heat and, electricity due to the presence of free electrons. It was also, known as black lead. It is a very good lubricant. Graphite is, thermodynamically most stable allotropes of carbon., Aqua dag Suspensions of graphite in water., Oil dag Suspension of graphite in oil lubricants., (iii) Fullerenes Fullerenes are made by the heating of graphite in, an electric arc in the presence of inert gases such as helium or, argon. These are the only pure form of carbon because they, have smooth structure without having dangling bonds. C60, molecule contains 12 five membered rings and 20 six membered, rings. The five membered rings are connected to six membered, rings while six membered rings are connected to both five and, six membered rings. These are used in microscopic ball, bearings, light weight batteries, in synthesis of new plastics, and new drugs., , www.aiimsneetshortnotes.com
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250, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Amorphous forms of carbon are:, (i) Coal The different forms of coal are peat (60% C), lignite, (70% C), Bituminous (78% C), Semibituminous (83% C) and, anthracite (90% C). Bituminous is most common variety of coal., (ii) Coke, , It is obtained by destructive distillation of coal., DD, , Coal ¾® coke ( 80° - 90% C), (iii) Charcoal or wood charcoal It is obtained by heating, wood strongly in absence of air. When heated with steam, it, becomes more activated. It is used to remove colouring matters, and odoriferous gases., (iv) Bone black or animal charcoal It is obtained by, destructive distillation of bones in iron retort. By products are, bone oil or pyridine. It is used as adsorbant. On burning, it, gives bone ash which is calcium phosphate and used in the, manufacture of phosphorous and phosphoric acid., (v) Lamp-black It is obtained by burning vegetable oils in, limited supply of air. It is used in the manufacture of printing, ink, black paint, varnish and carbon paper., (vi) Carbon-black It is obtained by burning natural gas in, limited supply of air. It is added to rubber mixture for making, automobile tyres., , Some Important Compounds of Carbon, Coal Gas, Preparation By destructive distillation of coal., Composition, H 2 = 45 - 55% N 2 = 2 - 12%, CH 4 = 25 - 35% CO2 = 0 - 3%, CO = 4 - 11% O2 = 1 - 1.5%, Ethylene, acetylene, benzene, etc = 3 - 5%, , Uses It is used as illuminant, as fuel and to provide inert, atmosphere in the metallurgical processes., , Natural Gas, It is found along with petroleum below the surface of earth., Composition, CH 4 = 60 - 80%, Higher hydrocarbons = 2 - 12%, C2H 6 = 5 - 10%, C3H 8 = 3 - 18%, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 251, Uses It is used as a fuel. Its partial combustion yields carbon black, (reinforcing agent for rubber)., , Oil Gas, Preparation, Heated in, , Kerosene ¾¾¾¾® Mixture of simple hydrocarbons, absence of air, , Uses It is used as fuel in laboratories in Bunsen burners., , Wood Gas, Preparation Destructive distillation of wood gives wood gas, (CH 4 , C2H 6 , H 2 ), , Uses It is used as fuel., , Liquified Petroleum Gas (LPG), It is used in cylinders for domestic purposes., Composition n-butane + Iso-butane, , Uses It is used as domestic fuel., A strong foul smelling substance ethyl mercaptan or thioethanol, (C2H5SH ) is also added to LPG to detect its leakage because LPG is a, colourless and odourless gas., , Carbon Monoxide (CO), Preparation, D, , (i) 2C ( s) + O2( g) ¾® 2 CO( g), 373 K, , (ii) HCOOH ¾¾¾¾® H 2O + CO, Conc. H2SO 4, , (iii) It is manufactured in the form of water gas and producer gas., 473 K - 1273 K, , C ( g) + H 2O ( g) ¾¾¾¾¾¾® CO ( g) + H 2( g), 1442443, Water gas, 1273 K, , 2C ( s) + O2( g) + 4N 2( g) ¾¾¾® 2CO( g) + 4 N 2( g), 144, 42444, 3, Producer gas, , www.aiimsneetshortnotes.com
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254, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Silicon Dioxide (SiO 2 ), Silicon dioxide is a covalent three dimensional network solid in, which each silicon atom is covalently bonded in a tetrahedral, manner to four oxygen atoms. Silica in its normal form is almost, non-reactive because of high Si—O bond enthalpy. It is attacked by, HF and NaOH., SiO2 + 2NaOH ¾® Na 2SiO3 + H 2O, SiO2 + 4HF ¾® SiF4 + 2 H 2O, , Zeolites, If aluminium atoms replaces few silicon atoms in 3-dimensional, network of silicon dioxide, overall structure known as alumino, silicate, acquires a negative charge. Cations such Na + , K + or Ca 2+, balance the negative charge, e.g. feldspar and zeolites. ZSM-5 is, used as a catalyst in petrochemical industry., , Carborundum, It is second hardest material known and has formula SiC (silicon, carbide). It is used as high temperature semiconductor, in transistor, diode rectifiers., , Glass, It is a transparent or translucent amorphous substance obtained by, fusion of sodium carbonate (or sodium sulphate), calcium carbonate, and sand (silica). It is not a true solid, so its melting point is not, sharp., General formula of glass is Na 2O × CaO × 6 SiO2., Coloured glasses are obtained by adding certain substance to the, molten mass., Colour, , Substance added, , Blue, , CoO, , Green, , Fe2+ and Cr, , Yellow, , Fe 3+ , uranate of sodium, , Purple, , MnO2, , Lemon-yellow, , CdS, , Red, , Cu2O, selenium oxide, , Amber, , Organic matter and C, , Ruby, , AuCl 3, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 255, Different varities of glass, Glass type, , Composition, , Properties, , Hard glass, , K 2O × CaO × 4SiO2, , Resistant to acid and chemicals, , Flint glass, , K 2O × PbO × 4SiO2, , High refractive index so used in, optical lenses and prisms, , Pyrex glass, , Mixture of borosilicate of Pb, Ca, and Na, , Low coefficient of thermal, expansion so can with stand, sudden changes in temperature, , Crooke’s glass, , Contains CeO2 along with general, composition, , Absorbs UV radiations so used in, making goggles, , Jena glass, , Contains mixture of Zn and Ba, borosilicates, , Resistant to heat, shock, etc., , Quartz glass, , Pure silica, , Optical instruments (vetreosil), , Glass is attacked by HF. This property is used in the etching of, glass., Na 2SiO3 + 8HF ¾® 2NaF + H 2SiF6 + 3H 2O, CaSiO3 + 8HF ¾® CaF2 + H 2SiF6 + 3H 2O, Hydrofluoro, silicic acid, , Compounds of Lead, Chrome Yellow (PbCrO 4 ), It is prepared by adding potassium chromate to lead chromate and is, used as a yellow pigment under the name chrome yellow. On, treating with alkali, it gives basic lead chromate or chrome red,, PbCrO4 × PbO., Basic lead carbonate, Pb(OH)2 × 2PbCO3, It is also known as white lead and is prepared by adding sodium, carbonate solution to any lead salt., 3Pb(NO3 )2 + 3Na 2CO3 + H 2O ¾® Pb(OH)2 × 2PbCO3, + 6NaNO3 + CO2 , It is used as white paint. The disadvantage of using white lead in, paints is that, it turns black by the action of H 2S of the atmosphere., Lead poisoning is called plumbosolvency which increases in the, excess of nitrates, organic acids and ammonium salts., , www.aiimsneetshortnotes.com
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256, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Group 15, The 15 group of the periodic table consists of nitrogen, phosphorus,, arsenic, antimony and bismuth. These elements are known as, pnicogens and their compounds as pniconides., , Occurrence, Molecular nitrogen comprises 78% by volume of the atmosphere. It, occurs as sodium nitrate, NaNO3 (called Chile saltpetre) and, potassium nitrate (Indian saltpetre.) Phosphorus occurs in minerals, of the apatite family, Ca 9(PO4 )6 × CaX 2 (X = F, Cl, or OH) (e.g., fluorapatite Ca 9(PO4 )6 × CaF2 ) which are the main components of, phosphate rocks., , Physical Properties of Group 15 Elements, (i) Electronic configuration Their valence shell electronic, configuration is ns2 np3, Element, , Atomic number, , Electronic configuration, , Nitrogen (N), , 7, , [He] 2 s2 , 2 p 3, , Phosphorus (P), , 15, , [Ne]3s2 , 3p 3, , Arsenic (As), , 33, , Antimony (Sb), , 51, , [Ar] 3d10 , 4s2 , 4p 3, [Kr] 4d10 , 5s2 , 5p 3, , Bismuth (Bi), , 83, , [Xe] 4f 14 , 5d10 , 6 s2 , 6 p 3, , (ii) Metallic character N and P are non-metals, As and Sb are, metalloids and Bi is metal., (iii) Physical state Nitrogen is the first element after hydrogen, which is diatomic gas in native form. All other elements in the, group are solids., (iv) Atomicity N 2 is diatomic while others are tetraatomic E4., (v) Melting and boiling points The melting point increases, from nitrogen to arsenic. The boiling points increase regularly, on moving down the group., (vi) Density, , It increases down the group., , (vii) Atomic radii It increases with increase in atomic number, as we go down the group., (viii) Allotropy All the elements (except Bi) exhibit allotropy., Nitrogen, —, a-nitrogen, b-nitrogen, Phosphorus —, White, red, black, Arsenic, —, Grey, yellow, black, Antimony —, Metallic yellow (explosive), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 257, (ix) Oxidation state, N, –3 to +5, , P, –3, +3, +4, + 5, , As, +3, + 5, , Sb, +3, + 5, , Bi, +3, + 5, , Nitrogen has a wide range of oxidation states., The stability of +3 oxidation state increases and stability of +5, oxidation state decreases on moving down the group due to inert, pair effect., (x) Ionisation enthalpy Ionisation energy of nitrogen is very, high due to its small size and half-filled highly stable, configuration. The ionisation energy decreases down the group., (xi) Electronegativity It decreases from nitrogen to bismuth., (xii) Catenation They exhibit the property of catenation but to, lesser extent due to weak E - E bond than 14 group elements., (xiii) Reactivity Elemental nitrogen is highly unreactive because of, its strong triple bond. (almost as inert as noble gases)., White phosphorus is extremely reactive and kept in water. It is, inflammable and can be ignited at 45°C., , Chemical Properties of Group 15 Elements, (i) Hydrides All the elements of this group form hydrides of type, EH3 , which are covalent and pyramidal in shape. Thermal, stability, basic strength, solubility in water, bond angle and, strength of M—H bond of group 15 elements follows the order as, mentioned, NH3 (107.4° ) > PH3 ( 92° ) > AsH3 ( 91° ) > SbH3 ( 90° ) > BiH3, Ammonia, , Phosphine, , Arsine, , Stibine, , Bismuthine, , Reducing character, covalent character, rate of combustion of, group 15 elements follows the order, NH3 < PH3 < AsH3 < SbH3 < BiH3, (ii) Halides All the elements of this group form trihalides, MX3, and except nitrogen all form pentahalides, MX5 , e.g. NCl 3 , NI 3 ,, PCl3 , BiCl3 , AsCl3 , PCl5 etc. Trihalides (except of N) behave as, Lewis acid and the order of their strength is PCl3 > AsCl3 > SbCl3, Trihalides of N behave as Lewis base and has the following order, of strength, NF3 < NCl3 < NBr3 < NI3, NCl3 is an explosive compound., , www.aiimsneetshortnotes.com
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258, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Oxides All the elements of this group form oxides of the type, M 2O3 and M 2O5 ., Oxides of N :, N 2O5 , N 2O4 ,N 2O3 NO N 2O, 144424443 14243, Strongly acidic, , Oxides of P :, , Neutral, , P2O3, , P4O10, Strongly acidic, , As4O6 is called white arsenic and is a poison., The acidic strength of pentoxides and trioxides decrease on, moving down the group, i.e., N 2O5 > P2O5 > As2O5 > Sb2O5, BiOCl is called pearl white., , Anomalous Behaviour of Nitrogen, Nitrogen differs from rest of the members of the group because of its, small size, high electronegativity, high ionisation energy, absence of, vacant d-orbitals and capacity to form pp- pp multiple bonds., Nitrogen is a diatomic gas (with triple bond) and chemically inert, under ordinary conditions. It does not show pentavalency and, distinctly non-metallic. It exhibits a large number of oxidation states, and forms oxides such N 2O, NO, NO2., , Nitrogen and Its Compounds, 1. Dinitrogen (N 2 ), Preparation, NH 4Cl( aq ) + NaNO2( aq ) ¾® N 2( g) + 2 H 2O( l ) + NaCl( aq ), Heat, , (NH 4 )2Cr2O7 ¾¾® N 2 + 4H 2O + Cr2O3, Ba(N3 )2 ¾® Ba + 3N 2, (Pure nitrogen), , Properties, 1. Nitrogen does not react with alkali metals except Li but reacts, with alkaline earth metals to give metal nitride., Heat, , 6Li + N 2 ¾¾® 2Li3N, Heat, , 3Mg + N 2 ¾¾® Mg3N 2, 2. Reaction with oxygen, N 2( g ) + O 2( g ), , 2000 K, , 2NO ( g), , www.aiimsneetshortnotes.com
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262, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 4. Brown ring test of nitrate, NO3- + 3Fe2+ + 4H + ¾® NO + 3Fe3 + + 2H 2O, [Fe(H 2O)6 ]2+ + NO ¾® [Fe(H 2O)5 NO]2+ + H 2O, [Brown], , 5. Metals like Fe, Cr, Ni, Al or Co becomes inactive or passive due, to stable oxide layers., , Structure of nitric acid, H, , H, , O, , O, , O—N, , O—N, O, , O, , Uses It is used, 1., 2., 3., 4., , in the manufacturing of fertilizers., for purification of silver and gold., in the manufacturing of explosives and as an oxidising agent., as nitrating reagent., , Phosphorus and Its Compounds, Allotropic Forms of Phosphorus, Phosphorus exists in three main allotropic forms. These are as follows., (i) White phosphorus (ii) Red phosphorus (iii) Black phosphorus, Black phosphorus is formed when red phosphorus is heated in a, sealed tube at 803 K. It does not oxidise in air., , Some points of distinction between white and red phosphorus, S.No., 1., , Property, , White, , Structure, , Red, , P, P, , 60°, , P, P, , P, , P, , P, P, , P, , P, , P, P, , P, , 2., , Odour, , Garlic smell, , Odourless, , 3., , Conductivity, , Bad conductor, , Semi-conductor, , 4., , Physiological, action, , Poisonous, translucent solid, , Non-poisonous, , 5., , Hardness, , Soft, , Brittle, , 6., , Action of KOH, , PH 3, , No action, , 7., , Action of Cl2, , PCl 3 or PCl 5, , On heating PCl 3 or PCl 5, , 8., , In dark, , Shines, , Does not shine, , www.aiimsneetshortnotes.com, , P, , P, P
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Telegram @neetquestionpaper, The p-Block Elements 265, Oxoacids of Phosphorus, O, , O, , O, O, , P, OH, , HO, , P, , OH, , OH, , OH, , OH, Orthophosphoric acid, (H3PO4), (Oxidation state = + 5), , Pyrophosphoric acid, (H4P2O7), (Oxidation state = + 5), , O, , O, , O, P, , P, , O, , O, , OH, , HO, , O, , P, HO, , P, , O, , P, , H, , OH, OH, , Orthophosphorous acid, (H3PO3), (Oxidation state = +3), , O, , P, OH, , H, , OH, H, , Cyclotrimetaphosphoric Hypophosphorous acid, acid, (HPO3)3, (H3PO2), (Oxidation state = + 5) (Oxidation state = + 1), , In toothpaste, CaHPO4 × 2H 2O is added as mild abrasive and, polishing agent., These P—H bonds are not ionisable to give H + and do not play any, role in basicity. Only those H-atoms which are attached with oxygen, in P—OH form are ionisable and cause the basicity. Thus, H3PO3, and H3PO4 are dibasic and tribasic respectively as the structure of, H3PO3 has two P—OH bonds and H3PO4 has three., , Group 16, The elements oxygen (O), sulphur (S), selenium (Se), tellurium, (Te) and polonium (Po) belong to group 16 of the Periodic Table., These elements are known as chalcogens, i.e. ore forming, elements., The name sulphur has been derived from sanskrit word ‘Sulveri’, meaning ‘killer of copper’., , Occurrence, Oxygen forms about 46.6% by mass of earth’s crust. Combined, sulphur exists primarily as sulphates such as gypsum CaSO4 × 2H 2O,, epsom salt MgSO4 × 7H 2O; baryte, BaSO4 and sulphide such as, galena, PbS; (zinc) blende, ZnS; copper pyrites, (CuFeS2 )., , www.aiimsneetshortnotes.com
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266, , Telegram @neetquestionpaper, , Handbook of Chemistry, , General Physical Properties of Group 16 Elements, (i) Electronic configuration, configuration is ns2 , np4, Element, , Atomic number, , Their valence shell electronic, Electronic configuration, , Oxygen (O), , 8, , [He] 2 s2 2 p 4, , Sulphur (S), , 16, , [Ne] 3s2 3p 4, , Selenium (Se), , 34, , [Ar] 3d10 , 4s2 4p 4, , Tellurium (Te), , 52, , [Kr] 4d10 , 5s2 5p 4, , Polonium (Po), , 84, , [Xe] 4f 14 , 5d10 , 6 s2 6 p 4, , (ii) Metallic and non-metallic character Down the group, metallic character increases due to decrease in ionisation, enthalpy., O, S, 14243, , Se Te, 1, 424, 3, , Po, {, , Non-metals, , Metalloids, , Metal, , (iii) Abundance, , O > S > Se > Te > Po, , (iv) Density It increases down the group regularly., (v) Melting point and boiling point Both show a regular, increase down the group due to increase in molecular weight and, van der Waals’ forces of attraction., (vi) Oxidation state, O, , S, , Se, , Te, , Po, , –1, –2, , –2 to +6, , –2 to +6, , –2 to +6, , –2 to +6, , In OF2, the oxidation state of oxygen is +2., (vii) Ionisation energy They possess a large amount of ionisation, energy which decreases gradually from O to Po due to increase in, size of atoms and increase in screening effect., (viii) Electron affinity They have high electron affinity which, decrease from O to Po. As the size of the atom increases, the extra, added electron feels lesser attraction by nucleus and hence,, electron affinity decreases., (ix) Electronegativity It decreases down the group due to decrease, in effective nuclear charge down the group., (x) Catenation 16 group elements follow the order as shown below, S—S > Se—Se > O—O > Te—Te, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 273, Preparation, , 1. It is prepared by boiling sodium sulphite solution, with flowers of sulphur and stirring till the alkaline reaction has, disappeared., Na 2SO3 + S ¾® Na 2S2O3, 2. It is also prepared by spring’s reaction., Na 2S + Na 2SO3 + I2 ¾® Na 2S2O3 + 2NaI, , Properties 1. It is a colourless, crystalline and efflorescent, substance., 2. It gives white ppt with a dilute solution of AgNO3 which quickly, changes into black due to the formation of Ag2S., S2O32- + 2Ag+ ¾® Ag2S2O3, White ppt, , Ag2S2O3 + H 2O ¾® Ag2S + H 2SO4, , Uses, 1. Due to its property of dissolving silver halide, it is used in, photography for fixing under the name hypo., 2Na 2S2O3 + AgBr ¾® Na3 [Ag(S2O3 )2 ] + NaBr, 2. During bleaching, it is used as an antichlor., Na 2S2O3 + Cl2 + H 2O ¾® Na 2SO4 + S + 2HCl, 3. It is used to remove iodine stain, for volumetric estimation of, iodine and in medicines., , Group 17, The 17 group of Periodic Table contains five elements fluorine (F),, chlorine (Cl), bromine (Br), iodine (I) and astatine (As), collectively known as halogens (salt forming elements). Astatine is, artificially prepared radioactive element., , General Physical Properties of Group 17 Elements, (i) Electronic configuration Their valence shell electronic, configuration is ns2 , np5, Element, , Atomic number, , Electronic configuration, , Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (At), , 9, 17, 35, 53, 85, , [He]2 s2 2 p 5, [Ne] 3s2 3p 5, [Ar] 3d10 , 4s2 4p 5, [Kr] 4d10 , 5s2 5p 5, [Xe] 4f 14 , 5d10 , 6 s2 6 p 5, , www.aiimsneetshortnotes.com
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274, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (ii) Physical state Intermolecular forces in halogens are weak, and increase down the group. Thus, F2 and Cl2 are gases, Br2 is, volatite liquid and I2 is solid., (iii) Atomicity All are diatomic in nature., (iv) Abundance Being very reactive in nature, they are not found, free in nature. Their presence in earth’s crust follows the order, F2 > Cl2 > Br2 > I2, (v) Colour They absorb light in the visible range forming excited, states and are thus, coloured in nature., F2, Pale yellow, , Cl2, Yellowish green, , Br2, I2, Reddish brown Deep violet, , (vi) Metallic character All the elements are non-metals and, metallic character increases down the group. Thus, I forms I+ ., (vii) Oxidation state, F, –1, , Cl, –1 to +6, , Br, –1 to +6, , I, –1 to +7, , At, –1, +1, +5, , (viii) Bond energy and bond length The bond length increases, from fluorine to iodine and in the same order bond dissociation, energy decreases. However, the bond dissociation energy of F2 is, lesser due to its smaller size. The order of bond dissociation, energy is Cl2 > Br2 > F2 > I2., But the order of bond length is F—F < Cl—Cl < Br—Br < I—I, (ix) Density It increases down the group in a regular fashion and, follows the order I > Br > Cl > F., (x) Ionisation enthalpy The ionisation enthalpy of halogens is, very high and decreases down the group. The iodine also forms I+, and I3 + and forms compounds like ICl, ICN, IPO4. In molten state,, the compounds conduct electricity showing ionic character., (xi) Electron affinity The halogens have the high values for, electron affinity. The order of electron affinity is, Cl > F > Br > I, Due to small size of fluorine (hence, high electron density), the, extra electron to be added feels more electron-electron repulsion., Therefore, fluorine has less value for electron affinity than, chlorine., (xii) Reduction potentials and oxidising nature E°red of, halogens are positive and decrease from F to I. Therefore, halogens, act as strong oxidising agents and their oxidising power decreases, , www.aiimsneetshortnotes.com
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276, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 150°C, X- +, ¾¾®, , 2OH -, , X 2( g ) +, , (Cold, dilute), , X 2( g ) +, , 6OH -, , (Hot, conc.), , OX -, , + H 2O, , (Hypohalite ion), , 70°C, , ¾¾® 5X - +, , XO3-, , + 3H 2O, , (Halate ion), , (iv) Oxoacids of halogens Higher oxoacids of fluorine such as, HFO2 , HFO3 do not exist because fluorine is most, electronegative and has absence of d-orbitals. +3 oxidation state, of bromine and iodine are unstable due to inert pair effect,, therefore, HBrO2 and HIO2 do not exist. Acidic character of, oxoacids decreases as the electronegativity of halogen atom, decreases. Thus, the order of acidic strength., >, HOF, >, HOCl, >, HOBr, (Hypofluorous acid), , (Hypochlorous acid), , (Hypobromous acid), , HOI, Acidic nature decreases, , (Hypoiodous acid), , ¾¾¾¾¾¾¾¾¾®, For the oxoacids of same halogens, acidic strength and thermal, stability increase as the number of O atoms increases., , Anomalour Behaviour of Fluorine, Fluorine (F) differs from other elements of the group because of its, exceptionally small atomic and ionic size and low F—F bond, dissociation energy. Fluorine is more reactive than other halogens., It always has oxidation state of –1, ionic and strongest oxidising, agent. It also forms strong hydrogen bonds., , Interhalogen Compounds, Interhalogens are the compounds that are formed by two different, halogens. Depending upon the ratio in which two halogens combine,, they are known to be of four types viz. larger halogen always be the, central atom., , Preparation, The type of interhalogen formed, however, depends upon the, conditions. Some of the reactions are discussed below., 437 K, 573 K, l Cl ( g) + F (g ) ¾ ¾¾® 2ClF(g ), l Cl (g ) + 3F (g ) ¾ ¾¾® 2ClF (g ), 2, 2, 2, 2, 3, Equal volume, l, , l, , Excess, 475-575 K, , ClF(g) + F2 (g) ¾¾¾® ClF3 (g), Br2 (l ) + 5F2 —® 2BrF5, Excess, , l, , l, , Br2 (l ) + 3F2 (g) ¾® 2BrF3 (l ), Diluted, with water, , l, , I2 + Cl2 ¾® 2ICl, Equimolar, , I2 + 3Cl2 ¾® 2ICl3, Excess, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 281, 18 Group, The 18 group of the Periodic Table consists of colourless, odourless gases, at room temperature, isolated by William Ramsay in 1898 from air., , General/Physical Characteristics of Group 18 Elements, (i) Electronic configuration Their valence shell electronic, configuration is ns2np6 except He., Element, , Atomic number, , Electronic configuration, , Helium (He), Neon (Ne), , 2, 10, , 1s2, [He] 2 s2 2 p 6, , Argon (Ar), , 18, , [Ne] 3s2 3p 6, , Krypton (Kr), , 36, , [Ar] 3d10 , 4s2 4p 6, , Xenon (Xe), , 54, , [Kr] 4d10 , 5s2 5p 6, , Radon (Rn), , 86, , [Xe] 4f 14 , 5d10 , 6 s2 6 p 6, , (ii) Physical state They are all gases under ordinary conditions of, temperature and pressure., (iii) Abundance In 1.0% air, the abundance follows the order, Ar > Ne > He > Kr > Xe, (iv) Atomicity The C p / CV = 1.67 shows their monoatomic nature., However under high energy conditions, several molecular ions, such as He+2 , HeH + , HeH 2+ and Ar2+ are formed in discharge, tubes. They only survive momentarily and are detected, spectroscopically., (v) Melting and boiling points Due to the increase in, magnitude of van der Waals’ forces, the melting point and boiling, point increases from He to Rn., (vi) Atomic radii The atomic radii increases from He to Rn. It, corresponds to the van der Waals’ radii. So it has greatest atomic, size in respective period., (vii) Density The density of noble gases increases down the group, (except density of Ne < He) ., (viii) Heat of vaporisation They have very low values of heat of, vaporisation due to weak van der Waals’ forces of attraction. The, value increases down the group., (ix) Solubility in water They are slightly soluble in water and, solubility increases from He to Rn., (x) Liquefication It is extremely difficult to liquify inert gases due, to weak van der Waals’ forces of attraction among their molecules., Hence, they posses low value of critical temperature also., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The p-Block Elements 283, 2XeF6 + SiO2 ¾® 2XeOF4 + SiF4, 2XeOF4 + SiO2 ¾® 2XeO2F2 + SiF4, 2XeO2F4 + SiO2 ¾® 2XeO3 + SiF4, is, called, xenontetronide, ion and XeO4XeO24, 6 is called perxenate ion., They form clathrates with many inorganic and organic molecules., , Structure of Xenon Compounds, F, F, , Xe, , F, , F, , F, Xe, , F, , F, , F, , Xe, F, , F, , F, F, , Distorted octahedral, (XeF6), , Square planar, (XeF4), , Linear, (XeF2), , O, F, , F, Xe, F, , Xe, F, , Square pyramidal, (XeOF4), , O, , O, O, , Pyramidal, (XeO3), , Uses of Noble Gas, 1. A mixture of He + O2 is used for respiration by deep sea divers., He is also used to fill balloons and air ships because of its, non-inflammable nature., 2. Ne is used in discharge lamps and signs, in botanical gardens, and the greenhouses as it stimulates growth of plants and, accelerate chlorophyll formation., 3. Ar is used for filling incandescent metal filament electric bulbs, and to provide an inert atmosphere in high temperature, metallurgical processes., 4. Rn is used in the treatment of cancer., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 20, The d and f-Block, Elements, The d-block of the periodic table contains the elements of the groups, 3-12 in which the d-orbitals are progressively filled. There are mainly, three series of the elements, 3d-series (Sc to Zn) 4d-series (Y to Cd), and 5d-series (La to Hg omitting Ce to Lu). The fourth 6d-series, which begins with Ac is still incomplete. The two series of the innertransition metals, (4f and 5f ) are known as lanthanoids and actinoids, respectively., , Transition Elements, Elements having partially filled d-orbitals in ground state or in, excited state, are known as transition elements. They have been placed, in the centre of the Periodic Table between s-block and p-block, elements., Iron is the most abundant and widely used transition metal., , General Electronic Configuration of, Transition Elements, Transition elements have the electronic configuration, ( n - 1)d1 - 10 ns0 - 2. Zn, Cd, Hg, the end members of first three series, have general electronic configuration ( n - 1)d10ns2. These elements do, not show properties of transition elements to any extent and are, called non-typical transition elements., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The d and f-Block Elements 285, Electronic configuration of transition elements, 3 -Series, At., Element, no., 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, , Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, , 4 -Series, , 5 -Series, , Electronic, configuration, , At., no., , Element, , Electronic, configuration, , [Ar]3d1 4s2, , 39, , Y, , [Kr]4 d1 5 s2, , 2, , 2, , 3, , 2, , 5, , 1, , 5, , 2, , 6, , 2, , 7, , 2, , 8, , 2, , 10, , 1, , [Ar]3d 4s, , [Ar]3d 4s, , [Ar]3d 4s, , [Ar]3d 4s, , [Ar]3d 4s, , [Ar]3d 4s, , [Ar]3d 4s, [Ar]3d, , 10, , [Ar]3d, , 4s, , 2, , 4s, , 40, 41, 42, 43, 44, 45, 46, 47, 48, , Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, , Element, , Electronic, configuration, , 57, , La, , [Xe]5 d1 6 s2, , 2, , 2, , 72, , Hf, , [Xe]4f 14 5d2 6 s2, , 4, , 1, , 73, , Ta, , [Xe]4f 14 5d 36 s2, , 5, , 1, , 74, , W, , [Xe]4f 14 5d 4 6 s2, , 5, , 2, , 75, , Re, , [Xe]4f 14 5d 56 s2, , 7, , 1, , 76, , Os, , [Xe]4f 14 5d 6 5 s2, , 8, , 1, , [Kr]4 d 5 s, , [Kr]4 d 5 s, [Kr]4 d 5 s, , [Kr]4 d 5 s, , [Kr]4 d 5 s, , 77, , Ir, , [Xe]4f 14 5d7 6 s2, , 0, , 78, , Pt, , [Xe]4f 14 5d 96 s1, , 1, , 79, , Au, , [Xe]4f 14 5d10 6 s1, , 2, , 80, , Hg, , [Xe]4f 14 5d10 6 s2, , [Kr]4 d 5 s, 10, , [Kr]4 d, , 10, , [Kr]4 d, , 10, , [Kr]4 d, , At., no., , 5s, , 5s, 5s, , General Physical Properties of Transition Elements, (i) Atomic and ionic size Ions of the same charge in a given, series exhibit regular decrease in radius with increasing atomic, number, because the new electron enters in a d-orbital and, nuclear charge increases by unity., In last of the series, a small increase in size is observed due to, electron-electron repulsion., Atomic and ionic radii increase from 3d-series to 4d-series but the, radii of the third (5d ) series elements are virtually the same as those of, the corresponding member of the second series. It can be explained, on the basis of lanthanoid contraction [poor shielding of 4f ]., (ii) Ionisation enthalpies In a series as we move from left to, right, ionization enthalpy increases due to increase in nuclear, charge but not in regular trend., The irregular trend in the first ionisation enthalpy of the 3d, metals, though of little chemical significance, can be accounted by, considering that the removal of one electron alters the relative, energies of 4s and 3d-orbitals., (iii) Oxidation states Transition metals show variable oxidation, state due to two incomplete outermost shells. Only stable, oxidation states of the first row transition metals are, Sc(+3), Ti(+4), V(+5), Cr(+3, +6), Mn(+2, +7),, Fe(+2, +3), Co(+2, +3), Ni(+2), Cu(+2), Zn(+2)., , www.aiimsneetshortnotes.com
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286, , Telegram @neetquestionpaper, , Handbook of Chemistry, , The transition elements in their lower oxidation states, (+2 and +3) usually form ionic compounds. In higher oxidation, state, compounds are normally covalent., Only Os and Ru show +8 oxidation states in fluorides and oxides., Ni and Fe in Ni(CO)4 and Fe(CO)5 show zero oxidation state., (iv) Enthalpy of atomisation Transition elements exhibit higher, enthalpies of atomisation. Because of the presence of a large, number of unpaired electrons in their atoms, they have stronger, interatomic interactions and hence, stronger bonds., (v) Trends in the M + /M standard electrode potentials, E °M 2+ / M is governed by three factors. Enthalpy of sublimation,, enthalpy of ionisation and enthalpy of hydration., The irregular trend of M 2+ / M electrods potentials in 3d-series is, due to irregular variation in ionisation enthalpy and heat of, sublimation., Except copper, 3d series elements are good reducing agents., If sum of the first and second ionisation enthalpies is greater than, ° + ) will be positive and, hydration enthalpy, standard potential (E M, /M, reactivity will be lower and vice-versa., , Trends in the M + / M, , +, , Standard Electrode Potentials, , An examination of the E ( M 3 + / M 2+ ) values shows the varying trends., The low value for Sc3 + /Sc 2+ reflects the stability of Sc3 + which has a, noble gas configuration. The highest value for Zn3 + /Zn 2+ is due to the, removal of an electron from the stable d10 configuration of Zn 2+ ., s, , (vi) Melting and boiling point Due to strong metallic bond, they, have high mp and bp. The mp of these elements become, maximum in the middle and then decreases with the increase in, atomic number. Manganese and technetium show abnormal, values in the trend. Tungsten has the highest m.p. (3410°C)., Mercury is liquid at room temperature (mp – 38.9°C) due to, absence of unpaired electrons, and weak metallic bonding., (vii) Density d-block elements have high density because of their, small atomic size and strong metallic bonding., Densities of 3d series elements, Density, g/cm, , 3, , Sc, 3.0, , Ti, , V, , Cr, , Mn, , Fe, , Co, , Ni, , Cu, , Zn, , 4.54 6.12 7.19 7.40 7.87 8.74 8.90 8.92 7.13, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The d and f-Block Elements 287, Osmium has slightly lower density (22.52 g cm -3 ) as compared to, iridium (22.61 g cm -2 ). Thus, iridium has the highest density, among transition metals., (viii) Atomic volume Atomic volume decreases along the period, due to decrease in atomic size., (ix) Chemical reactivity d-block elements are less reactive due to, high ionisation energies. Some are almost inert and known as, noble metals, e.g. Au, Pt, Os, Ir, etc., (x) Complex formation They are well known to form a large, number of complex compounds mainly due to, (a) small atomic size and high nuclear charge, (b) presence of partially filled or vacant d-orbitals, e.g.K 4 [Fe(CN)6 ], (xi) Magnetic properties, (a) Paramagnetic nature is due to the presence of unpaired, electrons in d-orbitals. Paramagnetic character increases, with increase in the number of unpaired electrons ( n ) and, highest for Mn(II) [among 3d-series]., (b) Diamagnetic substances are repelled by applied magnetic, field and have no unpaired electron., (c) In ferromagnetism, permanent magnetic character is, acquired by substance, e.g. Fe., Magnetic moment (m ) is given by, m = n ( n + 2) BM,, , (Bohr magneton), , (xii) Coloured ions Colour exhibited by transition metal ions is, due to the presence of unpaired electrons in d-orbitals and is due, to the d-d transitions of electrons. When visible light is incident, on the ion, an electron from a lower energy d-orbital is excited to, a higher energy d-orbital., Colour of a complex depends on the metal, its oxidation state and, its ligands, e.g. [Cu(H 2O)4 ]2+ is pale blue while [Cu(NH3 )4 ]2+ is, dark blue. CuSO4 × 5H 2O is blue in colour and anhydrous CuSO4, is colourless., Charge transfer also gives intense colour e.g. MnO-4 ion does not, contain any unpaired d-electron. Its purple colour is due to, charge transfer from O to Mn, thus O2- changes to O- and, Mn(VII) to Mn(VI). Charge transfer is possible only when the, energy levels on the two different atoms involved are fairly close., , www.aiimsneetshortnotes.com
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288, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (xiii) Catalytic properties The transition metals and their, compounds behave like catalyst due to, (a) the presence of partially filled d-orbitals resulting in variable, oxidation states., (b) formation of intermediate complex with reactants by lowering, the energy of activation., (c) their rough surface area, e.g. provides active sites for, adsorption of reactant molecules., Iron, in the preparation of NH3 (Haber’s process), finely divided, nickel for hydrogenation, Pt in the preparation of nitric acid, (Ostwald’s process) etc., Some important catalysts having transition metals are, 1. Zeigler Natta catalyst : TiCl4 + (C2H5 )3 Al, 2. Lindlar’s catalyst, : Pd/BaSO4, 3. Wilkinson’s catalyst, : [Ph3P]3 RhCl, 4. Adam’s catalyst, : Pt/PtO, 5. Brown’s catalyst or P-2 catalyst : Nickel boride, (xiv) Formation of alloys d-block elements have a strong tendency, to form alloys, because their atomic sizes are very similar and in, the crystal lattice, one metal can be readily replaced by another., Alloys so formed have high m.p. The metals Mo, W, Cr, Ni, and V, are used for the production of stainless steel., Amalgam is an alloy formed by mercury with other metals. Iron, and platinum do not form any alloy with mercury., List of Alloys, Alloy, , Composition (%), , Uses, , Stainless steel Fe = 73, Cr = 18, Ni = 8, C (traces), Coinage alloy Ag = 92.5, Cu = 7.5, or Coinage, silver, Dental alloy, Ag = 33, Hg = 52, Sn = 12.5,, Cu = 2, Zn = 0.5, Brass, Cu = 80, Zn = 20, Bronze, Cu = 80, Sn = 20, Gun metal, Cu = 87, Sn = 10, Zn = 3, Bell metal, Cu = 80, Sn = 20, German silver Cu = 60, Zn = 20, Ni = 20, Duralumin, Al = 95, Cu = 4, Mg and Mn = 1, , Cutlery, machine parts, Coins, Jewellery, , Misch metal, , Lighter flints, , Ce(25%) + lanthanide metals + 5%, Fe + traces of S, C, Si, Ca, Al, , For filling teeth, Utensils, condenser tubes, Utensils, statues, coins, Gun, gears, Bells, Gongs, Cutlery, resistant wires, Air ships, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The d and f-Block Elements 289, (xv) Interstitial compounds The vacant space present in a, crystal lattice is known as interstitial site or void. The non-metal, atoms (e.g. H, N, C, etc.) due to their small size when occupy such, place, the resulting compound is known as interstitial compound., Such compounds are hard and rigid, e.g. cast iron and steel., (xvi) Non-stoichiometric compounds The compounds not, having the elements in the exact ratio as in the ideal crystal are, known as non-stoichiometric compounds, e.g. in Fe0.94O1, the, Fe : O is approx 0.94 : 1 and not exactly 1 : 1. It is due to the, variability of oxidation state in the transition metal., (xvii) Spinel These are the mixed oxides in which oxygen atoms, constitute a fcc lattice, e.g. ZnFe2O4. It is a normal spinel in, which the trivalent ions occupy the octahedral holes and divalent, ions occupy the tetrahedral holes., In inverse spinel, the trivalent ion occupy the tetrahedral holes, and divalent ion occupy the octahedral holes. e.g. FeFe2O4 or, Fe3O4., Some important reagents having transition metals, 1. Baeyer’s reagent Dilute alkaline KMnO4, used to test the, presence of unsaturation., 2. Tollen’s reagent Ammoniacal solution of AgNO3 , i.e., [Ag(NH3 )2 ]OH, used to test the aldehyde group., 3. Nessler’s reagent Alkaline solution of K 2HgI4 is used to test, NH3 ( g) and NH +4 ., 4. Benedict’s solution CuSO4 solution + sodium citrate, + Na 2CO3 , used to test the aldehyde group., 5. Lucas reagent HCl (conc.) + anhydrous ZnCl2, used to, distinguish between 1°, 2° and 3° alcohols., , Applications of Transition Elements, 1. A mixture of TiO2 and BaSO4 is called titanox and a mixture of, ZnS + BaSO4 is called lithopone., 2. TiCl2 and TiO2 are used in smoke screens. TiO2 is also used as, white pigment of paints., 3. Tentalum is used in surgical venals and analytical weights., 4. Chromium is used in stainless steel and chrome plating., 5. Mo is used in X-rays tubes. Pt is used in resistance, thermometers., 6. Cd is used for making joints in jewellery., 7. Ce is used as a scavenger of oxygen and sulphur in many metals., , www.aiimsneetshortnotes.com
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292, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Structures, , O–, , O–, , Mn, , Mn, , O, , O, , O, O, , O, , Permanganate ion, , O–, , Manganate ion, , 3. Copper Sulphate (CuSO 4 × 5H2O), It is also known as blue vitriol., , Method of preparation It is obtained by the action of dil H 2SO4, on copper scrap in the presence of air., 2Cu + 2H 2SO4 + O2, , ¾® CuSO4 + 2H 2O, , (Air), , Properties, 1. On heating it turns white due to loss of water of crystallisation., At 1000 K, CuSO4 decomposes into CuO and SO3 ., 1000 K, , CuSO4 ¾¾¾® CuO + SO3, 2. It gives blue solution with NH 4OH and white ppt of Cu2I2 with, KI., , Uses It is used in electroplating, as mordant in dyeing, in making, bordeaux mixture [(Ca(OH)2 + CuSO4 )], etc., , 4. Silver Nitrate (AgNO 3 ), It is also called Lunar caustic., , Method of preparation It is prepared by heating silver with, dilute nitric acid., D, , 3Ag( s) + 4HNO3 ( aq ) ¾® 3AgNO3 ( aq ) + NO ( g) + 2 H 2O( l ), Dilute, , Properties, 1. It is colourless, crystalline compound which blackens when, comes in contact of organic substances (skin, cloth, etc.), 2. With potassium dichromate, it gives red ppt of Ag2CrO4., 3. On strong heating, it decomposes to metallic silver., D, , 2AgNO3 ( s) ¾® 2Ag ( s) + 2 NO2( g) + O2( g), 4. Ammoniacal solution of silver nitrate is known as Tollen’s, reagent., Uses It is used as laboratory reagent, in silvering of mirror, in the, preparation of inks and hair dyes, etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The d and f-Block Elements 293, Inner-Transition (f-block) Elements, The elements in which the filling of atomic orbitals by electrons in, valence shell take place in f-subshells, two levels inside the outer, subshell, are known as inner-transition elements. They are also known, as f-block elements., , Classification of f-Block Elements, They have been classified into two series., (a) 4f -series (first inner-transition series) The last electron enters, in 4f-orbital. The elements belonging to this series are also known, as lanthanoids., (b) 5f -series (second inner-transition series) The last electron, enters in 5f-orbital. The elements belonging to this series are also, known as actinoids., , Lanthanides, The fifteen elements from lanthanum (at. no. 57) to lutetium, (at. no. 71) are known as lanthanoids or rare earths. Their, properties are as follows :, , Electronic Configuration, The general electronic configuration of these elements is, [Xe]4 f 0 – 14 5d 0 - 1 6s2. The lanthanum, electronic configuration, [Xe]4 f 0 5d1 6s2 and lutetium, electronic configuration [Xe]4 f 14 5d1 6s2,, have no partially filled 4f-orbital in their ground state, are considered, as lanthanoids due to their properties close to these elements., , Oxidation State, The most common and most stable oxidation state of lanthanides is +3, but some elements also exhibit +2 and +4 oxidation states in which, they leave behind stable ions, e.g., Eu2+ = [Xe]4 f 7 , Yb2+ = [Xe]4 f 14, Ce4+ = [Xe]4 f 0,, , Tb4+ = [Xe]4 f 7, , An aqueous solution of Ce4+ is a good oxidising agent. The Eu2+ and, Yb2+ can exist in aqueous solution and are good reducing agents. But, there are exceptions also, e.g., Sm 2+ = [Xe]4 f 6; Tm 2+ = [Xe]4 f 13 ; Pr4+ = [Xe]4 f 1, , Magnetic Properties, Magnetic properties have spin and orbit contributions. Hence,, magnetic moments are given by the formula,, m = 4S (S + 1) + L ( L + 1), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 294, , Handbook of Chemistry, , Where, L = orbital quantum number, S = spin quantum number, All lanthanoid ions with the exception of La3 + , Lu3 + and Ce4+ , are, paramagnetic in nature. For the first row transition elements, the, orbital contribution is usually quenched out by interaction with the, electric fields of the ligands in its environment. Thus, as a first, approximation the magnetic moment can be calculated using the, simple spin only formula., m s = n( n + 2), , Lanthanoid Contraction, Steady decrease in the atomic and ionic (Ln3 + ) radii as the atomic, number of the lanthanoid elements increases is called lanthanoid, contraction. This is because the additional electron goes to 4f-subshell., These 4f-orbitals being large and diffuse, have poor shielding effect., The effective nuclear charge increases which causes the contraction in, the size of electron charge cloud. This contraction in size is quite, regular and is known as lanthanoid contraction., The f-f transitions are possible due to absorption of light from the, visible region., Consequences of Lanthanoid Contraction, (i) Covalent character of cations increases., (ii), (iii), (iv), (v), , The electronegativity of trivalent ions increases slightly., There is decrease in basic strength of oxides and hydroxides from La to Lu., There is small increase in standard electrode potential values., Sizes of Zr and Hf; Nb and Ta are similar, so they are called chemical twins., , Colour, The species containing unpaired electrons are coloured and so on in the, case of lanthanoid ions., , Melting and Boiling Points, Lanthanoids have high melting and boiling points but there is no, regular trend., , Density, Lanthanoids have densities varying from 6.67 to 9.7 g cm -3 , but there, is no regular trend for these values., , Electronegativity, For lanthanoids, the electronegativity values are almost same as that, of s-block elements. Lanthanoids form ionic compounds., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, The d and f-Block Elements 295, Ionisation Energies, The ionisation energy values of lanthanoids are not very high due to, their large size and comparable with those of alkaline earth metals., , Complex Compound, Due to their large ionic size, they have little tendency to form, complexes., , Chemical Reactivity, Due to their low values of ionisation energies, the lanthanoids are very, reactive., ac, id, , Ln, with C, 2773 K, , d, te, , N, , he, a, , LnX3, , O, H2, , LnN, , with halogens, , ith, w, , w, ith, , heated with, S, , H2, , w, it h, , in, , Ln2S3, , s, , s, rn, bu, , Ln2O3, , Ln(OH)3 + H2, , LnC2, , Chemical reactions of lanthanoids, , Alloys, They form alloy especially with iron e.g. misch metal which consists of, a lanthanoids metal 94 ~ 95%, iron ~ 5% and S, C, Ca and Al in traces., Mg mixed with 3% misch metal is used for making jet engine parts., , Actinoids, The fourteen elements from actinium (at. no. 89) on wards to, lawrencium (at. no. 103) are known as actinoids and constitute the 5fseries. From neptunium to onwards, the elements are man-made, (artificially prepared) and also known as transuranic elements., , Electronic Configuration, The last electron in such elements enters in the 5f atomic orbital., Their general electronic configuration is, [Rn]5 f 0 - 14 6d 0 - 1 7s2, There is not much difference between the energies of 5f and 6d, so it is, difficult to predict whether the electron has entered in 5f or 6d., , www.aiimsneetshortnotes.com
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296, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Oxidation State, The common oxidation state is +3 but other oxidation states are also, exhibited by actinoids upto the maximum being +7., , Magnetic Properties, The magnetic moments of actinoid ions are smaller than theoretical, values. It is hard to interpret due to large spin orbit coupling., , Actinoid Contraction, It is similar to lanthanide contraction due to poor shielding of, 5f-electrons. It is greater than lanthanoid contraction., , Melting and Boiling Points, They have high values for melting and boiling points but there is no, regular trend., , Density, The value of density vary from 7.0 gcm -3 to 20 gcm -3 . Again there is, no regular trend in density., , Reducing character, They are strong reducing agents as they have high E° values, approximately 2.0 V., , Reactivity, Actinoids are very reactive in nature and combine with oxygen and, halogens like lanthanoids., , Coloured Ions, Actinoid ions are coloured due to the presence of unpaired electrons, and f-f transitions., , Complex Formation, They have higher tendency to form complex compounds., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 21, Coordination, Compounds, Coordination compounds are those molecular compounds which retain, their identity in solid state as well as in dissolved state. In these, compounds, the central metal atom or ion is linked by ions or, molecules with coordinate bonds. e.g. potassium ferrocyanide,, K 4 [Fe(CN)6 ]., aq, , K 4 [Fe(CN)6 ], , º, , 4K + + [Fe(CN)6 ]4–, , Central metal atom, Ligands, K4[Fe(CN)6] Coordination sphere (entity), Counter ion, , Coordination number, , Double Salts, These are the addition molecular compounds which are stable in solid, state but dissociate into constituent ions in the solution. e.g. Mohr’s, salt, [FeSO4 × (NH 4 )2SO4 × 6H 2O] get dissociated into Fe2+ , NH +4 and, SO2–, 4 ions., , Terms Related to Coordination Compounds, 1. Complex Ion or Coordination Entity, It is an electrically charged species in which central metal atom or ion, is surrounded by number of ions or neutral molecules., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 298, , Handbook of Chemistry, , (i) Cationic complex entity It is the complex ion which carries, positive charge, e.g. [Pt(NH3 )4 ]2+ ., (ii) Anionic complex entity It is the complex ion which carries, negative charge, e.g. [Fe(CN)6 ]4– ., , 2. Central Atom or Ion, The atom or ion to which a fixed number of ions or groups are bound, is, called central atom or ion. It is also referred as Lewis acid. e.g. in, [NiCl2(H 2O)4 ], Ni is central metal atom. It is generally transition, element or inner-transition element. These central atoms/ions are also, referred to as Lewis acids., , 3. Ligands, Ligand is electron donating species (ions or molecules) bound to the, central atom in the coordination entity., These may be charged or neutral. Ligands are of the following types:, (i) Unidentate It is a ligand, which has one donor site, i.e. the, ligand bound to a metal ion through a single donor site, e.g., H 2O, NH3 , etc., (ii) Didentate, e.g., , It is the ligand, which has two donor sites., COO½, COO-, , CH 2 ¾ NH 2, ½, CH 2 ¾ NH 2, , (Oxalate ion), (ox), , (Ethylene diammine), (en), , (iii) Polydentate It is the ligand, which has several donor sites., e.g. [EDTA] 4- is hexadentate ligand., CH 2COO–, H 2C ¾ N, CH 2COO–, H 2C ¾ N, , CH 2COO–, CH 2COO–, , [Ethylenediamminetetraacetate ion], , (iv) Ambidentate ligands These are the monodentate ligands, which can ligate through two different sites, e.g. NO-2 , SCN - , etc., (v) Chelating ligands Di or polydentate ligands cause cyclisation, around the metal atom which are known as chelates. Such ligands, uses two or more donor atoms to bind a single metal ion and are, known as chelating ligands., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Coordination Compounds 299, More the number of chelate rings, more is the stability of complex., The stabilisation of coordination compounds due to chelation is known, as chelate effect., p-acid ligands are those ligands which can form s-bond and p-bond, by accepting an appreciable amount of p electron density from metal, *, atom pulling facts to empty p or p, -orbitals., , 4. Coordination Number, It is defined as the number of coordinate bonds formed by central, metal atom, with the ligands., e.g. in [PtCl6 ]2- , Pt has coordination number 6., In case of monodentate ligands,, Coordination number = number of ligands, In polydentate ligands,, Coordination number = number of ligands ´ denticity, , 5. Coordination Sphere, The central metal/ion and the ligands attached to it, are enclosed in, square bracket which is known as coordination sphere. The ionisable, group written outside the bracket is known as counter ions., , 6. Coordination Polyhedron, The spatial arrangement of the ligands which are directly attached to, the central atom or ion, is called coordination polyhedron around the, central atom or ion. e.g. [Co(NH3 )6 ]3 + is octahedral, [Ni(CO)4 ] is, tetrahedral and [PtCl4 ]2- is square planar., , 7. Oxidation Number of Central Atom, The charge of the complex if all the ligands are removed along with the, electron pairs that are shared with the central atom, is called oxidation, number of central atom., e.g. [Cu(CN)4 ]3 - , oxidation number of copper is +1, and represented as, Cu(I)., , Types of Complexes, Homoleptic Complexes, Complexes in which the metal atom or ion is linked to only one kind of, donor atoms, are called homoleptic complexes. e.g. [Co(NH3 )6 ]3 + ., , Heteroleptic Complexes, Complexes in which the metal atom or ion is linked to more than one, kind of donor atoms are called heteroleptic complexes. e.g., [Co(NH3 )4Cl2 ]+ ., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 300, , Handbook of Chemistry, , Labile and Inert Complexes, Complexes in which the ligand substitution is fast are known as labile, complexes and in which ligand substitution is slow, are known as, inert complexes., , Effective Atomic Number (EAN), This concept was proposed by Sidgwick. In a complex, the EAN of, metal atom is equal to the total number of electrons present in it., EAN = Z - ON of metal + 2 ´ CN, (where, Z = atomic number of metal atom, ON = oxidation number of metal, and, CN = coordination number of complex), An ion with central metal atom having EAN equal to next inert gas, will be more stable., , IUPAC Naming of Complex Compounds, Naming is based on set of rules given by IUPAC., 1. Name of the compound is written in two parts (i) name of cation,, and (ii) name of anion., 2. The cation is named first in both positively and negatively, charged coordination complexes., 3. The dissimilar ligands are named in an alphabetical order, before the name of central metal atom or ion., 4. For more then one similar ligands, the prefixes di, tri, tetra, etc, are added before its name. If the di, tri, etc already appear in the, complex then bis, tris, tetrakis are used., 5. If the complex part is anion, the name of the central metal ends, with suffix ‘ate’., 6. Names of the anionic ligands end in ‘O’, names of positive, ligands end with ‘ium’ and names of neutral ligands remains as, such. But exception are there as we use aqua for H 2O, ammine, for NH3 , carbonyl for CO and nitrosyl for NO., 7. Oxidation state for the metal in cation, anion or neutral, coordination compounds is indicated by Roman numeral in, parentheses., 8. The name of the complex part is written as one word., 9. If the complex ion is a cation, the metal is named same as the, element., 10. The neutral complex molecule is named similar to that of the, complex cation., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Coordination Compounds 301, Some examples are, (i) [Cr(NH3 )3 (H 2O)3 ]Cl3, triamminetriaquachromium (III) chloride, (ii) [Co(H 2NCH 2CH 2NH 2 )3 ]2(SO4 )3, tris (ethane-1,2-diammine) cobalt (III) sulphate, (iii) [Ag(NH3 )2 ] [Ag(CN)2 ], diamminesilver (I) dicyanoargentate(I), (iv) K 4 [Fe(CN)6 ], potassiumhexacyanoferrate (II), , Isomerism in Coordination Compounds, Coordination compounds exhibit the following types of isomerism:, , 1. Structural Isomerism, In this isomerism, isomers have different bonding pattern. Different, types of structural isomers are, (i) Linkage isomerism This type of isomerism is shown by the, coordination compounds having ambidentate ligands., e.g.[Co(NH 3 )5 (NO2 )]Cl and [Co(NH3 )5 (ONO)]Cl or pentammine, nitrito-N-cobalt (III) chloride and pentamminenitrito-O-cobalt, (III) chloride., (ii) Coordination isomerism This type of isomerism arises, from the interchange of ligands between cationic and anionic, complexes of different metal ions present in a complex, e.g., [Cr(NH3 )6 ] [Co(CN)6 ] and [Co(NH3 )6 ] [Cr(CN)6 ], (iii) Ionisation isomerism This isomerism arises due to, exchange of ionisable anion with anionic ligand, e.g., [Co(NH3 )5 SO4 ]Br and [Co(NH3 )5 Br]SO4, (Red), , (Violet), , (iv) Solvate isomerism This is also known as hydrate, isomerism. In this isomerism, water is taken as solvent. It has, different number of water molecules in the coordination sphere, and outside it, e.g., [Co(H 2O)6 ]Cl3 , [Co(H 2O)4Cl2 ]Cl × 2H 2O, [Co(H 2O)3 Cl3 ] × 3H 2O, , 2. Stereoisomerism, Stereoisomers have the same chemical formula and chemical bonds but, they have different spatial arrangement. These are of two types :, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 302, , Handbook of Chemistry, , (i) Geometrical isomerism Geometrical isomers are further of, two types i.e. cis and trans isomers. This isomerism is common in, complexes with coordination number 4 and 6., , Geometrical isomerism in complexes with coordination, number 4, (i) Tetrahedral complexes do not show geometrical isomerism., (ii) Square planar complexes of formula [MX 2L2 ] (X and L are, unidentate) show geometrical isomerism. The two X ligands, may be arranged adjacent to each other in a cis isomer, or, opposite to each other in a trans-isomer, e.g., H3N, , Cl, , H 3N, , NH3, , Pt, , Pt, Cl, , Cl, , cis, , Cl, , NH3, , trans, , (iii) Square planar complex of the type [MABXL ] (where A, B, X , L ,, are unidentate ligands) shows three isomers, two cis and one, trans., The structures of these isomers can be written by fixing the, position of one ligand and placing other ligands trans to it., A, , A, , X, , B, , L, , A, , B, , M, , M, L, , B, , X, , I, , X, M, , X, , L, , II, , e.g., , A, , M, B, , L, , Identical IV, , III, , [Pt(NH3 )(Br)(Cl)(Py)]., , Geometrical isomerism in complexes with coordination, number 6, Octahedral complexes of formula [MX 2L4 ], in which the two X ligands, may be oriented cis or trans to each other, e.g. [Co(NH3 )4Cl2 ]+ ., L, X, , X, L, , M, X, , L, , L, M, , L, , L, , L, , L, , X, , cis, , trans, , Octahedral complexes of formula [MX 2 A2 ], where X are unidentate, ligands and A are didentate ligand, form cis and trans isomers, e.g., [CoCl2(en)2 ]., In octahedral complexes of formula [MA3 X3 ], if three donor atoms of, the same ligands occupy adjacent positions at the corners of an, octahedral face, it is known as facial (fac) isomer, when the positions, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Coordination Compounds 303, are around the meridian of the octahedron, it is known as meridional, (mer) isomer. e.g. [Co(NH3 )3 (NO2 )3 ], NH3, , NO2, NO2, , H3 N, , H3N, , Co, NO2, , H3 N, , NH3, Co, NO2, , H3N, , NO2, , NO2, , fac, , mer, , (ii) Optical isomerism These are the complexes which have chiral, structures. It arises when mirror images cannot be superimposed, on one another. These mirror images are called enantiomers. The, two forms are called dextro (d) and laevo (l) forms., Tetrahedral complexes with formula [M ( AB)2 ] show optical, isomers and octahedral complexes (cis form) exhibit optical, isomerism., , Bonding in Coordination Compounds, Werner’s Theory, Metals exhibit two types of valencies in the formation of complexes., These are primary valencies and secondary valencies., 1. Primary valencies correspond to oxidation number (ON) of the, metal and are satisfied by anions. These are ionisable and, non-directional., 2. Secondary valencies correspond to coordination number (CN) of, the metal atom and are satisfied by ligands. These are, non-ionisable and directional. Hence, geometry is decided by, these valencies., 3. Metal ion should satisfy both primary and secondary valancies., , Limitations, Werner theory was unable to account for the following., (i) Definite geometry of coordination compounds., (ii) Presence of magnetic and optical properties of coordination, compounds., To overcome the limitations of Werner’s theory, various theories were, put forward such as valence bond theory, cyrstal field theory., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 304, , Handbook of Chemistry, , Valence Bond Theory (VBT), This theory was proposed by L. Pauling in 1930 s. According to this, theory, when a complex is formed, the metal ion/atom provides empty, orbitals to the surrounding ligands. Coordination number shows the, number of such empty orbitals, i.e. number of empty orbitals is, equal to the coordination number. These empty orbitals hybridised, before participation in bonding and the nature of hybridisation, depends on the nature of metal and on the nature of approaching, ligand., , Inner orbital Complexes or Outer Orbital Complexes, When outer d-orbital nd shells are used in bonding, the complexes are, called outer orbital complexes. They are formed due to weak field, ligands or high spin ligands and hybridisation is sp3 d 2. They have, octahedral geometry., When d-orbitals of ( n - 1) shell are used, these are known as, inner orbital complex., They are formed due to strong field ligands or low spin ligands and, hybridisation is d 2sp3 . They have also octahedral geometry., 1. 6-ligands (unidentate), octahedral entity, (i) Inner orbital complex [Co(NH3 ) 6 ]3+, Orbitals of Co3+ ion, 3d, , 4s, , 4p, , d2sp3 hybridised orbitals of Co3+, , 3d, , 4s, , 4p, , 3+, , [Co(NH3)6], , Six pairs of electrons from (d2sp3 hybridisation), six NH3 molecules, , All electrons are paired, therefore complex will be diamagnetic in nature., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 306, , Handbook of Chemistry, , (ii) Outer orbital complex, [CoCl 4 ] –, Orbitals of Co3+ ion, 3d, 4s, 4p, sp3 hybridised orbitals of Co3+, sp3 hybridised, , 3d, , 4s, , 4p, , [CoCl4]–, 3d, , 4s, , 4p, , Four pairs of, electrons from 4Cl – (sp3 hybridisation), , Since, complex has unpaired electrons, so it will be paramagnetic in, nature., , Limitations of VBT, This theory could not explain the quantization of the magnetic data,, existence of inner orbital and outer orbital complex, change of, magnetic moment with temperature and colour of complexes., , Crystal Field Theory (CFT), This theory was proposed by H. Bethe in 1929 and van Vleck. Orgel,, in 1935, applied this theory to coordination compounds. In this theory,, ligands are treated as point charges in case of anions and dipoles in, case of neutral molecules., The five d-orbitals are classified as, (i) Three d-orbitals i.e. dxy , d yz and dzx are oriented in between the, coordinate axes and are called t2 g -orbitals., (ii) The other two d-orbitals, i.e. dx 2 axes are called e g -orbitals., , y2, , and dz 2 oriented along the, , Due to approach of ligands, the five degenerate d-orbitals split., Splitting of d-orbitals depends on the nature of the crystal field., The energy difference between t2g and eg level is designated by D, and is called crystal field splitting energy., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Coordination Compounds 307, By using spectroscopic data for a number of coordination compounds,, having the same metal ions but different ligand, the crystal field, splitting for each ligand has been calculated. A series in which ligand, are arranged in order of increasing magnitude of crystal field splitting,, is called spectrochemical series., Spectrochemical series, I- < Br- < SCN - < Cl- < S2- < F - < OH –, 4–, < C2O2–, < NH3 < en < CN – < CO., 4 < H 2O < NCS < EDTA, , Crystal Field Splitting in Octahedral Complexes, In case of octahedral complexes, energy separation is denoted by Do, (where subscript o is for octahedral)., In octahedral complexes, the six-ligands approach the central metal ion, along the axis of dx 2 - y 2 and dz 2 orbitals. These are e g orbitals., Energy of e g set of orbitals > energy of t2 g set of orbitals., The energy of e g orbitals will increase by (3/5) Do and t2 g will decrease, by (2/5) Do ., If Do < P, the fourth electron enters one of the e g orbitals giving the, configuration t32 g e1g . Ligands for which Do < P are known as weak field, ligands and form high spin complexes., If Do > P, it becomes more energetically favourable for the fourth electron, to occupy a t2 g orbital with configuration t24g e°g . (where, P = energy, required for e- pairing in an orbital). Ligands which produce this effect, are known as strong field ligands and form low spin complexes., d x2 – y2 , d z2, , Energy, , Bary, centre, Metal, d-orbitals, dx2 – y2, dz2, dxy , dxz, dyz, , Average energy, of the d-orbitals in, spherical crystal field, , eg, , 3D, 5 o, Do, 2D, 5 o, , t2g, dxy , dxz, dyz, Splitting of d-orbitals, in octahedral crystal field, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 308, , Handbook of Chemistry, , Crystal Field Splitting in Tetrahedral Complexes, In tetrahedral complexes, four ligands may be imagined to occupy the, alternate corners of the cube and the metal ion at the center of the cube., In such complexes d-orbital splitting is inverted and is smaller as, compared to the octahedral field splitting., Energy of t2 set of orbitals > Energy of e set of orbitals., Orbital splitting energies are so low that pairing of electrons are not, possible so these form high spin complexes., dxy , dyz, dzx, , Energy, , t2, 2D, 5 t, , Metal, d-orbitals, , Average energy, of the d-orbitals in, spherical crystal field, , dx2 – y2, dz2, dxy , dyz, dxz, , Dt, , 3D, 5 t, e, dx2 – y2, dz2, Splitting of d-orbitals, in tetrahedral crystal field, , Colour in Coordination Compounds, The crystal field theory attributes the colour of the coordination, compounds due to d-d transition of the electron, i.e. electron jump from, t2 g level to higher e g level., In the absence of ligands, crystal field splitting does not occur and, hence the substance is colourless., e.g., , [Ti(H 2O]6 ]3 + — Violet in colour, [Cu(H 2O)4 ]2+ — Blue in colour, etc., , Limitations of CFT, 1. It does not consider the formation of p bonding in complexes., 2. It is also unable to account satisfactorily for the relative, strengths of ligands, e.g. it does not explain why H 2O is stronger, ligand than OH - ., 3. It gives no account of the partialy covalent nature of metal-metal, bonds., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Coordination Compounds 309, Ligand Field or Molecular Orbital Theory, This theory was put forward by Hund and Mulliken. According to this, theory, all the atomic orbitals of the atom participating in molecule, formation get mixed to give rise an equivalent number of new orbitals,, called the molecular orbitals. The electrons are now under the, influence of all the nuclei., , Stability of Coordination Compounds, The stability of complex in solution refers to the degree of association, between the two species involved in the state of equilibrium. It is, expressed as stability constant (K )., [( MLn ) y - ], e.g., [MLn ] y - ;, K =, M + + nLx [M + ] [Lx - ]n, , º, , The factors on which stability of the complex depends :, (i) Charge on the central metal atom As the magnitude of, charge on metal atom increases, stability of the complex increases., (ii) Nature of metal ion The stability order is 3d < 4d < 5d series., (iii) Basic nature of ligands Strong field ligands form stable, complex., The instability constant or the dissociation constant of, compounds is defined as the reciprocal of the formation or stability, constant., , Importance and Applications of Coordination Compounds, 1. They are used in many qualitative and quantitative analysis., 2. Hardness of water is estimated by simple titration with, Na 2 EDTA., 3. Purification of metals can be achieved through formation and, subsequent decomposition of their coordination compounds., 4. They have great importance in biological systems., 5. They are used as catalyst for many industrial processes., 6. In medicinal chemistry, there is a growing interest of chelating, therapy., , Organometallic Compounds, They contain one or more metal-carbon bond in their molecules. They, are of the following types:, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 310, , Handbook of Chemistry, , 1. Sigma (s ) Bonded Compounds, Metal-carbon bond is sigma bond, e.g. (C2H5 )4Pb, Zn(C2H5 )2,, R—Mg—X, etc., , 2. Pi(p) Bonded Compounds, In which molecules/ions containing p bonds act as a ligand, e.g., ferrocene, dibenzene chromium and Zeise’s salt., Zeise’s salts is K[PtCl3(h2 - C 2H4 )] in which ethylene acts as a ligand, which do not have a lone pair of electron., In ferrocene, Fe (h5 - C 5H5 ) 2, h represents the number of carbon, atoms with which metal ion is directly attached., , 3. s and p Bonded Compounds, Metal carbonyls are their examples. Metal-carbon bond of metal, carbonyls have both s and p-bond character. They have CO molecule as, ligand, e.g., CO CO, , CO, Ni, OC, , Fe, , CO, , CO, CO, , [Ni(CO)4], , CO CO, Fe(CO)5, , Wilkinson’s catalyst (Rh(PPh3) 3Cl] is used as homogeneous catalyst, in the hydrogenation of alkenes. Zeigler-Natta catalyst, [TiCl4 + (C 2H5 ) 3Al] acts as heterogeneous catalyst in the, polymerisation of ethylene., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 22, , Environmental, Chemistry, Environmental chemistry is the branch of chemistry which is, concerned with the chemical phenomenon occurring in the, environment., , Classification of Environment, 1. Atmosphere, Atmosphere is a gaseous mixture of air that surrounds the earth. Its, different layers are as follows :, (i), , Troposphere It is the lowest region of the atmosphere, extending from earth’s surface to the lower boundary of the, stratosphere. It contains water vapours and is greatly affected by, air pollution. It extends upto the height of ~ 10 km from sea level., , (ii) Stratosphere The layer of the earth’s atmosphere above the, troposphere and below the mesosphere, is called stratosphere., Ozone layer is present in this region., (iii) Mesosphere It is the region of the earth’s atmosphere above, the stratosphere and below the thermosphere. It is the coldest, region (temperature – 2 to – 92°C) of atmosphere., (iv) Thermosphere The upper region of the atmosphere above the, mesosphere is called thermosphere. It is the hottest region, (temperature up to 1200°C)., (v), , Exosphere It is the uppermost region of atmosphere. It, contains atomic and ionic O2, H 2 and He., , 2. Hydrosphere, It is the aqueous envelop of the earth, e.g. oceans, lakes etc., , www.aiimsneetshortnotes.com
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312, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 3. Lithosphere, The solid rocky portion of the earth constitute the lithosphere., , 4. Biosphere, The biological envelop which supports the life is called biosphere., e.g. animals, human beings., , Environmental Pollution, It may be described as contamination of environment with harmful, wastes mainly arising from certain human activities. These activities, release materials which pollute atmosphere, water and soil., , Types of Pollutions, (i), , Natural pollution This type of pollution is caused by the, natural sources, e.g. volcanic eruptions, release of methane by, paddy fields and cattles, forest fires etc., , (ii) Man-made pollution This type of pollution is resulting from, human activities like burning of the fuels, deforestation,, industrial effluents, pesticides etc., , Pollutants, Any substance produced either by a natural source or by human, activity which causes adverse effect on the environment is called, pollutant., Pollutants can be of the following types depending upon the following, factors :, , Classification on the Basis of Their Degradation, (i) Biodegradable pollutants Pollutants capable of being, degraded by biological or microbial actions are called, biodegradable pollutants, e.g. domestic sewage., (ii) Non-biodegradable pollutants The substances which are, normally not acted upon by microbes are called non-biodegradable, pollutants. These undergo biological magnification., They can further be of two types :, (i) Wastes, e.g. glass, plastic, phenols., (ii) Poisons, e.g. radioactive substances, Hg salts, pesticides, heavy, metals., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Chemistry 313, Classification on the Basis of Their Occurrence in Nature, (i), , Primary pollutants These are present in same form in which, these are added by man, e.g. DDT, pesticides, fertilizers etc., , (ii) Secondary pollutants These occur in different forms and are, formed by the reaction between the primary pollutants in the, presence of sunlight, e.g. HNO3 , H 2SO4, PAN, ozone etc., , Classification on the Basis of Their Existence in Nature, (i), , Quantitative pollutants These are naturally present in, nature and also added by man. These become pollutants when, their concentration reaches beyond a threshold value in the, environment, e.g. CO2, nitrogen oxide etc., , (ii) Qualitative pollutants These are not present in the nature, but are added by nature only due to human activities, e.g., pesticides, fungicides, herbicides etc., , Tropospheric Pollution, It is caused by gaseous pollutants and particulate matter., , Gaseous air pollutants Oxides of sulphur (SOx ), oxides of nitrogen, (NOx ), oxides of carbon (CO, CO2 ), hydrogen sulphide (H 2 S),, hydrocarbons. Ozone and other oxidants etc., Particulate pollutants Dust, fumes, mist, smoke, smog etc., , Air Pollution, Air pollution occurs when the concentration of a normal component of, the air or a new chemical substance added or formed in air, build up to, undesirable proportions causing harm to humans, animals, vegetation, and materials., , Air Pollutants, The chemical substances and particles causing pollution are called air, pollutants. The major air pollutants are :, (i) Oxides of sulphur The most common species is sulphur, dioxide (SO 2) It is produced by petrol combustion, coal, combustion, petrol refining and smelting operation., It obstruct the movement of air in and out of lungs. It is particularly poisonous to trees causing chlorosis and dwarfing. In the, presence of air, it is oxidised to SO3 which is also an irritant., 2 SO2 + O2 ( air) ¾® 2 SO3, , www.aiimsneetshortnotes.com
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314, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Taj Mahal is reported to be affected by SO2 and other pollutants, released by oil refinery of Mathura. The SO3 reacts with water in, the air (or in the lungs) to form H 2SO4., (ii) Oxides of nitrogen NO2 and NO are obtained by combustion, of coal, gasoline, natural gas, petroleum refining, chemical, industries and tobacco smoke. In upper atmosphere, these are, emitted by high flying jets and rockets., Breathing NO2 causes chlorosis to plants and chronic lung, conditions leading to death in human beings. These oxides, destroy ozone (O3 ) layer., 2NO( g) + O2( g) ¾® 2NO2( g), NO( g) + O3 ( g) ¾® NO2( g) + O2( g), (iii) Smoke and dust These are obtained in cement works, iron, and steel works, gas works, power generating stations. Coal, miners suffer from black lung disease and textile workers, suffer from white lung disease., (iv) Ammonia It is produced by fertilizer works., (v) Mercaptans These are obtained from oil refineries, coke, ovens etc., (vi) Zn and Cd These are obtained from zinc and cadmium, industries., (vii) Freon (or CFC’s) Their source is refrigerator., (viii) Hydrocarbons These are formed by incomplete combustion of, fuel used in automobiles. These are carcinogenic. They harm, plants and also break down of tissues., (ix) Oxides of Carbon, (a) Carbon monoxide (CO) It is produced by incomplete, combustion of gasoline in motor vehicles, wood, coal,, inceneration and forest fires. It induces headache, visual, difficulty, coma or death. It blocks the normal transport of, oxygen from the lungs to other parts of the body, by, combining with haemoglobin of the blood. (Its affinity, towards haemoglobin is about 300 times more than the oxygen.), (b) Carbon dioxide (CO2 ) causes mild narcotic effects,, stimulation of the respiratory centre and leads to, asphyniation. The increasing concentration of CO2 also, changes the climatic conditions, especially by raising the, global temperature. This phenomenon is known as the, green house effects., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Chemistry 315, Green House Effect and Global Warming, The phenomenon in which atmosphere of earth traps the heat coming, from the sun and prevents it from escaping into the outer space is, called green house effect. Certain gases, called green house gases, [carbon dioxide, methane, ozone, chlorofluoro carbon compounds, (CFCs) and water vapour] in the atmosphere absorb the heat given by, earth and radiate back it to the surface of the earth. Thus, warming of, the earth led to the warming of air due to green house gases, which is, called global warming., , Consequences of Green House Effect, (or Global Warming), 1. The green house gases are useful in keeping the earth warm, with an average temperature of about 15° to 20°C., 2. There may be less rainfall in this temperature zone and more, rainfall in the dried areas of the world., 3. Increase in the concentration of CO2 in the atmosphere leads to, increase in the temperature of the earth’s surface. As a result,, evaporation of surface water will increase which further help in, the rise of temperature and results in the melting of glaciers and, polar ice caps and hence, level of sea water may rise., , Acid Rain, The pH of normal rain water is 5.6 due to the formation of H + ions by, dissolution of CO2 from atmosphere., H 2O( l ) + CO2( g), H 2CO3 ( aq ), , j, H CO ( aq ) j H ( aq ) + HCO-( aq ), Carbonic acid, +, , 2, , 3, , 3, , when the pH of rain water drops below 5.6 it is called acid rain (by, Robert Augus.) Oxides of N and S are responsible for making rain, water acidic. Much of the NOx and SOx entering in the atmosphere are, converted into HNO3 and H 2 SO4 respectively. The detailed, photochemical reactions occurring in the atmosphere are given as, NO + O3 ¾® NO2 + O2, 2NO2 + O2 ¾® 2NO3, NO2 + NO3 ¾® N 2O5, N 2O5 + H 2O ¾® 2HNO3, HNO3 is removed as a precipitate or as particulate nitrates after, reaction with bases (like NH3 , particulate lime etc)., , www.aiimsneetshortnotes.com
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316, , Telegram @neetquestionpaper, , Handbook of Chemistry, , SO2( g) +, , (Hydrocarbon, NO x ), 1, O2( g) + H 2O( l ) ¾¾¾¾¾¾¾¾® H 2SO4( aq ), Soot particles, 2, , The presence of hydrocarbons and NOx step up the oxidation rate of, the reaction. Soot particles are also known to be strongly involved in, catalysing the oxidation of SO2. Acid rain causes extensive damage to, buildings and sculptural materials of marble, limestone, slate, mortar etc., CaCO3 + H 2SO4 ¾® CaSO4 + CO2 + H 2O, , Particulate Pollutants, These are the minute solid particles or liquid droplets in air., Particulates in the atmosphere may be viable or non-viable., 1. Viable particulates : bacteria, fungi, algae etc., 2. Non-viable particulates : smoke, dust, mists, fumes., , Smog, It is a mixture of smoke (composed of tiny particles of carbon, ash and, oil etc from coal combustion) and fog in suspended droplet form. It is of, two types:, , (i) London Smog or Classical Smog, It is mixture of coal, smoke plus fog. The fog part is mainly SO2 and, SO3 . Chemically, it is a reducing mixture and so, it is called reducing, smog. It causes bronchial irritation and acid rain. It occurs in cool, humid climate., , (ii) Photochemical Smog or Los Angeles Smog, The oxidised hydrocarbons and ozone in a warm, dry and sunny, climate cause photochemical smog. Its brown colour is due to the, presence of NO2. It occurs in very large populations and in high, vehicular density cities., The nitrogen dioxide by absorbing sunlight in blue and UV region, decomposes into nitric oxide and atomic oxygen followed by a series of, the other reactions producing O3 , formaldehyde, acrolein and, peroxyacetylnitrates., NO2( g) + hn ¾® NO( g) + O( g), O( g) + O2( g) ¾® O3 ( g), ·, , RH + O ¾® RO,, ·, , ·, , ·, , ·, , RO + O2 ¾® RO3, , RO3 + NO ¾® RO2 + NO2, ·, , RO2 + NO2 ¾® Peroxyacetylnitrate, Hydrocarbons + O2 , NO2 , NO, O, O3 ¾® Peroxides, formaldehyde,, peroxyacetylnitrate (PAN), acrolein etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Chemistry 317, It is oxidising in nature and causes irritation to eyes, lungs, nose,, asthamatic attack and damage to plants., , Stratospheric Pollution (Depletion of Ozone Layer), Ozone is a light bluish gas and absorbs UV radiations of the sun which, are harmful to living beings, but now a days ozone layer is being, depleted by CFCs (chlorofluorocarbons)., UV radiations cause the chlorofluorocarbons to dissociate to form, highly reactive chlorine free radical which reacts with ozone to form, chlorine monoxide., CF2Cl2( g) + hn ¾®, Cl·( g) + ClF2( g), (Free radical), , ·, , Cl( g) + O3 ( g) ¾® ClO·( g) + O2( g), , ClO·( g) + O( g) ¾® Cl·( g) + O2( g), Cl· (free radical) can react with more O3 . Many O3 molecules can thus be, destroyed for each chlorine atom produced. It has been shown that over, one thousand ozone molecules can be destroyed by one Cl free radical., , The Ozone Hole, Ozone hole is formed over Antarctica, and some parts of non-polar, regions also. In other parts of stratosphere NO2, CH 4 react with ClO·, and Cl· respectively and act as natural sink for ClO· and Cl·, ClO·( g) + NO2( g) ¾® ClONO2( g), Cl·( g) + CH 4( g) ¾® ·CH3 ( g) + HCl ( g), These reactions consume Cl· and ClO· hindrance to ozone depletion., In Antarctica, during winters, special types of clouds, called polar, stratospheric clouds (PSCs) are formed. These clouds are of two types, Type I Clouds They contain some solidified nitric acid trihydrate, (HNO 3 × 3H2O) formed at about – 77°C., Type II Clouds They contain some ice formed at about – 85°C., These clouds play important role in ozone depletion by hydrolysing, chlorine nitrate., ClONO 2( g ) + H2O( g ) ¾® HOCl( g ) + HNO 3( g ), ClONO 2( g ) + HCl( g ) ¾® Cl2( g ) + HNO 3( g ), Hypochlorous acid and Cl2 are formed which are reconverted into, reactive chlorine atoms with the help of sunlight which causes ozone, depletion., , www.aiimsneetshortnotes.com
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318, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Polar vortex During winters, when polar stratospheric clouds are, formed over Antarctica, stable wind patterns in the stratosphere, encircle the continent which is called polar vortex. It is tight, whirlpool of winds which is so rigid that air within it is isolated from, the sun and forms the warmer air of temperate region to fill up ozone, hole. After the spring, the intensity of sunlight increases and the, vortex breaks down and ozone rich air from the temperate region, rushes in and replenishes the ozone hole., , Consequences of Depletion of Ozone Layer, (a), , Loss of sight The UV radiation damage the cornea and lens of, the eyes., , (b), , Effect on immune system The UV radiations are also likely, to suppress immune system., , (c), , Skin cancer The UV radiation is known to be cancer causing, agent., , Water Pollution, The contamination of water by foreign substances which would, constitute a health hazard and make it unfit for all purposes (domestic,, industrial or agriculture etc) is known as water pollution. The polluted, water may have foul odour, bad taste, unpleasant colour etc., Maximum prescribed concentration of some metals in drinking water, is as follows, Metal, , Maximum concentration in ppm, , Fe, , 0.2, , Al, , 0.2, , Cu, , 3.0, , Zn, , 5.0, , Mn, , 0.05, , Cd, , 0.005, , Sources of Water Pollution, (i) Domestic sewage Discharge from kitchens, baths, etc., (ii) Industrial water Wastes from manufacturing processes, which includes acids, alkalies, pesticides, insecticides, metals,, fungicides etc., (iii) Oil From oil spills or washings of automobiles., (iv) Atomic explosion Processing of radioactive materials., (v) Suspended particles (organic or inorganic) Viruses,, bacteria, algae, protozoa etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Chemistry 319, (vi) Wastes from fertilizer Industries such as phosphates,, nitrates, ammonia etc., (vii) Clay Ores, minerals, fine particles of soil., , Effects of Impurities in Water, (a) Fluorides Mottling of teeth enamel, above 1 mg/L fluoride, causes fluorosis., (b) Sulphates Sulphates of Na, K, Mg causes diarrhoea., (c) Lead It damages kidney, liver, brain and central nervous, system., (d) Cadmium and mercury They causes kidney damage., (e) Zn It causes dizziness and diarrhoea., (f) Arsenic It can cause cramps and paralysis., (g) Phosphates from fertilizers They promote algae growth, and reduce dissolved oxygen concentration of water. This process, is known as eutrophication., , Aerobic and Anaerobic Oxidation, The oxidation of organic compounds present in sewage in the presence, of good amount of dissolved or free oxygen (approx. 8.5 mg/L) by, aerobic bacteria is called aerobic oxidation. When dissolved or free, oxygen is below a certain value, the sewage is called stale., Anaerobic bacteria bring, H 2 S, NH3 , CH 4 , (NH 4 )2S etc., anaerobic oxidation., , out, This, , putrification by producing, type of oxidation is called, , The optimum value of dissolved oxygen for good quality of water is, 4-6 ppm (4-6 mg/L). The lower the concentration of dissolved oxygen,, the more polluted is the water., , Biological oxygen demand (BOD) It is defined as the amount of, free oxygen required for biological oxidation of the organic matter, under aerobic conditions at 20°C for a period of five days. Its unit is, mg/L or ppm. Clean water would have BOD value of less than 5 ppm, whereas highly polluted water could have a BOD value of 17 ppm or, more., An average sewage has BOD of 100 to 150 mg/L., , Chemical oxygen demand (COD) It is the measure of all types of, oxidisable impurities (biologically oxidisable and biologically inert, organic matter such as cellulose) present in the sewage. COD values, are higher than BOD values., , www.aiimsneetshortnotes.com
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320, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Control of Water Pollution, (i) Recycling of waste water, (ii) Use of chemicals : Lead poisoning can be cured by giving the, patient an aqueous solution of calcium complex of EDTA. Lead, ions displace calcium in the EDTA complex to form chelated lead, and Ca 2+ . The soluble lead chelate is excreted with the urine., Ca—EDTA + Pb2+ ¾® Pb - EDTA + Ca 2+, (iii) Special techniques such as adsorption, ion exchangers, reverse, osmosis, electrodialysis etc., (iv) Waste water reclamation, , Sewage Treatment, It involves the following steps:, (i) Preliminary process Passing sewage through screens to, remove large suspended matter and then through mesh screens, to remove solids, gravels, silt etc., (ii) Settling process (sedimentation) The residual water when, allowed to stand in tanks, the oils and grease, float on the surface, and skimmed off and solids settle down. The colloidal material is, removed by adding alum, ferrous sulphate etc. Primary sludge, can be separated., (iii) Secondary treatment or biological treatment It is aerobic, chemical oxidation or aeration which converts carbon of the organic, matter to CO2, nitrogen into NH3 and finally into nitrite and, nitrates, dissolved bases form salts such as NH 4NO2 , NH 4NO3 and, Ca(NO3 )2 etc., and secondary sludge is obtained., (iv) Tertiary treatment It is treatment of waste water with lime, for removal of phosphate which is then coagulated by adding, alum and ferric chloride and removed by filtration., Water is disinfected by adding chlorine., Secondary sludge forms a good fertilizer for soil as it contains nitrogen, and phosphorus compounds., , Soil or Land Pollution, The addition of substances in an indefinite proportion changes the, productivity of the soil. This is known as soil or land pollution., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Chemistry 321, Sources of Soil Pollution, (i) Agricultural pollutants e.g. chemicals like pesticides, fertilizers,, bacteriocides, fumigants, insecticides, herbicides, fungicides., (ii) Domestic refuge and industrial wastes., (iii) Radioactive wastes from research centres and hospitals., (iv) Soil conditioners containing toxic metals like Hg, Pb, As, Cd etc., (v) Farm wastes from poultries, dairies and piggery farms., , Control of Soil Pollution, (i) Use of manures Manures prepared from animal dung is, much better than the commonly used fertilizers., (ii) Use of bio-fertilizers These are the organisms which are, inoculated in order to bring about nutrient enrichment of the soil., e.g., nitrogen fixing bacteria and blue-green algae., (iii) Proper sewage system A proper sewage system must be, employed and sewage recycling plants must be installed., (iv) Salvage and recycling Rag pickers remove a large number, of waste articles such as paper, polythene, card board, rags,, empty bottles and metallic articles. These are subjected to, recycling and this helps in checking soil pollution., , Radioactive Pollution, Cosmic rays that reach the earth from outer space and terrestrial, radiation from radioactive elements are natural radiations. This, natural or background radiation is not a health hazard due to its low, concentration., Man made sources of radiations include mining and refining of, plutonium and thorium, atomic reactors and nuclear fuel. These are, produced during preparation of radio-isotopes. These are of two types :, electromagnetic (radio waves UV, IR, a-rays) and particulate., , Other Sources of Radioactive Pollution, (i) Atomic explosions Atomic explosions produce radioactive, particles which are thrown high up into the air as huge clouds., The process releases large amount of energy as heat. Due to, atomic explosion nuclear fall out. These radioactive elements, may reach the human beings through food chain., (ii) Radioactive wastes Wastes from atomic power plants come, in the form of spent fuels of uranium and plutonium. People, working in such power plants, nuclear reactors, fuel processors, etc., are vulnerable to their exposure., , www.aiimsneetshortnotes.com
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322, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Radio isotopes Many radioactive isotopes like C14 , I125 , P32, and their compounds are used in scientific researches. The waste, water of these research centres contains the radioactive elements, which may reach the human beings through water and food, chains., , Effects of Radiations, 1. Strontium-90 accumulates in the bones to cause bone cancer and, tissue degeneration in number of organs., 2. I-131 damages WBCs, bone marrow, lymph nodes and causes, skin cancer, sterility and defective eye sight., 3. These may cause ionisation of various body fluids, chromosomal, aberrations and gene mutations., 4. Radioactive iodine may also cause cancer of thyroid glands., 5. Cesium-137 brings about nervous, muscular and genetic, change., 6. Uranium causes skin cancers and tumours in the miners., 7. Radon-222 causes leukemia, brain tumours and kidney, cancers., , Bhopal Gas Tragedy, In Dec. 2, 1984 a dense cloud of methyl isocyanate gas (MIC) leaked from a storage, tank of the Union Carbide Ltd plant in Bhopal. It caused a great loss of life to people, and animals. Methyl isocyanate was prepared by the reaction of methyl amine, with phosgene and stored in abundance., CH3NH2 + COCl2, Methyl amine Phosgene, , ¾® CH3 ¾ N== C== O + 2HCl, MIC, , Green Chemistry–An Alternative Tool, for Reducing Pollution, Green chemistry may be called chemistry involved in the design,, development, and implementation of chemical products and processes, to reduce or eliminate the use and generation of substances hazardous, to human health and the environment., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Environmental Chemistry 323, Thus, the goal of green chemistry is to promote the development of, products and processes that reduce or eliminate the use or generation, of toxic substances associated with the design, manufacture, and use of, hazardous chemicals. Some important principles and method of green, chemistry are :, 1. It is better to prevent waste than to treat or clean up waste after, it is formed., 2. Synthetic methods should be designed to maximize the, incorporation of all materials used in the process into the final, product., 3. Whenever possible, synthetic methodologies should be designed, to use and generate substances that possess little or no toxicity, to human health and the environment., 4. Chemical products should be designed to preserve efficiency of, function while reducing toxicity., 5. The use of auxiliary substance (e.g. solvents, separation agents, etc.) should be avoided as far as possible., 6. Energy requirements should be recognised for their, environmental and economic impacts and should be minimized., 7. Synthetic methods should be conducted at ambient temperature, and pressure., , Green Chemistry in Day-to-Day life, (i) Dry cleaning of clothes Tetra chloroethene (Cl2C == CCl2 ), was earlier used as solvent for dry cleaning. Now-a-days, hydrogen peroxide (H 2O2 ) is used for the purpose of bleaching, clothes in the process of laundary., (ii) Bleaching of paper, (ii) Synthesis of chemicals, Catalyst, , CH 2 ==CH 2 + O2 ¾¾¾¾¾® CH3CHO ( 90%), Pt (II)/Cu (II), (in water), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 23, Purification and, Characterisation of, Organic Compounds, Purification of Organic Compounds, Organic compounds extracted from a natural source or synthesized in, the laboratory requires purification. Various methods are used for the, purification and are based on the nature of the compound and the, impurity present in it. The purity of a compound is ascertained by, determining its melting point or boiling point or by chromatographic, and spectroscopic techniques., , Methods of Purification of Solids, (i), , Cystallisation, , In this process, a saturated solution of, impure substance is prepared in hot solvent and heated with, animal charcoal which adsorbs the impurities. The solution is, filtered and filtrate on cooling deposits crystals of pure, compound. Success of the process depends upon the selection of, the solvent. The impurities must be least soluble., , A process in which crystal formation is initiated by adding crystals of, pure substance, is known as seeding., (ii) Fractional crystallisation It is based on the different, solubilities of different compounds in a solvent. The compound, having less solubility crystallises out first on cooling leaving, behind others in solution. Sometimes mixture of two solvents,, e.g. alcohol and water, chloroform and petroleum ether, give, better results., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 325, , Purification and Characterisation of Organic Compounds, , (iii) Sublimation Some solids directly convert into vapours when, heated without converting into liquid. These are known as, sublimate and this process is called sublimation. The substances, which sublime can be purified by this method provided the, impurities present does not sublime. Camphor, naphthalene and, anthracene are purified by sublimation., , Methods of Purification of Liquids, (i), , Simple distillation The vaporisation of a liquid by heating, and subsequent condensation of vapours by cooling is known as, distillation. The liquids boiling under ordinary conditions of, temperature and pressure without decomposition and containing, non-volatile impurities are purified by simple distillation., , (ii) Fractional distillation It is employed for separating mixture, of two or more volatile liquids having boiling points close to each, other, e.g. acetone (boiling point 60°C) and methanol (boiling, point 65°C). Components of petroleum are separated by this, method. The vapours of the liquids are passed through the, fractionating column which provides greater space for their, cooling. The vapours of high boiling substance condense and fall, back into distillation flask., (iii) Distillation, , under reduced pressure or vacuum, distillation Some liquids decompose when heated to their, boiling points, e.g. glycerol. Such liquids can be purified by, distillation under reduced pressure much below than their boiling, points., , (iv) Steam distillation The liquids insoluble in water, steam, volatile in nature, having high molecular weight and high vapour, pressure are purified by steam distillation provided the impurities, present are not steam volatile. The liquid boils when the sum of, vapour pressures due to the organic liquid ( p1 ) and that due to, water ( p2 ) becomes equal to the atmospheric pressure (p). i.e., p = p1 + p2. Since, p1 is lower than, p the organic liquid vaporises, at lower temperature than its boiling point. e.g. o-hydroxy, acetophenone and p-hydroxy acetophenone are separated by this, method., (v), , By separating funnel In this method, a mixture of two, immiscible liquids can be separated and the process is also called, differential extraction., , www.aiimsneetshortnotes.com
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326, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Chromatographic Method, It was discovered by Tswett (1906)., It is based upon the principle of selective adsorption of various, components of a mixture between the two phases : stationary or fixed, phase and mobile phase., The various chromatographic techniques are:, , 1. Adsorption Chromatography, Stationary phase – solid or ion exchange resin. Mobile phase –liquid or, gas., It includes liquid-solid chromatography, gas-solid chromatography or, ion exchange chromatography., Two types of chromatographic techniques based on the principle of, differential adsorption are as follows., , (a) Column Chromatography, It is an example of adsorption chromatography. Adsorbents used are, alumina, silica gel, cellulose powder, animal charcoal, keiselguhr etc., Liquid solvents used are benzene, petroleum ether, alcohol etc., When the solvent is poured over the mixture present at the top of a, column packed with adsorbent, the components are separated into, number of layers called zones, bands or chromatograms due to, preferential adsorption., , (b) Thin Layer Chromatography, It involves separation of substances of a mixture over a thin layer of an, adsorbent coated on glass plate. The thin layer (about 0.2 mm thick) of, an adsorbent (silica gel or alumina) is spread over a glass plate of, suitable size. The plate is known as thin layer chromatography plate or, chromoplate., The solution of the mixture to be separated is applied as small spot, about 2 cm above one end of TLC plate. The glass plate is then placed, in a closed jar containing the eluant. As the solvent rises up the plates,, the component of mixture moves up along with the eluant to different, distance depending on their degree of adsorption and separation takes, place., , Retardation Factor i.e. R f Value, Rf =, , distance moved by the substance from base line ( x ), distance moved by the solvent from base line ( y ), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 327, , Purification and Characterisation of Organic Compounds, , 2. Partition Chromatography, Fixed phase-liquid supported on inert solid. Mobile phase –liquid or, gas., This process is known as liquid-liquid partition chromatography or, liquid-gas partition chromatography on the basis of its different phases., , 3. Paper Chromatography, The principle of paper chromatography is based on the fact that solutes, have the capacity to migrate through filter paper at different rates as a, solution is drawn into strip of paper by capillary action., In paper chromatography, the dissolved substance is applied as a small, spot about 2-3 cm from the edge of a strip or square of filter paper and, is allowed to dry. This strip is then suspended in a large close, container where atmosphere is saturated with the solvent system. The, end containing the sample is dipped into the mobile phase which has, already been saturated with the stationary phase. When the solvent, front has reached at the other end of the paper, the strip is removed, and the zones are located by analytical methods., The ratio of the distance travelled by a component to the distance, travelled by the solvent front is characteristic of each component and, is known as the Rf value., distance in cm from starting line to the centre of zone, Rf =, distance in cm from starting line to the solvent front, , Elution The continuous pouring of solvent from the top of the column is known, as elution or running of column. Solvent is known as eluant., The most weakly adsorbed component is eluted first by least polar solvent while, more strongly adsorbed component is eluted later by highly polar solvents., , Chemical Methods of Purification, The substance to be purified is treated with a suitable chemical, reagent to form a stable derivative. It is then separated by suitable, method and decomposed to get the pure compounds., , Examples, (i) Mixture of amines (1°, 2° and 3°) is separated by Hinsberg’s, method., (ii) Acetic acid from pyroligneous acid is separated by forming, calcium salt., , www.aiimsneetshortnotes.com
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328, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Acids are separated by forming sodium derivatives with, NaHCO3 ., (iv) Absolute alcohol is obtained from rectified spirit by quick lime, process and azeotropic distillation., , Azeotropic Distillation, Azeotropes are constant boiling mixtures which distil off without any, change in composition at a fixed temperature. Therefore, components, of an azeotropic mixture cannot be separated by fractional, distillation. A very common example of azeotropic mixture is rectified, spirit which contains 95.87% ethyl alcohol and 4.23% water by weight, which boils at 351.1 K., Such mixtures are separated by adding another component which, generate a new lower boiling azeotrope that is heterogeneous (i.e., producing two immiscible liquid phases). e.g. C6H6 is added to H2O, and ethyl alcohol azeotrope to separate them., , Qualitative Analysis of Organic Compounds, 1. Detection of Carbon and Hydrogen, This is done by heating the given organic compound with dry cupric, oxide in a hard glass test tube when carbon present is oxidised to, carbon dioxide and hydrogen is oxidised to water., D, , C + 2CuO ¾® CO2 + 2Cu, D, , 2H + CuO ¾® H 2O + Cu, Carbon dioxide turns lime water milky., Ca(OH)2 + CO2, From C, , ¾® CaCO3 ¯ + H 2O, Milky, , Water condenses on the cooler parts of the test tube and turns, anhydrous copper sulphate blue., CuSO4 + 5H 2O ¾® CuSO4× 5H 2O, White, , Blue, , Lassaigne’s Test, The organic compound is fused with a small piece of Na metal. When, element (N , S, X ) of the organic compound combine to give NaCN,Na 2S, or NaX, the red hot tube is plunged in distilled water, boiled and, filtered. The filtrate is called Lassaigne’s extract or sodium, extract. The Lassaigne’s extract is usually alkaline. If not, it is made, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 329, , Purification and Characterisation of Organic Compounds, , alkaline by adding a few drops of a dilute solution of sodium hydroxide., The purpose of fusing the organic compounds with sodium metal is to, convert halogens, N, S, P etc., present in the organic compound to their, corresponding soluble sodium salts (ionic compounds)., D, , Na + C + N ¾® NaCN, D, , 2Na + S ¾® Na 2 S, D, , Na + X ¾® NaX, , (where, X = Cl, Br, I), , 1. Detection of Nitrogen, To a part of this Lassaigne’s extract a few drops of a freshly prepared, solution of ferrous sulphate is added, because a dilute solution of, FeSO4 after a long time oxidise to basic ferric sulphate which is useless, for analysis. The contents are warmed a little, cooled and then acidified, with dil. H 2 SO4. Appearance of a green or Prussian blue colouration, indicates the presence of nitrogen., 6CN – + Fe2+ ¾® [Fe(CN)6 ]4–, xH 2O, , 3[Fe(CN)6 ]4– + 4Fe3 + ¾¾® Fe4 [Fe(CN)6 ]3 × xH 2O, Prussian blue, , If S is also present alongwith N, a red colour in place of Prussian blue, in the test of nitrogen appears, due to the formation of Fe(SCN)2+ ., Hydrazine does not give Lassaigne’s test for nitrogen since it does not, contain carbon. In order to test the presence of N in such compounds,, during fusion with Na, some charcoal or preferably starch (which, contains C but not N, S, halogens etc.) is added. Under these, conditions, C of starch or charcoal combines with N of the compound to, form NaCN which will now give a positive test for nitrogen., Lassaigne’s test is not shown by diazonium salts because diazonium, salts usually lose N2 on heating much before they have a chance to, react with fused sodium metal., , 2. Detection of Sulphur, (i) Sodium fusion extract is acidified with acetic acid and lead, acetate is added to it. A black precipitate of PbS indicates the, presence of sulphur., S2- + Pb2 +, ¯, PbS, Black, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 331, , Purification and Characterisation of Organic Compounds, , The carbon dioxide is absorbed in concentrated solution of KOH., 12, mass of CO2 ´ 100, Percentage of carbon =, ´, 44 mass of organic substance, Percentage of hydrogen =, , 2, mass of H 2O ´ 100, ´, 18 mass of organic substance, , On heating with CuO, elements other than C and H are also modified, as follows :, When organic compound contains nitrogen, the oxides of nitrogen, (NO, N 2O etc.) are absorbed by caustic potash. These are removed by, the use of bright copper gauge., 4Cu + 2NO2 ¾® 4CuO + N 2, Cu + N 2O ¾® CuO + N 2, Nitrogen is not absorbed by KOH solution., When organic compound contains halogens, they are removed by, using silver gauge by forming non-volatile silver halide., When sulphur is present, it is removed by forming lead sulphate by, using fused lead chromate and halogens form lead halides., , Estimation of Nitrogen, (i) Duma’s method This method is used for nitrogenous, compounds. Though tedious but it is better than Kjeldahl’s method., In this method, the nitrogenous compound is heated strongly with, CuO in the atmosphere of CO2 and the mixture obtained is passed, over a roll of heated bright Cu gauze. The oxides of nitrogen again, reduce to N 2. The resultant mixture is passed in KOH. All gases, except N 2 are fairly absorbed. Nitrogen is collected over KOH and, its volume at NTP is measured., Cx H yN z + ( 2x + y/ 2) CuO ¾® xCO2 + y/ 2 H 2O + z / 2 N 2, + ( 2x + y/ 2) Cu, Percentage of nitrogen =, =, , 28 ´ volume of N 2 at NTP ´ 100, 22400 ´ wt. of organic compound, mass of nitrogen ´ 100, mass of organic substance, , www.aiimsneetshortnotes.com
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332, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (ii) Kjeldahl’s method, In this method, nitrogen containing compound is heated with conc., H 2SO4. The acid mixture obtained is then heated with excess of, NaOH. The liberated ammonia gas is absorbed in an excess of, standard solution of H 2SO4. The amount of NH3 produced is, determined by estimating the amount of H 2SO4 consumed in, reaction., Organic compound + conc. H 2 SO4 + (small amount of K 2SO4 and, 2NaOH, , CuSO4 ® (NH 4 )2SO4 ¾¾® Na 2 SO4 + 2NH3 + 2 H 2O, 2NH3 + H 2SO4 ¾® (NH 4 )2SO4, Ammonia is passed through H 2 SO4 or HCl of known volume and, normality. The volume of acid neutralised by NH3 is calculated by, neutralising the acid left by NaOH solution., 1.4 ´ N ´ V, Percentage of nitrogen =, mass of organic compound, N = normality of acid, V = volume of acid in mL neutralised by ammonia., (In practice, K 2 SO4 is added to raise the boiling point of H 2 SO4 and, CuSO4 is added to catalyse the reaction)., Kjeldahl’s method is not reliable as results obtained are generally, low. It cannot be applied to compounds containing nitrogen directly, linked to oxygen or nitrogen such as nitro, nitroso, azo and nitrogen, present in ring as in pyridine., , Estimation of Halogen (Carius Method), In this method, halogen containing compound is heated with fuming, HNO3 in presence of AgNO3 contained in carius tube. On heating, C, and H are oxidised to CO2 and H 2O and halogen present forms AgX., Organic compound + Fuming HNO3 + AgNO3 ® AgX, It is estimated gravimetrically., Percentage of halogen, Atomic mass of halogen atom ´ mass of AgX ´ 100, =, mol. mass of AgX ´ mass of organic compound, , Estimation of Sulphur, In this method, sulphur containing compound is heated in carius tube, with Na 2O2 or fuming HNO3 . On heating S is oxidised to H 2SO4. It is, precipitated as BaSO4 by adding excess of BaCl2 solution in water., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 333, , Purification and Characterisation of Organic Compounds, , Organic compound + Oxidising agent (Na 2O2 or fuming HNO3 ) ®, BaCl 2, , H 2 SO4 ¾¾® BaSO4., It is estimated gravimetrically,, Percentage of sulphur =, , 32 ´ mass of BaSO4 ´ 100, 233 ´ mass of organic compound, , Estimation of Phosphorus, In this method, organic compound is heated with fuming HNO3 that, converts ‘P’ present in compound to phosphoric acid. It is precipitated, as (NH 4 )3 PO4 × 12MoO3 by adding NH3 and ammonium molybdate., Alternatively, phosphoric acid may be precipitated as MgNH 4PO4 by, adding magnesia mixture which on ignition yields Mg2P2O7 ., Organic compound + Fuming nitric acid ® H3PO4, Magnesia, , Ignition, , ¾¾¾¾®, mixture, (MgSO 4 + NH4 OH + NH4 Cl), , Percentage of phosphorus =, , MgNH 4PO4 ¾¾¾¾¾® Mg2P2O7, (magnesium, pyrophosphate), , 62 ´ mass of Mg2P2O7 ´ 100, 222 ´ mass of organic compound, , Now a days CHN elemental analyser is used to estimate the C, H and, N in the organic compound., , Estimation of Oxygen, The mixture of gaseous product containing oxygen is converted to, carbon monoxide. This mixture is passed through warm iodine, pentoxide (I2O5 ) when carbon monoxide is oxidised to carbon dioxide, producing iodine., Heat, Compound ¾¾®, O2 + Other gaseous products, , 1373 K, , 2 C + O2 ¾¾¾® 2 CO ´ 5, I2O5 + 5 CO ¾¾® I2 + 5CO2 ´ 2, 32 ´ m1 ´ 100, \Percentage of oxygen =, %, 88 ´ m, m = mass of organic compound taken., m1 = mass of carbon dioxide produced., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 24, , General Organic, Chemistry, Organic Chemistry, The hydrides of carbon (hydrocarbons) and their derivatives are called, organic compounds. The branch of chemistry which deals with these, compounds is called organic chemistry., Berzelius (1808) defined organic chemistry as the chemistry of, substances found in living matter and gave the vital force theory., Synthesis of urea, the first organic compound synthesised in, laboratory, by Wohler, gave death blow to the vital force theory., D, , (NH 4 )2SO4 + 2KCNO ¾¾¾® 2NH 4CNO ¾® NH 2CONH 2, - K 2SO 4, , urea, , Acetic acid is the first organic compound synthesised from its elements., , Reasons for Large Number of Organic Compounds, (a) Catenation It is the tendency of self combination and is, maximum in carbon. A carbon atom can combine with other carbon, atoms by single, double or triple bonds. Thus, it forms more, compounds than the others., (b) Tetravalency and small size Carbon being tetravalent, is, capable of bonding with four other C-atoms or some other, monovalent atoms. Carbon can form compound with oxygen,, hydrogen, chlorine, sulphur, nitrogen and phosphorus. These, compounds have specific properties depending upon the nature of, the element or group attached with the carbon., Furthermore, these compounds are exceptionally stable because of, the small size of carbon., , General Characteristics of Organic Compounds, 1. These are the compounds of carbon with H, O, N, S, P, F, Cl, Br and I., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 335, 2. These are generally found in living organisms., e.g. carbohydrates, proteins etc., 3. These may be gases, liquids or solids., 4. Being covalent in nature, these have low boiling point and, melting point and soluble in organic solvents., 5. These are generally volatile and inflammable., 6. They do not conduct electricity because of the absence of free ions., 7. They posses distinct colour and odour., , Representation of Different Formula, An organic compounds can be represented by the following ways :, , 1. Complete formula, In it, all the bonds present between any two atoms are shown clearly., H H H H, ½ ½, ½, ½, e.g., H¾ C ¾ C ¾ C ¾ C ¾H, ½ ½, ½, ½, H Cl H H, , 2. Condensed Formula, In it, all the bonds are not shown clearly., e.g., , CH3 CH CH 2CH3, ½, Cl, , or CH3CH(Cl)CH 2CH3, , 3. Bond Line Formula, In it, every fold and free terminal represents a carbon and lines, represent the bonds. e.g., Cl, , In such formulae, it is assumed that required number of H-atoms are present,, wherever, they are necessary (to satisfy tetravalency of carbon), e.g., CH3––C, , CH––CH2CH3, , CH3, CH2, , CH––C, , C–– OH, , OH, OH, , CH3––CH2––COOH, O, , www.aiimsneetshortnotes.com
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336, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Three-dimensional Representation of, Organic Molecule, The three-dimensional (3-D) structure of organic molecule can be, represented on paper by using certain convention, e.g. by using, solid (, ) and dashed (, )wedge formula, the 3-D image of a, molecule from a two-dimensional picture can be perceived. 3-D, representation of methane molecule on paper has been shown below :, dashed wedge, (bond away from observer), , H, , bond in, the plane, of paper, , C, , H, , H, , H, , solid wedge, (bond towards observer), , wedge-and-dash representation of CH ., , Classification of Organic Compounds, Organic Compounds, Closed chain, or cyclic or ring, compounds, , Open chain or acyclic, or aliphatic compounds., e.g. alkane,alkene etc., , Heterocyclic, , Homocyclic or carbocyclic, , O, , N, S, H, Pyrrole Thiophene, Furan, (These all are also aromatic.), , Alicyclic, , Aromatic, , e.g., Cyclopropane, , Cyclobutane, , Benzenoid, e.g., , Cyclohexane, Non-benzenoid, O, , ,, e.g., , Benzene Naphthalene, tropolone, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 337, Classification of Carbon Atoms, 1. On the Basis of Number of C Attached, (i) Primary carbon atom When carbon atom is attached with, one other carbon atom only, it is called primary or 1° carbon, atom., (ii) Secondary carbon atom When carbon atom is attached, with two other carbon atoms, it is called secondary or 2°carbon, atom., (iii) Tertiary carbon atom When carbon atom is attached with, three other carbon atoms, it is called tertiary or 3° carbon atom., (iv) Quaternary carbon atom When carbon atom is attached, with four other carbon atoms, it is called quaternary or 4° carbon, atom., Reactivity order of carbon atoms is as follows 3° > 2° > 1°., 1°, , CH3, ½ 4°, 1°, 2°, CH3 ¾ CH 2 ¾ C ¾, ½, CH3, , e.g., , 1°, , 3°, , 1°, , CH ¾ CH3, ½, CH3, 1°, , On the Basis of Position of Functional Group, (i) a-carbon, group., (ii) b-carbon, , Carbon which is directly attached to the functional, Carbon which is directly attached to the a-carbon., , Classification of Hydrogen Atoms, 1°-hydrogen (primary) attached to 1°-carbon., 2°-hydrogen (secondary) attached to 2°-carbon., 3°-hydrogen (tertiary) attached to 3°-carbon., a-hydrogen(s) Hydrogens which are attached to a-carbon atom., b-hydrogen(s) Hydrogens which are attached to b-carbon atom., e.g., , b, , a, , b, , a, , b, , a, , CH3 ¾ CH 2 ¾ Cl,, CH3 ¾ CH 2 ¾ COOH, CH3 ¾ CH 2 ¾ CHO, , www.aiimsneetshortnotes.com
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338, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Functional Group, The atom, e.g. ¾ Cl, ¾ Br etc., or group of atoms e.g. —COOH, —CHO,, which is responsible for the chemical properties of the molecule, is, called functional group., Double and triple bonds are also functional groups., R—OH, R is called alkyl group, it contains only single bond; alkenyl group, contains double bond and alkynyl group contains triple bond., , Homologous Series, The series in which the molecular formula of adjacent members differ, by a ¾ CH 2 unit, is called homologous series and the individual, members are called homologues. e.g. The homologous series of alkene, group is, ü C2H 4, ïC H, ï 3 6, difference of ¾ CH 2 unit or 14 unit mass, ý, ï C4H 8, ïþ C5H10, The general characteristics of this series are :, 1. All the homologues contain same functional group. That’s why, their chemical properties are almost similar., 2. All the members of a series have same general formula, e.g., Series, , General formula, , Alkanes, , C nH, , n+, , Alkenes, , C nH, , n, , Alkynes, , C nH, , n-, , Alcohol and ether, , C nH, , n+, , Aldehyde and ketone, , C nH nO, , Acid and ester, , C nH nO, , O, , 3. All the members can be prepared by almost similar methods., 4. With increase in the molecular weight of a series, the physical, properties varies gradually., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 339, Nomenclature of Organic Compounds, Trivial System, It is the oldest system in which names are derived from source or some, property. These are mainly derived from Latin or Greek names. e.g., acetic acid (acetum = vinegar), oxalic acid (oxalus), malic acid (pyrus, malus), citric acid (citrum), formic acid (obtained from red ant, (formicus)]., , IUPAC System, The IUPAC (International Union of Pure and Applied Chemistry), system, given in 1957, is superior and widely used. IUPAC amends, these rules from time to time. Here, we are following the 1993, recommendations of IUPAC nomenclature. Following rules are used to, write the IUPAC name of an organic compound., , Rule I, Longest chain rule The chain containing the principal functional, group, secondary functional group and multiple bonds as many as, possible is the longest possible chain. In the absence of functional, group, secondary group and multiple bonds, the chain containing the, maximum number of C-atoms will be the longest possible chain. e.g., C––C––C––C––C––C––C, C, C, , C, , Longest chain, , Choose the word root from the table given below for the longest, possible chain., Word Root for Carbon Chain, Chain length, , Word root, , Chain length Word root, , C, , Meth-, , C, , Hept, , C, , Eth-, , C, , Oct, , C, , Prop-, , C, , Non, , C, , But-, , C, , Dec, , C, , Pent, , C, , Undec, , C, , Hex-, , C, , Dodec, , www.aiimsneetshortnotes.com
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342, , Telegram @neetquestionpaper, , Handbook of Chemistry, , If side chain contains a multiple bond or a functional group, the ring is, treated as a substituent e.g., 3, , 1, , 2, , CH2––CH––CH2, 3-cyclo propylprop-1-ene, , Other examples are :, O, 1, , 6, 5, , CH3, 2, 3, , 4, , CH2CH3, , 3-ethyl-2-methylcyclohex-2-en-1-one, , Naming Spiro Compounds, Prefix ‘spiro’ is used for the compounds in which one carbon is common, between two rings :, Here, smaller ring is numbered first, e.g., 7, , 8, , 9, , 1, 4, , 6, , 2, 3, , 5, , 8, , 2, , 5, , O, , 7, , spiro [3.4] octane, , 1, , 10, , 4, , 6, , 3, , 6-oxaspiro [4.5] decane, , number of atoms in ring, in ascending order, , Naming Bicyclo Compounds, Prefix ‘bicyclo’ is used for such compounds, e.g., 1, , 6, , 2, , 7, 8, , 6, 5, , 3, , 4, , bicyclo [3.2.1] octane, , 1, 5, , 2, , 4, 3, , bicyclo [2.1.1] hexane, , number of atoms in each ring, in descending order, , In bicyclo compounds, numbering is done first in larger ring, then in, smaller ring., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 343, Naming Aromatic Compounds, IUPAC accepted their common trivial names, e.g., Cl, , benzene, , chlorobenzene, , OH, , phenol, , CHO, , benzaldehyde, , CH3, , toluene, , NH2, , COOH, , aniline, , benzoic acid, , NO2, , CN, , benzonitrile, , Cl, , nitrobenzene, , CH2CH2CH2Br, , Cl, , Cl, , 1,4-dichlorobenzene, , 1-bromo-3-(4-chlorophenyl) propane, , Isomerism, The compound having same molecular formula but differ in properties, are known as isomers and the phenomenon is known as isomerism., There are two main types of isomerism i.e., , 1. Structural Isomerism, In this type of isomerism, compounds have same molecular formula, but different structures., It can further be of following types :, (i) Chain Isomerism, It arises when two or more compounds have similar molecular formula, but different carbon skeletons, e.g. for C5H12. we have, CH3 ¾ CH 2 ¾ CH 2 ¾ CH 2 ¾ CH3, n - pentane, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 345, OH, , O, H, a-hydrogen, cyclohexanone, (keto form), , enol form, , 2. Stereoisomerism, The compounds having same molecular formula but different spatial, arrangement of atoms or groups are called stereoisomers and the, phenomenon is called stereoisomerism., Stereoisomerism is of two types : optical isomerism and geometrical, isomerism., (i) Optical Isomerism, Compounds having similar physical and chemical properties but differ, only in behaviour towards plane polarised light are called enantiomers, or optical isomers and the phenomenon is known as optical isomerism., e.g., CH3, , H, , CH3, , C––OH, , HO––C, , CH2CH3, , H3CH2C, , H, , 2-butanol, mirror, , The isomer which rotate the plane of polarised light towards, right (clockwise) is known as dextrorotatory or d-form while that, which rotates towards left (anticlockwise) is known as laevorotatory, or l-form., Generally asymmetric or chiral compounds show optical isomerism., Chiral compounds are those which contain chiral centre i.e. chiral, carbon, the carbon all the four valencies of which are satisfied by four, different groups. Allenes, spiranes and biphenyl compounds, although, have absence of chiral centre, but are asymmetric. That’s why they are, also optically active., Number of optical active isomers = 2n (where, n = chiral carbon). If two, end are similar number of optical active isomers = 2n - 1 (if n = even), and meso form = 2, = 2n - 1 - 2( n - 1)/ 2., , n -1, 2 ., , If n = odd, number of optical active isomers, , www.aiimsneetshortnotes.com
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346, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Terms Related to Optical Isomerism, (a) Enantiomers The non-superimposable mirror images are called, enantiomers. e.g., Me, , Me, Cl, Br, , H, H, , Cl, Br, , Me, , H, H, Me, , (b) Diastereomers The isomers which are non-superimposable and, not related to each other as mirror image, are called, diastereomers., Me, , Me, Cl, Br, , H, H, , H, Br, , Me, , Cl, H, Me, , diastereomers, , They have different physical and chemical properties., (c) Meso form The compound in which half part of a molecule is the, mirror image of other half, is called meso form. Generally, a meso, compound have two or more chiral centres and a plane of, symmetry., It is optically inactive due to internal compensation, thus, it is not, possible to convert it into d and l-form e.g., COOH, *, H––C––OH, , plane of symmetry, , H––C––OH, *, , COOH, meso compound, , (d) Racemic mixture It is a mixture of enantiomers in 1 : 1. It is, optically inactive due to external compensation., Separation of a racemic mixture into d and l form is called, resolution. It can be done by mechanical method, biochemical, method and chemical method., (e) Atropisomers These are the isomers that can be, interconvertable by rotation about single bond but for which the, rotation barrier is large enough that they can be separated and do, not convert readily at room temperature., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 347, (f) Specific rotation It is given by the expression, [a ] =, , a, observed rotation (degree), =, l´d, length ´ density, , Nomenclature of Enantiomers, (i) D-L configuration The optical isomer in which H is present, towards left hand side and the other group towards right hand side,, is D-form while in which, H is present towards right and the other, group occupy the left position, is L-form. This system is applicable, mainly for compounds containing one chiral atom., (ii) Threo-erythro system When the same groups are present at the, same side of the carbon chain, the form is called erythro form. When, the same groups are present on the opposite side of the carbon chain,, the form is called threo form. e.g., CH3, H, H, , OH, Cl, CH3, , erythro form, , CH3, H, Cl, , OH, H, CH3, , threo form, , (iii) R-S system This system was proposed by Cahn, Ingold and, Prelog. In this system, configuration R is given to the isomer in which, sequence of groups is clockwise and S is given to the isomer in which, sequence of groups is anticlockwise., Priority sequence is decided by following rules :, 1. Priority is given to the atom having high atomic number, e.g. in, Cl, Br and F, the priority order is Br > Cl > F., 2. In case of group of atoms, priority is decided by the atomic, number of first atom. e.g. in —COOH, —OH and ¾ NH 2 priority, order is, ¾ OH > ¾ NH 2 > ¾ COOH, 3. If the first atom of the group of atoms is same, the priority is, decided by second atom of the group, e.g. among —COOH,, ¾ CH 2OH and—CHO, priority order is, ¾ COOH > ¾ CHO > ¾ CH 2OH, , www.aiimsneetshortnotes.com
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348, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 4. When a multiple bond is present in a group, the atom at the end, of the multiple bond is like as if it is equal to equivalent number, of single bond, e.g., ––C––C––, C, , is equivalent to, , C, , ––C, , C––, , N C, Similarly, –C, , is equivalent to, , N, , ––C––N––, N C, , 1, , 1, , OH, e.g., , 4 H––C––CH3, 3, , 4, , NH2, , 3, , Interconversion, , 2, , 2, , 3, 1, , 2, , Clockwise;, R configuration, , 4, , Priority order OH > NH2 > CH3 > H, 3, , 4, , H3 C, , H, , 2, , 4, 1, , 3, , H, , 1, , Clockwise;, R configuration, , 2, , H, , (ii) Geometrical Isomerism, The isomers having same molecular formula but different spatial, arrangement of atoms about the double bond are known as geometrical, isomers and this phenomenon is called geometrical isomerism, e.g., H3C, H, , C, , C, , CH3, H, , cis-2-butene, , H3C, H, , H, C, , C, CH3, , trans-2-butene, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 349, For exhibiting geometrical isomerism, the essential conditions are :, 1. The compound must contain at least one double bond., 2. The groups present at the double bonded carbon atoms, must be, different. However, one similar group should be present at the, adjacent double bonded carbon atoms., Number of geometrical isomers (if two ends are not similar = 2n, where, n = number of double bonds)., , Types of Geometrical Isomers, (a) Cis-trans isomers In cis-isomer, similar groups are present on, the same side of the double bond and in trans-isomer, similar, groups are present on the opposite side of the double bond. e.g., H3C, H3C, CH3, H, C ==C, C ==C, H, CH3, H, H, cis- form, , trans- form, , Cycloalkanes also exhibit cis-trans isomerism., H3 C, H, , CH3, H, , CH3, , H, , cis-form, , trans-form, , OH, , cis, , H, , H3 C, , OH, , OH, , OH, , trans, , OH, , cis, , OH, , (b) Syn-anti isomers compounds containing C ==N bond (as in, aldoxime), N ==N bond (as in H 2N 2O) exhibit this type of isomerism., e.g., H3 C, , H, , C, , H3 C, , N, syn, , H, , C, N, , OH, , HO, , anti, , (c) E-Z isomers In E-isomer, bulkier (heavier) groups are present, on the opposite side of the double bond and in Z-isomer, heavier, groups are present on the same side of the double bond. E is, entgegen means opposite and Z is Zusammen means together, e.g., Cl, , H, C, bulkier, , C, , Cl, , Br, Z isomer, , bulkier, Z-3-hexene, , www.aiimsneetshortnotes.com
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350, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Fission of a Covalent Bond, 1. Homolytic Fission, In this, one of the electrons of the shared pair in a covalent bond goes, with each of the bonded atoms. The neutral chemical species thus, formed, is called free radical. Generally, homolytic fission takes place, in non-polar, covalent molecules in the presence of sunlight or high, temperature., Sunlight, , A· + B ·, 1, 424, 3, , A ¾ B ¾¾®, , free radicals, , Cl2 — ¾® 2Cl·, Sunlight, , e.g., , Free radicals are highly reactive, neutral and electron deficient species., , 2. Heterolytic Fission, In this, the bond breaks in such a fashion that the shared pair of, electrons goes with one of the fragments., more electronegative, , A ¾ B ¾®, , A+, , +, , Bnucleophile, , electrophile, less electronegative, , or, , A ¾ B ¾®, , Anucleophile, , +, , B+, electrophile, , Carbon bearing a positive charge is called carbocation and carbon, bearing negative charge is called carbanion., Heterolytic fission generally takes place in polar covalent molecules, but in non-polar molecules, it takes place in the presence of catalyst, like AlCl3 (anhy.), FeCl3(anhy.) etc., , Attacking Reagents, These are of two types :, , 1. Electrophiles or Electrophilic Reagents, These are electron deficient species i.e. behave as Lewis acids. The, following species behave as electrophiles :, (i) All non-metal cations and metal cations which have vacant, d-orbitals. e.g. Cl+ , NO+2 , CH3CO+ etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 351, (ii) Lewis acids (incomplete octet), e.g. BF3 , ZnCl2 (anhydrous),, FeCl3 (anhydrous), AlCl3 (anhydrous), ··CH 2 etc., (iii) Non-metal (acidic) oxides e.g. CO2 , SO2 etc., , 2. Nucleophiles or Nucleophilic Reagents, These are electron rich species i.e. behave as Lewis bases., These attack at electron deficient area., The following species behave as nucleophiles :, (i) All anions e.g. Cl- , NH 2- , OH - etc., ··, , ··, , ··, , ··, , (ii) Lewis bases e.g. ··NH3 , H 2O, R ¾ O ¾ R, R ¾ OH etc., (iii) Benzene, alkenes etc., Nucleophilicity order is, H - > CH3- > NH -2 > RO- > OH In case of same nucleophilic site, nucleophilicity parallels basicity i.e., as the basicity increases, nucleophilicity also increases., If nucleophilic sites (or attacking atoms) are different nucleophilicity, varies inversely with electronegativity., , 3. Ambiphiles, These species behave like both electrophiles as well as nucleophiles., Organic compounds containing a multiple bond between carbon and a, more electronegative atom can act as ambiphiles. e.g., H, H, , d··, C ==O··, ··, , d+, , d+, , ;, , electrophile nucleophile, , d-, , CH3 ¾ C ººN ··, , electrophile nucleophile, , Reaction Intermediates, These are formed as a intermediate during the course of a reaction., These are short lived and highly reactive., Free radicals, carbocations, carbanions, carbenes and nitrenes are, important reactions intermediates., , www.aiimsneetshortnotes.com
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352, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 1. Free Radicals, These are the product of homolysis and contain an odd electron. These, are highly reactive planar species with sp2-hybridisation., Their order of stability is, ·, , ·, , ·, , (C6H5 )3C > (C6H5 )2 CH > C6H5CH 2, , ·, , ·, , > CH 2 ==CH ¾ CH 2 > 3° > 2° > 1° > CH 2 ==CH, , 2. Carbocations, These are the product of heterolysis and contain a carbon bearing, positive charge. These are electron deficient species. Carbocations, contain six electrons in the valence shell., These are also planar chemical species, i.e. sp2-hybridised with an, empty p-orbital., s, s, s C, , empty p-orbital, , The stability order of carbocations is :, +, , +, , +, , (C6H5 )3 C+ > (C6H5 )2CH > (CH3 )3C > C6H5CH 2 > 2°, +, , +, , +, , > CH 2 ==CH ¾ CH 2 > 1° > C6H5 > CH 2 ==CH, , 3. Carbanions, These are also the product of heterolysis and contain a carbon, bearing negative charge and 8 electrons in its valence shell., s, These have pyramidal shape with sp3 -hybridised carbon s C s, (having one lone pair), The order of stability of carbanions is, -, , -, , -, , (C6H5 )3 C- > (C6H5 )2CH > C6H5CH 2 > CH 2 ==CH ¾ CH 2, -, , > CH3 > 1° > 2° > 3° carbanions, , 4. Carbenes, These are divalent carbon species having two non-bonding electrons, along with two bond pairs., These are obtained by photolysis or pyrolysis, e.g., hn, or D, , CH 2 ==C ==O ¾¾® ··CH 2 + ··C ==O, ketene, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 353, These being electron deficient behave as Lewis acids. These are of two, types :, (i) Singlet carbene In it, the C-atom is sp2-hybridised. The, unhybridised orbitals contain no electrons and a hybridised orbital, contains two electrons :, s, s C, , empty, 2, , sp -hybridised with 2 unbonded electrons, , s, , Singlet carbene has bent structure and is less stable than triplet, carbene., The order of stability of singlet carbenes is, ··, , ··, , ··, , ··, , CH 2 > CF2 > C Cl2 > C Br2, , (ii) Triplet carbene In it, the central C-atom is sp-hybridised. The, unhybridised orbitals contain 1 electron each., unhybridised orbitals with 1 electron, s C s, , Triplet carbene has linear geometry., , 5. Nitrene, These are neutral monovalent nitrogen species in which N atom has, two unshared pair of electrons with a mono valent atom or group, attached., These are obtained by thermolysis of azides and as reactive as, carbenes., These are of two types : singlet nitrene and triplet nitrene, Y, , Y, N, , Z, Singlet Nitrene, , N, Z, Triplet Nitrene, , www.aiimsneetshortnotes.com
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354, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 6. Arynes, , 2, , sp, It contains a formal carbon-carbon triple bond in, aromatic molecule., The additional bond is formed between two, sp2, neighbouring C-atoms by sideways overlapping of two, sp2-orbitals. The new bond lies along with side of the ring and has little, interaction with the p electron cloud lying above and below the ring., The sideways overlapping is weak and thus, makes the benzene more, reactive., , Inductive Effect, It is just like shifting of shared pair of electrons in polar covalent, molecules. If shared pair is more shifted towards the more, electronegative atom, the less electronegative atom acquires slight, positive charge and more electronegative atom acquires partial, negative charge, e.g., -d, , +d, , CH3 ®¾ Cl, It is a permanent effect and propagates through carbon chain. Atoms, or groups having greater electron affinity than hydrogen, are said to, have electron attracting or negative inductive effect ( - I ) while that, having, smaller electron affinity than hydrogen are said to have, electron releasing or positive inductive effect ( + I ). e.g., + dd, , +d, , -d, , CH3 ®¾ CH 2 ®¾ Cl, , + ddd, , + dd, , +d, , -d, , CH3 ®¾ CH 2 ®¾ CH 2 ®¾ Cl, 1°alkyl halide, , Here, Cl has - I effect and alkyl group has + I effect., Order of groups producing - I effect is, +, , R3N > NO2 > CN > SO3H > CHO > CO > COOH > F >, Cl > Br > I > OH > OR > NH 2 > C6H5 > H, Order of groups producing + I effect is, O- > ¾ COO- > 3° alkyl group > 2° alkyl group, > 1° alkyl group > CH3 > H, , Applications of Inductive Effect, 1. Presence of groups showing + I effect increases the stability of, carbocation while presence of groups showing - I effect, decreases their stability., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 355, 2. Strength of acid increases with the attachment of group showing, - I effect and decreases with the attachment of group showing, + I effect., 3. Presence of + I effect showing groups increases the basic, strength of amines., 4. Reactivity of carbonyl compound is increased by - I effect, showing groups., 5. Reactivity of alkyl halides towards SN 1 is increased by, + I showing groups., , Electromeric Effect, It is defined as the polarity produced in a multiple bonded compound, as a reagent approaches it. In the presence of attacking reagent, the, two p electrons are completely transferred to any of the one atom. This, effect is temporary., This may be of + E type (when displacement of electron pair is away, from the atom or group) or of - E type (when the displacement is, towards the atom or group). e.g., H, H, , H, C, , C, , H, , H, , Reagent, Å, , –, , [E Nu ], , H, , Reagent, , C, , O, , C+–––C, E+, , H, H, , C––O–, , [E+Nu–], , Nu–, , Hyperconjugation, It involves delocalisation of s electron of a C—H bond of an alkyl group, attached directly to an atom of unsaturated system or to an atom with, an unshared p-orbital., H, CH2––CH, , CH2, , H+, CH2, , –, , CH––CH2, , This effect is also called no bond resonance or Baker Nathan, effect., , Applications of Hyperconjugation, (i) Stability of alkenes More the number of a-hydrogen atoms,, more stable is the alkene., , www.aiimsneetshortnotes.com
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356, , Telegram @neetquestionpaper, , Handbook of Chemistry, a, CH3, , a, H3C––C, , a, CH3, , C, , CH3, a, , a, > CH3CH, , C, , a, CH3, CH3, a, , a, > CH3––CH, , a, CH––CH3, , (ii) Stability of carbocation Greater the number of alkyl groups, attached to a positively charged carbon atom, the greater is the, stability., +, , +, , +, , (CH3 )3 C+ > (CH3 )2 CH > CH3 ¾ CH 2 > CH3, , Resonance Effect, When all the properties of a molecule cannot be shown by a single, structure and two or more structures are required to show all the, properties of that molecule, then the structures are called resonating, structures or canonical forms and the molecule is referred as, resonance hybrid. This phenomenon is called resonance., In resonance,, 1. The arrangement of atoms must be identical in all the formulae., 2. The energy content of all the canonical forms must be nearly, same., 3. Each canonical form must have the same number of unpaired, electrons., It involves delocalisation of p electrons. This effect may be of + R type, or - R type., , Positive Resonance Effect ( +R ), Electron donating groups with respect to conjugate system show, +R effect. Central atom of functional groups should be more, electronegative than the surrounding atoms or groups to show, + R effect. e.g. halogens, —OH, —OR, —OCOR, —NH 2,—NHCOR etc., –, NH2, , +, , NH2, , +, , NH2, , +, , NH2, , –, , –, –, , Electron donating groups producing, + R effect are ortho and para, directing. They activate the benzene ring towards the electrophilic, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 357, substitution reactions except halogens. Halogens slightly deactivate, the benzene ring towards the electrophilic substitution reaction. More, the E.D.G, more is the basic nature., , Negative Resonance Effect ( -R ), Electron withdrawing groups with respect to conjugate system show, - R effect. Central atom of functional groups should be less, electronegative than surrounding atoms or groups to show -R effect., e.g. halogens, — COOH, — COOR, — CHO,— CN,—NO 2 etc., H––C, , O, , H––C––O–, , H––C––O–, , H––C––O–, , +, , +, +, , Electron withdrawing group (E.W.G.) producing - R effect are meta, directing. They deactivate the benzene ring towards the electrophilic, substitution reaction. More the E.W.G, more is the acidic nature., , Stability of Canonical Forms, It can be judged by the following rules :, 1. Non-polar structure is more stable than the polar structure., 2. Among polar structures, structure with maximum number of, covalent bonds is most stable., 3. The structure with maximum charge separation is more stable., 4. Structure with positive charge on more electropositive element, and negative charge on more electronegative element is more, stable., , Resonance Energy, Number of p bonds µ contributing structures µ resonance energy µ, stability., In benzene, resonance energy is 36 kcal/mol., , Relation Between Resonance and Bond order, Bond order =, , e.g., , Total number of bonds betwen two atoms, Total number of resonating structures, BO =, , 2+1, = 1.5, 2, , www.aiimsneetshortnotes.com
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358, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Types of Organic Reactions, Reactions are of following types :, , 1. Addition Reactions, These reactions are given by unsaturated compounds or compounds, containing multiple bonds., In these reactions, the reagent adds to the substrate molecule., These are of two types (depending upon the nature of attacking, species) :, (i) Electrophilic addition reactions In these reactions, H +, (or electrophile) is added to the substrate in the rate determining, step., These reactions are given by alkenes and alkynes. e.g., X, C, , C, , + H+, , +, C—C, , X, , –, , C— C, , H, , H, , (ii) Nucleophilic addition reactions In these reactions,, nucleophile is added to the substrate in the rate determining step., These reactions are given by carbonyl compounds. e.g., C, , O, , + CN –, nucleophile, , C, , O–, CN, , +, H, , OH, C, , CN, , 2. Substitution Reactions, In these reactions, one atom or group of atoms, called the leaving, group, is substituted by a nucleophile or an electrophile. On this basis, these reactions are of two types :, (i) Electrophilic substitution reactions When leaving group is, replaced by an electrophile, the reaction is called electrophilic, substitution reaction., + NO2+, , NO2, , Electrophile, , (ii) Nucleophilic substitution reactions In these reactions,, nucleophiles are the attacking species., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, General Organic Chemistry 359, , These are of two types :, (a) SN 1 (Nucleophilic substitution unimolecular) reaction is, a two step process, e.g., R ¾ X ¾® R + + X R+ +, , OH -, , ¾® ROH, , nucleophile, , For such reaction, rate = k [R - X ], The reactivity of alkyl halides towards SN 1 reaction is, 3° > 2° > 1° alkyl halide., (b) S N 2 (Nucleophilic substitution bimolecular) reaction, is a single step process e.g., d-, , OH -, , d-, , + R ¾ X ¾® H OK RK X ¾® R ¾ OH + X -, , nucleophile, , For such reactions, rate = k [RX ] [OH - ], These reactions involve inversion of configuration., For such reactions the order of reactivity of alkyl halide is, 1° > 2° > 3°, , 3. Elimination Reactions, In these reactions, two groups from the same or adjacent atoms are, lost and electron deficient or unsaturated compound is formed., These can be of two types :, (i) a-elimination In it, both the groups are eliminated from the, same carbon atom. Such reactions are rare. e.g., -, , CHCl3 ¾® ··CCl3 ¾®, , ·CCl, ·, 2, , carbene, , (ii) b-elimination Here, the groups are eliminated from the adjacent, carbon atoms. These can further be E1 or E2 reactions .e.g., H3C, H3C, H, , Nu, CH3, CH3, , –Nu, , H3C, H3C, H, , H3C, , CH3, CH3, , –H, , CH3, C==C, , +, , H3C, , www.aiimsneetshortnotes.com, , CH3
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Telegram @neetquestionpaper, , 360, , Handbook of Chemistry, , 4. Rearrangement Reactions, Reactions involving the migration of an atom or a group from one atom, to another within the same molecule are called rearrangement, reactions., e.g. Hofmann bromamide reaction involving the conversion of 1°, amides to 1° amines on treatment with Br2 in the presence of KOH., O, , O, , R––C––NH2, 1° amide, , Br2 /KOH, (rearrangement), , R––C––N––Br, , OH–, –H2O, , H, O, R––C––N–––Br, –Br–, O, R––NH2, +, K2CO3, , KOH, , O, , C, , N––R, , rearrangement, , R––C––N, , Alkyl isocyanate, Acylnitrene, , This reaction involves the migration of alkyl group, R from C to N to, form alkyl isocyanate., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrocarbons 367, Conformations of Alkanes, Alkanes have C—C sigma ( s) bonds and rotation about C—C single, bond is allowed. This rotation results in different spatial, arrangements of atoms in space which can change into one another,, such spatial arrangements are called conformations or conformers or, rotamers., , Conformations of ethane, (i) Sawhorse projections, H, H, , H, , H, , H, , H, , H, , H, H, , H, , H, H, , eclipsed, , staggered, , (ii) Newman projections, H, H, , H, , H, , H, H, , H, , H, , H, , H, , H, H, , eclipsed, , staggered, , Intermediate conformation between eclipsed and staggered are, known as skew (gauche) conformations., Eclipsed form is least stable but staggered form is most stable due to, greater distance between the bond pairs or lesser torsional strain., The energy difference between the two extreme forms is of the order of, 12.5 kJ mol -1., , Alkenes, These are unsaturated non-cyclic hydrocarbons, sp2-hybridisation with 120° bond angle., , which, , have, , Alkenes are also called olefins [oil forming] which indicates their high, reactive nature., Alkenes have general formula Cn H 2n , where n = 2, 3, 4 …, e.g., C2H 4 (ethene), C3H 6 (propene), etc., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrocarbons 369, Physical Properties of Alkenes, Alkene as a class resemble alkanes in physical properties, except in, types of isomerism and difference in polar nature., C1 to C3 are gases, the next fourteen are liquids and the higher, members are solids., Alkenes show a regular increase in boiling point with increase in size., , Chemical Properties of Alkenes, (i) Addition of halogens, CCl 4, , CH 2 ==CH 2 + Br ¾ Br ¾¾®, ethene, , CH 2 ¾ CH 2, ½, ½, Br, Br, 1,2 -dibromoethane, , CH3 ¾ CH ==CH 2 + Cl ¾ Cl ¾® CH3 ¾ CH ¾ CH 2, propene, ½, ½, Cl, Cl, 1,2 -dichloropropane, , (ii) Addition of hydrogen halides HCl, HBr, HI add up to, alkenes to form alkyl halides as per their reactivity order, HI > HBr > HCl, Addition reaction of HBr to unsymmetrical alkenes, (Markownikoff ’s rule) According to Markownikoff's rule,, the negative part of the addendum (adding molecule) gets, attached to that carbon atom which possesses lesser number of, hydrogen atom., H, Br, ½, ½, H ¾ C ¾ C ==C ¾ H + HBr ¾® H3C ¾ C ¾ CH3, ½, ½ ½ ½, H H H, H, prop-1-ene, , 2- bromopropane, , Anti-Markownikoff addition or peroxide effect or, Kharash effect In the presence of organic peroxide, addition, of only HBr molecule on unsymmetrical alkene takes place, contrary to the Markownikoff’s rule., CH3 ¾ CH ==CH 2 + HBr ¾¾¾¾¾® CH3CH 2 CH 2 Br, prop-1ene, , (C6H5 CO) 2 O 2, , 1- bromopropane, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrocarbons 377, Structure of Benzene, On the basis of Kekule, structure of benzene has cyclic arrangement of, six carbon atoms with alternate single and double bonds and one, hydrogen atom attached to each carbon atom., , Aromaticity, Aromatic compound should possess the following characteristics :, (i) Planarity., (ii) Complete delocalisation of the p electrons in the ring., (iii) Presence of ( 4n + 2)p electrons in the ring where n is an integer, ( n = 0, 1, 2, K ). This is often referred to as Huckel rule., , Methods of Preparation, (i) Cyclic polymerisation of ethyne Refer to text on page 371., (ii) Decarboxylation of aromatic acids, ÈÅ, , COONa, + NaOH, , CaO, D, , + Na2CO3, , OH, (iii), , Zn, D, , + ZnO, , Physical Properties of Benzene, Aromatic hydrocarbons are non-polar molecules and are usually, colourless liquids or solids with a characteristic aroma., Aromatic hydrocarbons are immiscible with water but readily miscible, with organic solvents., Aromatic compounds burn with sooty flame., , Chemical Reactions of Benzene, Benzene gives electrophilic substitution reactions., According to experimental evidences, electrophilic substitution reaction, involve following three steps :, (a) Generation of electrophile, (b) Formation of carbocation intermediate, (c) Removal of proton from the carbocation intermediate., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrocarbons 381, Carcinogenicity and Toxicity, Benzene and polynuclear hydrocarbons containing more than two, benzene rings fused together are toxic and said to possess cancer, producing (carcinogenic) property. e.g., , H3C, 1-2-benzanthracene, , 3-methylcholanthrene, , Petroleum, It is a dark coloured oily liquid with offensive odour, found at various, depths in many region below the earth’s surface. It is also called rock, oil, mineral oil or crude oil. It is covered by an atmosphere of a, gaseous mixture known as natural gas., It contains mainly alkanes, cycloalkanes, aromatic hydrocarbons,, sulphur, nitrogen and oxygen compounds., When subjected to fractional distillation, it gives different fractions at, different temperatures., S.No., , Fraction, , Boiling range, , Composition, , Uses, Fuel gases,, refrigerants,, production of carbon, black, hydrogen., , 1., , Uncondensed gases Room, temperature, , C1 - C 4, , 2., , Crude naphtha, , C 5 - C10, , 30–150°, , (Its refractionation, gives, (i) Petroleum ether, , 3., , 30 - 70°, , C5 - C6, , Solvent, , 70 - 120°, , C6 - C8, , 120 - 150°, , C 8 - C10, , Fuel, petrol gas, Solvent, drycleaning, , (ii) Gasoline, (iii) Benzene, derivative, Kerosene, , 150–250°, , C11 - C16, , Fuel, illuminants, oil, gas, , www.aiimsneetshortnotes.com
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382, S.No., 4., , Telegram @neetquestionpaper, , Handbook of Chemistry, Fraction, Heavy oil, , Boiling range, , Composition, , 250–400°, , C15 - C18, , Above 400°C, , C17 - C 40, , (Its refractionation, gives, , Uses, Fuel for diesel, engines, , (i) Gas oil, (ii) Fuel oil, (iii) Diesel oil, 5., , 6., , Residual oil, (Its vacuum, distillation gives, (i) Lubricating oil, , C17 - C20, , Lubrication, , (ii) Paraffin wax, , C20 - C 30, , Candles, boot polish, , (iii) Vaseline, , C20 - C 30, , Toilets, lubrication, , (iv) Pitch, , C 30 - C 40, , Paints, road, surfacing, , Petroleum coke, , As fuel, , LPG (Liquified Petroleum gas), It is a mixture of butane and iso-butane with a small amount of propane., A strong foul smelling substance, called ethyl mercaptan (C2H5SH) is, added to LPG cylinders, to help in the detection of gas leakage., , CNG (Compressed Natural Gas), It consists mainly of methane (95%), which is a relatively unreactive, hydrocarbon and makes its nearly complete combustion possible., , Artificial Methods for Manufacturing Petrol, From higher alkanes, petrol or gasoline is obtained by cracking or, pyrolysis., From coal, petrol can be synthesised by following two processes :, (i) Bergius process, FeO3, , Coal + H 2 ¾¾¾¾® Mixture of hydrocarbons or crude oil., 450 -500°C, 250 atm, , The yield of gasoline by this method may be as high as 60%., (ii) Fischer- Tropsch process, 1200°C, , Co/Ni, , C + H 2O ¾¾® CO + H 2 ¾¾¾¾® mixture of hydrocarbons., 1424, 3, 200°C, steam, water gas, , 5 -10 atm, , The best catalyst for this process is a mixture of Co, thoria,, magnesia and kieselguhr., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Hydrocarbons 383, The overall yield in this process is slightly higher than Bergius, process., , Octane Number, The quality of petrol is expressed in terms of octane number which is, defined as the percentage of iso-octane by volume in a mixture of, iso-octane and n-heptane which has the same antiknock properties as, the fuel under test., The octane number is 100 for iso-octane (2,2,4-trimethylpentane), Natural gas has octane number 130., TEL (tetraethyl lead) is used as antiknocking compound., Octane number is increased by isomerisation, alkylation or, aromatisation., , Cetane Number, Quality of diesel oils is measured in terms of cetane number which is, defined as the percentage of cetane (hexadecane) by volume in a, mixture of cetane and a-methyl naphthalene which has the same, ignition property as fuel oil under similar experimental conditions., It is 100 for cetane and 0 for a-methyl naphthalene., , www.aiimsneetshortnotes.com
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392, , Telegram @neetquestionpaper, , Handbook of Chemistry, , From Phenol, OH, + PCl5, , C6H5Cl + HCl + POCl3, , Physical Properties of Aryl Halides, 1. Aryl halides are colourless liquids or colourless solids with, characteristic odour., 2. Boiling point generally increases with increase in the size of aryl, group or halogen atom. Boiling point order, Ar—I > Ar—Br > Ar—Cl > Ar—F, 3. The melting point of p -isomer is more than o- and m-isomer., This is because of more symmetrical nature of p-isomer., 4. Due to resonance in chlorobenzene, C—Cl bond is shorter and, hence, its dipole moment is less than that of cyclohexylchloride., , Chemical Properties of Aryl Halides, 1. Nucleophilic Substitution Reactions, Aryl halides are less reactive towards nucleophilic substitution, reaction. Their low reactivity is attributed due to the following reasons:, (i) Due to resonance, C—X bond has partial double bond character., (ii) Stabilisation of the molecule by delocalisation of electrons., (iii) Instability of phenyl carbocation., However, aryl halides having electron withdrawing groups, (like ¾ NO2 , ¾ SO3H, etc.) at ortho and para positions undergo, nucleophilic substitution reaction easily., Cl, , OH, (i) NaOH, 623 K, 300 atm, (ii) H+, , Presence of electron withdrawing group ( ¾ NO2 ) increases the, reactivity., , www.aiimsneetshortnotes.com
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412, , Telegram @neetquestionpaper, , (a) Rectified spirit It contains 9.5% ethyl alcohol and 4.5% water. It is an, azeotrope (constant boiling mixture) and boils at 74°C., (b) Absolute alcohol Alcohol containing no water, i.e. 100% C2H5 OH is known, as absolute alcohol. It is prepared as follows., (i) Quick lime process, (ii) Azeotropic method, (c) Methylated spirit The rectified spirit rendered poisonous by addition of, 4-5% methyl alcohol, traces of pyridine and some copper sulphate and is, known as methylated spirit or denatured alcohol., (d) Power alcohol Alcohol mixed with petrol or fuel and used in internal, combustion engines is known as power alcohol., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 29, Amines, Amines constitute an important class of organic compounds derived by, replacing one or more hydrogen atoms of NH3 molecule by alkyl/aryl, group(s)., R ¾ NH 2, R ¾ NH ¾ R, R¾N¾ R, C6H5 ¾ NH 2, secondary (2°), primary (1°), aromatic amine, ½, R, tertiary (3°), , In the IUPAC system, the amines are named as alkanamines, e.g., C2H5, CH3 ¾ CH 2 ¾ NH 2 , CH3CH 2 ¾ NH ¾ CH3 , CH3 ¾ CH 2 ¾ N, ethanamine, N-methyl ethanamine, C2H5, N,N-diethylethanamine, , Structure, The nitrogen atom in amine is sp3 -hybridised. The three hybrid orbitals, are involved in bond formation and one hybrid atomic orbital contains the, lone pair of electrons, giving the pyramidal geometry of amines., N, H3C, , CH3, , CH3, , In arylamines, ¾ NH 2 group is directly attached to the benzene ring., NH2, , aniline, (benzenamine), , N(CH3)2, , (N,N-dimethylbenzenamine), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Amines 445, (v) Reduction of amides, O, ½½, (i) LiAlH4, R ¾ C ¾ NH 2 ¾¾¾¾¾® R ¾ CH 2NH 2, (ii) H2O, , (vi) Gabriel’s phthalimide reaction, O, , C, C, , O, , NH, , KOH, , C, , (Alc.), , C, , phthalimide O, , O, – +, , NK, , C, , RX, , C, , O, potassium phthalimide, , NR, , O, N-alkyl phthalimide, – +, , COOK, – +, , KOH, , COOK, , + RNH2, 1° amine, , potassium phthalate, , It only produces 1° amines. This method is not suitable for, 1° arylamine because aryl halide does not give nucleophilic, substitution reaction., (viii) Hofmann bromamide degradation reaction, O, ½½, R ¾ C ¾ NH 2 + Br2 + 4NaOH ¾® RNH 2 + Na 2CO3, + 2NaBr + 2H 2O, In Hofmann degradation reaction, the amine formed has one, carbon less than the parent amide. To obtain primary amine with, same number of carbon atoms from primary amide, reduction is, done with LiAlH 4/ether., , Physical Properties of Amines, 1. The lower aliphatic amines are gases with fishy smell., 2. Primary amines with three or more carbon atoms are liquid and, higher members are all solids., 3. Lower aliphatic amines are water soluble because they can form, hydrogen bonds with water molecules, however the solubility, decreases with increase of hydrophobic alkyl group/chain., 4. Boiling point order is :, primary > secondary > tertiary, , www.aiimsneetshortnotes.com
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446, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 5. Tertiary amine does not have intermolecular association due to, the absence of hydrogen atom available for hydrogen bond, formation., , Chemical Properties of Amines, (i) Basic Strength of Amines Amines act as Lewis bases due to, the presence of lone pair of electrons on the nitrogen atom., More the value of K b (dissociation constant of base), higher is the, basicity of amines. Lesser the value of pK b, higher is the basicity, of amines., Aliphatic amines (CH3NH 2 ) are stronger bases than NH3 due to, the electron releasing +I effect of the alkyl group., Among aliphatic amines, the order of basic strength in aqueous, solution is as follows, (C2H5 )2NH > (C2H5 )3 N > C2H5NH 2 > NH3, (CH3 )2NH > CH3NH 2 > (CH3 )3 N > NH3, Aromatic amines are weaker bases than aliphatic amines and, NH3 , due to the fact that the electron pair on the nitrogen atom is, involved in resonance with the p-electron pairs of the ring., Electron releasing groups (e. g ¾ CH3 , ¾ OCH3 , ¾ NH 2 etc.), increase the basic strength of aromatic amines while electron, withdrawing groups (like ¾ NO2 , ¾ X, ¾ CN etc. ) tend to, decrease the same., o-substituted aromatic amines are usually weaker bases than, aniline irrespective of the nature of substituent whether electron, releasing or electron withdrawing. This is called ortho effect and, is probably due to steric and electronic factors., (ii) Alkylation All the three types of amines react with alkyl, halides to form quaternary ammonium salt as the final product, provided alkyl halide is present in excess., - HBr, , ··, , C2H5 Br, , C2H5NH 2 + C2H5 Br ¾¾® (C2H5 )2NH ¾¾¾® (C2H5 )3N, –HBr, , C2H5Br, +, , (C2H5 )4 NBr-, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Amines 451, Separation of Mixture of Amines (1°, 2° and 3°), (a) Fractional distillation This method is based on the boiling points of, amines and is used satisfactorily in industry., (b) Hofmann’s method Diethyloxalate is called Hofmann’s reagent with which, mixture of amines is treated., 1° amine forms solid dialkyl oxamide ( CONHR)2 ., 2° amine forms liquid dialkyl oxamic ester (CONR2 ¾ COOC2H5 ), 3° amines do not react., (c) Hinsberg’s method see chemical reactions on Page 448., , Benzene Diazonium Chloride (C6 H5N2+Cl– ), Preparation (Diazotisation reaction), +, , 273 -278 K, , -, , C6H5NH 2 + NaNO2 + 2HCl ¾ ¾ ¾ ¾ ¾® C6H5 N ºº N ¾ Cl, + NaCl + 2H 2O, The excess acid in diazotisation reaction is necessary to maintain, proper acidic medium for the reaction and to prevent combination of, diazonium salt formed with the undiazotised amine., Diazonium salts are prepared and used in aqueous solutions because, in solid state, they explode., , Physical Properties, It is a colourless crystalline solid, soluble in water. It has tendency to, explode when dry., , Stability of Arenediazonium salts, It is relatively more stable than the alkyldiazonium salt. The, arenediazonium ion is resonance stabilised as is indicated by the, following resonating structures:, +, , N, , N, , +, , N, , –, , N, +, , +, , N, , +, , –, , N, , N, , –, , N, , +, , +, Various resonating structures of arenediazonium ion, , www.aiimsneetshortnotes.com, , +, , N, , N
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Telegram @neetquestionpaper, , 30, Polymers, The word polymer has a Greek origin, which means many units, (parts). Polymer is defined as a chemical substance of a high molecular, mass formed by the combination of a large number of simple, molecules, called monomers, e.g., n (CH2 == CH2 ) ¾® ¾, [ CH2 ¾ CH2 ¾]n, Ethylene, , Polyethylene, , Polymerisation, The process by which the monomers combine with each other and, transform into polymers, is known as polymerisation., n [Monomer] ¾® Polymer, , Difference between Polymers and Macromolecules, Polymers are also called macromolecules due to their large size but converse, is not always true. A macromolecule may or may not contain monomer units,, e.g. chlorophyll (C55H72 O5N4Mg) is a macromolecule but not a polymer, since, there are no monomer units present. So, we can conclude that all, polymers are macromolecules while all macromolecules are not polymers., , Classification of Polymers Based on Source of Origin, (i) Natural polymers Those polymers which occur in nature, i.e., in plants or animals, are called natural polymers., Natural polymer, , Occurrence, , Starch, , Main reserve food of plants, , Cellulose, , Main structural material of plants, , Proteins, , Act as building blocks in animals., , Natural rubber, , Occurs as latex (a colloidal dispersion of rubber in, water) in the bark of many tropical trees, particularly, from Hevea Brasiliensis., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Polymers 459, (ii) Synthetic polymers The polymers which are prepared in the, laboratory are known as synthetic polymers or man-made, polymers, e.g. polythene, synthetic rubber, PVC, nylon-6,6,, teflon, orlon etc., (iii) Semi-synthetic polymers Polymers obtained by making, some modification in natural polymers by artificial means, are, known as semisynthetic polymers, e.g. cellulose acetate (rayon),, vulcanised rubber etc., , Classification of Polymers Based on Structure, (i) Linear polymers These are the, polymers in which the monomer units, are linked to one another to form long, Linear chain polymer, linear chains. These linear chains are, closely packed in space. The close, packing results in high densities, tensile strength and high, melting and boiling points. e.g. high density polyethene, nylon, and polyesters are linear polymers., (ii) Branched chain polymers In, such polymers, the monomer units are, linked to form long chains with some, branched chains of different lengths, Branched chain polymer, attached to the main linear chain. As, a result of branching, these polymers are not closely packed in, space. Thus, they have low densities, low tensile strength as well, as low melting and boiling points. Some common examples of, such polymers are low density polyethene, starch, glycogen etc., (iii) Cross-linked, , network, , polymers, polymers These, , or, , are, formed from bi functional and, tri functional monomers. In such, Cross linked polymer, polymers, the monomer units are, linked together to form three dimensional network. These are, expected to be quite hard, rigid and brittle. Examples of cross, linked polymers are bakelite, glyptal, melamine-formaldehyde, polymer etc., , www.aiimsneetshortnotes.com
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460, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Classification of Polymers Based on, Mode of Polymerisation, (i) Addition polymers The polymers formed by the polymerisation, of monomers containing double or triple bonds (unsaturated, compounds) are called addition polymers. Addition polymers have, the same empirical formula as their monomers., Addition polymers can further be classified on the basis of the types, of monomers into the following two classes:, , Homopolymers The polymers which are obtained by the, polymerisation of a single type of monomer are called, homopolymers., n(CH 2 ==CH 2 ) ¾®, , —, ( CH 2 ¾ CH 2 ¾, )n, , Ethene, , Polythene, , Copolymers The polymers which are obtained by the, polymerisation of two or more different types of monomers are, called copolymers., n(CH2, , CH—CH, , CH2) + n(CH2, , CH), , 1, 3-Butadiene, , Styrene, , —CH, [, 2—CH, , CH—CH2 —CH2—CH ]n, , Buna-S (Butadiene styrene copolymer), , (ii) Condensation polymers The polymers which are formed by, the combination of monomers with the elimination of small, molecules such as water, alcohol, hydrogen chloride etc., are known, as condensation polymers, e.g. nylon 6,6 is formed by the, condensation of hexamethylene diamine with adipic acid and water, molecules are eliminated in the process., nH 2N(CH 2 )6NH 2 + nHOOC(CH 2 )4COOH ¾®, ¾[ NH(CH 2 )6NHCO(CH 2 )4CO —, ]n, , + nH 2O, , Nylon 6,6, , These are generally copolymers. A condensation homopolymer is, nylon-6., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Polymers 461, Classification of Polymers Based on, Molecular Forces, (i) Elastomers These are rubber like solid polymers in which the, polymer chains are held together by weakest intermolecular, forces, e.g. natural rubber, buna-S, buna-N etc., The weak binding forces permit the polymers to be stretched. A, few ‘cross links’ are introduced in between the chains, which help, the polymer to retract to its original position after the force is, released as in case of vulcanised rubber., (ii) Fibres Fibres belong to a class of polymers which are, thread-like and can be woven into fabrics. These are widely used, for making clothes, nets, ropes, gauzes, etc. Fibres possess high, tensile strength because the chains possess strong intermolecular, forces such as hydrogen bonding. The fibres are crystalline in, nature and have sharp melting points. A few examples of this, class are nylon-6,6, terylene and polyacrylonitrile (PAN)., (iii) Thermoplastics These are linear polymers and have weak, van der Waals’ forces acting in the various chains. These forces, are intermediate of the forces present in the elastomers and in, the fibres. When heated, they melt and form a fluid which sets, into a hard mass on cooling. Thus, they can be cast into different, shapes by using suitable moulds, e.g. polyethene and polystyrene., Plasticizers are high boiling esters or haloalkanes. These are added to, plastics to make them soft like rubber., (iv) Thermosetting plastics These are normally semifluid, substances with low molecular masses. When heated, they, become hard and infusible due to the cross-linking between the, polymer chains. As a result, they form three dimensional, network. A few common thermosetting polymers are bakelite,, melamine-formaldehyde resin and urea formaldehyde resin., , Types of Polymerisation Reactions, 1. Chain Growth or Addition Polymerisation, It involves formation of reactive intermediate such as free radical, a, carbocation or a carbanion. For this polymerisation monomers used are, unsaturated compounds like alkenes, alkadienes and their derivatives., Depending upon the nature of the reactive species involved, chain, growth polymerisation occurs by the following mechanisms:, (i) Free radical addition polymerisation, (ii) Cationic polymerisation, (iii) Anionic polymerisation, , www.aiimsneetshortnotes.com
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464, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Distinction Between Chain Growth Polymerisation and, Step Growth Polymerisation, S.No., , Chain growth polymerisation, , Step growth polymerisation, , 1., , It proceeds by a chain mechanism, characterised by initiation, chain, propagation and chain termination., , It proceeds by an equilibrium step, mechanism. The step growth process, is usually much slower than chain, growth polymerisation., , 2., , Only one repeating unit is added at a, time., , Any two species present can react, with elimination of some by product., , 3., , Reaction mixture contain only monomers, All the molecular species are present, polymers and the growing chain., at every stage of polymerisation., , Molecular Mass of Polymers, The growth of the polymer chain depends upon the availability of the, monomers in the reaction. Thus, the polymer sample contains chain of, varying lengths and hence, its molecular mass is always expressed as, an average molecular mass., , Number-Average Molecular Mass (Mn ), If N 1 molecules have molecular mass M1 each, N 2 molecules have, molecular mass M 2 each, N 3 molecules have molecular mass M3 each, and so on,, SN i M i, then,, Mn =, SN i, It is determined by osmotic pressure method., , Mass-Average Molecular Mass ( M w ), Supposing, as before that N 1 , N 2 , N 3 etc., molecules have molecular, mass M1 , M 2 , M3 etc., respectively,, Mw =, , then,, , SN i M i2, SN i M i, , It is determined by light scattering and ultracentrifugation method., , Polydispersity Index, It is the ratio of the mass average molecular mass to the number, average molecular mass, PDI =, , Mw, Mn, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Polymers 465, For natural polymers, PDI is usually equal to one which means that, they are monodisperse. In other words, such polymers are more, homogeneous. On the contrary, synthetic polymers generally have, PDI > 1 which means that they are less homogeneous., , Polyolefins, These are obtained by the addition polymerisation of ethylene and its, derivatives., , 1. Polythene, Polymer of ethylene or ethene., (i) Low density polythene (LDP), 350 K-570 K, , n(CH 2 ==CH 2 ) ¾¾¾¾¾¾¾®, 1000 to 2000 atm, (Traces of oxygen, or a peroxide, initiator), , ¾[CH 2 ¾ CH 2 ¾, ]n, LDP, , It is tough, flexible, transparent, chemically inert as well as poor, conductor of electricity. It has moderate tensile strength but good, tearing strength., It is used in the insulation of electricity carrying wires and, manufacture of squeeze bottles, toys and flexible pipes., (ii) High density polyethylene (HDP), 333-343 K, , )n, n(CH 2 ==CH 2 ) ¾¾¾¾® ¾( CH 2 ¾ CH 2 —, 6-7 atm, (Ziegler Natta, catalyst), , HDP, , It has high density due to close packing. It is also chemically inert, and poor conductor of electricity. It is tougher and harder than, LDP., It is used for making containers, house wares, bottles, toys, electric, insulation etc., , 2. Polystyrene (Styrene), The monomers are styrene molecules. It is thermoplastic. It is used for, making toys, radio and TV cabinets., é, æ, ù, ç, ê, ú, (C6H5 COO) 2, ç, ê, ú, n CH==CH 2 ¾¾¾¾¾¾® ç CH ¾ CH 2, ê½, ú Benzoyl peroxide ½, çç, êC H, ú, ë 6 5, è C6H5, û, Styrene, , ö, ÷, ÷, ÷, ÷÷, øn, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Polymers 467, Polyamides, The polymers which contain an amide linkage in chain are known as, polyamide, e.g. nylon-6,6., , 1. Nylon-6,6, It is obtained by the condensation of adipic acid, hexamethylenediamine with the elimination of water molecule., , nH 2N(CH 2 )6NH 2, , and, , O, O, ½½, ½½, + n HO ¾ C ¾ (CH 2 )4 ¾ C ¾ OH ¾¾¾®, – n H 2O, , adipic acid, , Hexamethylenediamine, , O, H O, H, ½½, ½, ½ ½½, ¾( N ¾ (CH 2 )6 ¾ N ¾ C ¾ (CH 2 )4 ¾ C ¾, )n, Nylon-6,6, , The polyamides are identified by numbers. These numbers refer to the, number of carbon atoms in diamine and in the dibasic acid. As in the, above case, the carbon atoms are 6 in each case, therefore the product, is described as nylon-6,6., , Properties and Uses, Nylon-6,6 is a linear polymer and has very high tensile strength. It, shows good resistance to abrasion. Nylon-6,6 is usually fabricated into, sheets. It is used in bristles for brushes and in textile., , 2. Nylon-6, Nylon-6 is obtained by heating caprolactum with water at a high, temperature., O, Oxidation, O2, , NOH, NH2OH, , H2SO4, (Beckmann, rearrangement), , Cyclohexanone, , Cyclohexanoxime, , O, H2C, , C, , NH, CH2, , H2C, , CH2, CH2, , Caprolactum, , www.aiimsneetshortnotes.com
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470, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Properties and Uses, It is very hard and tough. It has assumed great importance these days, particularly in making of crockery. They do not break even when, droped from a height., , 3. Urea-Formaldehyde Resin, O, ½½, NH 2 ¾ C ¾ NH 2 +, Urea, , Heat, , ¾¾®, , 2HCHO, Formaldehyde, , O, ½½, HOCH 2 ¾ NH ¾ C ¾ NH ¾ CH 2OH, ½ Polymerisation, ¯, O, ½½, ¾, ( CH 2 ¾ NH ¾ C ¾ NH ¾ CH 2 ¾, )n, Urea-formaldehyde resin, , 4. Natural Rubber, Natural rubber is a coiled linear 1,4-polymer of isoprene., CH3, ½, CH 2 ==C ¾ CH==CH 2, Isoprene, , In the polymer chain of natural rubber, the residual double bonds are, located between C2 and C3 of the isoprene unit. All these double bonds, have cis configuration, and thus natural rubber is cis-1,4-polyisoprene., CH3, , H, , CH3, CH2, , H2 C, , CH2, , CH2, CH3, , H, , CH2, , CH2, , H, , A section of the polymeric chain of natural rubber, , In the natural rubber, there is no polar substituent. The only, intermolecular forces are van der Waals’ forces. The cis-configuration, gives the polymeric chain of natural rubber a coiled structure. As a, result, it can be stretched by the application of a force. When the force, is removed, the chain returns back to its original coiled shape., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Polymers 471, Natural rubber is soft and sticky. It can be used only in the, temperature range 10°C–50°C. At higher temperature, it becomes soft, and at low temperature, it becomes brittle. It has high water absorption, capacity. It is attacked by oxidising agents and organic solvents. As, such, it cannot be used very extensively for commercial purposes., , Vulcanisation of Rubber, The properties of natural rubber can be modified by introducing —S—S—, polysulphide crosslinks in its structure. This process of introducing —S—S—, crosslinks in the structure of natural rubber by heating with sulphur at 110°C is, called vulcanisation of rubber., Vulcanisation is carried out by adding sulphur (3-5%) and zinc oxide to the rubber,, and then heating the object at about 110°C for about 20–30 minutes. Zinc oxide, accelerates the rate of vulcanisation. Vulcanisation introduces polysulphide, (—S—S—) bonds between the adjacent chains. These crosslinks tend to limit the, motion of chains relative to each other., , 5. Neoprene, Polymer formed by polymerisation of chloroprene is called neoprene or, synthetic rubber., Cl, Cl, ½, ½, Polymerisation, n(CH 2 ==C ¾ CH ==CH 2 ) ¾¾¾¾¾® ¾, [ CH 2 ¾ C == CH ¾ CH 2 ¾, ]n, Chloroprene, , Neoprene, , It is used for the manufacturing conveyers belts, gasket and hoses., , 6. Buna-N, It is a copolymer of buta-1,3-diene and acrylonitrile. It is formed as, follows, n CH 2 ==CH ¾ CH ==CH 2 + n CH ==CH 2, buta-1,3- diene, ½, CN, Acrylonitrile, Polymerisation, , CN, ½, ( CH 2 ¾ CH==CH ¾ CH 2 ¾ CH 2 ¾ CH ¾)n, ¾, Buna-N, , Properties and Uses, It act as insulator in nature and is used for making conveyor belts and, printing rollers., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Polymers 473, When its solution in a suitable solvent is evaporated, it leaves a tough, but non-flexible film. It is, therefore, used in the manufacture of paints, and lacquers., , 3. Terylene (Dacron), It is a condensation product of ethylene glycol and terephthalic acid., Polymerisation is carried out at 420 to 460 K in the presence of, catalyst mixture of zinc acetate and antimony trioxide., O, , O, , HOCH2CH2—O H + nHO—C, , C—OH, , Ethylene glycol, Terephthalic acid, Polymerisation, , O, , O, , O—CH2CH2O—C, , C, , Terylene or dacron, , n, , Properties and Uses, Terylene is highly resistant to the action of chemical and biological, agents. Its fibres are quite strong and durable. It can also be blended, with wool or cotton to obtain fabrics of desired composition., Terylene is used in the manufacture of a variety of clothes such as, terycot, terywool and terysilk as a result of blending with other yerns., It is also used for preparing magnetic recording tapes, conveyer belts,, aprons for industrial workers etc., , Biopolymers and Biodegradable Polymers, Synthetic polymers are mostly non-biodegradable i.e. it is very difficult, to dispose off the polymeric waste, e.g. polythene bags., Nature has provided us a variety of polymers which can be produced, by the biological systems in plants and animals. These are called, biopolymers, e.g. polysaccharides, proteins, nucleic acids, etc. In the, biological system, these polymers decompose or hydrolyse in the, presence of different enzymes. This means that they are biodegradable., Aliphatic polyesters are the common examples of biodegradable, polymers., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 31, Biomolecules, Biomolecules are the organic compounds which form the basis of life,, i.e. they build up the living system and responsible for their growth, and maintenance., The sequence that relates biomolecules to living organism is, Biomolecules ® Organelles ® Cells ® Tissues ® Organs ® Organ, systems ® Living organism., , Carbohydrates, Optically active polyhydroxy aldehydes (aldoses) or ketones (ketoses) or, the compounds which produce these units on hydrolysis are known as, carbohydrates. They are also called saccharides., , Classification of Carbohydrates, (i) Reducing and Non-reducing Sugars, Based upon reducing and non-reducing properties, carbohydrates are, classified as reducing and non-reducing sugars. Carbohydrates that, reduces Fehling’s reagent or Tollen’s reagent are termed as, reducing carbohydrates. e.g. All monosaccharides and disaccharides, (except sucrose). But carbohydrates which do not reduce such reagents, are known as non-reducing carbohydrates. e.g. sucrose and, polysaccharides., , (ii) Sugars and Non-sugars, On the basis of taste, carbohydrates are classified as sugars and, non-sugars. The monosaccharides and oligosaccharides having sweet, taste are collectively known as sugars. Polysaccharides which are, insoluble in water and not sweet in taste, are known as non-sugars., (Latin Saccharum = sugar) due to sweet taste of simpler members., , www.aiimsneetshortnotes.com
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476, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Monosaccharides, Oligosaccharides and, Polysaccharides, Depending upon the number of simple molecules produced upon, hydrolysis, carbohydrates are classified as, monsaccharides,, oligosaccharides and polysaccharides :, , I. Monosaccharides, These cannot be hydrolysed further to simpler molecules and, subdivided into tetroses, pentoses or hexoses depending upon the, number of carbon atoms. These are also called homopolysaccharides., Aldotetroses, Aldopentoses, Aldohexoses, Ketohexoses, , e.g Erythrose, Threose, e.g Xylose, Ribose, e.g Glucose, Galactose, e.g Fructose, , All naturally occurring monosaccharides belong to D-series., Killiani synthesis is used to convert an aldose into next higher aldose., , 1. Glucose, It is also known as Dextrose. It is present in grape sugar, corn sugar,, blood sugar (C6H12O6 )., , Manufacture, By hydrolysis of starch with hot dil mineral acids and by hydrolysis of, sucrose., C12H 22O11 + H 2O ¾® C6H12O6 + C6H12O6, H+, , sucrose, , glucose, , fructose, , H+, , + nH 2O ¾¾¾¾¾® n C6H12O6, , (C6H10O5 )n, , 393 K; 2-3 bar, , starch or cellulose, , glucose, , Extra glucose is stored in liver as glycogen., , a and b-glucose, In intermolecular hemiacetal formation (cyclic structure), —CHO is, converted into —CHOH which can have two configurations as shown, below, H—C1—OH, , HO—C1—H, , a-form (i), , b-form (ii), , Glucose having (i) configuration about C1 is the a-glucose and having, (ii) configuration about C1 is b-glucose. The carbon C1 is known as, anomeric carbon and these compounds are called anomers. Both the, forms are optically active. a-D-glucose has specific rotation +111.5° and, b-D-glucose has specific rotation + 19.5°., , www.aiimsneetshortnotes.com
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490, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Nucleic Acids, Important Terms of Nucleic Acids, (i) Nitrogenous base Derived from purines having two rings in, their structure. e.g. Adenine (A) and Guanine (G) and derived, from pyrimidines having one ring in their structure e.g., Thymine (T), Uracil (U) and Cytosine (C)., Two H–bonds are present between A and T (A = T) while three, H-bonds are present between C and G (C ººG)., (ii) Pentose sugar It is either ribose or deoxy ribose (not having, oxygen at C2)., (iii) Nucleoside Ribose–/deoxyribose + one base unit from A, G, C,, T or U., (iv) Nucleotides Nucleotides consist of 5-carbon, nitrogenous base +1,3-phosphate groups., , sugar, , +, , NH2, N, , OH, , N, , 5¢, , HO—P—O—CH2, , O, , 4¢, , O, , C, H, , H, , 3¢, , 1¢, , H, , N, , N, , C, , 2¢, , OH OH, , (v) Ribonucleotide Phosphate unit + Ribose + one base unit, from A, G, C, or U., (vi) Deoxyribo nucleotide, base from A, G, C or T., , Phosphate unit + Deoxyribose + one, , DNA and RNA, Nucleic acid is polynucleotide, present in the living cells or bacterial cells, having no nucleus and in viruses having no cells. These are of two types:, (i) DNA Deoxyribonucleic acid., DNA + H 2O ® Phosphoric acid + deoxyribose + A, G, C, T, (ii) RNA Ribonucleic acid., RNA + H 2O ® Phosphoric acid + Ribose + A, G, C, U, , www.aiimsneetshortnotes.com
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491, , Biomolecules, , Telegram @neetquestionpaper, Structure of DNA, It consists of two polynucleotide chains, each chain form a right, handed helical spiral with ten bases in one turn of the spiral. The two, chains coil to double helix and run in opposite direction. These are held, together by hydrogen bonding., , Structure of RNA, It is usually a single strand of ribonucleotides and take up right, handed helical conformation. Up to 12000 nucleotides constitute an, RNA., It can base pair with complementary strands of DNA or RNA., According to standard base pairing rules-G pairs with C, A pairs with, U or T. The paired strands in RNA–RNA or RNA–DNA are anti, parallel as in DNA., In both DNA and RNA, heterocyclic base and phosphate ester linkages, are at C1 and C5 ¢ respectively of the sugar molecule., , Types of RNA, (i) Messanger RNA (m-RNA) It is produced in the nucleus and, carries information for the synthesis of proteins., (ii) Transfer RNA (Soluble or Adoptive RNA) (s-RNA, t-RNA) It, is found in cytoplasm. Its function is to collect amino acids from, cytoplasm for protein synthesis., , Functions of Nucleic Acids, 1. Direct the synthesis of proteins., 2. Transfer the genetic information (hereditary characters)., , m, t, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 492, , Handbook of Chemistry, , Lipids, The constituents of animals and plants soluble in organic solvents, (ether, chloroform, carbon tetrachloride), but insoluble in water are, called lipids. (Greek lipose = fat), , Types of Lipids, (i) Simple lipids, (a) Fats and oils on hydrolysis give long chain fatty acids, + glycerol., (b) Waxes, , Long chain fatty acids + long chain alcohols., , Vegetable and animal oils and fats have similar chemical, structure and are triesters of glycerol, called glycerides., Simple glycerides contain one type of fatty acids. Mixed, glycerides contain two or three types of fatty acids., , Common saturated fatty acids CH3 ¾ (CH 2 )n COOH., When n = 4 caproic acid; n = 6 caprylic acid; n = 8 capric acid,, n = 10 lauric acid n = 12 myristic acid; n = 14 palmitic acid,, n = 16 stearic acid., , Common unsaturated fatty acids, C17H33COOH oleic acid; C17H33COOH linoleic acid., , (ii) Phospholipids Phosphate + glycerol + fatty acids + a nitrogen, containing base., , Function of phospholipids are, 1. As emulsifying agents since they carry hydrophilic polar, groups and hydrophobic non-polar groups., 2. They absorb fatty acids from the intestine and transport to, blood cells., (iii) Glycolipids They contain one or more simple sugars and are, important components of cell membranes and chloroplast, membranes., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Biomolecules 493, (iv) Terpenes Menthol, camphor are common plant terpenes., Carotenoids and pigments are also terpenes., (a) Essential oils The volatile, sweet smelling liquids, obtained from flowers, leaves, stems, etc. Example of, terpenes are esters of lower fatty acid, e.g. clove oil, rose oil,, lemon oil., (b) Drying oils The oils which are converted into tough,, transparent mass when exposed to air by oxidation, polymerisation process are called drying oils. e.g. Linseed oil,, perilla, poppy seed oils., Cotton seed oil and til oil are semidrying oils., Acid Value, Saponification Value, , Iodine Value, Reichert–Meissel Value (R/M Value), , Hormones, These are the chemical substances which are produced by endocrine, (ductless) glands in the body. Hormones acts as chemical, messengers., Some examples of ductless (endocrine) glands are thyroid, pitutary,, adrenal, pancreas, testes and ovaries., Hormones are divided into three types :, (i) steroids, (ii) proteins or polypeptides, (iii) amines., , www.aiimsneetshortnotes.com
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494, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Insulin is a protein hormone which is secreted by b-cells of the, pancreas. Insulin was the first polypeptide in which the amino acid, sequence was experimentally determined. Its deficiency leads to, diabetes mellitus., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 32, Chemistry in, Everyday Life, The branch of science which makes use of chemicals for the treatment, of diseases [therapeutic effect] is called chemotherapy., , Medicines or Drugs, Chemicals which may be used for the treatment of diseases and for, reducing the suffering from pain are called medicines or drugs., Some important classes of drugs are :, , 1. Antacids, The chemical substances which neutralize the excess acid in gastric, juice and raise the pH to an appropriate level in stomach are called, antacids., The most commonly used antacids are weak bases such as sodium, bicarbonate [sodium hydrogencarbonate, NaHCO3 ], magnesium, hydroxide [Mg(OH)2 ] and aluminium hydroxide [Al(OH)3 ]., Generally liquid antacids are more effective than tablets because they, have more surface area available for interaction and neutralisation of, acid., Milk is a weak antacid., Histamine stimulates the secretion of pepsin and hydrochloric acid., The drug cimetidine [Tegamet] was designed to prevent the interaction, of histamine with the receptors present in the stomach wall., Cimetidine binds to the receptors that triggers the release of acid into, the stomach. This result in release of lesser amount of acid. Now, ranitidine (zantac), omeprazole and lansoprazole are used for, hyperacidity., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 496, , Handbook of Chemistry, , 2. Tranquilizers (Psychotherapeutic Drugs), Chemical substances used for the treatment of stress, anxiety,, irritability and mild or even severe mental diseases, are known as, tranquilizers. These affect the central nervous system and induce sleep, for the patients as well as eliminate the symptoms of emotional, distress. They are the common constituents of sleeping pills., Noradrenaline is one of the neurotransmitter that plays a role in, mood changes. If the level of noradrenaline is low, the signal sending, activity becomes low, and the person suffers from depression. In such, situations antidepressant drugs are required. These drugs inhibit the, enzymes which catalyse the degradation of noradrenaline. If the, enzyme is inhibited, this important neurotransmitter is slowly, metabolized and can activate its receptor for longer periods of time,, thus counteracting the effect of depression. Iproniazid and phenelzine, are two such drugs., Barbituric acid and its derivatives viz. veronal, amytal, nembutal,, luminal, seconal are known as barbiturates. Barbiturates are hypnotic,, i.e. sleep producing agents., O, , O, , O, NH, , Ph, , NH, , Et, O, , N, , O, , O, , N, , O, , Et, Et, , NH, N, , O, , H, , H, , H, , barbituric acid, , lumainal, , veronal, , O, , Equanil is used to control depression and hypertension., Non-hypnotic chlorodiazepoxide and meprobamate are relatively mild, tranquilizers suitable for relieving tension., , 3. Analgesics, Medicines used for getting relief from pain without causing impairment, of consciousness are called analgesics. These are of two types :, , (i) Narcotics, Drugs which produce sleep and unconsciousness are called narcotics., These are habit forming drugs. For example, morphine and codeine., Morphine diacetate is commonly known as heroin., , (ii) Non-narcotics, These are non-habit forming chemicals which reduce mild to moderate, pain such as headache, toothache, muscle and joint pain, etc. These are, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemistry in Everyday Life 497, also termed as non-addictive. These drugs do not produce sleep and, unconsciousness. Aspirin (2-acetoxybenzoic acid) is most commonly, used analgesic with antipyretic properties. Now these days because of, its anti-blood clotting action, aspirin is widely used to prevent, heart-attacks., O, O—C—CH3, COOH, , (Acetylsalicyclic acid), aspirin, , Aspirin is toxic for liver and sometimes also causes bleeding from, stomach. So, naproxen, ibuprofen, paracetamol,diclofenac sodium are, other widely used analgesics., , 4. Antipyretics, These are the chemical substance which reduce body temperature, during high fever. Paracetamol, aspirin, phenacetin (4-hydroxy, acetanilide), analgin and novalgin, etc., are common antipyretics. Out, of these, paracetamol (4-acetamidophenol) is most common., OH, , NHCOCH3, paracetamol, , 5. Antimicrobials, An antimicrobial tends to kill or prevent development of microbes or, inhibit the pathogenic action of microbes such as bacteria, fungi and, virus selectively., Sulpha drugs constitute a group of drugs which are derivatives of, sulphanilamide and have great antimicrobial capacity, thus, these are, widely used against diseases such as dyptheria, dysentry,, tuberculosis, etc., , www.aiimsneetshortnotes.com
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498, , Telegram @neetquestionpaper, , Handbook of Chemistry, , N, SO2NH2, , SO2NH, N, , NH2, , NH2, , sulphanilamide, , N, , sulphadiazine, , CH3, , SO2NH, N, , NH2, sulphadimidine, , SO2NH__C, , SO2NH, N, , CH3, , NH2, sulphapyridine, , NH, NH2, , NH2, sulphaguanidine, , In these structure, drugs are analogues of p-amino benzoic acid., Different types of antimicrobial drugs are as follows :, , (i) Antibiotics, These are the substances (produced wholly or partially by chemical, synthesis) which in low concentrations inhibit the growth of, microorganisms or destroy them by intervening in their metabolic, processes., Antibiotics are products of microbial growth and thus, antibiotic, therapy has been likened to ‘setting one thief against another’., Antibiotics are of two types :, (a) Bactericidal antibiotics have cidal (killing) effect on microbes., For example, penicillin, ofloxacin, amino glycosides, etc., (b) Bacteriostatic antibiotics have a static (inhibitory) effect, on microbes. For example, erythromycin, tetracycline,, chloramphenicol, etc., Penicillin was the first antibiotic discovered (by Alexander Fleming) in, 1929. It is a narrow-spectrum antibiotic. Ampicillin and amoxicillin are, semi-synthetic modifications of penicillin. Penicillin is not suitable to all, persons and some persons are allergic to it. Consequently, it is essential to, test the patients for sensitivity (or allergy) to penicillin, before it is, administered., In India, penicillin is manufactured at Pimpri and Rishikesh (Uttarakhand)., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemistry in Everyday Life 499, Broad-spectrum, antibiotics also, called, wide-spectrum, antibiotics, which are effective against several different types of, harmful microorganisms. These antibiotics can kill or inhibit a wide, range of gram positive or gram negative bacteria. e.g. Tetracycline,, chloramphenicol (given in case of typhoid, dysentery, fever etc.), ofloxacin, etc., , (ii) Antiseptics, These are the chemicals which either kill or prevent the growth of, microorganisms. Antiseptics are applied to the living tissues such as, wounds, cuts, ulcers and skin diseases in the form of antiseptic creams, like furacin and soframycin. Some important examples of antiseptics are, (a) Dettol is a mixture of chloroxylenol and terpineol., OH, , H3 C, , CH3, , CH3, Cl, , H3C, , chloroxylenol, , CH3, , OH, , terpineol, , (b) Bithional is added to soaps to impart antiseptic properties to, reduce the odour produced by bacterial decomposition of, organic matter on the skin., Cl, , OH HO, , Cl, , S, Cl, , bithional, , Cl, , (c) Tincture of iodine is a 2-3% solution of iodine in alcohol,, which is a powerful antiseptic for wounds., (d) Iodoform (CHI3 ) is also used as an antiseptic for wounds., (e) Boric acid in dilute aqueous solution is a weak antiseptic for, eyes., , (iii) Disinfectants, These are the chemical substances which kill microorganisms but are, not safe to be applied to the living tissues. They are generally used to, kill the microorganisms present on inanimate objects such as floors,, drainage system, instruments, etc., , www.aiimsneetshortnotes.com
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500, , Telegram @neetquestionpaper, , Handbook of Chemistry, , Some common examples of disinfectants are as follows :, (a) 1% phenol solution is disinfectant while in lower, concentration 0.2% solution of phenol is antiseptic., (b) 0.2-0.4 ppm aqueous solution of chlorine is used for, sterilisation of water to make it fit for drinking purpose., (c) SO at very low concentrations behaves like disinfectant., (d) Formaldehyde (HCHO) in the gaseous forms is used for, disinfecting rooms and operation theatres in hospitals., , 6. Antifertility Drugs, These are the chemical substances used to control the pregnancy., These are also called oral contraceptives. They belong to the class of, natural products, known as steroids., Birth control pills essentially contain a mixture of synthetic estrogen, and progesterone derivatives. Norethindrone is widely used as, antifertility drug., , Chemicals in Food, 1. Artificial Sweetening Agents, Sucrose (table sugar) and fructose are the most widely used natural, sweeteners. But they add calories to our intake and promote tooth, decay. To avoid these problems many people take artificial sweeteners., Organic substances which have been synthesized in lab are known to, be many times sweeter than cane sugar. Such compounds are known, as artificial sweetening agents or artificial sweeteners., Some important artificial sweeteners are given below :, , (i) Saccharin (o-sulphobenzimide), Discovered by while he constant in Fahlberg was working at Hopkins, university in 1879., CO, , CO, , SO2, saccharin, , –, , NNa+, , NH, SO2, , sodium salt of saccharin, soluble in water, , It is the most popular artificial sweetener. It is 550 times as sweet as, cane sugar, since it is insoluble in water, so it is sold in the market, its, soluble form are its sodium or calcium salts., It is non-biodegradable so excreted from the body in urine (unchanged)., It’s use is of great value for diabetic persons and people who need to, control intake of calories., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemistry in Everyday Life 501, (ii) Aspartame, It is the methyl ester of the dipeptide derived from phenylalanine and, aspartic acid. It is also known as ‘Nutra sweet’., O, , O, , O, , HO¾C¾CH2¾CH¾C¾NH¾CH¾C¾OCH3, NH2, , CH2, , It decomposes at baking or cooking temperatures and hence, can be, used only in cold food and soft drinks., Aspartame has the same amount of calories as sugar (4 cal per gram)., Aspartame should not be used by people suffering from the genetic, disease known as PKU (phenyl ketone urea). Because in such people, decomposition of aspartame gives phenylpyruvic acid. Accumulation of, phenylpyruvic acid is harmful especially to infants that causes brain, damage and mental retardation., , (iii) Alitame, It is quite similar to aspartame but more stable than aspartame. It is, 2000 times as sweet as sucrose. The main problem for such sweetener, is the control of sweetness of the substance to which it is added, because it is high potency sweetener., S, O, , NH2, , H, N, , O, OH, , N, H, , O, , (iv) Sucralose, It is a trichloro derivative of sucrose. It’s appearance and taste are like, sugar. It is stable at cooking temperature. It is almost 600 times as sweet, as sucrose. However, it neither provide calories nor causes tooth decay., HO, O, Cl, , OH, , Cl, , O, OH, , O, OH, , Cl, OH, , www.aiimsneetshortnotes.com
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502, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (v) Cyclamate, It is N-cyclohexylsulphamate. It is only 20 times sweeter than cane, sugar., s r, , NHSO3Na, , cyclamate, , 2. Food Preservatives, These are the chemical substances added to food to prevent their, spoilage due to microbial growth (bacteria, yeasts and moulds) and to, retain their nutritive value for longer periods ., The most commonly used preservatives include table salt, sugar,, vegetable oil, vinegar, citric acid, spices and sodium benzoate, (C6H5COON a). Salts of sorbic acid and propanoic acid are also used as, preservatives for cheese, baked food, pickles, meat and fish products., (i) Sodium benzoate is metabolised by conversion into hippuric, acid (C6H5CONHCH 2COOH), which is ultimately excreted in, urine. It is used in soft drinks and acidic foods., (ii) Antioxidants like BHT (butylated hydroxy toluene) and BHA, (butylated hydroxy anisole) retard the action of oxygen on the, food and help in the preservation of food materials., OH, (CH3)3C, , OCH3, C(CH3)3, C(CH3)3, , CH3, , OH, , (BHT), , (BHA), , Cleansing Agents, The word detergent means cleansing agent. Actually detergent word is, derived from Latin word ‘detergere’ means “to wipe off”., Cleansing agents are the substances which remove dirt and have, cleansing action in water. These are also called surfactants., Detergents can be classified into two types., (i) Soapy detergents or soaps, and, (ii) Non-soapy detergents or soapless soap., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemistry in Everyday Life 503, 1. Soaps, Soaps are sodium or potassium salts of higher fatty acids (containing, large number of carbon atoms) e.g. stearic acid, oleic acid and palmitic, acid. Sodium salts of fatty acids are known as hard soaps while the, potassium salts of fatty acids are known as soft soaps., Hard soaps are prepared by cheaper oil and NaOH while soft soaps are, prepared by oil of good quality and KOH. The soft soaps do not contain, free alkali, produce more lather and are used as toilet soaps, shaving, soaps and shampoos., , Preparation of soaps, Soaps containing sodium salts are formed by heating fat (glyceryl ester, of fatty acid) with aqueous sodium hydroxide solution. This reaction is, known as saponification., O, CH2—O—C—C17H35, O, CH—O—C—C17H35 + 3NaOH, O, CH2—O—C—C17H35, , CH2—OH, –+, , 3C17H35COONa + CH—OH, (soap), sodium, stearate, , CH2—OH, glycerol, , fat, (Glyceryl ester of stearic acid), , Oil/Fat + NaOH ¾®, , Soap + Glycerol, , The solution left after removing the soap contains glycerol, which can, be recovered by fractional distillation. To improve the quality of soaps, desired colours, perfumes and medicinal chemical substances, are, added., , Types of Soaps, Different types of soaps are made by using different raw materials., (i) Toilet soaps These are prepared by using better grade of fat, or oil and care is taken to remove excess alkali. Colour and, perfumes are added to make these more attractive., (ii) Floating soaps These can be prepared by beating tiny air, bubbles into the product before it hardens., (iii) Transparent soaps These are made by dissolving the soap, in ethanol and then evaporating the excess solvent., (iv) Medicated soaps Medicated soaps are prepared by adding, some antiseptics like dettol or bithional., , www.aiimsneetshortnotes.com
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504, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (v) Shaving soaps These contain glycerol to prevent rapid, drying. A gum called rosin is added while making them. It forms, sodium rosinate which lather well., (vi) Laundry soaps These contain fillers like sodium rosinate,, sodium silicate, borax and sodium carbonate., (vii) Soap chips These are made by running a thin sheet of, melted soap on a cool cylinder and scraping off the soaps in, small broken pieces., (viii) Soap granules, , These are dried miniature soap bubbles., , (ix) Soap powder and scouring soaps These contain a, scouring agent (abrasive) such as powdered pumice or finely, divided sand and builders like sodium carbonate and trisodium, phosphate. Builders increases the cleansing action of soaps by, making them to act more quickly., , Disadvantages of Soaps, Soap is good cleansing agent and is 100% biodegradable, i.e., microorganisms present in sewage water can completely oxidise soap, to CO2. As a result, it does not create any pollution problem. However,, soaps have two disadvantages:, (i) Soaps cannot be used in hard water since calcium and, magnesium ions present in hard water produce curdy white, precipitates of calcium and magnesium soaps., 2, , 2C17H35COON a + CaCl2 ¾® (C17H35COO)2Ca + 2NaCl, insoluble, , 2, , 2C17H35COON a + MgSO4 ¾® (C17H35COO)2Mg + Na 2SO4, insoluble, , These insoluble soaps separate as scum in water and causes, hindrance to washing because the precipitate adheres onto the, fibre of the cloth as gummy mass. Thus, a lot of soap is wasted if, water is hard., (ii) Soaps cannot be used in acidic solutions since acids precipitate, the insoluble free fatty acids which adhere to the fabrics and thus,, reduce the ability of soaps to remove oil and grease from fabrics., RCOONa + H, soap, , ¾®, , RCOOH, , + Na, , free fatty acid, precipitate out, , www.aiimsneetshortnotes.com
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506, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 2. Cationic Detergents, These are quaternary ammonium salts of amines with acetates,, chlorides or bromides as anion. For example,, ù, é, CH3, ú, ê, ½, êCH (CH ) ¾ N + ¾ CH ú Br, 2 15, 3ú, ê 3, ½, ú, ê, CH3, ûú, ëê, cetyltrimethyl ammonium, bromide, , Cationic detergents are used in hair conditioner. They have germicidal, properties but are expensive therefore, these are of limited use., , 3. Non-ionic Detergents, Such detergents does not contain any ion in their constitution. One, such detergent can be obtained by reaction of stearic acid and, polyethylene glycol., HO ¾ CH 2 ¾ CH 2 ¾ OH + n CH 2 ¾ CH 2 ¾®, ethylene glycol, , O, ethylene oxide, , HO ¾ (CH 2CH 2O)n ¾ CH 2CH 2OH, polyethylene glycol, , CH3 (CH2 )16 COOH (stearic acid) H2O, , CH3 (CH 2 )16COO(CH 2CH 2O)n CH 2CH 2 ¾ OH, polyethylene glycol stearate, , Liquid dish washing detergents are non-ionic type. Mechanism, of cleansing action of this type of detergents is the same as that of soaps., , Advantages of synthetic detergents over soaps, 1. Synthetic detergents can be used even in case of hard water, whereas soaps fail to do so., 2. Synthetic detergents can be used in the acidic medium while, soaps cannot because of their hydrolysis to free acids., 3. Synthetic detergents are more soluble in water and hence, form, better lather than soaps., 4. Synthetic detergents have a stronger cleansing action than, soaps., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemistry in Everyday Life 507, Chemistry in Colouring Matter, The natural or synthetic colouring matter which are used in solution to, stain materials especially fabrics are called dyes., All colouring substances are not dyes, e.g. azobenzene, a coloured, substance does not act as dye., A dye have following characteristics :, 1. It must have a suitable colour., 2. It can be fixed on the fabric either directly or with the help of, mordant., 3. It must be resistant to the action of water, acid and alkalies., The groups, responsible for colour, are called chromophore, e.g., O, ½½, ¾ N ==N ¾ , ¾ N ®O , C ==O, C ==S etc., The substance which do not given colour itself but intensify the colour, of chromophore, are called auxochrome., e.g., —OH , —SO3H , —COOH , —NH 2 , ¾ NHR ¾ , ¾ NR2., , Classification of Dyes on the Basis of Constitution, (i) Nitro or nitroso dye Chromophore NO2 or NO group,, Auxochrome = —OH group, e.g. picric acid, martius yellow,, Gambine, naphthol yellow-S., (ii) Azo dye, e.g. bismark brown, methyl orange, methyl red, congo, red, etc., (iii) Anthraquinone dye e.g. alizarin, (iv) Indigo is the oldest known dye. Other examples are tyrian, purple, indigosol., (v) Phthalein dye e.g. phenolphthalein, fluorescein, eosin,, mercurochrome., (vi) Triarylmethane dye, e.g. malachite green, rosaniline., , Classification of Dyes on the Basis of Application, (i) Direct dyes These dyes applied directly to fibre and are, more useful to the fabrics containing H-bonding like cotton,, rayon, wool, silk and nylon, e.g. martius yellow, congo red, etc., (ii) Acid dyes These are water soluble and contain polar acidic, groups which interact with the basic group of fabric, e.g., Orange-1, congo red, methyl orange, etc. These dyes does not, have affinity for cotton but are used for silk, wool, etc., , www.aiimsneetshortnotes.com
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508, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (iii) Basic dyes These dyes contain basic group (like NH 2 group), and react with anionic sites present on the fabric. These are, used to dye nylons and polyester, e.g. butter yellow, magenta, (rosaniline), aniline yellow, etc., (iv) Vat dyes Being water insoluble, these cannot be applied, directly. These are first reduced to a colourless soluble form by a, reducing agent in large vats and then, applied to fabrics. After, applying, these are oxidised to insoluble coloured form by, exposure to air or some oxidising agents, e.g. Indigo, tyrian, purple, etc., (v) Mordant dyes These are applied with the help of a binding, material (e.g. metal ion, tannic acid or metal hydroxide) called, mordant. Depending upon the metal ion used, the same dye can, give different colours. Alizarin is an important example of such, dyes., (vi) Ingrain dye These dyes are synthesised directly on the, fabric. These are water insoluble and particularly suitable for, cotton fibres. Azo dyes belong to this group of dye., (vii) Disperse dye These are applied to the fabric in the form of, their dispersion in a soap solution in the presence of a, stabilising agent like cresol, phenol, benzoic acid, etc. These are, used to colour synthetic fabrics like nylon, orlon, polyesters and, cellulose acetate. Anthraquinone dyes and monoazo dye are the, examples of dispersed dye., , Chemistry in Cosmetics, Cosmetics are used for decorating, beautifying or improving, complexion of skin. Some of the cosmetics of daily use are as, , Creams, These are stable emulsions of oils or fats in water and contain, emmollients (to prevent water loss) and humectants (to attract water), as two fundamental components., , Perfumes, These solutions have pleasant odour and invariably consist of, three ingredients: a vehicle (ethanol + H 2O), fixative e.g. sandalwood, oil, benzoin, glyceryl diacetate etc.) and odour producing substance,, (e.g. terpenoids like linalool, anisaldehyde ( p-methoxy- benzaldehyde, etc.), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Chemistry in Everyday Life 509, Talcum Powder, It is used to reduce irritation of skin. Talc (Mg3 (OH)2Si4O10 ), chalk, ZnO,, zinc sterate and a suitable perfume are the constituents of talcum powder., , Deodorants, These are applied to mask the body odour. These possess antibacterial, properties. Aluminium salts, ZnO, ZnO2 , (C17H35COO)2Zn can be used, in deodorant preparation., , Rocket Propellants, Substances used for launching rockets are called rocket propellants., These are the combination of an oxidiser and a fuel., Depending upon the physical states of oxidiser and fuels, rocket, propellants are classified as, , (i) Solid Propellants, These are further divided into two classes :, (a) Composite propellants In these propellants, fuel is, polymeric binder such as polyurethane or polybutadiene and, oxidiser is ammonium per chlorate or potassium perchlorate., (b) Double base propellants These mainly use nitroglycerine, (liquid) and nitrocellulose (solid). The nitrocellulose gels in, nitroglycerine sets in as a solid mass., , (ii) Liquid Propellants, Oxidiser = N 2O4 , liquid O2 , HNO3 and Fuel = kerosene, alcohol,, hydrazine or liquid hydrogen., There are of two types :, (a) Monopropellants In such propellants, the substance act an, fuel as well as oxidiser. e.g. CH3NO2 , H 2O2 , CH3ONO2 etc., (b) Bi-liquid propellants Fuels = kerosene, alcohol etc., and, oxidiser = liquid O2, liquid N 2O4 or HNO3 ., , (iii) Hybrid Propellants, In these, solid fuel and liquid oxidiser is used, e.g. acrylic rubber (solid, fuel) and liquid N 2O4 (liquid oxidiser)., SLV-3 (space launch vehicle-3) and ASLV (Augmented space launch, vehicle) the Indian satellites used composite solid propellants., In space shuttle, liquid O2 + liquid H 2 is used., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 33, Nuclear, Chemistry, The branch of chemistry which deals with the study of composition of, atomic nucleus, nuclear forces, nuclear reactions and radioactive, materials, is called nuclear chemistry., , Nucleons and Nuclear Forces, Protons and neutrons which reside in the nucleus, are called nucleons, and forces binding them in the nucleus, are called nuclear forces., These are short range forces operating over very small distances, (1 fermi = 10 15 cm)., These forces are 1021 times stronger than the electrostatic forces., n 0 and p are held together by very rapid exchange of nuclear, particles, called ( p ) mesons (discovered by Yukawa). Its mass is, 273 times more than the mass of the electron and it may be positively, charged (p ), negatively charged (p ) or neutral (p0)., 1, 1H, , +, , 1p, , 1, , +, , 1p, , 0n, , 0, , ¾® 0n1, ¾® 1H1, , Parameter of Nucleus, (i) Radius of nucleus It is proportional to the cube root of the, mass number of element., R = R0 ´ A1/ 3, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Nuclear Chemistry 511, where, A = mass number, R = radius of nucleus, R0 = proportionality constant = 1.4 ´10 13 m = 1.4 ´ 10, Radius of the nucleus = 10, (ii) Nuclear density, , 13, , - 10, , 12, , 15, , cm, , cm, , It is calculated as, d =, , 3 ´ mass, 4p R30, , density of all nuclei is constant., It is very large ( » 1017 kg / m3 ) compared to atomic density, ( » 103 kg/m3 )., 4, (iii) Volume of nucleus Volume of nucleus = pR3 = 10 36 cm3, 3, (Volume of atom = 10 24 cm3 ), , Factors Affecting Stability of Nucleus, Stability of nucleus is affected by following factors :, , 1. Neutron-proton Ratio or n/p Ratio, It is the main factor for determining the stability of nucleus., The nuclei located in the zone of stability or belt of stability are stable., , Number of neutrons (n), , 140, 120, 100, , Stability belt, , a-emission, / =1, , b-emission, , 80, 60, 40, 20, 20 40 60 80 100 120, Number of protons(p), , Nuclei lying above this zone, have higher n / p ratio and undergo, b-emission to get the zone of stability., Here, a n 0 is transformed into p and give b and antineutrino. Thus,, emission of b-particles increases the number of proton and decreases, the number of neutrons., 1, 1, 0, 0 n ® 1H + 1e + antineutrino, Nuclei lying below this zone, have low n / p ratio and undergo positron, emission or K-electron capture, to get the zone of stability., , www.aiimsneetshortnotes.com
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512, , Telegram @neetquestionpaper, , Handbook of Chemistry, , During K-electron capture, p is converted into n 0 and X-rays are, emitted. e.g., 55, + 1e0 ¾® 25 Mn55 (K - e capture), 26Fe, Generally nuclei with n / p ratio higher than 1.56 undergo spontaneous, fission., , 2. Magic Numbers, Nuclei having 2, 8, 20, 28, 50, 82 and 126 protons or neutrons are, stable, hence these numbers are called magic numbers., Nuclei with even numbers of both p and n 0 are generally more stable, than those with their odd numbers., , Group Displacement Law, This law was given by Soddy, Russel and Fajans in 1913 to decide the, position of element, obtained after radioactive disintegration, in the, Periodic Table., According to this law, ‘In an a-emission, the daughter nuclei will, occupy a position which is two places left to the position of parent, nuclei and in a b-emission, the daughter nuclei will occupy a position, one place right to the parent nuclei., , Disintegration Series, These are the decay series in which heavy nuclei decay by a series of a, and b-emissions finally resulting in the formation of stable isotopes of, lead., There are three natural disintegration series while the fourth series,, called the neptunium series is artificial., , Radioactive Disintegration Series, 4, , 4 +1, , Name, , Thorium, , Neptunium, , Uranium, , Actinium, , Parent element, , 232, 90 Th, , 241, 94Pu, , 238, 92 U, , 235, 92 U, , Prominent, element, , 232, 90 Th, , 237, 93Np, , 238, 92 U, , 227, 89 Ac, , End product, , 82 Pb, , 209, 83Bi, , 82 Pb, , Number of, particles lost, , a =6, , a=8, , a=8, , a =7, , b=4, , b=5, , b =6, , b=4, , Series, , 208, , 4 +2, , 4 +3, , 206, , 82 Pb, , To find a series, mass number is divided by 4., , www.aiimsneetshortnotes.com, , 207
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Telegram @neetquestionpaper, Nuclear Chemistry 513, Artificial Radioactivity, The phenomenon of conversion of a stable nuclei into a radioactive, nuclei by bombarding it with a high speed projectile is called artificial, radioactivity or induced radioactivity (given by Curie and Joliot)., The element with atomic number greater than 92 (after U) are, obtained by this process. These are called transuranium elements., These all are synthetic and radioactive., e.g., , 13 Al, , 27, , + 0 n1 ¾®, projectile, , 11Na, , 24, , + 2He4 ¾®, , 12Mg, , 24, , +, , 1e, , 0, , radioactive, stable, , n 0 , p , deuteron (1H 2 ) and a-particles ( 2He4 ) are used as projectile., , Artificial Transmutation, The conversion of a non-radioactive element into another, non-radioactive elements by artificial means, i.e. by bombarding with, some fundamental particles, is called artificial transmutation. e.g., 14, 7N, , + 2He4 ¾® 8O17 + 1H1, , Nuclear Reactions, In these reactions, the nuclei of atoms interact with other nuclei or, elementary particles such as a , b, p, d , n etc., and results in the, formation of a new nucleus and one or more elementary particles., A nuclear reaction can be represented as, parent nuclei (projectile, obtained particle) daughter nuclei., e.g. the reaction,, 9, 4, ¾® 6C12 + 0 n1 is represented as, 4 Be + 2He, a- particle, 9, , 4 Be, , neutron, , 12, , ( a, n ) 6C ., , Energy of a nuclear reaction, Q, = (total mass of products - total mass of reactants) ´ 931.5 MeV., For exoergic reactions, Q is negative and for endoergic reactions,, Q is positive., , Types of Nuclear Reactions, (i) Projectile capture reactions In these reactions, the projectile, is absorbed with or without the emission of g-radiations. e.g., 92U, , 238, , +, , 1, 0, , ¾®, , 92U, , 239, , +g, , www.aiimsneetshortnotes.com
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514, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (ii) Particle-particle reactions In these reactions, an elementary, particle is also obtained along with the product e.g., 11Na, , 23, , + 1H1 ¾®, , 12Mg, , 23, , 1, , +, , 0, , elementary, particle, , (iii) Spallation reactions In these reactions, high speed projectiles, with energies approximately 40 MeV chip fragments from a heavy, nucleus, leaving a small nucleus, e.g., 29Cu, , 63, , + 2He4 + (400 MeV) ¾®, , 37, 17 Cl, , +141H1 +16 0, , 1, , (iv) Fission reactions In these reactions, a heavy nucleus is broken, down into two or more medium heavy fragments with the emission, of a large amount of energy, e.g., 92U, , 235, , +, , 1, 0, , ¾®, , 141, 56Ba, , + 36Kr92 + 30 n1 + 200 MeV, , (v) Fusion reactions In these reactions, lighter nuclei fuse together, to give comparatively heavier nuclei. e.g., 2, 3, ¾® 2He4 + 0 1 + 17.6 MeV, 1H + 1H, These reactions are the source of tremendous amount of energy., , Applications of Radioactivity, 1. Estimation of Age (Dating Technique), (i) Carbon dating technique It is used to determine the age of, wood, animal fossils etc. It is based upon the ratio of C14 to C12, which remains constant in living organisms but decreases in dead, sample. By comparing these two, the age is determined., The age is calculated by using the formula,, t=, , 2.303, N, log10, k, N, , N 0 = ratio of C14 / C12 in atmosphere, N = ratio of C14 / C12 in dead, matter., (ii) Uranium dating technique The age of earth, minerals, rocks, etc., is determined by this technique. It is based upon the, U 238 / Pb206 ratio., Age, t =, , é Pb206 ù, 2.303, log10 ê1 + 238 ú, k, U, ë, û, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Nuclear Chemistry 515, 2. Medicinal Use, Radioisotopes are used to diagnose and cure many diseases. These can, be used in three ways., (i) In vivo studies 51Cr is used for such technique., (ii) In therapeutic procedure (to cure diseases) Co - 60 is used, for the treatment of cancer, Na-24 is injected to trace the flow of, blood, I-131 is used for the treatment of thyroid and P-32 is used, for leukemia., (iii) Imaging procedure I-131 is used to study the structure, and activity of thyroid gland. I-123 is used in brain imaging and, Tc-99 M is used in bone scans., Radioisotopes are also widely used to find the reaction, mechanism, in industry and in agriculture., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 34, Analytical, Chemistry, Introduction, The branch of chemistry which deals with the identification of, constituents of a substance and calculation of their amounts is called, analytical chemistry., , Branches of Analytical Chemistry, The branches of analytical chemistry are, (a) Qualitative analysis It deals with the identification of, various constituents present in a given material. It further be, classified as, 1. Qualitative analysis of inorganic compounds, 2. Qualitative analysis of organic compounds, (b) Quantitative analysis It deals with the measurement of, amounts/volume/strength of a substance/solution., , Qualitative Analysis of Inorganic Compounds, It involves the following steps :, 1. Preliminary tests, 2. Dry tests, 3. Wet tests for anions, 4. Wet tests for cations, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Analytical Chemistry 517, Preliminary Tests, (i) Solubility Compounds that dissolve in water to the extent of, approximately 0.02 mol per litre (0.02M) are usually classified, as ‘soluble’ compounds, while those that are less soluble are, classified as “insoluble” compounds. No gaseous or solid, substances are infinitely soluble in water., 1. All common inorganic acids are soluble in water. Low molecular, weight organic acids are soluble., 2. All common compounds of the group IA metal (Na, K, etc) and, the ammonium ion, NH +4 , are soluble in water., 3. All common nitrates NO3- , acetates,, perchlorates, ClO-4 , are soluble in water., , CH3COO– ,, , and, , 4. (a) All common chlorides, Cl- , are soluble in water except AgCl,, Hg2Cl2 and PbCl2., (b) The common bromides Br- , and iodides I- , show, approximately the same solubility behaviour as chlorides, but, there are some exceptions. As the halide ions (Cl- , Br- , I- ), increase in size, the solubilities of their slightly soluble, compounds decrease. Although HgCl2 is readily soluble in, water, HgBr2 is only slightly soluble and HgI2 is even less, soluble., (c) The solubilities of the pseudo-halide ions, CN - (cyanide) and, SCN - (thiocyanate), are quite similar to those of the, corresponding iodides. Additionally, both CN - and SCN show strong tendencies to form soluble complex compounds., 5. All common sulphates, SO24 , are soluble in water except PbSO4 ,, Hg2SO4 and BaSO4. CaSO4 and Ag2SO4 are sparingly soluble., 6. All common metal hydroxides are insoluble in water except, those of the group IA metals and the lower members of the group, IIA metals, beginning with Ca(OH)2., , 7. All common carbonates CO32- , phosphates, PO34- , and arsenates, AsO34- , are insoluble in water except those of the group IA, metals and NH +4 × MgCO3 is fairly soluble., 8. All common sulphides, S2- are insoluble in water except those of, the group IA and group IIA metals and the ammonium ion., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 518, , Handbook of Chemistry, , (ii) Colour change on heating Certain oxides change colour on, heating and this fact can be used to identify salt., Colour, , Oxides, In cold, , On heating, , ZnO, , white, , yellow, , Fe2O 3, , brown, , black/red, , PbO, , red, , yellow, , Observation, , Inference, NH+4, , Sublimate formed with smell of NH3, , 2+, , salts, , Sublimate formed without smell of NH3, , Hg, , Brown fumes, , Some nitrates, , salts, , Dry Tests, (a) Borax bead test If borax, Na 2B4O7 × 10H 2O is heated on the, platinum loop, a transparent colourless glass like bead of, sodium metaborate (NaBO2 ) and boric anhydride (B2O3 ) is, formed., D, , Na 2B4O7 ¾® 2NaBO2 + B2O3, Characteristics coloured beads are produced with salts of, copper, iron., CuO + B2O3 ¾®, , Cu(BO2 )2, copper (II) metaborate, , Results have been summarised in table., Colour in Oxidising and Reducing Flames in, Borax-Bead Test, Oxidising flame, Hot, , Cold, , Reducing flame, Hot, , Green, , Blue, , Colourless, , Yellowish- brown, Violet, Yellow, Rose-violet, Yellow, , Yellow, Reddish-brown, Colourless, Rose-violet, Colourless, , Green, Grey, Brown, Red, Yellow, , Cold, Opaque, red-brown, Green, Grey, Brown, Violet, Yellowish- brown, , www.aiimsneetshortnotes.com, , Metal, Copper, Iron, Nickel, Molybdenum, Gold, Tungsten
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Telegram @neetquestionpaper, Analytical Chemistry 519, Oxidising flame, Hot, Yellow, Yellow, Yellow, Orange-red, , Reducing flame, , Cold, Pale yellow, Greenish -yellow, Colourless, Colourless, , Hot, , Metal, , Cold, , Green, Brownish, Grey, Colourless, , Bottle-green, Emerald -green, Pale violet, Colourless, , Uranium, Vanadium, Titanium, Cerium, , (b) Microcosmic salt bead test A test similar to borax bead, test is used for identification of coloured cations if microcosmic, salt, Na(NH 4 )HPO4 × 4H 2O, is used., D, , Na(NH 4 )HPO4 ¾®, , NaPO3, , transparent, bead, , + H 2O + NH3 , , NaPO3 + CoO ¾® NaCoPO4, (blue bead), , Results have been summarised in the following table., Microcosmic Salt Bead Test, Oxidising flame, , Reducing flame, , Green when hot, blue when cold, Yellowish-or reddish-brown when, hot, yellow when cold, Green, hot and cold, Violet, hot and cold, Blue, hot and cold, Brown, hot and cold, Yellow, hot and cold, Yellow when hot, yellow-green, when cold, Pale yellow when hot, colourless, when cold, Colourless, hot and cold, , Colourless when hot, red when cold, Yellow when hot, colourless to green, when cold, Green, hot and cold, Colourless, hot and cold, Blue, hot and cold, Grey when cold, Green when cold, Green, hot and cold, , Copper, Iron, , Metal, , Green when hot, blue when cold, , Tungsten, , Yellow when hot, violet when cold, , Titanium, , Chromium, Manganese, Cobalt, Nickel, Vanadium, Uranium, , (c) Sodium carbonate bead test The sodium carbonate bead, is prepared by fusing a small quantity of sodium carbonate on a, platinum wire loop in the Bunsen flame; a white, opaque bead is, produced. If this is moistened, dipped into a little KNO3 and then, into a small quantity of a manganese salt (for example) and the, whole mixture is heated in the oxidising flame, a green bead of, sodium manganate (Na 2MnO4 ) is formed., D, , MnO + Na 2CO3 + O2 ¾® Na 2MnO4 + CO2, , www.aiimsneetshortnotes.com
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520, , Telegram @neetquestionpaper, , Handbook of Chemistry, , A yellow bead is obtained with chromium salt due to formation of, sodium chromate (Na 2CrO4 )., 2Cr2O3 + 4Na 2CO3 + 3O2 ¾® 4Na 2CrO4 + 4CO2, (d) Flame test Paste of salt and conc. HCl is taken into the lower, oxidising zone and colour imparted to the flame by salts is, observed. Salts, particularly of group V (Ba2 + , Ca2 + , Sr2 + ) are, identified by colours of the flame and summarised in Table, Flame Tests, Colour, , Cation, , Golden yellow, Violet, Carmine-red, Brick-red, Apple-green, , Na +, K+, Li +, Ca 2 +, Ba 2 + , Mo2 +, , Green, , Cu2 + , (BO 33 - ), Tl 3 +, , Crimson-red, , Sr 2 +, , The yellow colouration due to sodium masks is that of potassium. In, such cases view the flame through cobalt glass, the yellow sodium, colour is absorbed and the potassium flame appears crimson., , Wet Tests for Anions, Salt or mixture is treated with dil. H 2SO4 and also with conc. H 2SO4, separately and by observing the types of gases evolved, confirmatory, tests of anions are performed., Observation with Dilute H2SO4, S. No., 1., , Observation, , Acid radical, , Confirmatory test*, , Brisk effervescence, with evolution of, colourless and, odourless gas, , CO23, (carbonate), , Gas turns lime water (or baryta, water) milky but milkyness, disappears on passing gas in excess, (A)*, , 2., , Brown fumes, , NO2(nitrite), , Add KI and starch solution—blue, colour (B)*, , 3., , Smell of rotten eggs, (H2S smell) on, heating, , S2(sulphide), , Gas turns lead acetate paper black, (C), Sodium carbonate extract (SE) +, sodium nitroprusside solution ®, purple colour (D), , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Analytical Chemistry 529, Odour, Mousy, Fruity, Penetrating smell, Pleasant, Smell of bitter almonds, Vinegar smell, Garlic smell, Wine like, , Substance, Acetamide, acetonitrile, Esters, HCHO, CH 3CHO and HCOOH, Ketones (aliphatic and aromatic), C 6H 5CHO, nitrobenzene, nitrotoluene, CH 3COOH, Thiophenol, thioalcohol, Alcohol, , Element Detection, See chapter purification and characterisation of organic compounds., , Tests of Functional Groups, 1. Tests for Carboxylic (—COOH) Group, (i) Litmus paper test Dip blue litmus paper in the aqueous, , –+, , COOH + NaHCO3, benzoic acid, , ®, , solution or suspension of the compound, it turns red., (ii) Sodium bicarbonate test In a test tube take a little, quantity of the compound and then, add a saturated solution of, sodium bicarbonate. Formation of brisk effervescence shows the, presence of —COOH group., COONa + H2O + CO2, sodium benzoate, , (iii) Ester formation Heat a small quantity of organic compound, with ethyl alcohol and a few drops of conc H 2SO4. Cool the, solution and pour in a tube containing water. A fruity smell, due, to formation of an ester, indicates the presence of carboxylic, group., conc. H SO, , 2, 4, R —COOH + C2H5OH ¾¾¾¾¾®, RCOOC2H5 + H 2O, , ester, (fruity smell), , 2. Tests for Alcoholic (—OH) Group, (i) Ceric ammonium nitrate test To small amount of organic, compound or its aqueous solution, add a few drops of ceric, ammonium nitrate solution. A red colour indicates the presence, of alcoholic hydroxy group., 2ROH + (NH 4 )2Ce(NO3 )6 ¾® Ce(NO3 )4 ×( ROH)2 + 2NH 4NO3, red colour, , www.aiimsneetshortnotes.com
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530, , Telegram @neetquestionpaper, , Handbook of Chemistry, , (ii) Lucas test This test is used to distinguish between primary,, secondary and tertiary alcohols. In this test, treat 2 mL of, organic compound with about 8 mL of Lucas reagent, (for preparing Lucas reagent dissolve 32 g of anhy ZnCl 2 in 20, mL of conc HCl and shake.), (a) Immediate formation of turbidity indicates the presence of, , tertiary alcohol., (b) Formation of turbidity after 4-5 min shows the presence of, , secondary alcohols., (c) If solution remains clear, then primary alcohol is present., , 3. Tests for Phenolic (Ph—OH) Group, (i) Ferric chloride test To aqueous or alcoholic solution of, compound, add few drops of ferric chloride (FeCl3 ) solution., Formation of green, red or violet colour shows the presence of phenol., 6C6H5OH + FeCl3 ¾® 3H + + [Fe(OC6H5 )6 ]3 – + 3HCl, violet, , (ii) Liebermann’s nitroso reaction Fuse a little amount of, compound with a crystal of NaNO2 in a test tube. Cool the, mixture and add 1 mL conc H 2SO4. A deep green to blue solution, is formed which turns red when poured in a large excess of, water. The red aqueous solution becomes again deep green or, blue if made alkaline with NaOH. It shows the presence of, phenol., —OH, , HNO2, , NO, , HO, , NOH, , OO, , phenol, C6H5OH, H2SO4, , OH, O, , N, , O, , N, , NaOH, , s, , O, , Blue, , Note Nitrophenol does not respond to FeCl3 test as well as Liebermann’s, nitroso reaction., , www.aiimsneetshortnotes.com
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532, , Telegram @neetquestionpaper, , Handbook of Chemistry, , H.SO2NH, C—, H.SO2NH, , NH2 2R.CHO, , SO3, , Schiff’s reagent (colourless), , R.CHSO2.NH, C, , OH, , +, , s, , NH2 HSO3, , R.CHSO2.NH, OH, , violet colour, , (iv) Benedict’s solution test Boil the compound with 2–3 mL of, Benedict’s solution for few minutes. Appearance of a red-yellow, ppt confirms the presence of aliphatic aldehydes., Note This test is usually given by only aliphatic aldehydes, thus used, to differentiate between aliphatic and aromatic aldehydes., , æR, 5. Tests for Ketone ç, çR, è, , ö, C==O ÷ Group, ÷, ø, , Sodium nitroprusside test Add 0.1 g of solid or 0.2 cc of liquid, compound to 2 cc of sodium nitroprusside solution and then, make it, alkaline with 2–3 drops of sodium hydroxide. A red or purple colour, indicates the presence of ketone (benzophenone does not give this test)., 6. Tests for Primary Amine (—NH2 ) Group, (i) Carbylamine test Warm a little quantity of the compound, with 2 drops of chloroform and 2 mL of alcoholic caustic potash., An intolerable offensive odour of carbylamine indicates the, presence of primary amine., R —NH 2 + CHCl3 + 3KOH ¾®, primary, amine, , R × NC + 3KCl + 3H 2O, , carbylamine, , (ii) Dye test Dissolve about 0.2 g of the compound in dil HCl and, cool. Now, add cold solution of 10% aq NaNO2 solution. Pour all, this content into a beaker containing alkaline b-naphthol, solution. Formation of a red or orange dye indicates the presence, of aromatic primary amino group., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Analytical Chemistry 533, NH2 + NaNO2 + 3HCl, aniline, , +, , N, , 0°–10°C, , s, , NCl + 2H2O + HCl + NaCl, , benzene diazonium chloride, , OH, N, , OH, –HCl, , N Cl + H, , N, , N—, , benzene diazonium, chloride, b-naphthol, , phenyl azo-b-napthhol, (red dye), , Note Dye test is given only by aromatic amines, , 7. Tests to Distinguish between Primary, Secondary and, Tertiary Amines, (i) Nitrous acid test Prepare a solution of nitrous acid by, adding ice cold dil HCl to a solution of 1% aq NaNO 2. Add, gradually this solution to 0.2 g of the organic compound in, 10 mL dil HCl., (a) Formation of brisk effervescence shows the presence of, aliphatic primary amine., R —NH 2 + HNO2 ¾® ROH + H 2O + N 2 , (b) Formation of an oily dark coloured liquid indicates the, presence of secondary amine., R, R, , NH + HNO2 ¾®, , secondary, amine, , R, R, , N × NO, , + H 2O, , nitroso compound (oily), , (c) No reaction indicates the presence of aliphatic tertiary, amine while production of green or brown colour indicates, the presence of aromatic tertiary amines., (ii) Hinsberg’s test Take about 0.2 g of the compound, add 1 mL, of 5% NaOH and 3 mL pyridine. Shake well and add few drops of, benzene sulphonyl chloride with continuous shaking and cool it., , www.aiimsneetshortnotes.com
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536, , Telegram @neetquestionpaper, , Handbook of Chemistry, , 4. Iodoform, Acetone when treated with potassium iodide and sodium hypochlorite, (NaOCl), gives iodoform., NaOCl + KI ¾® NaOI + KCl, H3C, H3C, , C==O + NaOI ¾®, , I3C, H3C, , NaOH, , C==O, - +, , ¾¾® CH3COON a + CHI3 ¯, , Iodoform, (yellow ppt.), , Titrimetric Exercises, Some Important terms, (a) Titration The process by which the concentration or strength, of a chemical substance is measured by using the solution of, known strength is called titration., (b) Analyte and titrant The substance being analysed is called, analyte and that which is added to analyte in a titration is called, titrant., (c) Equivalence point or end point It is point at which the, reaction between two solutions is just complete. It is generally, represented by change in colour, pH, conductivity etc., (d) Standard solution Solution of known concentration is, called standard solution., (e) Primary standard substance The substance, standard, solution of which can be prepared directly by dissolving its, definite weight in definite volume of solvent is called primary, standard substance, e.g. crystalline oxalic acid, anhydrous, Na 2CO3 , Mohr’s salt etc., The substance, which occur in pure state, are non-hydroscopic,, non-deliquescent, generally behave as primary standard, substance., (f) Secondary standard substance Their standard solution, cannot be prepared directly. e.g. KMnO4 , NaOH, KOH etc., (g) Indicator, , It shows the end point of a titration., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Appendix 1, , Greek Letters & Their Names, a, b, g, d, z, h, q, i, k, l, m, u, p, r, s, t, f, c, y, w, , alpha, beta, gamma, delta, zeta, eta, theta, iota, kappa, lambda, mu, nu, pi, rho, sigma, tau, phi, chi, psi, omega, , Appendix 2, , Fundamental Physical Constants, S. No., , Physical constant, , 1., 2., , Acceleration due to gravity, Atomic mass unit, , 3., , Symbol, , Value, -2, , g, amu (u), , 9.81 ms, 1.660453 ´ 10 -27 kg, , Avogadro constant, , NA, , 6.02217 ´ 10 23 mol -1, , 4., , Boltzmann constant, , K, , 1.38062 ´ 10 -23 JK -1, , 5., , Electronic charge, , e, , 1.602192 ´ 10 -19 C, , 6., , Faraday constant, , F, , 9.64867 ´ 10 4 C mol -1, , 7., 8., , Gas constant, Molar volume of ideal gas at (STP), , R, Vm, , 8.314 JK -1 mol -1, 2.24136 ´ 10 -2 m 3 mol -1, , 9., , Planck constant, , h, , 6.62620 ´ 10 -34 Js, , 10., , Rydberg constant, , RH, , 1.973731 ´ 107 m -1, , 11., 12., , Standard pressure (atmosphere), Velocity of light of vacuum, , p, c, , 101325 Nm -2, 2.997925 ´ 10 8 ms -1, , Additional Constants, p = 3.1416, ln X = 2.303 log10 X, , www.aiimsneetshortnotes.com
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7, , 6, , 5, , 4, , 3, , 2, , 1, , Period, , Group, , 4 s, , 2, 1IA, , 12 s, , Beryllium, 9.0121, , 21 s, , 3, 11IB, , 38 s, , Calcium, 40.079, , 26 s, , 8, 27 s, , 9, VIII, 28 s, , 10, 29 s, , 11, IB, 30 s, , 12, IIB, 31 s, , Aluminium, 26.962, , Al, 32 s, , Siloon, 28.086, , Si, , 14 s, , Carbon, 12.011, , C, , 6 s, , 14, IVA, G, , 33 s, , Phosphorus, 30.914, , P, , 15 s, , Nitrogen, 14.007, , N, , 7, , 15, VA, G, , 34 s, , Sulphur, 32.066, , S, , 16 s, , Oxygen, 15.999, , O, , 8, , 16, VIA, , 73 s, , Nioblum, 92.906, , G, , 2, , 35, , L, , Chlorine, 35.453, , 42 s, , Chromium, 51.996, , 43 s, , Manganese, 54.938, , 44 s, , Iron, 55.845, , 45 s, , Cobalt, 58.933, , 46 s, , Nickel, 58.693, , 47 s, , Copper, 63.546, , 48 s, , Zinc, 65.39, , 49 s, , Gallium, 69.723, , 50 s, , IGermanium, 72.61, , 51 s, , Arrsenic, 7.822, , 52 s, , Selenium, 78.96, , 74 s, , 75 s, , 76 s, , Molybdenum Technetium Ruthenium, 101.07, (98), 95.94, , 77 s, , Rhodium, 102.906, , 78 s, , Palladium, 106.42, , 79 s, , Silver, 107.868, , 80 s, , Cadmium, 112.411, , 81 s, , Indium, 114.818, , 82 s, , Tin, 118.710, , 83 s, , Antimony, 121.80, , 84 s, , Tellrium, 177.60, , 85 s, , Iodine, 125.904, , I, , 53 s, , Bromlne, 79.904, , G, , G, , 36, , Argon, 39.948, , G, , 86, , Xenon, 131.29, G, , Xe, , 54, , Krypton, 83.30, , G, , 18 s, , Neon, 20.180, , Ne, , 10, , Hellum, 4.003, , He, , Cl Ar, , 17 s, , Fluorine, 18.998, , F, , 9, , Hydrogen, 1.006, , G, , 88 s, , Barium, 137.327, , 89 s, , Lanthanum, 138.906, , 104 x, , Halnium, 178.49, , 105 x, , Tantalum, 180.948, , 106 x, , Tungsten, 183.84, , 107 x, , Rhenium, 186.207, , 108 x, , Osmium, 190.23, , 109 x, , Indium, 192.217, , 110 x, , 111 x, , Gold, 198.967, , 112 x, , Mercury, 200.59, , 113, , Thallium, 204.383, , 114 x, , Lead, 207.2, , 115, , Bismuth, 208.980, , 116 x, , Polonium, (209), , 117, , Aatatine, (210), , 118, , Radon, (222), , www.aiimsneetshortnotes.com, , Radium, (226), , Metals, Metallods, Non-metals, , Francium, (223), , Actinium, (227), , Rutherfordium, (261), , 59 s, , Seaborgium, (263), , 60 s, , Bohrium, (262), , 61 x, , Hassium, (265), , 62 s, , 63 s, , 64 s, , 65 s, , f-Block Elements, , Meitnerium Damstadtium Rontgenium Ununbium, (266), (272), (277), (269), , 66 s, , Nihonium, (286), , 67 s, , Ununquadium, , 68 s, , 69 s, , 70 s, , 71 s, , Moscovium Ununhexium Tennessine Oganesson, (294), (290), (294), , 91 s, , Thorium, 232.038, , Prolactinium, 231.036, , 93 s, , 94 s, , 95 x, , Europium, 151.064, , 96 x, , Gadolinium, 157.25, , 97 x, , Terbium, 158.925, , 98 x, , Dyaproaium, 162.50, , 99 x, , Holmium, 164.930, , 100 x, , Erbium, 167.26, , 101 x, , Thulium, 168.934, , 102 x, , Ylterbium, 173.04, , 103 x, , Lutetium, 174.957, , Ultanium, 238.029, , Neptunium, (237), , Plutonium, (244), , Amercium, (243), , Curium, (247), , Barkellum, (247), , Californium Damstadtium, (269), (251), , Fermium, (257), , Mendelevium, (258), , Nobelium, (259), , Lawrencium, (262), , U Np Pu Am Cm Bk Cf Es Fm Md No Lr, , 92 s, , Praseodymium Neodymium Promethium Samarium, 140.908, (145), 144.908, 150.36, , Th Pa, , 90 s, , Cerium, 140.116, , Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu, , 58 s, , Dubium, (262), , Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Uub Nh Uuq Mc Uuh Ts Og, , 87 s, , Platinum, 195.078, , 72 s, , Zirconium, 91.224, , 1, , H, , Caesium, 132.505, , 57 s, , Yttrium, 88.906, , 25 s, , 7, VIIB, , 13 s, , Boron, 10.811, , B, , 5 s, , 13, IIIA, , Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr, , 24 s, , 6, VIB, , Name, Atomic, mass, , Atomic, number, Symbol, , 17, 18, VIIA 0(zero), , Pt Au Hg Tl Pb Bi Po At Rn, , 56 s, , 55 s, , 41 s, , Vanadium, 50.942, , V, , 23 s, , 5, VB, , d-Block Elements, , O, , 8, , Oxygen, 15.9994, , G, , Key to chart, , p-Block Elements, , Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te, , 40 s, , Titanium, 47.867, , Ti, , 22 s, , 4, 1VB, , Not found in nature X, , Liquid L, Solid S, , STATE, Gas G, , (New notation for long form), As version for modern periodic table., , Modern Periodic Table, , Cs Ba La Hf Ta W Re Os Ir, , Strontium, 87.62, , Rubidium, 85.468, , Y, , 39 s, , Scandium, 44.956, , Ca Sc, , 20 s, , Magnesium, 24.305, , Rb Sr, , 37 s, , Potassium, 39.098, , K, , 19 s, , Sodium, 22.990, , Na Mg, , 11 s, , Lithium, 6.941, , Li Be, , 3 s, , Hydrogen, 1.008, , H, , 1 s, , 1, IA, , s-Block, Elements, , Telegram @neetquestionpaper, Appendix 3, , Periodic Table
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Telegram @neetquestionpaper, Appendix 4, , Important Conversion Factors, Common Unit of Mass and Weight, 1 pound = 453.59 gram = 0.45359 kilogram, 1 kilogram = 1000 gram = 2.205 pound, 1 gram = 10 decigram = 100 centigram, = 1000 milligram, atomic mass unit = 1.6606 ´ 10 -24 gram, 1 metric tonne = 1000 kilogram = 2205 pound, , Common Units of Length, 1 inch = 2.54 centimetre (exactly), 1 mile = 5280 feet, = 1.609 kilometre, 1 yard = 36 inches, = 0.9144 metre, 1 metre = 100 centimetre, = 39.37 inches, , Common Units of Volume, , = 3.281 feet, , 1 quart = 0.9463 litre, , = 1.094 yard, , 1 litre = 1.056 quart, , 1 kilometre = 1000 metre, , 1 litre = 1 cubic decimetre = 1000 cubic, centimetre = 0.001 cubic metre, 1 millilitre = 1 cubic centimetre, = 0.001 litre = 1.056 ´ 10 -3 quart, , = 1094 yard, = 0.6215 mile, 1 Angstrom = 1.0 ´ 10 -8 centimetre, = 0.10 nanometre, , 1 cubic foot = 28.316 litre = 29.902 quart, , = 1.0 ´ 10 -10 metre, , = 7.475 gallon, , = 3.937 ´ 10 -9 inch, , Common Units of Energy, , Common Units of Pressure, , 1 Joule = 1 ´ 107 erg, 1 thermochemical calorie = 4.184 joule, The amount of heat required to the temperature of, one gram of water from 14.5°C to, 15.5°C = 4.184 ´ 107 erg, = 4.129 ´ 10 -2 litre-atmosphere, = 2.612 ´ 1019 electron volt, 1 erg = 1 ´ 10 -7 joule, = 2.3901 ´ 10 -8 calorie, 1 electron volt = 1.6022 ´ 10, , -19, , joule, , -12, , erg, , = 1.6022 ´ 10, , 1 litre-atmosphere = 24.217 calorie, = 101.32 joule, = 1.0132 ´ 10 9 erg, , 1 atmosphere = 760 millimetre, of mercury, = 1.013 ´ 10 5 pascal, = 14.70 pound per square inch, 1 bar = 10 5 pascal, 1 torr = 1 millimetre of mercury, 1 pascal = 1 kg/ms 2 = 1 N/m 2, , Common Units of, Temperature, SI Base Unit : Kelvin (K), K = – 273.15°C, K = °C + 273.15, °F = 1.8 (°C) + 32, °F - 32, °C =, 1.8, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Appendix 5, , Popular Scientist & Their Work, 1. Angstrom, Anders Jonas He, worked mainly with emission spectra, Fraunhofer absorption lines, wavelengths. Since 1905, spectral, wavelengths have been expressed in Å., 1Å = 10 - 10 m or 1Å = 10 -8 cm, , 2. Arrhenius, Svante (August) He, demonstrated that electroytes are, conductors due to the movement of, ions. He gave the following equation to, show the effect of temperature at rate, constant., k = Ae - E a /RT, This equation is known by the name, Arrhenius equation., , 3. Aston, Francis William He, designed the mass spectrograph and, discovered the isotopes of neon., , 4. Avogadro , Amedeo He proposed, a method for computing molecular, weights from vapour densities. He also, proposed that equal volumes of all gases, contain equal numbers of molecule, under similar temperature and pressure, condition. [Avogadro’s law]., , 5. Bartlett, Neil Bartlett synthesize, first compound of a noble gas in 1962,, i.e., xenon hexachloroplatin., , 6. Becquerel, Antoine Henri He, discovered radioactivity in fluorescent, salts of uranium., , 7. Berzelius, Jons Jacob He, discovered several elements, i.e., Ce, Se,, Li, Th and V. He proposed vital force, theory of organic compounds., , 8. Bohr, Niels Henrik David He, proposed atomic model in 1913 to, explain line spectrum of hydrogen., , 9. Boltzmann, Ludwig Eduard He, worked on the kinetic theory of gases, and on thermodynamics., , 10. Boyle, Robert He worked on, gases, flame tests and acid base, indicators. He was the first to give a, definition of a chemical element., , 11. Bragg, Sir William Henry He, worked on X-ray crystallography, analysis., , 12. Bronsted, Johannes, Nicolaus He proposed acid base, theory as Lowry-Bronsted theory., , 13. Bunsen, Robert Wilhelm He, popularized the use of Bunsen burner, and developed the Bunsen cell., , 14. Cavendish, Henry He correctly, distinguished between hydrogen and, carbon dioxide., , 15. Charles, Jacques Alexandre, Cesar He proposed Charles law. He, became the first person to make an, ascent in a hydrogen balloon., , 16. Crookes, Sir William He, discovered cathode rays and, developed an improved vacuum tube., , 17. Curie, Marie She had discovered, radium and polonium., , 18. Dalton, John He is best, remembered for Dalton’s atomic, theory., , 19. de-Broglie, Louis-Victor Pierre, Raymond He is the best known, for wave particle duality of light. He, h, gave the following relation l = . This, p, is called de-Brogile equation., , 20. Debye, Peter Joseph, William He introduced the idea of, electric dipole moments in molecules., , 21. Dumas, Jean Baptiste, Andre He devised a method of, measuring vapour density., , www.aiimsneetshortnotes.com
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544, , Telegram @neetquestionpaper, , Handbook of Chemistry Key Terms, Definitions & Formulas, , 22. Einstein, Albert He proposed theory, of relativity., , 23. Fahrenheit, Gabriel Daniel He, developed the mercury in glass, thermometer and devised a temperature, scale to go with it i.e., Fahrenheit scale., , 24. Faraday, Michael He proposed laws, of electrolysis., , 25. Fleming, Sir Alexander He, discovered the antibiotic penicillin., , 26. Frankland, Sir Edward He, produced organometallic compounds, (zinc dialkyls) firstly., , 27. Gay-Lussac, Joseph He gives the, laws of chemical combination in gases, helped to establish the atomic theory., , 28. Gibbs Josiah Willard He developed, the theory of chemical thermodynamics, and function free energy as G = H - TS., , 29. Graham, Thomas He was, associated with diffusion of gases and, colloids., , 30. Haber, Fritz He proposed industrial, method for production of NH 3., , 31. Heisenberg, Werner Karl He is the, best known for his Uncertainty principle., , 32. Huckel, Erich He proposed Huckel, rule for aromaticity., , 33. Kekule, Friedrich August Von, Stradonitz He proposed structure of, benzene., , 34. Kelvin, Lord, , He introduced the, concept of absolute zero and developed, Kelvin temperature scales., , 35. Lavoisier, Antoine Laurent He, discovered oxygen and nitrogen in air., He also devised a rational nomenclature, for chemical compounds., , 36. Le- Chatelier He proposed the, principle for chemical equilibrium,, known as the Le-Chatelier’s principle., , 37. Lewis, Gilbert Newton He, introduced the concept of Lewis, acids and bases. He also introduced, the concept of a stable octet of, electrons., , 38. Maxwell, James Clark He was, one of the founders of the kinetic, theory of gases., , 39. Mary Hordgkin She was a British, chemist who used the technique of, X-ray crystallography to educidate, the structures of biomolecules., , 40. Mendeleef, Dmitri, Ivanovich He framed the Periodic, Table of the elements based on, atomic masses., , 41. Nernst, (Hermann), Walther He mainly worked on, electrochemistry and, thermochemistry., , 42. Ostwald, Friedrich, Wilhelm He worked on, hydrolysis, viscosity, ionization and, catalysis., , 43. Pauli, Wolfgang Ernst He, proposed Pauli’s exclusion principle, which explained the electronic make, up of atoms., , 44. Planck, Max Karl Ernst, Ludwig He formulated the, quantum theory., , 45. Ramsay Sir William He, discovered the noble gases [Ne, Ar,, Kr Xe and Rn]., , 46. Soddy, Frederick He proposed, the existence of isotopes., , 47. Thomson, Sir Joseph John He, is the best known for the discovery of, electron and atomic model., , 48. Urey Harold Clayton He is the, best known for the discovery of, deuterium (12D) [Heavy hydrogen]., , 49. Wohlder, Friedrich He, synthesised the first organic, compound urea (NH 2CONH 2) in 1828., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Appendix 8, , Important Facts, S. No., 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., , Property, Smallest cation, Largest cation, Solid with highest density, Liquid with highest density, Elements named in honour of the countries, Most electronegative elements, Most abundant elements on earth, Most abundant metal in earth crust, Liquid metal, Lustrous non-metal, Hardest among non-metals, Soft metals, Best ductile metals, Best conductor metal, Most poisonous element, Element with maximum number of isotopes, Most electropositive metal, Liquid non-metal, Metal kept in paraffin wax, Coinage metals, , Element/Ion, +, , H, Cs+, Iridium (Ir), Mercury (Hg), Ru, Ge, Po, Am, Fluorine (F), Oxygen (O), Aluminium (Al), Mercury (Hg), Iodine (I2), Diamond, Na, K, Au, Ag, Silver (Ag), Pu, Ag, Caesium (Cs), Br, Li, Ag, Au, Cu, Al, , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Appendix 9, , Composition and Uses of Different Alloys, S. No., , Alloy, , 1., , Stainless steel, , 2., , Invar, , 3., , Alinco, , 4., , Tungsten steel, , 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., , Composition, Fe = 73%, Cr = 18%, Ni = 8% and cabon, Fe = 64%, Ni = 36%, Fe = 63%, Ni = 20%, Al = 12%, Co = 5%, Fe = 83%, Tungsten (W) = 14%, and carbon, Fe = 85%, Mn = 13% and, carbon, , Uses, For making cutlery, ornamental,, pieces and automobile parts., For making measuring, instruments and clock, pendulums., For making permanent magnets., , For making cutting tools for high, speed lathes., Manganese steel, For making rock drills, rail lines,, burglar proof safes and crushing, machinery, Nickel steel, Ni = 4.2%, For making electromagnets and, ocean cables., Permalloy, Fe = 21%, Ni = 78% and carbon For making shafts and ocean, cables., Silicon steel, Fe = 85%, Si = 15%, Pumps and pipes for carrying, acids., Utensils, condenser tubes and, Brass, Cu = 60 - 80%, cartridges. Utensils,coins,, Zn = 40 - 20%, statues., Bronze, Cu = 75 - 90%, Sn = 25 - 10%, Monel metal, Cu = 30%, Ni = 67%,, For acid containers, acid pumps, Fe + Mn = 3%, etc., Bell metal, Cu = 80%, Sn = 20%, Bells, Gongs, Gun metal, Cu = 87%, Sn = 10%, Zn = 3% Guns, casting, gears., German silver, Cu = 50%,, Utensils, ornaments., Zn = 25%, Ni = 25%, Constantan, Cu = 60%, Ni = 40%, For making resistance boxes,, thermocouples., Phosphor bronze Cu = 95%, Sn = 4.8%, Springs electrical equipments., P = 0.2%, Aluminium, Cu = 90%, Al = 10%, Coins, picture frames, cheap, bronze, jewellery., Coinage silver, Ag = 90%, Cu = 10%, Silver coins., Dental alloy, Ag = 33%,, For filling teeth cavities., Hg = 52%, Sn = 15%, Palladium silver, Ag = 40%, Pd = 60%, Potentiometer wires and, winding of some special, instruments., Silver solder, Ag = 63%,, Soldering and for jointing, Cu = 30%, Zn = 7%, metals., Sterling silver, Ag = 80%, Cu = 20%, A standard quality of silver used, in jewellery., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, Appendix 10, , Preparation of Common Laboratory Reagents, I. Concentrate Acids, S.No., 1., 2., 3., 4., , Name, Acetic acid (glacial), Conc. hydrochloric acid, Conc. nitric acid, Conc. sulphuric acid, , Approximate, concentration, 17.6 M (17.6 N), 11.7 M (11.7 N), 15.6 M (15.6 N), 18 M (36.0 N), , Specific, gravity, , Percentage by, weight, , 1.06, 1.19, 1.42, 1.84, , 99.5%, 36.0%, 69.5%, 98.0%, , II. Dilute Acids, S. No., , Concentration, , Method of preparation, , 1., , Dil. acetic acid, , Name, , 5 M (5 N), , 2., , Dil. hydrochloric acid, , 5 M (5 N), , 3., , Dil. nitric acid, , 5 M (5 N), , 4., , Dil. sulphuric acid, , Dilute 285 mL of glacial acetic acid with, distilled water and make up the volume, of 1 L., Add 430 mL of conc. HCl in the distilled, water and make up the volume to 1 L., Add 320 mL of conc. nitric acid to, distilled water and make up the volume, to 1 L., Pour 140 mL of conc. sulphuric acid, slowly and with constant stirring in, 500 mL of distilled water. Cool and make, up the volume to 1 L., , 2.5 M (5 N), , III. Bases, 1., 2., , 3., , Ammonia solution (Liquor 15 M (15 N), ammonia), Dil. ammonia solution, 2 M (2 N), (Ammonium hydroxide), Sodium hydroxide, , 5 M (5 N), , As supplied, Pour 266.6 mL of the conc. ammonia, solution in distilled water and make, up the volume of 1 L., Dissolve 200 g sodium hydroxide, pellets in 1 L of distilled water., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 551, , Handbook of Chemistry Key Terms, Definitions & Formulas, , IV. Other Important Reagents, S. No., , Name, , Concentration, , Molar, mass, , 1., , Ammonium acetate, , 2 M (2 N), , 77, , 2., , Ammonium chloride, , 5 M (5 N), , 53.5, , 3., , Ammonium, carbonate, , 1.7 M (3.5 N), , 96, , 4., , Ammonium, molybdate, , 5., , Ammonium oxalate, , 0.5 M (1 N), , 142, , 6., , Ammonium sulphate, , 1 M (2 N), , 132, , 7., , 0.5 M (0.5 N), , 244, , 8., , Barium chloride, (BaCl 2 × 2H 2O), Bromine water, , Approx., saturated, , 160, , 9., , Calcium chloride, , 0.5 M (0.5 N), , 219, , 10., , Chlorine water, , 11., , Copper sulphate, , 12., , Cobalt nitrate, , 13., , Dimethyl glyoxime, , 14., , Diphenylamine, , 15., , Disodium hydrogen, phosphate, Na 2HPO4 × 12H 2O, , 71, , 14%, , 249.5, , 0.15 M, (0.075 N), , 291, , 1%, 0.5%, , 0.3 M (N), , 358, , Method of preparation, Dissolve 154 g of the salt in, distilled water and dilute to 1 L., Dissolve 267.5 g of the salt in, distilled water and dilute to 1 L., Dissolve 160 g of ammonium, carbonate in 140 mL liquor, ammonia and make up the, solution 1 L with distilled water., Dissolve 100 g of the salt in a, mixture of 100 mL of liquor, ammonia solution and add 250 g, of ammonium nitrate and dilute, it to 1L with distilled water., Dissolve 71 g of the salt in, distilled water and dilute to 1L., Dissolve 132 g of the salt in, distilled water and dilute to 1L., Dissolve 61 g of the salt in, distilled water and dillute to 1L., Add 2 mL of bromine in 100 mL of, distilled water shake the mixture, well. Keep it in a dark bottle., Dissolve 55 g of the salt in, distilled water and make up the, volume to 1L., Prepare chlorine by treating solid, KMnO4 with conc. HCl. Saturate, 1 L of distilled water with chlorine, gas and keep the solution in a, dark coloured bottle., Dissolve 14 g of the salt in, distilled water and make up the, volume to 100 mL., Dissolve 43.65 g of the salt in, distilled water and make up the, volume to 1L., Dissolve 1.0 g of the solid in 100, mL ethyl alcohol., Dissolve 0.5 g of the solid in 85 mL, of conc. sulphuric acid and dilute it, with care with distilled water to, 100 mL., Dissolve 120.0 g of the salt in, distilled water and make up the, volume to 1L., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, , 552, , Handbook of Chemistry Key Terms, Definitions & Formulas, , S. No., , Name, , Concentration Molar, mass, , 16., , Ferric chloride, FeCl 3 × 6H 2O, , 17., , Iodine solution, , 18., , Lead acetate, (CH 3COO) 2Pb, , 0.5 M (N), , 19., , Lime water Ca(OH) 2, , 0.02 M, (0.04 N), , 74, , 20., , Litmus solution (blue), , 21., , Litmus solution (red), , 22., , Methyl orange, , 23., , Mercuric chloride, , 0.25 M (0.5 N), , 272, , 24., , Nessler’s reagent, K 2[HgI4 ], , 25., , Potassium chromate, K 2CrO4, , 0.25 M (0.5 N), , 194, , 26., , Potassium, dichromate (K 2Cr2O7), , 0.15 M (1 N), , 294, , 27., , Potassium, ferrocyanide, , 0.15 M (0.5 N), , 368, , 0.33 M (1 N), , 270, , 254, , Method of preparation, Dissolve 90 g of the salt in, distilled water containing 10 mL, of conc. hydrochloric acid and, make up the volume of 1 L., Dissolve 1.0 g of iodine crystals in, a solution of 2 g potassium iodide, in minimum amount of water, and dilute the solution to, 100 mL., Dissolve 200 g of solid salt in 500, mL of distilled water containing, 15 mL acetic acid and make up, the volume to 1 L with distilled, water., Shake 2–3 g of calcium hydroxide, with 1 L distilled water, filter the, solution after sometimes and, keep it in a reagent bottle. Bottle, should be securely stoppered in, order to protect the reagent, from CO2 of atmosphere., Dissolve 10 g of litmus in distilled, water and make the volume to, 1 L., To the blue litmus solution add, about 10 drops of dilute, hydrochloric acid., Dissolve 1 g of the solid in 1L of, distilled water., Dissolve 70 g of the salt in small, amount of distilled water and, make up the volume to 1 L with, distilled water., Dissolve 23 g of mercuric iodide, and 16 g of potassium iodide in, distilled water and make up the, volume to 100 mL. Add 150 mL of, 4 M NaOH solution. Allow it to, stand for 24 h and decant the, solution. Solution should be, stored in a dark coloured bottle., Dissolve 49 g of the salt in, distilled water and make up the, volume to 1L., Dissolve 49.0 g of the salt in, distilled water and make up the, volume to 1L., Dissolve 46.l0 g of the salt in, distilled water and dilute to 1L., , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 553, , Handbook of Chemistry Key Terms, Definitions & Formulas, S. No., 28., 29., , 30., , 31., , Name, , Concentration Molar, mass, , Potassium, ferricyanide, Potassium iodide KI, , 0.2 M (0.5 N), , 329, , 0.5M (0.5 N), , 166, , Potassium, permanganate, KMnO4, Potassium, thiocyanate, , 0.06 M (0.3 N), , 158, , 0.5 M (0.5 N), , 97, , 32., , Phenolphthalein, , 33., , Silver nitrate AgNO3, , 34., , Sodium acetate, , 35., , Sodium nitroprusside, , 36., , Starch, , 37., , Yellow ammonium, sulphide (NH 4) 2 Sx, , 1%, 0.1 M, , 170, , 5 M (5 N), , 82, , 6N, , Method of preparation, Dissolve 55.0 g of the salt in, distilled water and dilute to 1L., Dissolve 83.0 g of the salt in, distilled water and make up the, volume to 1L., Dissolve 10.0 g of the salt in 1L, distilled water. Heat the solution, and filter it through glass wool., Dissolve 49.0 g of the salt in, distilled water and make up the, volume to 1L., Dissolve 1.0 g of the solid in 100, mL of ethyl alcohol., Dissolve 17 g of the salt in 250 mL, of distilled water and store it in a, brown coloured bottle., Dissolve 410 g of salt in distilled, water and dilute to 1L., Dissolve 4 g of the solid in 100 mL, of distilled water., Prepare a paste of about 1.0 g of, soluble starch in cold water and, pour it gradually in 100 mL of, boiling water with constant, stirring. Boil it for 10 min and, cool., Take about 200 mL of conc., ammonia solution in a bottle and, saturate it with H 2S gas. Add 10 g, of flower of sulphur and 200 mL, of conc.NH 4OH. Warm gently and, shake well until sulphur is, completely dissolved. Dilute the, solution to 1L with distilled, water., , www.aiimsneetshortnotes.com
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558, , Telegram @neetquestionpaper, , Handbook of Chemistry Key Terms, Definitions & Formulas, , Appendix 12, , Nobel Laureates in Chemistry, Year, , Laureate, , Country, , 2018, , George Smith, , United states, , 2017, , Gregory Winter, Jacques Dubochet, , United Kingdom, Switzland, , Rationale, ‘‘For the phagedisplay of peptides and, antibodies’’, ‘‘For developing cryo-electron microscopy, for the high resolution structure, determination of bimolecules in solution’’, , Joachim Frank, United states, Richard Henderson United Kingdom, 2016, , Fraser stoddart, , United states, Netherlands, France, , 2015, , Ben Feringa, Jean pierre, Sauvage, Thomas Lindahl, Paul L. Modrich, Aziz Sancar, Eric Betzig, , 2014, , 2013, , 2012, , Sweden, United states, United state, United State, , Stefan W. Hell, Germany, William E. Moerner United State, Martin Karplus, United State,, Austria, Michael Levitt, United State/, Bretain, Arich Warshel, United State/Israeli, Brian Kobilka, United States, , 2010, , Robert United, states, Dan Shechtman, Robert Lefkowitz, Ei-ichi Negishi, , Japan, United States, , 2009, , Akira Suzuki, Richard, F. Heck, Thomas A. Steitz, , Israel, India, , 2008, , Ada E. Yonath, Venkatraman, Ramakrishnan, Martin Chalfie, , 2011, , Israel, United States, United States, , United States, , United States, , ‘‘For the design and synthesis of, molecular machines’’, , ‘‘For mechanistic studies of DNA repair’’, , ‘‘for the development of super-resolved, fluorescence microscopy’’, , ‘‘for the development of multiscale, models’’, ‘‘for complex chemical systems’’, ‘‘for studies of G-protein-coupled, receptors”, ‘‘for the discovery of quasicrystals”, "for palladium-catalyzed cross couplings in, organic synthesis", , “for studies of the structure and function, of the ribosome”, , “for the discovery and development of the, green fluorescent protein, GFP”, , Roger Y. Tsien, United States, Osamu Shimomura Japan[108], , www.aiimsneetshortnotes.com
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Telegram @neetquestionpaper, 559, , Handbook of Chemistry Key Terms, Definitions & Formulas, Year, , Laureate, , Country, , 2007, , Gerhard Ertl, , Germany, , 2006, , Roger D. Kornberg, , United States, , 2005, , Robert H. Grubbs, , United States, , 2004, , Richard R. Schrock, Yves Chauvin, Avram Hershko, , United States, France, Israel, , Irwin Rose, , United States, , 2003, , Aaron Ciechanover Israel, Roderick, United States, MacKinnon, Peter Agre, John B. Fenn, , United States, United States, , Koichi Tanaka, , Japan, , Kurt Wüthrich, , Switzerland, , Ryoji Noyori, , Japan, United States, , 1999, , K. Barry, Sharpless, William S. Knowles, Alan J. Heeger, Alan G., MacDiarmid, Hideki Shirakawa, Ahmed Zewail, , 1998, , Walter Kohn, , United States, , John A. Pople, , United Kingdom, , 2002, , 2001, , 2000, , United States, United States, United States, New Zealand, Japan, Egypt, United States, , Rationale, “for his studies of chemical processes on, solid surfaces”, "for his studies of the molecular basis of, eukaryotic transcription", "for the development of the metathesis, method in organic synthesis", , "for the discovery of ubiquitin-mediated, protein degradation", , "for discoveries concerning channels in, cell membranes [...] for structural and, mechanistic studies of ion channels", "for the development of methods for, identification and structure analyses of, biological macromolecules [...] for their, development of soft desorption’’, ‘‘for then development of soft desorption, ionisation methods for mass spectrometric, analyses of biological macromolecules", "for the development of methods for, identification and structure analyses of, biological macromolecules [...] for his, development of nuclear magnetic, resonance spectroscopy for determining, the three dimensional structure of, biological macromolecules in solution", "for discoveries concerning channels in, cell membranes [...] for the discovery of, water channels", "for their work on chirally catalysed, hydrogenation reactions", "for his work on chirally catalysed, oxidation reactions", , "for their discovery and development of, conductive polymers", "for his studies of the transition states of, chemical reactions using femtosecond, spectroscopy", "for his development of the, density-functional theory", "for his development of computational, methods in quantum chemistry", , www.aiimsneetshortnotes.com
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560, Year, 1997, , Telegram @neetquestionpaper, , Handbook of Chemistry Key Terms, Definitions & Formulas, Laureate, , Country, , Paul D. Boyer, , United States, , John E. Walker, Jens C. Skou, , United Kingdom, Denmark, , 1995, , Robert F. Curl Jr, Sir Harold W. Kroto, Richard E. Smalley, Mario J. Molina, , Unitedx States, United Kingdom, United States, United States, United States, , 1994, , F. Sherwood, Rowland, Paul J. Crutzen, George A. Olah, , 1993, , Kary B. Mullis, , Netherlands, United States /, Hungary, United States, , Michael Smith, , Canada, , 1996, , 1992, , Rudolph A. Marcus United States, , 1991, , Richard R. Ernst, , Switzerland, , 1990, , Elias James Corey, , United States, , 1989, , Sidney Altman, , 1988, , 1987, , Rationale, "for their elucidation of the enzymatic, mechanism underlying the synthesis of, adenosine triphosphate (ATP)", "for the first discovery of an, ion-transporting enzyme, Na+, K+ -ATPase", "for their discovery of fullerenes", "for their work in atmospheric chemistry,, particularly concerning the formation and, decomposition of ozone", , "for his contribution to carbocation, chemistry", "for contributions to the developments of, methods within DNA-based chemistry [...], for his invention of the polymerase chain, reaction (PCR) method", "for contributions to the developments of, methods within DNA-based chemistry [...], for his fundamental contributions to the, establishment of oligonucleotide-based,, site-directed mutagenesis and its, development for protein studies", "for his contributions to the theory of, electron transfer reactions in chemical, systems", "for his contributions to the development, of the methodology of high resolution, nuclear magnetic resonance (NMR), spectroscopy", "for his development of the theory and, methodology of organic synthesis", "for their discovery of catalytic properties, of RNA", , Canada United, States, Thomas Cech, United States, Johann, Federal Republic of "for their determination of the, Deisenhofer, Germany, three-dimensional structure of a, photosynthetic reaction centre", Robert Huber, Federal Republic of, Germany, Hartmut Michel, Federal Republic of, Germany, Jean-Marie Lehn, France, "for their development and use of, molecules with structure-specific, interactions of high selectivity", Donald J. Gram, United States, Charles J. Pedersen United States, , www.aiimsneetshortnotes.com
