Page 2 :
Production Team, , Anil Kumar Sharma, , Published at Delhi Bureau of Text Books , 25/2 Institutional Area, Pankha, Road, New Delhi-110058 by Prabhjot Singh, Secretary, Delhi Bureau of, Text Books and Printed by Arihant Offset, New Delhi-110043
Page 3 :
MANISHA SAXENA, IAS, , DO No. DE. 5/228/Exam/Message/S.M./2018, Dated, , MESSAGE, The importance of adequate practice during examinations can never be, overemphasized. I am happy that support material for classes IX to XII has been, developed by the Examination Branch of Directorate of Education. This material is, the result of immense hard work, co-ordination and cooperation of teachers and, group leaders of various schools. The purpose of the support material is to impart, ample practice to the students for preparation of examinations. It will enable the, students to think analytically & rationally and test their own capabilities and level of, preparation., The material is based on latest syllabus prepared by the NCERT and adopted, by the CBSE for the academic session 2020-21 and covers different levels of difficulty., I expect that Heads of Schools and Teachers will enable and motivate students to, utilize this material during zero periods, extra classes and regular classes best to, their advantage., I would like to compliment the team of Examination Branch for their diligent, efforts of which made it possible to accomplish this work in time. I also take this, opportunity to convey my best wishes to all the students for success in their, endeavours., , (MANISHA SAXENA)
Page 11 :
DIRECTORATE OF EDUCATION, Govt. of NCT, Delhi, SUPPORT MATERIAL, (2020-2021), , CHEMISTRY, Class : XI, , NOT FOR SALE, , PUBLISHED BY : DELHI BUREAU OF TEXTBOOKS
Page 14 :
Course Structure, Class : XI (Theory) (2020-21), Chemistry, , , Total period (Theory 160 + Practical 60), , Time : 3 Hours], , Total Marks : 70, , Unit No. Title, , No. of Periods Marks, , Unit I, , Some Basic Concepts of Chemistry, , 12, , 11, , Unit II, , Structure of Atom, , 14, , Unit III, , Classification of Elements and, , 08, , 04, , 14, , 21, , Periodicity in Properties, Unit IV, , Chemical Bonding and Molecular, Structure, , Unit V, , States of Matter: Gases, Liquids and solids, , 12, , Unit VI, , Chemical Thermodynamics, , 16, , Unit VII, , Equilibrium, , 14, , Unit VIII Redox Reactions, , 06, , Unit IX, , Hydrogen, , 08, , Unit X, , s -Block Elements, , 10, , Unit XI, , p -Block Elements, , 14, , Unit XII, , Organic Chemistry: Some Basic, , 14, , 16, , 18, , Principles and Techniques, Unit XIII Hydrocarbons, , 12, , Unit XIV Environmental Chemistry, , 06, , Total, , 160, , ii, , 70
Page 15 :
Unit I : Some Basic Concepts of Chemistry, , 8 Periods, , General Introduction: Importance and scope of chemistry., Nature of matter, laws of chemical combination, Dalton’s atomic theory:, concept of elements, atoms and molecules., Atomic and molecular masses, mole concept and molar mass,, percentage composition, empirical and molecular formula, chemical, reactions, stoichiometry and calculations based on stoichiometry., Unit II : Structure of Atom, 10 Periods, Bohr’s model and its limitations, concept of shells and subshells,, dual nature of matter and light, de Broglie’s relationship, Heisenberg, uncertainty principle, concept of orbitals, quantum numbers, shapes, of s, p and d orbitals, rules for filling electrons in orbitals - Aufbau, principle, Pauli’s exclusion principle and Hund’s rule, electronic, configuration of atoms, stability of half-filled and completely filled, orbitals., Unit III : Classification of Elements and Periodicity in Properties, , 06 Periods, Modern periodic law and the present form of periodic table, periodic, trends in properties of elements -atomic radii, ionic radii, inert gas radii,, Ionization enthalpy, electron gain enthalpy, electronegativity, valency., Nomenclature of elements with atomic number greater than 100, Unit IV : Chemical Bonding and Molecular Structure, , 14 Periods, , Valence electrons, ionic bond, covalent bond, bond parameters, Lewis, structure, polar character of covalent bond, covalent character of ionic, bond, valence bond theory, resonance, geometry of covalent molecules,, VSEPR theory, concept of hybridization, involving s, p and d orbitals, and shapes of some simple molecules, molecular orbital theory of, homonuclear diatomic molecules(qualitative idea only), hydrogen, bond., Unit V : States of Matter: Gases, Liquids and Solids, , 18 Period, , Three states of matter, intermolecular interactions, types of bonding,, melting and boiling points, role of gas laws in elucidating the, concept of the molecule, Boyle’s law, Charles law, Gay Lussac’s law,, Avogadro’s law, ideal behaviour, empirical derivation of gas equation,, iii
Page 16 :
Avogadro’s number, ideal gas equation. Deviation from ideal behaviour,, liquefaction of gases, critical temperature, kinetic energy and molecular, speeds (elementary idea), Liquid State: vapour pressure, viscosity and surface tension (qualitative, idea only, no mathematical derivations), Solid state: Classification of solids based on different binding, forces: molecular, ionic, covalent and metallic solids, amorphous and, crystalline solids (elementary idea). Unit cell in two dimensional and, three dimensional lattices, calculation of density of unit cell, packing, in solids, packing efficiency, voids, number of atoms per unit cell in a, cubic unit cell, point defects, electrical and magnetic properties., Unit VI : Chemical Thermodynamics, , 16 Periods, , Concepts of System and types of systems, surroundings, work, heat,, energy, extensive and intensive properties, state functions. First law, of thermodynamics -internal energy and enthalpy, heat capacity and, specific heat, measurement of ΔU and ΔH, Hess’s law of constant heat, summation, enthalpy of bond dissociation, combustion, formation,, atomization, sublimation, phase transition, ionization, solution, and dilution. Second law of Thermodynamics (brief introduction)., Introduction of entropy as a state function, Gibb’s energy change for, spontaneous and non- spontaneous processes, criteria for equilibrium., Third law of thermodynamics (brief introduction)., Unit VII : Equilibrium, , 14 Periods, , Equilibrium in physical and chemical processes, dynamic nature of, equilibrium, law of mass action, equilibrium constant,factors affecting, equilibrium- Le Chatelier’s principle, ionic equilibrium- ionization of, acids and bases, strong and weak electrolytes, degree of ionization,, ionization of poly basic acids, acid strength, concept of pH, Henderson, Equation, hydrolysis of salts (elementary idea), buffer solution,, solubility product, common ion effect (with illustrative examples)., Unit VIII: Redox Reactions, , 06 Periods, , Concept of oxidation and reduction, redox reactions, oxidation number,, balancing redox reactions, in terms of loss and gain of electrons and, change in oxidation number, applications of redox reactions., , iv
Page 17 :
Unit IX: Hydrogen, , 08 Periods, , Position of hydrogen in periodic table, occurrence, isotopes, preparation,, properties and uses of hydrogen, hydrides-ionic covalent and interstitial;, physical and chemical properties of water, heavy water, hydrogen, peroxide -preparation, reactions and structure and use; hydrogen as a, fuel., Unit X : s-Block Elements (Alkali and Alkaline Earth Metals) 10 Periods, Group 1 and Group 2 Elements General introduction, electronic, configuration, occurrence, anomalous properties of the first element of, each group, diagonal relationship, trends in the variation of properties, (such as ionization enthalpy, atomic and ionic radii), trends in chemical, reactivity with oxygen, water, hydrogen and halogens, uses. Preparation, and Properties of Some Important Compounds: Sodium Carbonate,, Sodium Chloride, Sodium Hydroxide and Sodium Hydrogencarbonate,, Biological importance of Sodium and Potassium. Calcium Oxide and, Calcium Carbonate and their industrial uses, biological importance of, Magnesium and Calcium, Unit XI : p-Block Elements, , 18 Periods, , General Introduction to p-Block Elements :, Group 13 Elements : General introduction, electronic configuration,, occurrence, variation of properties, oxidation states, trends in chemical, reactivity, anomalous properties of first element of the group, Boron physical and chemical properties, some important compounds, Borax,, Boric acid, Boron Hydrides, Aluminium: Reactions with acids and, alkalies, uses., Group 14 Elements : General introduction, electronic configuration,, occurrence, variation of properties, oxidation states, trends in chemical, reactivity, anomalous behaviour of first elements. Carbon-catenation,, allotropic forms, physical and chemical properties; uses of some, important compounds: oxides. Important compounds of Silicon and a, few uses: Silicon Tetrachloride, Silicones, Silicates and Zeolites, their, uses., Group 15 Elements : General introduction, electronic configuration,, occurrence, oxidation states, trends in physical and chemical properties;, Nitrogen preparation properties and uses; compounds of Nitrogen,, preparation and properties of Ammonia and Nitric Acid, Oxides of, v
Page 18 :
Nitrogen(Structure only) ; Phosphorus - allotropic forms, compounds, of Phosphorus: Preparation and Properties of Phosphine, Halides and, Oxoacids (elementary idea only)., Unit XII : Organic Chemistry -Some Basic Principles and Technique, , 14 Periods, General introduction, methods of purification, qualitative and, quantitative analysis, classification and IUPAC nomenclature of organic, compounds. Electronic displacements in a covalent bond: inductive, effect, electromeric effect, resonance and hyper conjugation. Homolytic, and heterolytic fission of a covalent bond: free radicals, carbocations,, carbanions, electrophiles and nucleophiles, types of organic reactions., Unit XIII: Hydrocarbons, , 12 Periods, , Classification of Hydrocarbons Aliphatic Hydrocarbons:, Alkanes - Nomenclature, isomerism, conformation (ethane only),, physical properties, chemical reactions including free radical, mechanism of halogenation, combustion and pyrolysis., Alkenes - Nomenclature, structure of double bond (ethene), geometrical, isomerism, physical properties, methods of preparation, chemical, reactions: addition of hydrogen, halogen, water, hydrogen halides, (Markownikov's addition and peroxide effect), ozonolysis, oxidation,, mechanism of electrophilic addition., Alkynes - Nomenclature, structure of triple bond (ethyne), physical, properties, methods of preparation, chemical reactions: acidic character, of alkynes, addition reaction of - hydrogen, halogens, hydrogen halides, and water., Aromatic Hydrocarbons: Introduction, IUPAC nomenclature,, benzene: resonance, aromaticity, chemical properties: mechanism of, electrophilic substitution. Nitration, sulphonation, halogenation, Friedel, Craft's alkylation and acylation, directive influence of functional group, in monosubstituted benzene. Carcinogenicity and toxicity., Unit XIV : Environmental Chemistry, , 06 Periods, , Environmental pollution - air, water and soil pollution, chemical, reactions in atmosphere, smog, major atmospheric pollutants, acid rain,, ozone and its reactions, effects of depletion of ozone layer, greenhouse, effect and global warming- pollution due to industrial wastes, green, chemistry as an alternative tool for reducing pollution, strategies for, control of environmental pollution., vi
Page 19 :
PRACTICALS, Evaluation Scheme for Examination, , Marks, , Volumetric Analysis, , 08, , Salt Analysis, , 08, , Content Based Experiment, , 06, , Project Work, , 04, , Class record and viva, , 04, , Total, , 30, , PRACTICAL SYLLABUS, Total Periods 60, Micro-chemical methods are available for several of teh practical experiments., Wherever possible such techniques should be used :, A. Basic Laboratory Techniques, 1. Cutting glass tube and glass rod, 2. Bending a glass tube, 3. Drawing out a glass jet, 4. Boring a cork, B. Characterization and Purification of Chemical Substances, 1. Determination of melting point of an organic compound., 2. Determination of boiling point of an organic compound, 3. Crystallization of impure sample of any one of the following: Alum,, Copper Sulphate, Benzoic Acid., C. Experiments based on pH, (a) Any one of the following experiments :, - Determination of pH of some solutions obtained from fruit juices,, solution of known and varied concentrations of acids, bases and salts, using pH paper or universal indicator., - Comparing the pH of solutions of strong and weak acids of same, concentration., - Study the pH change in the titration of a strong base using universal, indicator., (b) Study the pH change by common-ion in case of weak acid and weak bases., D. Chemical Equilibrium., vii
Page 20 :
CHEMISTRY (Code No. 043), Question Paper Design, Class-XI (2020–21), Time : 3 Hours, S. Typology of Questions, No. , , , , Max. Marks : 70, Very, short, Answer, (VSA), , Short, Answer-I, (SA–I), (2 marks), , Short, Answer-II, (SA-II), (3 marks), , Long, Answer, (LA), (5 marks), , Total, Marks, , %, Weightage, , 2, , 1, , 1, , –, , 7, , 10%, , 6, , 2, , 2, , 1, , 21, , 30%, , 6, , 2, , 2, , 1, , 21, , 30%, , 6, , 1, , 2, , –, , 14, , 20%, , 1, , 2, , 2, , –, , 11, , 16%, , –, , 1, , –, , 1, , 7, , 10%, , 20×1=20, , 7×2=14, , 7×3=21, , 3×5=15, , 70(37), , 100%, , (1 marks), , Remembering :, 1. , Exhibit memory of previously, learned material by recalling, facts, terms, basic concepts and, answers., 2. , Understanding :, Demonstrate understanding of, facts and ideas by organizing,, comparing, translating, interpreting, giving descriptions and, stating main ideas., Applying :, 3. , Solve problems to new situations by applying acquired, knowledge, facts, techniques, and rules in a different way., Analyzing :, 4. , Examine and break information, into parts by identifying motives, or causes. Make inferences and, find evidence to support generalizations., 5. , Evaluating :, Present and defend opinions, by making judgments about, information, validity of ideas, or quality of work based on a, set of criteria., Creating :, 6. , Compile information together, in a different way by combing, elements in a new pattern or, proposing alternative solutions., TOTAL, , viii
Page 21 :
Question Wise Break Up, Type of Ques., , Mark per Ques., , Total No. of Ques., , Total Marks, , VSA / Objective, , 1, , 20, , 20, , SA-I, , 2, , 7, , 14, , LA-I, , 3, , 7, , 21, , LA-II, , 5, , 3, , 15, , Total 37, , 70, , 1. No chapter was weightage. Care to be taken to cover all the chapters., 2. Suitable internal variations may be made for generating various templates, keeping the overall weightage to different form of questions and typology, of questions same., Choice(s):, There will be no overall choice in the question paper., However, 33% internal choices will be given in all the sections., , ix
Page 22 :
Chemistry - XI, Index, S. No., , Chapter Name, , Page No., , 1., , Some Basic Concepts of Chemistry, , 1, , 2., , Structure of Atom, , 19, , 3., , Classification of Elements and Periodicity in Properties, , 41, , 4., , Chemical Bonding and Molecular Structure, , 59, , 5., , State of Matter : Gases, Liquids and Solids, , 74, , 6., , Chemical Thermodynamics, , 88, , 7., , Equilibrium, , 105, , 8., , Redox Reactions, , 125, , 9., , Hydrogen, , 140, , 10., , s-Block Elements, , 158, , 11., , p-Block Elements, , 170, , 12., , Organic Chemistry : Some basic Principles and Techniques, , 182, , 13., , Hydrocarbons, , 210, , 14., , Environmental Chemistry, , 234, , , , Sample Papers - I, II, III & IV, , 249-269, , x
Page 23 :
Some Basic, Concepts of, Chemistry, FAST TRACK : QUICK REVISION, , , , , , , , Matter : Anything that has mass and occupies space., Precision : If refers to the closeness of various measurements for the same, quantity., Accuracy : It refers to the agreement of a particular value to the true value, of the result., Mass and weight : Mass of a substance is the amount of matter present in, body, while weight is the force exerted by gravity on an object. The mass, of a substance is constant whereas its weight may vary from one place to, another due to change in gravity., , , , Volume : 1 L = 1 dm3 = 103cm3 = 10–3 m3, , , , Temperature : K = °C + 273.15;, , =, , Standard Temperature Pressure (STP) : 0°C (273.15 K) temperature, and 1 atm pressure., , Normal Temperature Pressure (NTP) : 20°C (293.15 K) temperature, and 1 atm pressure., , Standard Ambient Temperature Pressure (SATP) : 25°C (298.15 K), temperature and 1 atm pressure, , Scientific Notation : Expressing a number in the form N × 10n, and N, can vary between 1 to 9.99., , Significant figures : These are meaningful digits which are known with, certainty., , Laws of Chemical Combination :, Ø Law of Conservation of Mass (Antonie Lavoisier) : Mass can, neither be created nor be destroyed., , , Ø Law of Definite Proportions (Joseph Proust) : A given compound, always contains the same elements in the same proportion by mass.
Page 24 :
Ø Law of Multiple Proportions (John Dalton) : When two elements, combine to form two or more compounds, then the different masses, of one element, which combine with a fixed mass of the other, bear, a simple ratio to one another., Ø Gay Lussac’s Law : When gases combine or are produced in a, chemical reaction, they do so in a simple ratio provided all gases, are in the same temperature and pressure., e.g., 2H2 (g) + O2 (g) →, 2 Vol 1 Vol , , , , , , 2H2O (g), , 2 Vol, , (at same T, P), , Atomic Mass : It is defined as the average relative mass of an atom of an, element as compared to the mass of an atom of carbon – 12 taken as 12., Atomic mass is represented by ‘u’ (unified mass)., , 1u = 1.66056 × 10–24 g, , , Molecular mass : It is algebraic the sum of the atomic mass of the elements, present in the molecule., , For example : Molecular mass of CH4 = (1 × 12) + (4 × 1) = 16 u, , , , , , , , , , , Avogadro Number : It is the amount of atoms or molecules present in, one mole of a substance., , Avogadro number (NA) = 6.022 × 1023 mol–1, , Molar Mass : The mass of one mole of a substance in grams is called its, molar mass., For example : Molar mass of CH4 = (1 × 12) + (4 × 1) = 16g mol–1, , Mole (n) : It is amount of a substance that contains as many particles or, entities as the number of atoms in exactly 12 grams of pure C-12., 1 mole of a substance = Molar mass of substance = Avogadro’s Number, of chemical units = 22.4L volume at STP of gaseous substance, , e.g., 1 mole of CH 4 = 16g of CH 4 = 6.022 × 10 23 molecules of, CH4 = 22.4L at STP, n =, , , , , 2, , =, , =, , =, , Molar Volume (Vm) : It is volume occupied by one mole of gas at STP., , Molar volume of a gas = 22.4L at STP (273 K, 1atm) or 22.7L at STP (273, K, 1 bar), Chemistry Class XI
Page 25 :
Calculating Molar Volume: PV = nRT, , ∴ V =, Or, , , , nRT 1mol x 0.082L atm K -1mol-1 x 273K, =, = 22.4L, P, 1 atm, , V =, , 1 bar, , Percentage Composition : Mass % of the element, , , =, , , , , , , Empirical Formula : It represents the simplest whole number ratio of, various atoms present in a compound. For e.g., CH is the empirical formula, of benzene., Molecular Formula : It shows the exact number of different of atoms, present in a molecule of a compound. For e.g., C6H6 is the molecular, formula of benzene., Relationship between empirical and molecular formulae :, Molecular formula = n × Empirical formula, , Where;, , , n=, , Information Conveyed by a chemical equation :, , N2(g), , +, , 3H2(g), , →, , 2NH3(g), , (i) 1 molecule of N2 +, , 3 molecules of H2 →, , 2 molecules of NH3, , (ii) 1 mole of N2, , +, , 3 mole of H2, , →, , 2 mole of NH3, , (iii) 1 × 28g of N2, , +, , 3 × 2 g of H2, , →, , 2 × 17 g of NH3, , (iv) 1 × 22.4L of N2, , +, , 3 × 22.4L of H2, , →, , 2 × 22.4L of NH3, , at STP , , , , , at STP , , at STP, , Limiting Reagent : It is the reactant which gets consumed first or limits, the amount of product formed., Mass Percent : It is the mass of the solute in grams per 100 grams of the, solution., Some Basic Concepts of Chemistry, , 3
Page 26 :
Mass percent=, , , Parts per million (ppm) : It is part of solute per million part of solution, by mass., , ppm =, , , Molarity (M) : It is number of moles of solute dissolved per litre (dm3), of the solution., , Molarity =, , , Molarity equation :, , , , , M1V1, , =, , M2V2, , (Before dilution) (After Dilution), , Molarity of a solution decreases on increasing temperature., Molarity of pure water is 55.56 mol L–1, , , Molality (m)—It is number of moles of solute dissolved per 1000g (1kg), of solvent., , Molality =, , No. of moles of solute, mass of, of solvent, solvent in, Mass, in kg, kg, , Molality is independent of temperature., , , Mole Fraction(x) is the ratio of number of moles of one component to, the total number of moles (solute and solvents) present in the solution., , x1 =, , and x2 =, , The sum of all the mole fractions in a solution is equal to one. i.e., x1 + x2 = 1, , , , 4, , Chemistry Class XI
Page 27 :
MIND MAP, SOME BASIC OF CONCEPTS OF CHEMISTRY, , Some Basic Concepts of Chemistry, , 5
Page 28 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Which of the following is dependent of temperature ?, , 2., , (a), , Molarity, , (b) Molality, , (c), , Mole fration, , (d) Mass percentage, , 4 g of NaOH dissolved in 100 ml solution. Molarity of the solution is, , 3., , (a), , 1M, , (b) 10 M, , (c), , 0.1 M, , (d) 4 M, , Which has the maximum number of molecules among the following ?, , 4., , (a), , 44g of CO2, , (b) 44g of O2, , (c), , 8g of H2, , (d) 64g of SO2, , 10 mol of Zn react with 10 mol of HCl. Calculate the number of moles, of H2 produced., , 5., , (a), , 5 mol, , (b) 10 mol, , (c), , 20 mol, , (d) 2.5 mol , , The number of oxygen atoms in 4.4g of CO2 is approximately, , 6., , (a), , 1.2 × 1023, , (b) 6 × 1022 , , (c), , 6 × 1023, , (d) 12 × 1023, , The molarity of a solution obtained by mixing 750 mL of 0.5 M HCl with, 250 ml of 2 M HCl will be, , 7., , (a), , 0.975 M, , (b) 0.875 M, , (c), , 1.00 M, , (d) 1.175 M , , Number of atoms of He in 100 u of He ( Atomic mass of He is 4 u), (a), , 25, , (b) 50, , (c), , 100, , (d) 400, , 6.02 ×1020 molecules of urea are present in 100 mL of its solution. The, concentration of the solution is, , 8., , 6, , (a), , 0.02 M, , (b) 0.01 M, , (c), , 0.001 M, , (d) 0.1 M , , Chemistry Class XI
Page 29 :
9., , 10., , Ans:, , A gaseous hydrocarbons gives upon combustion, 0.72 g of water and 3.08, g of CO2. The empirical formula of the hydrocarbon is :, (a), , C6H5, , (b) C7H8 , , (c), , C2H4, , (d) C3H4, , The density of solution prepared by dissolving 120 g of urea ( Mol. mass, = 60 u) in 1000 g of water is 1.15 g/mL. The molarity of the solution is, (a), , 0.50 M, , (b) 1.78 M , , (c), , 1.02 M, , (d) 2.05 M, , 1. (a), 2. (a), 3. (b), 4. (a), 5. (a), 6. (b), 7. (a), 8. (b),, 9. (b), 10. (d), FILL IN THE BLANKS, , 1., , 17 g of NH3 gas will occupy a volume of _____________ cm3 at NTP., , 2., , The number of Li atoms in _____________ g. is 6.022×1024 atoms., , 3., , (1/12)th of the mass of carbon atom is _____________, , 4., , Number of atoms of oxygen in 24 g of O3 is _____________, , 5., , The number of moles of barium carbonate which contains 1.5 moles of, oxygen atoms is _____________, , 6., , A mixture having 2 g of H2 and 32 g of oxygen occupies a volume of, _____________ at NTP., , 7., , If the phosphate of a metal has the formula MPO4 the formula of the, metallic sulphate is _____________, , 8., , At NTP, the mass of 1 litre of gas is 3 g. Molecular mass of the gas is, _____________, , 9., , The percentage mass of magnesium in chlorophyll is 2.68% The number, of magnesium atoms in 2 g of chlorophyll is _____________, , 10., , The mass of one molecule of carbon dioxide is _____________, , 11, , Percentage of nitrogen in urea is ___________, , 12, , Number of carbon atoms present in 18 g of glucose ( C6H12O6), Some Basic Concepts of Chemistry, , 7
Page 30 :
13., , 0.5 mole of triatomic gas contains ____________________atoms., , 14., , A binary compound contains 50% A (at. mass = 16) and 50% B (at. mass, 32). The empirical formula of the compound is _____________., , 15., , The number of hydrogen atoms in 60 u of ethane is____________, , Ans:, , 1., , 22400, , 2., , 70 g, , 3., , 1u, , 4., , 9.033 × 1023, , 5., , 0.5, , 6., , 44.8 litre, , 7., , M2(SO4)3, , 8, , 67.2, , 9., , 1.34×1021, , 10. 7.3×10–23, , 11. 46.67, , 12. 3.61×1023, , 13. 9.033 × 1023, , 14. A2B, , 15. 7.226 × 1024, , TRUE AND FALSE TYPE QUESTIONS, Write true or false for the following statements, 1., , Equal volumes of different gases under similar conditions of temperature, and pressure contain equal number of molecules., , 2., , 1 mole of C12H22O11 contain 22 hydrogen atoms., , 3., , Nitrogen forms five oxides. It proves the law of multiple proportions., , 4., , The atomicity of phosphorus is four., , 5, , Molarity change with change in temp., , 6., , Empirical formula = (Molecular formula)n., , 7., , Gram-atomic mass of an element may be defnined as the mass of, Avogadro’s number of atoms., , 8., , Gay-Lussac’s law of chemical combination is valid for all substances., , 9., , Avogadro’s number varies with temperature and pressure., , 10., , 18 g of water vapour and 18 g of ice will contain the same number of, molecules., , Ans:, , , 8, , 1. (T), 6. (F), , 2. (F), 7. (T), , Chemistry Class XI, , 3. (T), 8. (F), , 4. (T), 9. (F), , 5. (T), 10. (T)
Page 31 :
MATCH THE COLUMNS, 1., Column X, , Column Y, , a., , 8 g CH4, , i., , 0.1 mol, , b., , 1.7 g NH3, , ii., , 0.5 mol, , c., , HCHO, , iii. 40% carbon, , d., , C6H12O6, , iv. Vapour density = 15, , 2., Column X, , Column Y, , a., , Molarity, , i., , For very dilute solution, , b., , Molality, , ii., , No units, , c., , mole fraction, , iii. Mol L–1, , d., , ppm, , iv. independent of temperature, , 3., Column X, , Column Y, , a., , 40 g of He, , i., , 6.022×1023 atoms, , b., , 35 g of Li, , ii., , 10 atoms, , c., , 40 u of He, , iii. 6.022×1024 atoms, , d., , 16 g of O2, , iv. 3.011×1024 atoms, , 4., Column X, , Column Y, , a., , Petrol, , i., , Heterogenous mixture, , b., , Graphite, , ii., , Compound, , c., , Sucrose, , iii. Element, , d., , Milk, , iv. Hamogeneous mixture, , Ans:, , , 1. a.(ii), b.(i), c.(iv), d.(iii), , 2. a.(iii), b.(iv), c.(ii), d.(i), , 3. a.(iii), b.(iv), c.(ii), d.(ii), , 4. a.(iv), b.(iii), c.(ii), d.(i), , Some Basic Concepts of Chemistry, , 9
Page 32 :
ASSERTION AND REASON TYPE QUESTIONS, Directions for Q. No.1-5, A, , If both Assertion & Reason are true and the reason is the correct, explanation of the assertion., , B, , If both Assertion & Reason are true but the reason is not the correct, explanation of the assertion., , C, , If Assertion is true statement but Reason is false., , D, , If both Assertion and Reason are false statements., , 1., , Assertion : A solution of table salt in a glass of water is homogeneous, Reason : A solution having same composition throughout is, heterogeneous, , 2., , Assertion : The molecular weight of oxygen is 32 amu., Reason : The atomic weight of oxygen is 16 amu, , 3., , Assertion : No of moles of H2 in 0.224 L of hydrogen is 0.01 mole., Reason : 22.4 L of H2 at STP contain 6.023 × 1023 moles., , 4., , Assertion : Atomic mass of Na is 23., Reason : An atom of sodium is 23 times heavier than 1/12th mass of, C-12 isotope., Assertion : Number of atoms of He in 60 u of He is 15., Reason : Atomic weight of He is 4 u., , 5., , Ans:, , 1.C, , 2.A, , 3.C, , 4.A, , 5.A, , ONE WORD ANSWER TYPE QUESTIONS, 1., , What is the SI unit of density?, , 2., , What is the SI unit of molarity?, , 3., , Calculate the number of atoms in 32 u of He. , , 4., , What is the volume of 17 g of NH3 gas at STP?, , 5., , [Ans. : 8], [Ans. : 223.4 L], , How many molecules of SO2 are present in 11.2 L at STP?, , [Ans. : 3.011×1023], , 6., , Which has more number of atoms ? 1.0 g Na or 1.0 g Mg, [Ans. : 1.0 g Na], 10, , Chemistry Class XI
Page 33 :
7., , How any oxygen atoms are present in 16 g of ozone (O3)?, , [Ans. : 2.007 ×1023], , 8., , Calculate the number of molecules present in 22.0 g of CO2., , [Ans. : 3.011×1023], , 9., , A substance has molecular formula C6H12O6. What is its empirical formula., , 10., , Empirical formula of a compound X (Molar mass = 78 mol-1) is CH. Write, its molecular formula., 1-MARK QUESTIONS, , 1. , , Name two chemical compounds used in treatment of cancer., , 2. , , What is AZT ? Mention its use in medical science., , 3. , , Classify following as pure substances and mixtures : air, glucose, gold,, sodium and milk., , 4. , , Which measurement is more precise 4.0g or 4.00g ?, , 5., , How many significant figures are there in (i) 3.070 and (ii) 0.0025 ?, , , , [Ans. 4.00 g], [Ans. (i) 4 (ii) 2], , 6., , Express the following in the scientific notation : (i) 0.0048 (ii) 234,000, , 7., , If ten volumes of dihydrogen gas react with five volumes of dioxygen, gas, how much volume of water vapour would be produced ?, , [Ans. 10 volumes], , 8., , Define unified mass (u)., , 9., , Define molar volume of a gas., , 10. , , At STP, what will be the volume of 6.022 × l023 molecules of H2 ?, , , 11. , , [Ans. 22.4L], , 1L of a gas at STP weighs 1.97g. What is molecular mass ?, , , , [Ans. 44.128 g mol–1], , 12. , , Write the relationship between empirical formula and molecular formula., , 13. , , Which is more informative ? Empirical formula or Molecular formula., Some Basic Concepts of Chemistry, , 11
Page 34 :
14. , , How are 0.5 mol Na2CO3 and 0.5 M Na2CO3 different from each other ?, , 15. , , Why molality is preferred over molarity of a solution ?, , 16. , , Define molarity of a solution., , 17. , , What is the effect of temperature on molarity of solution ?, , 18. , , What is limiting reactant in a reaction ?, 2-MARKS QUESTIONS, , 1. Classify following substances as element, compounds and mixtures : water,, tea, silver, steel, carbon dioxide and platinum., 2. The body temperature of a normal healthy person is 37°C. Calculate its, value in°F., 3. At what temperature will both the Celsius and Fahrenheit scales read the, same value?, 4. Convert 5L into m3., 5. What does the following prefixes stand for :, (a) pico, (b) nano, (c) micro, (d) deci, 6. How many significant figures are present in the following :, (i) 4.00005, (ii) 0.004, 7. Convert ‘450 pm’ into SI unit and write the answer in scientific notation, upto 2 significant figures., , [Ans. 4.5 × 10–10 m], 8. Hydrogen peroxide and water contain 5.93% and 11.2 % of hydrogen, respectively. Show that the data illustrate law of multiple proportions., 9. The density ( in g mL–1) of a 3.60 M sulphuric acid solution that is 29%, H2SO4 ( Molar mass = 98 g mol-1) by mass will be ......., , [Ans. 1.21 g/mL], 10 The cost of table salt ( NaCl ) is Rs. 10 per Kg. calculate its cost per mole., ( Molar mass of NaCl is 58.5 gmol-1), [Ans. 0.58 Rs], 11 Calculate the mole fraction of the solute in a 1.00 molal aqueous, solution., [Ans. 0.0177], 12, , Chemistry Class XI
Page 35 :
12 Dissolving 120 g of urea ( Molar mass of urea = 60 g mol-1 ) in 1000 of, water gave a solution of density 1.15 g/mL. Calculate the molarity of the, solution., [Ans. 2.05 M], 13 Calculate the percentage of N in urea. (Molar mass of urea = 60 g, mol-1), [Ans. 46.66], 14 25 ml of 3.0 M HCl are mixed with 75 mL 0f 4.0 M HCl. If the volumes, are additive, the molarity of the final mixture will be., [Ans. 3.75 M], 15 How many atoms and molecules are present in 124 gm of phosphorus, (P4), [Ans. Atoms = 4 NA & Molecules = NA], 16 45.4 L of dinitrogen reacted with 22.7 L of dioxygen and 45.4 L of nitrous, oxide was formed. , The reaction is given below : 2N2 (g) + O2 (g) —→ 2N2O (g), , Which law is being obeyed in this experiment? Write the statement of the, law., 17 Give one example each of a molecule in which empirical formula and, molecular formula is, (i) Same (ii) Different., 18 Calculate the number of moles in the following masses :, (i) 7.85g of Fe; , (ii) 7.9mg of Ca, , 19 Calculate the percent of carbon, hydrogen and oxygen in ethanol, (C2H5OH), [Ans. 52.14%, 13.13%, 34.73%], 20 How much copper can be obtained from 100 g of CuSO4 ? [Ans. 39.8g], 21 Calculate the amount of water (g) produced by the combustion of 16 g of, methane., [Ans. 36g], 22, , How many moles of methane are required to produce 22 g CO2 (g) after, combustion?, [Ans. 0.5 mol], , 23 A solution is prepared by adding 2 g of a substance A to 18 g of water., Calculate the mass per cent of the solute., [Ans. 10%], 24 Calculate molarity of water if its density is 1.00 g mL-1. , [Ans. 55.56 M], , Some Basic Concepts of Chemistry, , 13
Page 36 :
25, , Calculate the molarity of NaOH in the solution prepared by dissolving its, 4 g in enough water to form 250 mL of the solution., [Ans. 0.4 M], , 26 The density of 3 M solution of NaCl is 1.25 g mL-1. Calculate molality of, the solution., [Ans. 2.8m], 27 NH3 gas can be prepared by Haber’s process as, N2(g) + 3H2 (g) →, 2NH3(g). At a particular moment concentration of all the species is, 2 moles; calculate the concentration of N2 and H2 taken initially., , [Ans. 3 mole, 5 moles], 3-MARKS QUESTIONS, 1. Calculate the average atomic mass of Mg using the followinf data:, , , % Natural Abudance, , Molar mass, , 24Mg, , 80, , 24, , 25Mg, , 10, , 25, , 26Mg, , 10, , 26, , 2. The following data are obtained when dinitrogen and dioxygen react, together to form different compounds :, , , (i), , (ii), , (iii), , (iv), , Mass of dinitrogen 14, , 14, , 28, , 28, , Mass of dioxygen, , 32, , 32, , 80, , 16, , Which law of chemical combination is obeyed by the above experimental, data ? Give its statement., 3., , Calculate :, , (i) Mass in gram of 5.8 mol N2O, , (ii) Number of moles in 8.0 g of O2, , (iii) Molar mass if 11.2 L at STP weigh 8.5 g., , , [Ans. (i) 255.2 g (ii) 0.25 mol (iii) 17 g mol–1], , 4. In three moles of ethane (C2H6), calculate the following :, , (i) Number of moles of carbon atom,, , (ii) Number of moles of hydrogen atoms,, (iii) Number of molecules of ethane., , , 14, , [Ans. (i) 6 moles, (ii) 18 moles, (iii) 1.81×1024], , Chemistry Class XI
Page 37 :
5. 16 g of an ideal gas SOx occupies 5.6 L at STP. What is its molecular, mass ? What is the value of X ?, [Ans. 64u, x = 2], 6. Calculate the number of moles :, (i) 5.0 L of 0.75 M Na2CO3, (ii) 7.85 g of Fe, , (iii) 34.2 g of sucrose (C12H22O11) , [Ans. (i) 3.75, (ii) 0.14, (iii) 0.1], 7. Calculate the number of atoms in each of the following :, (i) 52 moles of Ar. (ii) 52u of He (iii) 52g of He., , , [Ans. (i) 3.13 × 1025 (ii) 13 (iii) 7.83 × 1024], , 8. Vitamin C is essential for the prevention of scurvy. Combustion of, 0.2000g of vitamin C gives 0.2998g of CO2 and 0.819g of H2O. What is, the empirical formula of vitamin C ?, [Ans. C3H4O3], 9., , A compound contains 4.07% hydrogen, 24.27% carbon and 71.65%, chlorine. Its molar mass is 98.96 g. What are its empirical and molecular, formulas?, [Ans. CH2C1, C2H4Cl2], , 10. A compound made up of two elements A and B has A = 70%, B = 30%., Their relative number of moles in the compound is 1.25 and 1.88,, calculate :, (i) Atomic masses of the elements A and B, (ii) Molecular formula of the compound , if its molecular mass is found to, be 160., [Ans. (i) 56 and 16, (ii) A2B3], 11. The reaction 2C + O2 —→ 2CO is carried out by taking 24.0 g of carbon, and 96.0 g of O2. Find out., , (i) Which reactant is left in excess ?, (ii) How much of it is left ?, , (iii) How many grams of the other reactant should be taken so that nothing, is left at the end of the reaction ?, [Ans. (i) O2, (ii) 64 g, (iii) 72], 12. A 10 g sample of a mixture of calcium chloride and sodium chloride is, treated with Na2CO3 to precipitate calcium as calcium carbonate. This, CaCO3 is heated to convert all the calcium to CaO and the final mass of, CaO is 1.62 g. Calculate % by mass of NaCl in original solution., , , [Ans. 67.9%], Some Basic Concepts of Chemistry, , 15
Page 38 :
13. 3.0 g of H2 react with 29.0 g of O2 yield H2O., (i) Which is the limiting reagent., (ii) Calculate the maximum amount of H2O that can be formed, (iii) Calculate the amount of reactant left unreacted, , [Ans. H2 , 26.8g H2O & 5.2 g O2], 14 Zinc and hydrochloric acid react according to the reaction:, , Zn(s) + 2HCl(aq) —→ ZnCl2(aq) + H2(g), If 0.30 mol Zn are added to hydrochloric acid containing 0.52 mol of HCl,, How many moles of H2 are produced ?, , [ HCl is limiting reagent; H2 formed = 0.36 mol], 15 How many moles of Lead (II) chloride will be formed from a reaction, between 6.5 g of PbO and 3.2 g of HCl ? [ Atomic mass of Pb = 207 U], , [Ans. 0.029 mole], 16 What volume of oxygen at N.T.P is needed to cause the complete, combustion of 200 ml of acetylene ?Also calculate the volume of carbon, dioxide formed., [Ans. 500 mL of O2 & 400 mL of CO2], 5-MARKS QUESTIONS, 1 (i) A black dot used as a full stop at the end of a sentence has a mass of, about one attogram. Assuming that the dot is made up of carbon,, calculate the approximate number of carbon atoms present in the dot., [Hint : 1 attogram = 10–18g], [Ans. 5.02×104], (ii) Which one of the following will have largest number of atoms ?, (a) 1g Au (s), , , (b) 1g Na (s), , (c) 1g Li (s) (d) 1g of Cl2(g), [Ans.. (i) 39.81 g (ii) 1 g of Li], , 2. (i) What is the difference between empirical formula and molecular, formula ?, (ii) A welding fuel gas contains carbon and hydrogen only. Burning a, small sample of it in oxygen gas 3.38 g carbon dioxide, 0.690 g of, water and no other products. A volume of 10.0 L (measured at STP), of this welding gas is found to weigh 11.6 g. Calcuate, (i) Empirical formula, (ii) molar mass of the gas, and (iii) Molecular, formula., [Ans. (i) CH, (ii) 26 g mol–1, (iii) C2H2], 16, , Chemistry Class XI
Page 39 :
3. (i) What is the difference between Molarity and Molality., (ii) The Molarity of a solution of sulphuric acid is 1.35 M. Calculate its, molality. (The density of acid solution is 1.02 g cm–3)., [Ans.. 1.52 m], 4. (i) Define : (a) Mole fraction (b) Mass percentage., (ii) If the density of methanol is 0.793 kg L–1, what is its volume needed, for making 2.5 L of its 0.25 M solution ?, [Ans. 0.0025 L], , , HOTS QUESTIONS, , 1 In a compound CxHyOz , the mass % of C and H is 6:1 and the amount, of oxygen present is equal to the half of the oxygen required to react, completely CxHy. Find the empirical formula of the compound. , [Ans. C2H4O3], 2 A crystalline salt when heated becomes anhydrous and loses 51.2 % of, its weight. The anhydrous salt on analysis gave the following percentage, composition, Mg = 20.0% , S = 26.6 % , O = 53.33 %, Calculate the molecular formula of the anhydrous salt and the crystalline, salt. Molecular weight of the anhydrous salt is 120. , [Ans. MgSO4.7H2O], 3 An LPG cylinder weighs 14.8 Kg when empty. When full, it weighs, 29.0 kg and shows a pressure of 2.5 atm. In the course of use at 27°C,, the weight of cylinder is reduced to 23.2 Kg. Find the volume of, n-butane in cubic meters used up at 27°C and 1 atm (Molecular weight of, n-butane = 58)., [Ans. 2.463 m3], 4 2.5 g of CaCO3 was placed in 50 ml of a solution of HCl.1.05 g of CaCO3, was left after the reaction. Calculate:, (a) the weight of HCl per litre, (b) the Molarity of HCl, , [Ans. (a) 21.17 g, (b) 0.58 M], , Some Basic Concepts of Chemistry, , 17
Page 40 :
UNIT TEST, , Time allowed : 1 hour , , Maximum Marks : 20, , General instructions :, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , If 30 mL of H2 and 20 mL of O2 react to form water, what is left at, the end of the reaction ?, (a) 10 mL of H2, (c) 10 mL of O2 , , 2., , (b) 5 mL of H2, (d) 5 mL of O2, , 7.5 grams of a gas occupy 5.6 litres of volume at STP the gas is, (a) NO, , (1), , (b) N2O, , (c) CO, , (1), , (d) CO2, , 3., , What is AZT ? Write its use. , , (1), , 4., , Why molarity is preferred over molarity in expressing the concentration of solution ? , , (1), , 5., , Which has more number of atoms ? 1.0 g Na or 1.0g Mg?, , (1), , 6. How many atoms and molecules are present in 124 g of phosphorus (P4)? (2), 7., , (a) Write the name of two life saving drugs. , (b) Define accuracy and precision., , (2), , , , 8., , A sample of drinking water was found to be severely contaminated with, chloroform CHCl3. The level of contamination was 15 ppm (by mass)., (a) Express this in percent by mass., (b) Determine the molarity of chloroform in the water sample., (3), , 9., , A compound contains 4.07% hydrogen, 24.27% carbon and 71.65%, chlorine. Its molar mass is 98.96 g. What are its empirical and, molecular formula ? , , (3), , 10. (a) Explain the following terms:, , , (i) Gay Lussac’s law, , (ii) Limiting reagent, , (b) 3.0 g of H2 react with 30.0 g of O2 yield H2O., (i) Which is the limiting reagent?, , , (ii) Calculate the maximum amount of H2O that can be formed., , , , (iii) Calculate the amount of reactant left unreacted., *****, , 18, , Chemistry Class XI, , (5)
Page 41 :
Structure of, Structure, ofAtom, Atom, , Chapter - 2, , FAST TRACK : QUICK REVISION, •, , Information about fundamental particles of atom, , Name of, Constant, , UNIT, , Electron, , Proton, , Mass, , amu, , 0.000546, , 1.00728, , 10–31, , 1.673 ×, , Neutron, 1.008665, 10–27, , 1.675 × 10–27, , , , kg, , 9.109 ×, , Charge, , Coloumbs, , – 1.602 × 10–19 + 1.602 × 10–19 Zero, , , , esu, , – 4.8 × 10–10, , + 4.8 × 10–10, , Zero, , , , , Relative, Charge, , –1, , +1, , Zero, , •, , Electromagnetic radiations : Energy emitted from any source (in forms, of waves) in which electric and magnetic fields oscillated perpendicular to, each other and travelling with a velocity of light is known as EM radiation., , •, , Characteristics of waves :, , , , (a) Wavelength : The distance of one crest and, one trough in a wave. Denoted by ‘λ’., , , , (b) Frequency : Number of waves passing, through a given point in one second., Denoted by υ., (c) Amplitude : The height of crest or depth of a trough denoted by ‘a’., (d) Wave Number : Number of waves per unit length denoted by, =, , (or m–1)
Page 42 :
(e) Velocity : Linear distance travelled by a wave in one second., , , •, , velocity of light c, , =, , ∴ υ, , =, , =, , Energywise order for EM radiation., , cosmic < γ rays < X rays < UV < VIBGYOR < IR < Microwaves < Radiowaves, →, λ (Increases), υ (Decreases), Energy (Decreases), •, , Photon : A packet or particle of light energy is knows as Photon., , •, , Planck’s quantum theory : The energy emitted or absorbed by a source, is discontinuous in form of small packet of energy, called quantum., Quantum of light is called photon., , E a v, E = hv , , (h = Planck's constant), , E = nhv , , (h = 6.626×10–34 J sec), , If ‘n’ photons are emitted E = nhυ, •, , Photo electric effect : The phenomenon of ejection of electrons from a, metal surface when a light of suitable frequency falls on metal surface., hυ – hυ0 =, , mv2, , hυ ⇒ Energy of incident light on metal surface., hυ0 ⇒ Work function of metal., mv2 = Kinetic energy by which e– is emitted from metal surface., •, , de Broglie equation : All material particles in motion also exhibit wave like, properties., , h, h, =, λ, =, mv, p, , For microscopic particles mass is very less therefore Wavelength of wave, associated with it can be detected., 20, , Chemistry Class XI
Page 43 :
For macroscopic particles mass is large, λ of wave associated with it can, not be detected. Hence dominant wave character., Hence microscopic bodies have dual nature, where as macroscopic bodies, have particle nature., Heisenberg's Uncertainty Principle, It is impossible to determine the exact position and velocity of a moving, subatomic particle simultaneously with accuracy., ∆x × m∆v ≥, ∆x = uncertainty in position, ∆v = uncertainty in velocity, Bohr’s theory for H [H like one e– systems He+; Li2+], (1) e– revolving round the nucleus in circular path [stationary state; SHELL], [Here n = no. of shell of e–] and, , with a definite angular momentum, with definite energy, En =, , ⇒ – 2.18 × 10–18, , (2) As n increases, Energy of e– becomes less – ve [Due to less force of Proton, attraction], As n decreases, Energy of e– becomes More – ve [Due to more force of, attraction by protons], (3) In infinity shell e– has zero force of attraction therefore zero energy., (4) Electron energy only changes by definite values ∆E = Ef – Ei., Hydrogen spectrum : When e– in hydrogen atom is provided energy it gets, excited to higher shell from ground state, it comes back to ground state by, emitting energy in definite values., “Quanta” : The emission of light energy is known as emission spectra. It, corresponds to each atom depending upon which energy shell e– is excited., , Structure of Atom, , 21
Page 44 :
It is discontinuous spectra as ‘λ’ of light radiations do not merge with each, other like in VIBGYOR (Continous Spectra)., When e– falls from any excited state to, R = Rydberg constant = 109678 cm–1, , = 1,09,678, ni = 1, nf = 2, 3, 4, ...., , [Lyman series] (UV), , ni = 2, nf = 3, 4, 5, ...., , [Balmer series] (VIBGYOR), , ni = 3, nf = 4, 5, 6, , [Paschen series] IR., , ni = 4, nf = 5, 6, 7, , [Bracket series] IR., , ni = 5, nf = 6, 7, 8, , [Pfund series] IR., , Quantum numbers : The noumbers which completely define the state of, e– in an atom., (1) Principal Quantum No. : It describes the distance of e– from nucleus ‘n’, i.e., defines the shell no. It is denoted by ‘n’., n, , , = 1, 2, 3, 4, 5, ....., K, L, M, N, O ....., , (2) Azimuthal (l) Quantum No. : It defines the path of e– decided by angular, momentum of e–. Each angular momentum value corresponds to one, subshell. The no. of subshells in a shell is 0 to n – 1., n l (0 to n-1), 1 0, , l=0, , ‘s’, , subshell, , 2 0, 1, , l=1, , ‘p’, , subshell, , 3 0, 1, 2, , l=2, , ‘d’, , subshell, , 4 0, 1, 2, 3, , l=3, , ‘f ’, , subshell, , All subshells are wave functions for locating e–., In the same shell energy increase s < p < d < f., , 22, , Chemistry Class XI
Page 45 :
(3) Magnetic Quantum No. : It gives the no. of magnetic orientations, an e– can have in a subshell. That is number of orbitals in a sub-shell., ms = –l........o........+ l = (2l + 1)., (4) Spin Quantum No. : An e– is continuously spinning on its own axis., 1, 1, or –, 2, 2, An orbital can have maximum two e– one with clockwise and other with, anticlockwise spin., The value of s =, , Aufbau principle, (a) Electrons are filled in increasing order of energy of sub-shell., (b) As ‘n + l’value increases energy of e– increases in that sub-shell., (c) For two sub-shells with same ‘n + l’ value, as ‘n’ value increases, energy of e– increases., Pauli’s principle, No two electrons can have same set of four quantum numbers in an atom., Hund’s rule of maximum multiplicity, The pairing of e– in degenerate orbitals (different orbitals with same energy), will get paired only once they have been singly occupied with same spin., IMPORTANT POINTS, The filling of e– in subshells follows this order. (As per Aufbau principle), (A) 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p, < 7s < 5f < 6d < 7p, (B) Half filled and completely filled subshells have more stability than, incompletely filled subshells., Cr = [Ar] 4s1 3d5, Cu = [Ar] 4s1 3d10, (C) As the shell no. inc. size of subshell increases e.g., size of (2s > 1s) ; (3p, > 2p); (4d > 3d), , Structure of Atom, , 23
Page 46 :
(D) The region in an orbital where probability of finding the e– is zero is known, as Nodal plane (or Node)., The no. of [radial nodes] = n – l – 1 and Angular Nodes = l,, Total nodes = n–1., (E) ψ(psi) ψ2(psi square), A wave function for, locating an electron, , , , (F), , The square of wave function where, the probability of finding the e– is, maximum., [Each value of ψ2 is a region and defines, one orbital], , Orbit , , Orbital, , (1) A definite distance from (1) A probability region for locating, , the nucleus for finding the e– around the nucleus., , the e– [e– as a particle]. It is a wave function [e– as a wave], (1) It has definite size and, , e– in this orbit has, , definite energy., , 24, , Chemistry Class XI, , (2) It does not define definite size., But only a boundary region diagram, of a wave for locating the e–.
Page 47 :
MIND MAP - STRUCTURE OF ATOM, , Structure of Atom, , 25
Page 48 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Packet of energy is called, , 2., , (a), , Electron, , (b), , Photon, , (c), , Position, , (d), , Proton, , Orbital which is not possible, , 3., , (a), , 2p, , (b), , 3d, , (c), , 3s, , (d), , 3f, , the magnetic quantum number of an atom is related to the, , 4., , (a), , size of the orbital, , (b), , spin angular momentum, , (c), , orbital angular momentum, , (d), , orientation of the orbital in space, , The principal quantum number of an atom is related to the, , 5., , (a), , size of the orbital, , (b), , spin angular momentum, , (c), , orbital angular momentum, , (d), , orientation of the orbital in Spence, , The designation of an orbital with in = 4 and 1 = 3, , 6., , (a), , 4s, , (b), , 4p, , (c), , 4d, , (d), , 4f, , What transition in the hydrogen spectrum would have the same wavelength, as the Balmer transition n = 4 to n = 2 in the He+ spectrum?, , 7., , (a), , n = 4 to n =1, , (b), , n = 3 to n = 2, , (c), , n = 3 to n = 1, , (d), , n = 2 to n = 1, , The wave number of first line of Balmer series of hydrogen in 15200 cm-1., The wave number of the first Balmer line of Li2+ ion is, , 8., , (a), , 15200 cm-1, , (b), , 60800 cm-1, , (c), , 76000 cm-1, , (d), , 136,800 cm-1, , An electron is moving in Bohr's orbit. Its de Broglie wavelength is λ. What, is the circumference of the forth orbit?, , 26, , (a), , 2/λ, , (b), , 2λ, , (c), , 3λ, , (d), , 3/λ, , Chemistry Class XI
Page 49 :
9., , Which of the following statements in relation to the hydrogen atom is correct?, (a), , 3s-orbital is lower in energy than 3p-orbital, , (b), , 3p-orbital is lower in energy than 3-d-orbital, , (c), , 3s and 3p orbitals all have the same energy., , (d), , 3s, 3p and 3d orbitals all have the same energy., , 10. For principle quantum number, n = 4, the total number of orbitals having, 1 = 3 is, (a), , 3, , (b), , 7, , (c), , 5, , (d), , 9, , 11. The number of d-electrons retained in Fe2+ (At. no. of Fe = 26) ion is, (a), , 3, , (b), , 4, , (c), , 5, , (d), , 6, , 12. Pauli exclusion principle helps to calculate the maximum number of electrons, that can be accommodated in any, (a), , orbital, , (b), , subsell, , (c), , shell, , (d), , All of these, , Ans. 1. (b), 2. (d), 3. (d), 4. (a), 5. (d), 6. (d), 7. (d), 8. (c), 9. (d),, 10. (b), 11. (d), 12. (a), FILL IN THE BLANK, 1., , Bohr’s theory is based on ________ of radiation., , 2., , The angular momentum of the electron in the 4th energy shell in the hydrogen, atom is ________., , 3., , Lines of Balmer series appear in ________ region., , 4., , The maximum number of electrons in Fe3+ (At. No. 26) is ________., , 5., , Li2+ and He+ ions have spectrum similar to ________ atom., , 6., , Bohr’s atomic theory is not able to explain the atomic spectra of atoms, containing ________ electron., , 7., , An electron in the first shell will have ________ stability and _______, energy than an electron in the third shell., Structure of Atom, , 27
Page 50 :
8., , The space or three-dimensional region round the nucleus where there is, maximum probability of finding an electron of specific energy is called, an____, , 9., , According to ____ no two electrons in an atom will have all the four quantum, numbers ____, , 10. When there are two electrons in the same orbital they have ____ spins., 11. The s-subhells have ____ shape and the p-subshells have____, 12. The maximum number of electrons on a subshell is equal to ______ where, l = ______, Planck’s theory, , 2., , 2h, π, , 3., , Visible, , 4., , 23, , 5., , H-atom, , 6., , more than 1, , 7., , Larger, lower, , 8., , orbital, , 9., , Pauli exclusion principle; similar, , 10., , Opposite, , 11, , Spherical, dumb bell shape., , 12., , 2l + 1; azimuthal quantum numbers, , Ans. 1., , TRUE AND FALSE TYPE QUESTIONS, Write true or false for the following statements, 1., , Bohr’s theory cannot explain the spectra of multi-electron atoms., , 2., , Bohr’s theory based on the Planck’s quantum theory., , 3., , Size of orbital is determined by principal quantum number., , 4., , Fe2+ ion has more number of unpaired electrons than Fe3+., , 5., , The outer electronic configuration of chromium atom is 3d44s2., , 6., , The designation of an orbital n=4 and l=0 is 4s., , 7., , All photons of light have same energy., , 8., , Fe3+ has 3d5 configuration., 28, , Chemistry Class XI
Page 51 :
9., , The number of subshells is always equal to the order of the orbit., , 10. Two electrons in the same orbital has antiparallel spin., 11. The second orbit in He+ ion has radius as the first orbit in hydrogen atom., 12. Heisenberg principle is applicable to microscopic particles., 13. 3s orbital has 2 radial nodes., Ans. 1. (T), , 2. (T), , 3. (T), , 4. (F), , 5. (F), , 6. (T), , 8. (T), , 9. (F), , 10. (T), , 11. (T), , 12. (T),, , 13. (T), , 7. (F), , MATCH THE COLUMNS, 1., , Match the following, , , , 2., , List-I, , a., , Lyman series, , p. Visible region, , b., , Balmer series, , q. Infrared region, , c., , Paschen series, , r., , Absorption spectrum, , d., , Brackett series, , s., , Ultraviolet region, , Match the following, , , , 3., , List-II, , List-I, , List-II, , a., , Principal quantum number, , p. Spin of electrons, , b., , Azimuthal quantum number, , q. Size of orbital, , c., , Magnetic quantum number, , r., , Orientation of the orbital, , d., , Spin quantum number, , s., , Shape of the orbital, , Match the following, , , , List-I, , List-II, , a., , 2s, , p. Dough not shape, , b., , 2px, , q. Spherical, , c., , 3dxy, , r., , Dumb bell, , d., , 3dz2, , s., , Double dumb bell, , Structure of Atom, , 29
Page 52 :
4., , Match the following, , , a., b., , List-I, , List-II, , 2s, ψ2, , p. Two nodal planes, q. One radial node, , c. Heisenberg’s uncertainty, r., , d., , 3dyz, , s., , Electron probability density, principle, Microscopic particles, , ASSERTION AND REASON TYPE QUESTIONS, Directions: (Questions 1 to 4), A., B., C., D., , If both Assertion & Reason are true and the reason is the correct, explanation of the assertion., If both Assertion & Reason are true but the reason is not the, correct explanation of the assertion., If Assertion is true statement but Reason is false., If both Assertion and Reason are false statements., , Assertion : Number of orbitals in 3rd shell is 9., , 1., , Reason : Number of orbitals for a particular value of n = n2., Assertion : Two nodal planes are present in 3dxy., , 2., , Reason : Number of nodal planes = l , , Assertion : The energy of an electron is largely determined by its principal, quantum number., , 3., , Reason : The principal quantum number is a measure of the most probable, distance of finding the electrons around the nucleus., Assertion : An orbital cannot have more than two electrons, moreover, if, an orbital has two electrons they must have opposite spins., , 4., , Reason : No two electrons in an atom can have same set of all the four, quantum numbers., Ans. 1. A, , 30, , 2. A, , 3. A, , 4. A, , Chemistry Class XI
Page 53 :
ONE WORD ANSWER TYPE QUESTIONS, 1., , Write the name of the theory which explain the wave nature of light., , 2, , Write the name of the theory which explain the Black body radiations, and photo electric effect, , 3, , If the length of the crest of a wave is 4 pm. Write the wavelength of this, wave. , [Ans.8 pm], , 4., , A radiation emitted from a hot iron is photon or quantum ?, , 5., , Out of the d orbitals which does not have four lobes ?, , 6., , What is the lowest value of n that allows g orbitals to exist ?, , 7., , Which quantum number is not obtained from solution of Schrödinger wave, equation ?, , 8., , Which of the following orbitals are possible ?, , 1p, 2s, 2p and 3f, 9., , Write the name of non-directional subshell., , 10. Write the name of quantum number which determines the orientation of, orbitals ?, 11. Write the name of quantum number which determines the shape of orbitals., 12. How many orbitals are present in ‘g’ subshell ?, 1-MARK QUESTIONS, 1, , Write the relation between frequency and wave number., , 2, , Cs shows maximum photoelectric effect, why ?, , 3, , Distinguish between a photon and a quantum., , 4, , The line spectrum of an element is known as fingerprints of its atom., Comment., , 5, , What is the value of the Bohr’s radius for the third orbit of hydrogen atom?, , 6, , What type of metals are used in photoelectric cell ? Give one example. , [Ans. With large size, less work function.], , 7, , Which series of lines of the hydrogen spectrum lie in the visible region’?, , 8, , Mention the physical significance of y and y2., , 9, , Why did Heisenberg’s uncertainty principle replace the concept of definite, orbit by the concept of probability?, Structure of Atom, , 31
Page 54 :
10. What is uncertain in uncertainty principle ?, 11. Can a moving cricket ball have a wave character ? Justify your answer., 12. Heisenberg uncertainty principle has no significance in our everyday life., Explain., 13. Write the Schrodinger wave equation., 14. Why uncertainty in position is more when uncertainty in velocity is less for, an electron ?, 15. What are the four quantum numbers of 19th electron of copper ?, (Given : Atomic number of copper = 29), 16. How many electrons will be present in the sub-shells having ms, value, of – 1/2 for n = 4 ?, 17. Write the electronic configuration of Ni3+. (At. No. of Ni = 28), 18. How many radial and angular nodes are present in 2p orbital., [Ans. Radial nodes = 0, Angular nodes = 1], 2-MARKS QUESTIONS, Q. 1., , Define black body and black body radiations., , Q. 2., , Give the essential postulates of Bohr’s model of an atom. How did it, explain ?, , , , (i) the stability of the atom ?, , , , (ii) origin of the spectral lines in H-atom ?, , Q. 3., , What is quantisation ? How quantisation of energy was introduced, in Bohr’s model ?, , Q. 4., , What transition in the hydrogen spectrum would have the same, wavelength as the Balmer transition n = 4 to n = 2 of He+spectrum?, , , Q. 5., , Q. 6., , 32, , [Ans. n1 = 1 and n2 = 2], , What transition of Li2+ spectrum will have the same wavelength as, that of the second line of Balmer series in He+spectrum ?, [Ans. n2 = 6 to n1 = 3], Calculate the energy required for the process, He+(g) ——→ He2+ (g) + e–, Chemistry Class XI
Page 55 :
The ionization energy for the H atom in the ground state is 2.18 ×, 10–18 J atom–1] , [Ans. 8.72 × 10–18 J], , Q. 7., , Calculate the wave number for the longest wavelength transition in, the Balmer series of atomic hydrogen., [Ans. 1.523 × 106 m–1], , Q. 8., , To which orbit the electron in H atom will jump on absorbing 12.1, eV energy ? , [Ans. 3rd orbit], , Q. 9., , Calculate the energy associated with the first orbit of He+. What is, the radius of this orbit? [Ans. – 54.38 eV, 0.2645 Å], , Q. 10. What is the distance of separation between 3rd and 4th orbit of, H-atom ? , [Ans. 3.703 Å], Q. 11. The energy of electron in the first Bohr’s orbit is – 13.6 eV. Calculate, the energy of electron in the first excited state., [Ans. – 3.4 eV], Q. 12. Calculate the number of protons emitted in 10 hours by a 60 W sodium, lamp emitting radiations of wavelength 6000 Å., Q. 13. Which one has a higher energy, a photon of violet light with wavelength, 4000 Å or a proton of red light with wavelength 7000 Å ?, [Given. h = 6.62 × 10–34 J sec.], Q. 14. A 100 watt bulb emits monochromatic light of wavelength 400 nm., Calculate the number of protons emitted per second by the bulb., [Ans. 2.012 × 1020 s–1], Q. 15. What are the maximum number of emission lines when the excited, electron of a H atom in n = 4 drops to the ground state ? [Ans. 6], Q. 16. Which has more energy, light radiation of wavelength 400 pm or light, radiation of frequency 1015 Hz ?, Q. 17. Find the energy of electron in 4th shell of Li2+ ion., Q. 18. What is the wave number of an electron with shortest wavelength, radiation in Lyman spectrum of He+ ion?, Q. 19. Write short note on :, , (a) Continuous and discontinuous spectrum., , (b) Absorbtion and emission spectrum., Q. 20. Calculate the mass of the photon with wavelength of 3.6 Å., [Ans. 6.135 × 10–29 kg], Structure of Atom, , 33
Page 56 :
Q. 21. Calculate the mass of the photon with wavelength of 5 pm., Q. 22. On the basis of uncertainty principle show that an electron cannot, exist with in atomic nucleus., (Given : Nuclear radius = 10–I5 m), , , [Hint : Taking 10–15 m as ∆x, the ∆v comes much higher than the, velocity of light and hence is not possible], , Q. 23. Explain why the uncertainty principle is significant only from the, motion of subatomic particles and is negligible for macroscopic, particles?, Q. 24. List two differences between orbit and orbital ., Q. 25. Show that the circumference of the Bohr orbit for the hydrogen atom, is an integral multiple of the de Broglie wavelength associated with, the electron revolving around the orbit, Q. 26. Comment on “Bohr’s model is against the Heisenberg uncertainty, principle”., Q. 27. What are the similarities and difference in 2s and 2px orbitals and 1s, and 2s orbitals ?, Q. 28. Draw shape of d x 2 − y2 orbital., Q. 29. On the basis of Pauli’s exclusion principle show that the maximum, number of electrons in the M -shell (n = 3 ) of any individual atom, is 18., Q. 30. Designate each subshell with n = 4., Q. 31. List the possible values for all the quantum numbers for the following, subshell., (a) 2p, (b) 4f, Q. 32. Write down the electronic configuration of Fe3+ and Ni2+. How many, unpaired electrons are present? (Given Atomic number, Fe = 26,, Ni = 28)., Q. 33. Out of principal, angular, magnetic and spin quantum number, which, quantum number determines the ?, , , , , 34, , (a), (b), (c), (d), , Shape of the orbital, Number of orbitals in an orbit, Size of the orbital, Spin orientation of the electron., , Chemistry Class XI
Page 57 :
Q. 34. What is the Hund’s rule of maximum multiplicity ? Explain with, suitable example., Q. 35. Explain why :, , , (a), , The three electrons present in 2p subshell of nitrogen remain, unpaired., , , , (b), , Cr has configuration 3d5 4s1 and not 3d4 4s2., , Q. 36. (a), , , (b), , What is difference between 'l' and 'L'?, Nitrogen has 7 proton, 7 electron and 7 neutrons. Calculate the, number of electron, protons and neutrons in N3– ion., , Q. 37. Which one is having higher energy?, , , (a), , (b), , Last electron of Cl– or last electron of O2–., n = 4, l = 3 or n = 5, l = 2., 3-MARKS QUESTIONS, , Q. 1.(i) The energy associated with the first orbit in the hydrogen atom is, – 2.18 × 10–18 J atom-1. What is the energy associated with the fourth, orbit ?, , , (ii) Calculate the radius of Bohr’s third orbit for hydrogen atom., [Ans.– 1.36 × 10–19 J atom–l .4.761 nm], , Q. 2., , A bulb emits light of wave length 4500Å. The bulb is rated as 150, watt and 8% of the energy is emitted as light. How many photons are, emitted by the bulb per second ? , [Ans. n = 27.2 × 1018], , Q. 3., , When light with a wavelength of 400 nm falls on the surface of sodium,, electrons with a kinetic energy of 1.05 × 105 J mol-1 are emitted., , , , (a) What is the minimum energy needed to remove an electron from, sodium ?, , , , (b) What is the maximum wavelength of light that will cause a, photoelectron to be emitted ?, [Ans. a = 3.2255 × 1019 J, b = 616 nm], , Q. 4., , Compare the frequency of light radiations emitted when electron falls, from 5th shell to the 2nd shell in Li2+ ion and electron falls from 4th, shell to the 1st shell in He+ ion., Structure of Atom, , 35
Page 58 :
Q. 5., , Calculate the number of waves made by Bohr electron in one complete, revolution in its third orbit. , [Ans. 3], , Q. 6., , What should be the ratio of velocities of CH4 and O2 molecules, so that they are associated with de Broglie waves of equal, wavelength ? , [Ans. 2], , Q. 7., , Calculate the wavelength of an electron that has been accelerated in, a particle accelerator through a potential difference of 1 kv., , [Given 1eV = 1.6 × 10–19 J], Q. 8., , Q. 9., , [Ans. 3.87 × l0–7 m], , (i) Discuss the similarities and differences between a 1s and 2s orbital., (ii) Draw the shape of d z2 ., Calculate the wavelength of a tennis ball of mass 60 gm moving with, a velocity of 10 m per second., (h = 6.626 × 10–34 kg m2 s–1), [Ans. 10–3 metre], , Q. 10. Calculate the wavelength of 1000 kg rocket moving with a velocity, of 3000 km/hr., (h = 6.626 × 10–34 kg m2 s–1), [Ans. 7.9512 × 10–40 m], , , , Q. 11. Calculate the uncertain it in the velocity of a cricket ball of mass, 150 g, if uncertainity in its position is of the order of 1 Å., [Ans. 3.5 × 10–24 m s1], Q. 12. (a) What is de-Broglie wavelength for an electron moving with, velocity of light?, , , (b) What is the angular momentum of electron in 5th shell?, , Q. 13. Two particles A and B have wavelength λA = 5 × 10–10 m and λB =, 10 × 1010 m. Find their frequency, wave number and energies. Which, has more penetrating power and why ?, Q. 14. (a) Which has max. uncertainty regarding position and why ?, , , , Electron, proton and neutron., , (b) Find the number of waves associated with a light radiation of, time period 5 ns., , Q. 15. If an electron in He+ has angular momentum of 5h/2π. Find its energy, and wavelength associated with it. Find the kinetic energy of this, electron., 36, , Chemistry Class XI
Page 59 :
Q. 16 .(i) An atomic orbital has n = 2. What are the possible values of l and ml ?, , , (ii) List the quantum numbers (m1 and l) of electrons for 3d orbital., , , , (iii) Which of the following orbitals are possible ?, , 2d, 1s, 2p and 3f., Q. 17. (a) Write the maximum number of electron in a subshell with l = 3 and, n = 4., , , (b) Write the maximum number of electron that can be associated with, the following set of quantum numbers ?, , n = 3, l = 1 and ml = – 1, , , (c) Write the maximum number of electron that can be accomodated in, an atom in which the highest principal quantum number value is 4., , Q. 18. (i) Write the electronic configurations of the following ions :, (a) H– (b)Na+ (c)O2– (d) F–, , , (ii) What are the atomic numbers of elements whose outermost electrons, are represented by (a) 3s1(b) 2p3 and (c) 3p5 ?, , (iii) Which atoms are indicated by the following configurations ?, , , (a) [He] 2s1 (b) [Ne] 3s2 3p3 (c) [Ar] 4s2 3d1., , Q. 19., , , , , Calculate:, (a) Total number of spherical nodes in 3p orbital., (b) Total number of nodal planes in 3p orbital., (c) Nodal planes in 3d orbital., 5-MARKS QUESTIONS, , Q. 1.(a) Define Photoelectric effect ? Mention its one practical application in, daily life., , , (b) Electrons are emitted with zero velocity from a metal surface when, it is exposed to radiation of wavelength 6800 Å. Calculate threshold, frequency (νo) and work function (Wo ) of the metal., [Ans. νo = 4.41 × 1014 s–1 Wo = 2.92 × 10–19 J], , Q. 2.(a) The electronic energy in Bohr’s orbit is negative .How will you account, for it?, , , (b) The ionisation energy of hydrogen atom is 13.6 eV. What will be the, energy of the first orbit of He+ and Li2+ ions ?, [Ans. E1 of He+ = – 54.4 eV, E1 of Li2+ = – 122.4 eV ], Structure of Atom, , 37
Page 60 :
Q. 3.(a) Define the following terms :, (i), , , Threshold frequency, , (ii) Work function., , (b) The work function for Cs atom is 1 .9 eV. Find threshold wavelength, (λ0)and threshold frequency (ν0) of this light radiation. If Cs metal is, irradiated with a radiation of wavelength 500 nm find kinetic energy, and velocity of emitted electron., , Q. 4.(a) State de Broglie equation. Write its significance., , , (b) A beam of helium atoms moves with a velocity of 2.0 × 103 m s–1., Find the wavelength of the particle constituting the beam, (h = 6.626 × 10–34 J s) [Ans. 49.9 pm ], , Q. 5.(a) State Heisenbergs uncertainty principle. Give its mathematical, expression. Also give its significance., , , (b) Calculate the uncertainity in the position of a dust particle with mass, equal to 1 mg if the uncertainity in its velocity is 5.5 × l0–20ms–1., [Ans. 9.55 × 1010 m], , Q. 6.(a) Cricket ball, a tennis ball and a proton which has more uncertainity, in velocity and which follows Heisenberg uncertainity principle, maximum., , , (b) What is the similarity in de-Broglie and Heisenberg principle? Which, is different from Bohr theory for structure of atom?, , , , (c) Why energy in a given subshell is negative?, , Q. 7.(a) Write short notes on:, (i) Aufbau principle (ii) Pauli’s principle (iii) Hund’s rule., , , (b) Write the electronic configuration of the following ions :, , (i) Fe3+ (ii) Cu+, , , [Given Atomic number of Fe and, Cu are 26 & 29], , Q. 8.(a) Draw the shapes of the following orbitals., (i) 3dxy (ii) dz2, , , (b) What is the total number of orbitals associated with the principal, quantum number n = 3 ?, , (c) Using s, p, d, f notations, describe the orbital with the following, quantum numbers: (a) n = 3, l = 0, (b) n = 4, l = 2, (c) n = 5, l = 3, (d) n = 1, l = 0, 38, , Chemistry Class XI
Page 61 :
Q .9., , Explain the following :, , (i), , Energy of electron is not decided by : n, l ,m and s., , , (ii), , , Maximum number of electron with – 1/2 spin for n = 3 is 6,9,12, or none., , , , (iii) Maximum number of electron can be present for n + l = 4., , (iv) 3f subshell is not possible., , , (v), , Maximum number of electrons in a subshell is :, , (2l + l) or (4l + l) or n2, Q. 10.(a) A neutral atom has 2K, 8L and 15 M electrons. Find the total numbers, of electrons in s, p, d and f subshell., , , (b) How many unpaired electrons are present in the following ions :, , Al+, Cr2+, Co3+ and Mn2+, , , , (Given Atomic number : Al=13, Cr = 24, Co = 27 & Mn = 25), , (c) One electron is present in 4f subshell. What is the sum of n + l +, m1 + ms values assuming ‘f ’ subshell follows – 3 to + 3 order of, filling electron., , Q. 11. Answer the following :, (a) n + l value for 14th electron in an atom., , , (b) Increasing order of filling electron in 4f, 5p and 6d subshells., , (c) ‘m’ and ‘l’ value for last electron of Mg atom., (Given atomic number of Mg is 12), , , (d) Subshell in which last electron is present in Ga., (Given Atomic number of Ga is 31), , , , (e) Sum of spin of all the electron in element having atomic number 14., , Structure of Atom, , 39
Page 62 :
UNIT TEST, , Time allowed : 1 hour , , Maximum Marks : 20, , General instructions :, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Designation for an orbital with n = 4 and l = 3 is , (a) 4s, (b) 4p, (c) 4d, (d) 4f, , (1), , 2., , Maximum number of unpaired electrons in chromium is, (Given: Atomic number of Cr = 24) , (a) 4, (b) 5, (c) 6, (d) 7, , (1), , 3., , Which series of lines of the hydrogen spectrum lie in the visible, region’? , , (1), , 4., , Write the Schrodinger wave equation. , , (1), , 5., , Which of the following is not possible ?, (a) 2p, (b) 3d, (c) 3f, , (1), , (d) 4p, , 6., , Write four difference between orbit and orbital. , , (2), , 7., , Calculate the wave number for the longest wavelength transition in, the paschen series of atomic hydrogen. , , (2), , 8., , (a), , How many orbitals are associated with n = 4 ? , , (3), , (b), , How many electrons will be present in the sub-shells having, ms value of –1/2 for n = 3 ?, , (c), , Draw the shape of dz2. , , , 9., , Calculate the uncertainty in the position of a dust particle with mass, equal to 1 mg if the uncertainty in its velocity is 5.5 × 10-20 ms-1., , 10. (i), , , (ii), , (3), , The energy associated with the first orbit in the hydrogen atom is, –2.18 × 10–18 J atom–1. What is the energy associated with the, fifth orbit?, Calculate the radius of Bohr’s fifth orbit for hydrogen atom., , (iii) Calculate the radial and angular nodes in 2p orbital., (iv) Define the black body and black body radiations., *****, 40, , Chemistry Class XI, , (5)
Page 63 :
Classification of Elements, and Periodicity in, Properties, FAST TRACK : QUICK REVISION, •, , The first systematic classification of elements was provided by Russian, chemist D.I. Mendeleev., , 1. Mendeleev's periodic law, “The physical and chemical properties of elements are periodic functions, of their atomic weight.”, 2. It was modified to Modern Periodic law :, “The physical and chemical properties of elements are periodic functions, of their atomic numbers.”, It is the long form of periodic table :, 7 Horizontal rows are called Periods and 18 Vertical columns are called, Group, , , Group-1 are called Alkali metals, , Group-2 are called Alkaline earth metals., , , , Group-15 are called Pnicogens, , Group-16 are called Chalcogens, , , , Group-17 are called Halogens, , Group-18 are called Noble gases, , 3. 1st period – 2 elements , 2nd and 3rd period – 8 elements, 4th and 5th period – 18 elements, 6th period – 32 elements, 7th period – Incomplete (32 elements), 4. Groups, , , 1 and 2 – ‘s’ block elements last electron entered in ‘s’ subshell [s1, s2], , 3 to 12 – ‘d’ block elements last electrons entered in ‘d’ subshell [d1 to d10]., 13 to 18 – ‘p’ block elements last electrons enter in ‘p ’ subshell [p1 to p6]., Two f-block series lanthanoids and actinoids are placed in the bottom of, periodic table., Classification Of Elements And Periodicity In Properties, , 41
Page 64 :
5. (A) In ‘s’ and ‘p’ block elements the electrons enters in outer most shell., In ‘d’ block elements the electron enters in the penultimate shell (n – 1)., ‘f ’ block elements last electron enter the antepenultimate shell (n – 2)., (B) ‘f ’ block elements are placed in between ‘d’ block elements., ‘f ’ block elements in 2 rows [4f lanthanoids, 5f actinoids], 6. General outer electronic configuration, ‘s’ block : ns1, ns2 [Group 1 to 2], ‘p’ block : ns1np1 to ns2 np6 Group 13 to 18, ‘d’ block : ns0–2 (n – 1) d1 to 10 Group 3 to 12, ‘f ’ block : (n – 2)f 1 to 14 (n – 1)d0, 1 ns2, 7. General periodic trends in properties of elements, •, , ATOMIC RADIUS, (A) Left to right decreases due to effect of successive increasing nuclear change, without addition of a new shell., (B) From top to bottom atomic radius increases due to successive addition of, shell., (C) Noble gases have large radius than group 17 due to complete filling of, electron in outer shell electron-electron repulsion mildy increases., , •, , COVALENT RADIUS, It is half of the distance between the centre of nuclei of two adjacent similar, atoms which are bonded to each other by single covalent bond., , •, , van der Waal's Radius, van der Waal's radius is defined as one-half the distance between the centres, of nuclei of two nearest like atoms belonging to two adjacent molecules of, the element in the solid state., , 42, , Chemistry Class XI
Page 65 :
•, , METALLIC RADIUS, Half of the distance between the centres of the nuclei of two adjacent atoms, in the metallic crystal. A comparison of the three atomic radii show that, van der Waal's radius is maximum while the covalent radius has the least value., van der Waal's radius > Metallic radius > Covalent radius, , •, , IONIC RADIUS, (A) Cation radius < Atomic radius – due to more no. of protons than number, of electron coloumbic force increases, size decreases., , , , [Mg2+ <, , Mg+ <, , Mg], , (B) Anion radius > Atomic radius – Due to more number of electron than, number of protons, , , [N3–, , >, , O2– > F–], , Electron-Electron repulsion increase, coloumbic force of attraction, decreases., (C) For Isoelectronic species – More is the charge of cation lesser the size., More is the charge of anion, more is the size., (D) Order of size – O2– > F– > Na > Na+ > Mg2+, 8. (A) Ionisation enthalpy :, The minimum amount of energy which is required to remove the most, loosely bound electron from an isolated atom in the gaseous state is called, Ionisation enthalpy., M(g) + Energy —→ M+ + e–, IE3 > IE2 > IE1, (B) Variation of I.E along a period:, Ionisation enthalpy increase along the period because atomic radii, decrease and nuclear charge increase along the period., I ionisation enthalpy, Li < B < Be < C < O < N < F < Ar, II ionisation enthalpy, Be < C < B < N < F < O < Ne, (C) Variation down the group:, , Ionisation enthalpy decrease down the group because atomic radius, increase down the group., Metallic behaviour : Decrease from left to right due to increase in, ionisation enthalpy., Classification Of Elements And Periodicity In Properties, , 43
Page 66 :
Non metallic behaviour : Increase from left to right due to more number, of electron in outershell and added electron goes towards nucleus., 9. Screening effect or shielding effect:It is the decrease in the force of attraction between nucleus and outermost, electron due to presence of inner shell electrons. As a result, the outer most, electrons does not feel full charge of the nucleus. The actual charge felt by, an electron is called effective Nuclear charge., Shielding effect is in the following order s > p > d > f, d & f subshell show weak sheilding effect because their orbital size are large, and are more diffused., 10. Isoelectronic species:, Ions of different elements which have the same number of electrons but, different no. of protons are called isoelectronic ions., Na+, , Mg2+, , Al3+, , N3–, , O2–, , F–, , No. of Protons, , 11, , 12, , 13, , 7, , 8, , 9, , No. of electrons, , 10, , 10, , 10, , 10, , 10, , 10, , F– <, , O2– <, , N3–, , , , Ionic Radii, , Al3+ < Mg2+ < Na+ <, , 11. Electron gain enthalpy:, The enthalpy change when an extra electron is added to neutral gaseous atom, to form anion., , E(g) + e– → E– (g), ■ Trends : From left to right – Increase due to decrease in size, more, attraction of added electron by nucleus., ■ From top to bottom—Decreases as the added electron is away from, nucleus due to increase in size., ■ Cl has more negative electron gain enthalpy than fluorine – Due to small, size of fluorine extra added electron has more inter electronic repulsion, than chlorine which has large size., ■ Similarly Phosphorus and Sulphur have negative electron gain enthalpy, than nitrogen and oxygen respectively., ■ Maximum electron gain enthalpy – Chlorine (in periodic table), , 44, , Chemistry Class XI
Page 67 :
■ Electron gain enthalpy –, Halogen > Oxygen > Nitrogen > Metal of group 1 and 13 and non metal, of group 14 > metal of group 2., ■ 2nd electron gain enthalpy is always positive., 12. Electro negativity:, The tendency of an atom to attract the shared pair of electron towards itself, in a bonded state., ■ Fluorine is the most electronegative element in the periodic table., ■ Cesium is the least electronegative element in the periodic table., ■ Electro-negativity decreases down the group and increases along the period, Difference between electron gain enthalpy and Electronegativity., Electron gain enthalpy is the energy, but electronegativity is not the energy,, it is only the tendency of an atom in a molecule to attract the shared pair of, electrons. Three highest electronegative atoms F > O > N., Maximum electronegative Assign to F., * Lightest element : Hydrogen, * Lightest metal : Lithium, * Heaviest metal (highest density) : Osmium, * Most reactive metal : Caesium, * Most reactive nonmetal : Fluorine, * Most malleable metal : Gold, * Electrically best conductor : Silver, * Metals which are relatively volatile : Zn, Cd, Hg, * Strongest reducing agent in aqueous solution : Lithium, * Strongest oxidising agent : Fluorine, * The element of lowest ionisation energy : Caesium, * The element of highest ionisation energy : Helium, * The most electronegative element : Fluorine, * The element of highest electron gain enthalpy : Chlorine, * The group containing most electropositive metals : Group 1, * The group containing most electronegative metals : Halogens Group 17, * The group containing maximum number of gaseous elements : Group 18, , Classification Of Elements And Periodicity In Properties, , 45
Page 68 :
13. , , Second period element—Show different behaviour that I group element—, Due to (a) small size (b) High electron negativity (C) High polarising, power (d) absence of ‘d’ orbital., Na3[Al(OH)6] exists but Na[B(OH)4] not exists., , 14. , , The similarities in properties of first member of a group to second member, of just next higher group due to comparable atomic radius, nearly same, polarising power of ions is known as diagonal relationship., Li, , Be, , B, , C, , N, , Na, , Mg, , Al, , Si, , P, , Elements with number of e–, (a) 1, 2, 3, (b) 4, (c) 5, 6, 7, (d) 8, , 46, , Chemistry Class XI, , in valance shell, metals, metalloids, non-metals, noble gas
Page 69 :
Classification Of Elements And Periodicity In Properties, , 47, , (s, p, d, f), , MIND MAP, CLASSIFICATION OF ELEMENTS AND PERIODICITY IN PROPERTIES
Page 70 : MULTIPLE CHOICE QUESTIONS (MCQ), 1., , According to modern periodic law, the physical and chemical properties, of elements are the periodic functions of their ?, , 2., , (a), , Density, , (b) Atomic Number, , (c), , Mass Number, , (d) Atomic Mass, , Highest electropositive element in the periodic table is, (a), , Cs, , (b) Rb, , (c), , K, , (d) Na, , The correct order of ionic radii of the species N3–, O2–, Na+ and F– is, , 3., , 4., , (a), , Na+ < F– < O2– > N3–, , (b) F– < O2– < N3 > Na+, , (c), , O2– < N3– < F– > Na+, , (d) N3– < Na+ < F– > O2–, , The basic strength of the oxides follows the order, , 5., , (a), , Al2O3 > MgO > Na2O, , (b) Al2O3 < MgO < Na2O, , (c), , Na2O3 < MgO > Al3O2, , (d) Al2O3 > MgO > Na2O, , The correct order of the size of C, N, P, S follows the order, , 6., , (a), , N<C<P<S, , (b) C < N < S < P , , (c), , C<N<P<S, , (d) N < C < S < P, , Which of the following oxide is most acidic?, , 7., , (a), , Na2O, , (b) Al3O2, , (c), , P2O5, , (d) SO3 , , Downward in a group, electropositive character of elements, , 8., , (a), , increases, , (b) decreases, , (c), , remains same, , (d) none of these, , Element which has more negative electron gain enthalpy is, , 9., , (a), , F, , (b) O, , (c), , Cl, , (d) S , , The electronegivity of the following elements increase in the order, , 48, , (a), , C, N, Si, P, , (b) N, Si, C, P , , (c), , Si, P, C, N, , (d) P, Si, N, C, , Chemistry Class XI
Page 71 :
10., , The ionisation enthalpy of nitrogen is more than that of oxygen molecules, because of, (a), greater attraction of electrons by the nucleus, (b), extra stability of the half filled p-orbitals, (c), smaller size of nitrogen, (d), more penetrating effect, , Ans:, , 1. (b), 2. (a), 3. (a), 4. (b), 5. (d), 6. (d), 7. (a), 8. (c),, 9. (c), 10. (d), FILL IN THE BLANKS, , 1., , Lightest metal in s-block elements is _____________ ., , 2., , In the periodic table, horizontal rows are known as _____________ ., , 3., , Elements of s-blocks and p-blocks are collectively called ___________., , 4., , Most electropositive elements belong to ___________ group., , 5., , Most electronegative elements belong to ___________ group., , 6., , The elements above atomic number 92 are called ___________., , 7., , The inner-transition elements belong to ________ block of the periodic, table and are shown separately at the ________ of the periodic table., , 8., , An element having electronic configuration [Ar] 3d5, 4s2 belongs to, ____________ block., , 9., , Ca2+ has smaller ionic radius than K+ ion because it has ___________., , 10., , The maximum electronegativity is shown by ____________., , 11, , The maximum ionisation enthalpy is shown by ___________., , 12, , The cation is ________ and the anion is ________ than the parent atom., , Ans:, , 1., 2., 3., , 4., 5., 6., , Lithium, periods, normal elements or, representative elements, 1st, 17th, transuranic elements, , 7., 8., 9., , F -, bottom, s - , more protons, , 10. F 11. H, 12. smaller, bigger, , Classification Of Elements And Periodicity In Properties, , 49
Page 72 :
TRUE AND FALSE TYPE QUESTIONS, Write true or false for the following statements, 1., , First ionisation enthalpy of Be is higher than B., , 2., , Every period of the periodic table (except first period) starts with a member, of alkali metal., , 3., , The energy liberated during the removal of one electron from an atom is, called its ionisation potential., , 4., , Flourine has more negative electron gain enthalpy than chlorine., , 5, , Mg2+ ion has smaller size than Mg., , 6., , Electronegativity of F is larger than that of Cl but electron gain enthalpy, of Cl is larger than of F., , 7., , The decreasing order of electronegativity of F, O and N is F > O > N., , 8., , Group-18 contain maximum gaseous elements., , 9., , Al2O3 is an amphoteric oxide., , 10., , Helium has the highest ionisation enthalpy., , Ans:, , , 1. (T), 6. (T), , 2. (T), 7. (T), , 3. (T), 8. (T), , 4. (F), 9. (T), , 5. (T), 10. (T), , MATCH THE COLUMNS, 1., , Column A, , Column B, , a., , Highest element, , i., , Cesium, , b., , Highest metal, , ii., , Osmium, , c., , Heaviest metal, , iii. Lithium, , d., , Most reactive metal, , iv. Hydrogen, , 2., , Column A, , 50, , Column B, , a., , Fluorine, , i., , High negative electron gain enthalpy, , b., , Helium, , ii., , Most electropositive element, , c., , Chlorine, , iii. Most electronegative element, , d., , Cesium, , iv. Highest ionisation enthalpy, , Chemistry Class XI
Page 73 :
3., , Column A, a., b., c., d., , Column B, , Na2O, , i., , Amphoteric oxide, , Cl2O7, , ii., , Acidic oxide, , CO, , iv. Basix oxide, , Al2O3, , 4., , iii. Neutral oxide, , Column A, , Column B, , a., , s & p-block, , i., , Inner transition elements, , b., , d-block, , ii., , s-block elements, , c., , f-block, , iii. Transition elements, , d., , group-1 and group-2, , iv. Representative elements, , Ans:, , , 1. a.(iv), b.(iii), c.(ii), d.(i), , 2. a.(iii), b.(iv), c.(i), d.(ii), , 3. a.(iv), b.(ii), c.(i), d.(iii), , 4. a.(iv), b.(iii), c.(i), d.(ii), , ASSERTION AND REASON TYPE QUESTIONS, Directions for Q. No.1-5, A If both Assertion & Reason are true and the reason is the correct, explanation of the assertion., B If both Assertion & Reason are true but the reason is not the correct, explanation of the assertion., C If Assertion is true statement but Reason is false., D If both Assertion and Reason are false statements., 1., , Assertion : Ionic radius of Na+ is smaller than Na, Reason : Effective nuclear charge of Na+ is higher than Na, , 2., , Assertion : First ionisation enthalpy of N is higher than O., Reason : Extra stability of fully filled up 2p subshell of N atom, , 3., , Assertion : Electron gain enthalpy of Cl is more negative than F atom., Reason : F is more electronegative than Cl atom., , 4., , Assertion : First ionisation enthalpy of Galium is higher than aluminium., Reason : Weak sheliding effect of 3d subshell is Galium., Ans:, , 1. A, , 2. A, , 3. B, , 4. A, , Classification Of Elements And Periodicity In Properties, , 51
Page 74 :
ONE WORD ANSWER TYPE QUESTIONS, 1., , Metals are placed on which side of modern periodic table?, , 2., , Which block of modern periodic table represent inner transition elements?, , 3., , Name a halogen which has more negative electron gain enthalpy value?, , 4., , Which element is iso-electronic with Na+ ? [Ans. Ne], [Given a atomic number of Sodium (Na) : 11], , 5., An element is placed in 5th period and 3rd group what is its atomic number?, [Ans. 39], What is covalency of Al in [AlCl4]– ? , , 6., , [Ans. 4], , 7., Write the IUPAC Symbol for the element having atomic number 120., , [Ans. Ubn], 8., , Write the name of the group containing maximum number of gaseous, elements., , 9., , Write the name of the subshell which show weakest sheilding effect., , 10., , Write the name of most electropositive element in the periodic table., , 11., , In what period and group will an element with Z = 118 will be present., 1-MARK QUESTIONS, , 1. , , , Which pair of elements has similar properties?, 13, 31, 11 & 21, , 2. Name the element which exhibit diagonal relationship with Be., , [Ans. 13, 31], 3. Which group elements are known as halogens?, 4. , , The element with ns2, np5 configuration is non-metal or metal?, , 5. , , Define van der Waal's radius., , 6. , , Write the outer shell configuration of atomic number 31. [Ans. 4s2, p1], , 7. , , Find the group number and period number of element having atomic, number 52., [Ans. Period = 5th, Group = 16th], , 8. , , Arrange O2–, O–1, O in decreasing radius (size)., , 52, , Chemistry Class XI, , [Ans. O2– > O–1 > O]
Page 75 :
9. , , Why noble gas have bigger size than halogens?, , 10. , , Why first electron gain enthalpy of sulphur is more negative then oxygen?, , 11. Write general outer electronic configuration of 4f series elements., , [Ans. 6s2, 5d0–1, 4f1 to 14], [Ans. Kr+, Se–1], , 12. , , Write two isoelectronic species with Br (35)., , 13., , Show that 4th period can have maximum 18 elements in it., , 14. , , Second I.E. is always more than first I.E., why?, , 15. , , Electronegativity of F > Cl > Br > I, why?, , 16. , , Arrange F and Cl in terms of increasing chemical reactivity?, , 17. , , Second I.E. of Na is more than second IE of Mg. Why?, , 18. , , I.E. for cation is more than neutral atom. Why?, , 19. , , Define diagonal relationship with the help of an example., , 20. , , Out of O– and O, which has more negative electron gain enthalpy?, , 21. , , Mention any two anomalous properties of second period elements., 2-MARKS QUESTIONS, , 1. Cations are smaller than their parent atom whereas anions are larger in, size than their parent atom. Explain., 2. Ionisation energy of nitrogen is more than ‘O’ and ‘C’ both, why ?, 3. First ionisation energy of boron is less than Be but size of Be is less than, Boron. Why ?, 4. Electron gain enthalpy of Mg is positive. Explain., 5. Define co-valency., 6. The reactivity of halogens decrease down the group but of alkali metals, increases down the group. Why?, 7. Name a halogen, a metal and a group13 element which are liquid at, 30°C. , [Ans. Br, Hg, Ga], 8. The reducing power of elements increases down the group but reverse is, true for oxidising power along a period. Why ?, Classification Of Elements And Periodicity In Properties, , 53
Page 76 :
9. What is the formula of binary compound formed between :, (a) 1st element of I group and iodine ?, (b) 2nd element of II group and 1st element of 17th group ?, 10. Arrange in the following in increasing order of property indicated:, (a) Size I, F, Cl, Br, (b) Oxidising power I, F, Br, Cl, 11. Oxygen is more non-metallic than nitrogen but less than fluorine why ?, 12. LiCl, LiBr, LiI are covalent as well as ionic why ?, 13. PbCl2 is more stable than PbCl4. Why ?, , [Ans. Inert pair effect], , 14. [Magnesium and Lithium both form nitrides why ?, 15. Which has least I.E. [3p3, 3p6, 2p3, 2p6]?, 16. (a) I.E. of sulphur is lower than chlorine., , , , (b) Arrange the following in decreasing order of their electro-negativity:, F, O, N, Cl, C, H., , 17. Element ‘A’ in group 17 (2nd period), , , ‘B’ in group 16 (2nd period), , , , ‘C’ in group 15 (2nd period), , , , Arrange ‘A’, ‘B’ and ‘C’ in their decreasing order of electro-negativity, and ionisation enthalpy., , 18. Element ‘A’ 13 group forms ionic compounds. Write the :, , , (a) Formula of its oxide., , , , (b) Arrange the following in their decreasing electro-positive character, Mg, Na, Al, Si., , 19. Write the atomic number of element place diagonally to :, , , (a) Group 14, period 4, , , , (c) Group 17, period 4, , (b) Group 2, period 5, , 20. An element has outer shell electronic configuration 4s2 4p3. Find : , , (a) The atomic number of element place next below it., , , , (b) Atomic number of next noble gas., , 54, , Chemistry Class XI
Page 77 :
3-MARKS QUESTIONS, 1. What is metallic radius, Covalent radius, van der waal’s radius. Give one, example for each., 2. Oxygen has first electron gain enthalpy exothermic while second, endothermic still a large number of ionic oxides are formed. Why ?, 3. In some properties Boron shows different properties with respect to rest, of the membering the group. Justify., 4. Out of group 17, 18 and I, predict: , , (a) Which has most negative first electron gain enthalpy ?, , , , (b) Which shows most metallic behaviour ?, , , , (c) Which has highly positive electron gain enthalpy?, , 5. What are (a) representative elements, (b) Transition elements, (c), Lanthanoid and actinoids. Give their positions in modern periodic table., 6. Why LiF, NaF, KF, RbF, CsF are ionic ? But LiF is less ionic than CsF., 7. (a) Why Ca has larger atomic radius than Al ?, , , (b) Why 2s2 electron is difficult to remove than 2p electron ?, , 8. (a) Why the compounds of group 17 with group 13 elements are more, ionic and stable than with (group 1) elements? (b) Na2O is more ionic, than Li2O. why?, 9. Explain the following data :, , , Ionisation energy Cl < H < O < N < F., , 10. IE2 of 3rd period elements is as follows. Why ?, , , Mg < Si < Al < P < S < Cl < Ar < Na., , 11. Account fot the following:, (a) Halogens have very high negative electron gain enthalpy, (b) The electron gain enthalpy of Cl (Z = 17 )is more negative than that, of Fluorine ( Z = 9 )., (c) Ionisation enthaply of Nitrogen ( Z = 7 ) is more than oxygen ( Z =8)., 12. What are the d- block elements? Write any four properties of d - block, elements and give their general outer electronic configuration., , Classification Of Elements And Periodicity In Properties, , 55
Page 78 :
13. Explain the following:, , , (a) Modern Periodic law, , , , (b) Electro-negativity, , , , (c) Shielding effect, , 14. Among the second period elements the actual ionisation enthalpies are in, the order Li < B < Be < C < O < N < F < Ne. Explain why?, , , (i) Be has higher (DiH)1 than B, , , , (ii) O has lower (DiH)1 than N and F ?, , 15. What do you understand by the isoelectronic species ? Name a species, that will be isoelectronic with each of the following atoms or ions., (i) F–, , (ii) Ar, , (iii) Ca2+, , (iv) Rb+, , 16. (a) Show by a chemical reaction with water that Na2O is a basic oxide, and Cl2O7 is an acidic oxide., , , (b) Name a species that will be isoelectronic with each of the following, atoms or ions, (i) F– (ii) Ca2+, , 17. The first ionisation enthalpy values (in kJmol–1) of group-13 elements are:, B, 801, , Al, 577, , Ga, 579, , In, 558, , Tl, 589, , How would you explain this deviation from the general trend ?, 18. The first (IE1) and the second (IE2) ionisation enthalpies (kJ mol–1) of, three elements are given below:, IE1, IE2, , I, 403, 2640, , II, 549, 1060, , III, 1142, 2080, , , , Identify the element which is likely to be:-, , , , (a) a non metal, (b) an alkali metal, , , , (c) an alkaline earth metal, , 56, , Chemistry Class XI
Page 79 :
5-MARKS QUESTIONS, 1. (A) Which of the following have same chemical properties :, , , (a), , Atomic number 17, 53, , , , (b), , Atomic number 8, 52, , , , (c), , Both , , (d), , , None, , (B) Answer the following :, , , , (i), , B, Al, Ga (decreasing order of atomic radii)., , , , (ii), , C, S, N (decreasing order of (DHeg)1), , , , (iii) Al forms amphoteric oxide. Why ?, , , , (iv) Si is a semiconductor while ‘C’ is a non-metal, why ?, ∆iHΘ1, , ∆iHΘ2, , ∆egH01, , 1681, , 3374, , – 328, , II, , 1008, , 1846, , – 295, , III, , 2372, , 5251, , + 48, , 2. Element, , , I, , , , (a) The most reactive non-metal., , , , (b) The least reactive non-metal., , , , (c) The least reactive element. Give reasons also., [Ans. (a) 1 (b) II (c) III], , Classification Of Elements And Periodicity In Properties, , 57
Page 80 :
UNIT TEST, , Time allowed : 1 hour , , Maximum Marks : 20, , General instructions :, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Which of the following show the weakest sheilding effect ?, (a) s, , 2., , (b) p, , (c) d, , (d) f, , Which has highest electronegativity ? , (a) Cl, , (b) O, , (c) N, , (1), , (d) S, , 3., , Write the name of the group containing maximum number of, gaseous elements., 4. Write general outer electronic configuration of 4f series elements., 5. Write the IUPAC symbol for the element having atomic number 120., 6. (a) Explain why cation are smaller and anions larger in radii than, their parent atoms? , (b) Define accuracy & precision. , 7., , (1), , The first ionisation enthalpy values (in kJ mol–1) of group-13, elements are :, B, Al, Ga, In, Tl, 801, 577, 579, 558, 589, , (1), (1), (1), (2), , (2), , How would you explain this deviation from the general trend?, 8. (a), , (b), , 9., , Show by a chemical reaction with water than Na2O is a basic, oxide and Cl2O7 is an acidic oxide., Name a species that will be isoelectronic with each of the, following atoms or ions. (i) F– (ii) Ca2+, , (3), , Explain the following :, (a) Shielding effect, (b) Diagonal relationship, (c) Anomalous behavior of second period elements., , 10. (a), (b), , (c), (d), 58, , Alkali metals do not form dis-positive ions. Why? , (5), Why is the IUPAC name and symbol of the element having, atomic number 117., Are the oxidation state and covalency of Al in [Al(H2O)6]2+ same?, Why are there fourteen elements in the Lanthanide series?, *****, Chemistry Class XI
Page 81 :
Chemical Bonding, and Molecular, Structure, FAST TRACK : QUICK REVISION, w Kossel-Lewis Concept: Atoms take part in chemical combination to, complete octet in their valence shell. This is known as octet rule., w Limitation of Octet Rule: The octet rule, though useful but have some, exceptions e.g. BF3, NO2, PCl5, SF6 etc., w Lewis Symbol or Electron Dot Structure: Representing valence electrons, by dots placed around the letter symbol of the element., Types of Chemical Bonds:, (i) Covalent Bond:, (a) Formed by sharing of electrons., (b) It may be polar and nonpolar., (c) It is directional in nature., (ii) Ionic Bond:, (a) Formed by transfer of electrons., (b) Formation of ionic bond is favored by high lattice enthalpy, Low, ionization enthalpy of metal atom and more negative electron gain, enthalpy of nonmetal atom., (c) It is non directional in nature., w , Formal Charge (F.C.):, (i) It is charge appeared on individual atom in covalent molecule., (ii) F.C. = (Total No. of valence electrons in free atom) – (Total No. of, unshared electrons) – ½ (Total No. of shared electrons), Greater the F.C on atoms lesser the stability of that Lewis structure., w Lattice Enthalpy: Energy released when one mole of a crystalline solid is, formed constituent gaseous ions.
Page 82 :
Bond length:, (i) It is equilibrium distance between the nuclei of two bonded atoms in, a molecule., (ii) Greater the size of bonded atoms shorter the bond length., e.g., H – F < H – Cl < H – Br < H – I, (iii) Greater the s character shorter the bond length., e.g., Csp3 – H > Csp2 – H > Csp – H >, (iv) Bond length decreases with increase in bond order., e.g., C – C > C = C > C ≡ C, w Bond angle:, (i) It is angle between the orbitals containing bonding electron pairs, around central atom in a molecule or complex ion., (ii) Greater the electronegativity of central atom larger the bond angle, e.g., NH3 > PH3, (iii) Greater the number of lone pair around central atom smaller the bond, angle. e.g., CH4 > NH3 > H2O, w Bond Enthalpy:, (i) It is defined as amount of energy required to break one mole of bonds, of a particular type between two atoms in gaseous state., (ii) For diatomic molecules, Bond enthalpy = Bond dissociation enthalpy, (iii) For polyatomic molecules, Bond enthalpy = Average of all possible, bond dissociation enthalpies., (iv) Bond enthalpy α Bond order α 1/(Bond length), w Resonance:, (i) According to the concept of resonance, whenever a single Lewis, structure cannot describe a molecule accurately, a number of structures, with similar energy, position of nuclei, bonding and non-bonding pairs, of electrons are taken as canonical structures of the resonance hybrid, which describes the molecule accurately., (ii) Resonance averages the bond characteristics as a whole., w Partial ionic character of covalent bond A – B:, , , = 16(XA – XB) + 3.5(XA – XB) 2,, , , , where XA and XB are electro-negativities of A & B., , 60, , Chemistry Class XI
Page 83 :
w, , Partial covalent character in ionic bond (Fajan’s rule):, (i) Fajan’s rule is used to predict partial covalent character in ionic bond., (ii) Gretaer the polarizing power of cation and polarisability of anion, greater the covalent character in ionic bond., (iii) Polarising power of cation α Charge density [(Charge )/Radius)]., (iv) Polarisability of anion α size of anion., , w Dipole moment:, (i) Dipole moment (μ) = charge (Q) × distance of separation (d), (ii) Unit: Debye (D), 1D = 3.33564 × 10–30 Cm, (iii) Being vector quantity, dipole moment of polyatomic molecule is, taken as the resultant of all the bond moments., (iv) If μ= 0, molecule is non polar or symmetric., (v) If μ≠ 0, molecule is polar or asymmetric., w Hydrogen bond:, (i) It is dipole-dipole interaction between molecules in which ‘H’ atom is, inserted between two highly electronegative elements i. e. F, O or N, only., (ii) Hydrogen bond may be intra-molecular (when present within single, molecule) and intermolecular (when present b/w two same or different, molecules)., (iii) Hydrogen bonds are stronger intermolecular forces than van der Waal, forces., w Sigma (σ) and pi (π) bonds:, (i) Sigma bond is formed by axial overlapping and pi bond is formed by, sideways overlapping of atomic orbitals., (ii) Sigma bond is stronger than pi bond due to greater extent of, overlapping., (iii) Single covalent bond = 1 σ bond, Double covalent bond = 1 σ bond + 1 π bond, Triple covalent bond = 1 σ bond + 2 π bond, w VSEPR Theory: (VSEPR = Valence Shell Electron Pair Repulsion): The, shape of a molecule depends upon the number of valence shell electron, pairs (lp and bp) around the central atom and magnitude of repulsive forces, between them, i.e., lp – lp > lp – bp > bp – bp, Chemical Bonding And Molecular Structure, , 61
Page 85 :
Chemical Bonding And Molecular Structure, , 63, , MIND MAP, CHEMICAL BONDING AND MOLECULAR STRUCTURE
Page 86 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Which of the following molecules has both covalent and ionic bond, (a) CH3Cl, , 2., , (b) 3, , (d) BeCl2, , (c) 4, , (d) 1, , Which of the following molecules has maximum bond angle, (a) NH3, , 4., , (c) HCl, , What is the maximum number of water molecules that can attach with one, water molecule through intermolecular hydrogen bonds?, (a) 2, , 3., , (b) NH4Cl, , (b) CH4, , (c) H2O, , (d) CO2, , Identify correct statement regarding NH3 and BF3, (a) Both are Lewis acid , (b) Both are iso structural, (c) Both are Lewis base, (d) Have different values of dipole moment, , 5., , Identify the molecule having sideways overlapping of atomic orbitals, , (a) CH4, , (b) CO2, , (c) NH3, , (d) H2O, , 6. Which of the following chemical species is most stable?, (b) O2+, , (a) O2, 7., , (b) dxz, , (c) dx2 – y2, , (d) dz2, , Which of the following molecule has net dipole moment?, , (a) CO2, 9., , (d) O22–, , Which of the following d orbitals involved in Sp3d hybridization?, , (a) dxy, 8., , (c) O2–, , (b) H2O, , (c) BF3, , (d) CH4, , Which of the following compound has highest covalent character, , (a) LiCl, , (b) LiBr, , (c) LiF, , (d) LiI, , 10. The shape of XeF4 molecule according to VSEPR theory is, (a) Square planar , , (b) Square pyramid, , (c) Tetrahedral , , (d) Pyramidal, , Ans., 64, , 1.(b), , 2.(c), , 3.(c), , 4.(d), , Chemistry Class XI, , 5.(b), , 6.(b), , 7.(d), , 8.(b), , 9.(d), , 10.(a)
Page 87 :
FILL IN THE BLANKS, (i), , The energy required to completely separate one mole of solid ionic, compound into gaseous constituent ions is called……………………., , (ii), , Among alkali metal ions ………..ion has highest polarizing power., , (iii) According to molecular orbital theory molecules are said to be stable if, the number of electrons in bonding molecular orbitals is …………… the, number of electrons in antibonding molecular orbitals., (iv) Isoelectronic molecules and ions have identical…………………., (v) In PCl5 molecule the two equivalent axial P – Cl bonds are...............than, three equivalent equatorial P – Cl bonds., (vi) The state of hybridization of sulphur in SF6 is……………………., (vii) The strongest intermolecular hydrogen bonding in water is present at…°C., (viii) A triple covalent bond consists of……sigma and…….pi bonds., (ix) ………..bond is directional in nature., (x) Atomic orbitals are……….centric and molecular orbitals are…………, centric., Ans., , (i) Lattice enthalpy (ii) Li+, (vi) sp3d2, , (vii) 4, , (iii) more (iv) bond order (v) longer, (viii) 1, 2, , (ix) covalent (x) mono, poly, , TRUE AND FALSE TYPE QUESTIONS, Write true or false for following statements:, (i), , Energy of resonance hybrid is less as compared to the contributing, canonical structures., , (ii) BeF2 has more dipole moment than BeCl2., (iii) In water two O–H bond dissociation enthalpies are not identical., (ix) Only the half filled orbitals of nearly same energy can participate in, hybridization., (v) No bond is purely ionic or purely covalent., (vi) Chemical species having identical bond order have same bond dissociation, enthalpies., Chemical Bonding And Molecular Structure, , 65
Page 88 :
(vii) BF3 is stronger Lewis acid than BCl3., (viii) Among alkali metal halides LiI has highest covalent character., (ix) Resonating structures of a chemical species have no real existence., (x) XeF2 and ICl2– are iso structural., Ans., , (i) True, , (ii) False, , (iii) False, , (iv) False, , (v) True, , (vi) False, , (vii) False, , (viii) True, , (ix) True, , (x) True, , MATCH THE COLUMNS, 1., , Match the species in Column I with the geometry/shape in Column II., Column I, (i), (ii), , PCl5, ClF3, , +, , (iii) NH4, , (iv) H3O+, 2., , Column II, (a) Tetrahedral, (b) Pyramidal, (c) Bent T shape, (d) Trigonal bipyramid, , Match the species in Column I with the type of hybrid orbitals in Column II., Column I, (i), (ii), , BF3, , H2O, , (iii) PCl5, (iv) SF6, Ans., , Column II, (a) sp3d, (b) sp2, (c) sp3d2, (d) sp3, , 1., , (i) → (d), (ii) → (c), (iii) → (a),, , (iv) → (b)., , 2., , (i) → (b), (ii) → (d), (iii) → (a),, , (iv) → (c)., , ASSERTION AND REASON TYPE QUESTIONS, In the following questions a statement of assertion (A) followed by a statement, of Reason (R) is given. Choose the correct option out of the choices given below for each question:, (i) A and R both are correct, and R is correct explanation of A., (ii) A and R both are correct, but R is not the correct explanation of A., (iii) A is true but R is false., (iv) A and R both are false., 66, , Chemistry Class XI
Page 89 :
1. Assertion (A): Among the two O – H bonds in H2O molecule, the energy, required to break the first O – H bond and the other O – H bond is the same., Reason (R): This is because the electronic environment around the oxygen, is the same even after breakage of one O – H bond., 2. Assertion (A): Though the central atom of both NH3 and H2O molecules, are sp3 hybridised, yet H – N – H bond angle is greater than that of H – O – H., Reason (R): This is because nitrogen atom has one lone pair and oxygen, atom has two lone pairs., 3. Assertion (A): SF6 molecule is unstable., Reason (R): A stable molecule must have 8 electrons around the central, atom. i.e. octet rule should be satisfied., 4. Assertion (A): Pi bond is never formed alone. It is formed along with a, sigma bond, Reason (R): Pi bond is formed by sideway overlap of p- orbitals only., 5. Assertion (A): Ionic compounds tend to be non-volatile., Reason (R): Ionic compounds are solid., Ans., , 1. (iv), , 2. (i), , 3. (iv), , 4. (iii), , 5. (ii), , ONE WORD ANSWER TYPE QUESTIONS, 1. Write the formal charge on central oxygen atom in O3 molecule?, 2. Write the shape of AB2E3 type molecule., 3. Name the property used to measure the degree of polarity., 4. Name the covalent bond formed by axial overlapping of atomic orbitals., 5. Out of px, py, pz orbitals which p orbital takes part in sp hybridization?, 6. Name the molecular orbital having energy greater than that of combining, atomic orbitals., 7. Name the intermolecular forces responsible for liquid state of water., 8. Name the phenomena used to describe a molecule whose single Lewis, structure cannot describe it., 9. Name the geometry involved in sp3d hybridization., 10. Name the molecular theory that can explain magnetic character of, molecules., Ans. 1. +1, 2. Linear,, 3. Dipole moment,, 4. Sigma bond,, 5. pz, 6. Antibonding molecular orbital, 7. Hydrogen bond, 8. Resonance,, 9. Trigonal bipyramid,, 10. Molecular orbital theory, Chemical Bonding And Molecular Structure, , 67
Page 90 :
1-MARK QUESTIONS, 1. Why noble gases exist in mono atomic form?, 2. Write the Lewis structure of NO2–., 3. Why NH3 and BF3 have different shapes?, 4. How many sigma and pi bonds are present in HCN molecule?, 5. Why sigma bond is stronger than pi bond?, 6. Explain why BeH2 molecule has zero dipole moment although the Be – H, bonds are polar?, 7. Which has highest bond angle? NO2, NO2– , NO2+, 8. What is magnetic character of anion of KO2?, 9. Why do atoms combine?, 10. What is the significance of Lewis Symbols?, 11. Why density of water is maximum at 277K?, 12. Give structure of BrF5 according to VSEPR theory., 13. Why NH3 is liquid and PH3 is a gas?, 14. Why KHF2 exist but KHCl2 and KHBr2 does not?, , [Ans. HF…HF hydrogen bonding]., 15. Boiling point of p-nitrophenol is more than O-nitrophenol why?, 16. How paramagnetic character of a compound is related to the no. of unpaired, electrons?, 17. Define the term bond length., 18. He2 molecule does not exist. Give reason., 19. Why PCl5 dissociates to give PCl3 and Cl2?, 20. Write the state of hybridization of O in H2O., 21. Predict the shape of ClF3 according to VSEPR theory., 22. Why ice has less density than water?, 23. Why the H – P – H bond angle in PH3 is less than H – N – H bond angle in, NH3?, 24. At room temperature H2O exist as liquid while H2S exist as gas. Give, reason., 25. NH3 has higher boiling point than PH3. Give reason., 26., , 68, , Identify the chemical species having identical bond order: O22+, N2, O2,, O22-., Chemistry Class XI
Page 91 :
2-MARKS QUESTIONS, 1., , What is an Octet rule? What are its limitations?, , 2., , The enthalpy needed to break the two O – H bonds in water are as follows:, , H2O (g) → H (g) + O – H(g), , ∆aH10 = 502 kJ mol–1, , O – H (g) → H (g) + O(g), , ∆aH10 = 502 kJ mol–1, , What is the average bond enthalpy of H2O?, 3. Write two points of difference between sigma and pi bond., 4., , Define Hydrogen bond. Is it weaker or stronger than van der Waal forces?, , 5., , Define dipole moment. Give its significance., , 6., , Give applications of dipole moment., , 7., , Which is more polar and why, CO2 or N2O?, , 8., , Discuss the partial ionic character of covalent bond by taking an example., , 9., , Draw the resonating structures of O3 and calculate formal charges on each, O atom., , 10., , O-Nitrophenol is steam volatile while p-Nitrophenol is not. Give reason., , 11. Define bond enthalpy. Why the bond enthalpy of F2 is less than that of Cl2?, 12., , Define resonance. Draw resonating structures of CO2., , 13., , Assign reason for the following;, , (i), (ii), 14., , NH3 is freely soluble in water while PH3 is not., B2 is paramagnetic while C2 is not., , Out of NH3 and NF3 which is more polar. Explain with the help of dipole, moment., , 15. N2 is diamagnetic while O2 is paramagnetic. Explain on the basis of, Molecular orbital theory., 16. H2+ and H2– have same bond order. Which is more stable?, 17., , Differentiate between bonding and anti bonding molecular orbitals., , 18., , Discuss the conditions for the combination of atomic orbitals to form, molecular orbitals., Chemical Bonding And Molecular Structure, , 69
Page 93 :
4., 5., , Define bond order. Calculate the bond order in N2 and O2 molecules., , Give molecular orbital energy level diagram of CO. Write its electronic, configuration,magnetic behaviour and bond order., , 6. Which of the following in each pair has larger bond angle, (i) CO2 , BF3, (ii) H2O, H2S, (iii) CH4, C2H2, 7., , What is meant by resonance? Draw the resonating structures of carbonate, ion and explain why all the C – O bond lengths are identical in carbonate, ion?, , 8., , Compare relative stability of following species and predict their magnetic, properties:, O2, O2+, O2– (superoxide), O22– (peroxide), 9., , 10., , Draw the Lewis structure of the species as mentioned below:, (i) In which the central atom has incomplete octet., (ii) In which the central atom has an expanded octet,, (iii) An odd electron molecule is formed., , Explain the structure of PCl5 according to hybridization. Why all P – Cl, bonds lengths are not equivalent in PCl5?, 5-MARKS QUESTIONS, , 1., , Give reasons for the following:, (a) NH3 has higher boiling point than PH3., (b) Ionic compounds do not conduct electricity in solid state., (c) LiCl is more covalent than KCl., (d) NH3 is more polar than NF3., (e) H2O has bent structure., , 2. (a) Define the term bond dissociation enthalpy. How is it related to bond, order?, (b) Explain why N2 has greater bond dissociation enthalpy than N2+, while O2 has lesser bond dissociation enthalpy than O2+ ?, 3., , Draw the shape of following molecules according to VSEPR theory;, , XeO3, XeF2, XeOF4, SF4, XeF4, , Chemical Bonding And Molecular Structure, , 71
Page 94 :
HOTS QUESTIONS, 1., , The bond angle of H2O is 104.5° while that of F2O is 102°., , Solution: The bond pair of electrons are drawn more towards F in F2O,, whereas in H2O it is drawn towards O. So bp – bp repulsion in H2O is, greater than that in F2O., 2., , Anhydrous AlCl3 is covalent. From the data given below, predict whether, it would remain covalent or become ionic in aqueous solution., , ∆iH (AlCl3) = 5137 kJ mol–1,, , ∆hyd H(Al3+) = –4665 kJ mol–1,, , ∆hyd H(Cl–) = –381 kJ mol–1., Solution: Total energy released = 1∆hyd H(Al3+) + 3∆hyd H(Cl–), = [(–4665) + (3 × –381)] kJ mol–1 = –5808 kJ mol–1, , , , Total energy required = ∆i H(AlCl3) = 5137 kJ mol–1, , Since energy released is greater than the energy required, the compound, will ionize in aqueous solution., 3., , The dipole moment of HCl is 1.03 D, and the bond length is 127 pm., Calculate the percent ionic character of HCl molecule., , Solution: μcal = Q × r = (1.6×10–19C) × (127×10–12m) = 2.032×10–29C m, , , , 72, , = (2.032 ×10–29C m) ×, , % ionic character =, , 1D, = 6.09 D, 3.336 × 10 —30 Cm, , 1.03D, µ obs., × 100 =, 16.9%, × 100 =, 6.09D, µ cal, , Chemistry Class XI
Page 95 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Identify the molecule having sideways overlapping of atomic orbitals [1], (a) CH4, (b) CO2, (c) NH3, (d) H2O, , 2., , The shape of XeF4 molecule according to VSEPR theory is, (a) Square planar , (b) Square pyramid, (c) Tetrahedral , (d) Pyramidal, , [1], , 3., , Write the Lewis structure of NO2–., , [1], , 4., , Which has highest bond angle? NO2, NO2–, NO2+, , [1], , 5., , Draw the resonating structures of CO2., , [1], , 6., , The enthalpy needed to break the two O – H bonds in water are as follows:, H2O(g), , —→ H(g) + O – H(g), , O – H (g) —→ H(g) + O(g), What is the average bond enthalpy of H2O?, , ∆aH10 = 502 kJ mol–1, , ∆aH20 = 427 kJ mol–1, , [2], , 7., , Out of NH3 and NF3 which is more polar. Explain with the help of, dipole moment. , , [2], , 8., , Compare relative stability of following species and predict their, magnetic properties: O2, O2+, O2– (superoxide), O22– (peroxide), , [3], , 9., , Explain the structure of PCl5 according to hybridization. Why all, P – Cl bonds lengths are not equivalent in PCl5?, , [3], , 10. (i) N2 is diamagnetic while O2 is paramagnetic. Explain on the, basis of Molecular orbital theory. , , [2], , (ii) Give reasons for the following:, (a) NH3 has higher boiling point than PH3., (b) Ionic compounds do not conduct electricity in solid state., (c) LiCl is more covalent than KCl., , [3], , *****, Chemical Bonding And Molecular Structure, , 73
Page 96 :
States of Matter :, Gases, Liquids, and Solids, FAST TRACK : QUICK REVISION, w Magnitude of Intermolecular Forces: Hydrogen bonds > van der Waal, forces (dipole-dipole > dipole-induced dipole > Dispersion forces), w Gas Laws:, (i) Boyle’s Law: V α 1/P or PV = constant, or P1V1 = P2V2 (at constant n, T), (ii) Charles’ Law: V α T or, , V1 V2, =, T1 T2, , (at constant n, P), , (iii) Avogadro’s Law: V α n (at constant T, P), (iv) Gay Lussac’s Law: P α T (at constant n, V), w Combined Gas Law:, , P1V1 P2 V2, =, T1, T2, , w Ideal Gas Equation: PV = nRT, w Values of gas constant R:, (i) 0.0821 L atm K–1 mol–1, (ii) 0.083 L bar K–1 mol–1, (iii) 8.314 J K–1 mol–1, (iv) 1.99 Cal K–1 mol–1, w Density of gas (d): d = PM/RT ( M = molar mass of gas), w Absolute zero or lowest possible temperature: –273°C or zero Kelvin,, because at this temperature volume of gas becomes zero.
Page 97 :
w Dalton’s Law of partial pressure: Ptotal = p1 + p2 + p3 +…. (at constant, T&V) for non reacting gases., w Ideal Gas: A gas which obeys ideal gas equation at all temperature and, pressure., w Boyle’s temperature: Temperature at which a real gas behaves like an, ideal gas over an appreciable range of pressure., w Compressibility factor (Z): Z = PV/nRT, (i) For ideal gas Z =1, (ii) For non ideal gas Z ≠ 1, , (a) Positive deviation (Z > 1) : shows dominance of repulsive forces, , and hence less compressibility e.g. H2, He etc., , (b) Negative deviation (Z < 1) : shows dominance of attractive forces, , and hence more compressibility e.g. CH4, CO2 etc., w Conditions under which real gases deviates from ideal behavior: Low, T and high P., w Cause of deviation from ideal behavior: At low T and high P gas molecules, are close enough and hence volume occupied by the gas molecules and, attractive forces between them cannot be negligible., w Conditions under which real gases behaves ideally: High T and low P., , , an 2 , nRT, w van der Waals’ gas equation: P + 2 ( v − nb ) =, v , , w van der Waals’ constant ‘a’:, (i) It represents magnitude of attractive forces between gas molecules., (ii) Ease of liquefaction of gas a Tc (aTc = critical temperature), and Ease of liquefaction of gas aa, (iii) Unit of ‘a’ is L2 atm mol–2, w Van der Waals’ constant ‘b’:, (i) It represents co-volume or excluded volume i.e. effective volume of, gas molecules., (ii) It is four times of actual volume of gas, (iii) Unit of ‘b’ is L2 mol–1, States of Matter: Gases, Liquids and Solids, , 75
Page 98 :
w Critical temperature: It is the temperature above which a gas can not be, liquefied however large the pressure may be., 3, nRT, 2, 3, 3, w Average Kinetic Energy of Gas = RT mol–1 or, KT molecule–1, 2, 2, (k = Boltzmann constant = R/NA), , w Total Kinetic Energy of Gas =, , w Different types of Molecular speeds:, (i) Most probable speed: Ump= √(2RT/M), (ii) Average speed: Uav = √(8RT/πM), (iii) Root mean square speed: Urms = √(3RT/M) or √(3PV/M), w (i), (ii), , Vapour pressure a T, Vapour pressure α, , (iii) Vapour pressure a, , 1, Magnitude of intermolecular forces, , 1, Boiling point, , w Surface tension: It is tangential force acting along the surface of a liquid, perpendicularly on one centimeter length of it., w Viscosity: It is internal resistance to the flow possessed by a liquid., w Increase in temperature decreases surface tension and viscosity of liquid., , 76, , Chemistry Class XI
Page 99 :
MIND MAP : STATES OF MATTER, , States of Matter: Gases, Liquids and Solids, , 77
Page 100 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Which of the following property explains the spherical shape of rain, droplets:, (a) Viscosity , (b) Critical phenomena, (c) Surface tension , (d) Pressure, 2. A gas would be most likely to obey the ideal gas law at, (a) Low T and high P, (b) High T and high P, (c) Low T and low P , (d) High T and low P, 3. If P is the pressure and d is the density of gas, then P and d are related as:, (a) P α 1/d, (b) P α d, (c) P α d2, (d) P α 1/d2, 4. A gas can be liquefied, (a) above its critical temperature, (b) at its critical temperature, (c) below its critical temperature, (d) at any temperature, 5. Which of the following gas is expected to have highest value of Van der, Waal’s constant ‘a’, (a) NH3, (b) H2, (c) N2, (d) He, 6. The compressibility factor (Z) for an ideal gas is:, (a) 1.5, (b) 1.0, (c) 2.0, (d) zero, 7. Two separate bulbs contain ideal gas A and B. The density of A is twice, that of B.The molecular mass of A is half that of B. If the two gases are at, the same temperature, the ratio of pressure of A to that of B is:, (a) 2, (b) 1/2, (c) 4, (d) 1/4, 8. At which temperature the volume of a gas is expected to be zero., (a) 0 °C, (b) 273 K, (c) –273°C, (d) 273°C, 9. Dominance of strong attractive forces among the molecules of the gas:, (a) Depends on Z and indicates that Z=1, (b) Depends on Z and indicates that Z >1, (c) Depends on Z and indicates that Z < 1, (d) Is independent of Z, 10. Which of the following properties of liquid increases on increasing, temperature:, (a) Vapour pressure , (b) Viscosity, (c) Surface tension , (d) Boiling Point, Ans. 1.(c), 2.(d), 3.(b), 4.(c), 5.(a), 6.(b), 7.(c), 8.(c), 9.(c),, 78, , Chemistry Class XI, , 10.(a)
Page 101 :
FILL IN THE BLANKS, 1., 2., 3., 4., 5., 6., 7., 8., 9., 10, Ans., , , , Pressure vs volume graph at constant temperature is known as…………, Surface tension of a liquid ……………with increase in magnitude of, intermolecular forces., …………. is the temperature at which a real gas behave like an ideal gas, over appreciable range of pressure., Z > 1 indicates that the gas is ………….. compressible than expected from, ideal gas behavior., The average kinetic energy of gas molecules is directly proportional to, the………., Internal resistance in flow of liquids is called…………………, ……………… is the temperature above which a gas cannot be liquefied, however large the pressure may be., Poise (P) is the unit of …………….., The vapour pressure of any liquid is ……………. proportional to the, magnitude of the intermolecular forces and is ………….. proportional to, the temperature employed., Van der Waal constant………… represent co-volume and ……….., represent magnitude of attractive forces., 1. Isotherm, 2. increases 3. Boyle’s temperature 4. less, 5. Kelvin temperature 6. viscosity 7. critical temperature, 8. viscosity, 9. inversely, directly 10. ‘b’, ‘a’, TRUE AND FALSE TYPE QUESTIONS, , Write true or false for following statements:, 1. At a given temperature and pressure the density of N2 is more than that of, O2., 2. Liquid at higher altitudes boil at a lower temperature., 3. Gases having Z < 1 cannot be liquefied easily., 4. According to the kinetic molecular theory, the collision between gas, molecules is perfectly elastic., 5. Real gases deviate from ideal behavior at low temperature and high, pressure., 6. A gas can be liquified above its critical temperature by applying high, pressure., States of Matter: Gases, Liquids and Solids, , 79
Page 102 :
7., 8., 9., 10., , Mosquito cannot walk on kerosene oil because its surface tension is less, than that of water., No gas is ideal gas, all gases are real gases., Surface tension increases on increasing temperature., 0°C is known as absolute zero temperature., , Ans. 1. False, , 2. True, , 3. False, , 4. True, , 5. True, , 6. False, , 7. True, , 8. True, , 9. False, , 10. True, , MATCH THE COLUMNS, 1., , Column-I , , (i) Boyle’s Law, (a), , (ii) Charle’s Law, (b), , (iii) Dalton’s Law, (c), , (iv) Avogadro Law, (d), 2., , Column-I , , (i) Critical Temperature (a), , (ii) Vapour Pressure, (b), , (iii) Viscosity, (c), , (iv) Surface Tension, (d), , Column-II, V a n at constant T & P, Ptotal = p1 + p2 + p3 + ….at constant T&V, V a T at constant n & p, p a 1/V at constant n & P, Column-II, Boiling Point, Spherical shape of water droplet, Liquefaction of gases, Flow of Liquids, , Ans. 1. (i) → (d), (ii) → (c), (iii) → (b), (iv) → (a). , 2. (i) → (c), (ii) → (a), (iii) → (d), (iv) → (b)., ASSERTION AND REASON TYPE QUESTIONS, In the following questions a statement of assertion (A) followed by a, statement of Reason (R) is given. Choose the correct option out of the, choices given below for each question., (i), A and R both are correct, and R is correct explanation of A., (ii) A and R both are correct, but R is not the correct explanation of A., (iii) A is true but R is false., (iv) A is false but R is true., 1. Assertion (A): Gases do not liquefy above their critical temperature even, on applying high pressure., Reason (R): Above critical temperature, the molecular speed is high and, intermolecular attractions can not hold the molecules together because the, escape because of high speed., 80, , Chemistry Class XI
Page 103 :
2., , Assertion (A): At constant temperature, pV vs V plot for real gases is not a, straight line., Reason (R): At high pressure all gases have Z >1 but at intermediate, pressure most gases have Z <1., 3., , Assertion (A): At zero degree Kelvin,the volume occupied by a gas is, negligible., Reason (R): All molecular motion ceases at 0 K., 4. Assertion (A): CO2 has stronger intermolecular forces than CH4., Reason (R): Critical temperature of CO2 is more., 5., , Assertion (A): Lower the critical temperature of the gas, more easily can it, be liquefied., Reason (R): Critical temperature is the temperature above which a gas can, not be liquefied depending upon the pressure., Ans. 1. (i), , 2. (ii), , 3. (iii), , 4. (i), , 5. (iv), , ONE WORD ANSWER TYPE QUESTIONS, 1., , Write SI unit of pressure., , 2., , Write the value of lowest possible temperature., , 3., , Write the value of compressibility factor Z for ideal gas., , 4., , Write the unit of van der Waal constant which represent the magnitude of, attractive forces between gas molecules., , 5., , Name the gas law which relates volume and pressure of gas at constant, temperature., , 6., , Name the property responsible for spherical shape of water droplets., , 7., , Name the property which opposes the flow of liquids., , 8., , Two liquids A and B have vapour pressures 400 mm Hg and 450 mm Hg, respectively at a given temperature. Which liquid has higher boiling point?, , 9., , Critical temperature of N2 and O2 are 126 K and 154.3 K respectively., Which gas has greater magnitude of attractive forces?, , 10, , Mention the volume occupied by one mole of an ideal gas at STP., , Ans. 1. Pascal, , 2. –273°C, , 6. Surface tension, , 3. Z = 1, , 7. Viscosity, , 4. L2 atm mol–2, 8. Liquid A, , 5. Boyle’s law, , 9. O2, , 10. 22.7 L, , States of Matter: Gases, Liquids and Solids, , 81
Page 104 :
1-MARK QUESTIONS, 1. Define Dalton’s law of partial pressure of gases., 2. State Boyle’s law., 3. Write van der Waal equation for n mol of gas., 4. Write the conditions in terms of temperature and pressure under which, gases deviate from ideal behavior., 5. Write the relation between pressure and density of gas., 6. Write relation between average kinetic energy and temperature of a gas., 7. Define the term absolute zero., 8. In terms of Charles’ law explain why –273°C is known as lowest, temperature?, 9. Write SI unit for quantity (PV2 T2)/n2., 10. Define the term Critical temperature., 11. Define Boyle’s temperature., 12. Define surface tension., 13. What is the value of normal boiling point and standard boiling point of, water?, 14 At a particular temperature vapour pressure of ethanol is more than that of, water. Give reason., 15 Why vegetables are cooked with difficulty at a hill station?, 2-MARKS QUESTIONS, 1., 2., , Name the intermolecular forces present in: (i) H2O (ii) HCl, Critical temperature for carbon dioxide and methane are 31.1°C and, –81.9℃ respectively. Which of these has stronger intermolecular forces, and why?, 3. Explain the significance of van der Waal parameters., 4. A gas occupies 300 ml at 27°C and 730 mm pressure what would be its, volume at STP. , [Ans. 262.2 L], 5. Calculate the temperature at which 28g N2 occupies a volume of 10 litre at, 2.46 atm., [Ans. 299.6 K], 6. Compressibility factor, Z of a gas is given as Z = PV/nRT, (i) What is the value of Z for an ideal gas?, (ii) For real gas, what is the value of Z above Boyle’s temperature?, [Ans. (i) Z = 1 (ii) Z > 1], 82, , Chemistry Class XI
Page 105 :
7., , What will be the minimum pressure required to compress 500 dm3 of air at, 1 bar to 200 dm3 at 30°C. , [Ans. 2.5 bar], , 8., , Calculate the volume occupied by 8.8 g of CO2 at 31.1℃ and 1 bar pressure., R = 0.083 L bar K–1 mol–1., , [Ans. 5.05 L], , 9., , Calculate the temperature of 4 mol of a gas occupying in 5 dm3 at 3.32 bar., R = 0.083 bar dm3 K–1 mol–1. , [Ans. 50K], , 10, , The pressure of the atmosphere is 2 × 10–6 mm at about 100 mile from the, earth and temperature is – 180°C. How many moles are there in 1 mL gas, at this attitude?, [Ans. 3.45 × 10–13 mol], , 11., , Calculate average kinetic energy of CO2 molecules at 27°C., , [Ans. 3741.3 J mol–1], , 12., , Calculate root mean square speed of methane molecules at 27°C., [Ans. 6.84 × 104 cm s–1], , 13., , Name two phenomena that can be explained on the basis of surface tension., , 14., , The van der Waal constants of two gases are as follows:, Gas, A, B, , a (atm L mol–1), 1.39, 3.59, , b (L mol–1), 0.0391, 0.0427, , Which of them is more easily liquefiable and which has greater molecular, size?, 15., , Critical temperatures of NH3 and SO2 are 405.0 and 430.3 K respectively:, (i) Which one is easily liquefiable?, (ii) Which has higher value of van der Waal constant ‘a’?, 16. Arrange the following in the order of property indicated for each set:, (i) H2O, NH3, HCl, H2 (increasing magnitude of intermolecular forces), (ii) O2, H2, CO2, SO2 (ease of liquefaction), , (iii) O2, He, CO2, NH3 (decreasing critical temperature), , (iv) O2, He, CO2, CH4 (increasing value of van der Waal constant ‘a’), 17. Arrange Water, ethanol, ether and glycerine in the order of property given, below:, (i) increasing order of vapour pressure, (ii) increasing order of boiling point, (iii) decreasing order of surface tension, (iv) increasing order of viscosity, States of Matter: Gases, Liquids and Solids, , 83
Page 106 :
3-MARKS QUESTIONS, 1., , Explain the terms:, , (i) Viscosity, , (ii) Vapour pressure, , (iii) Boiling point temperature, , 2., , Calculate the total pressure in a mixture of 8 g of dioxygen and 4 g of, dihydrogen confined in a vessel of 1 dm3 at 27℃. [Ans. 56.025 bar], , 3., , What will be the pressure exerted by a mixture of 3.2 g of methane and 4.4, g of carbon dioxide contained in a 9 dm3 flask at 27°C . [Ans. 0.82 atm], , 4., , Pressure of one gram of an ideal gas A at 27°C is found to be 2 bar., When 2 g of another ideal gas B is introduced in the same flask at same, temperature, the pressure becomes 3 bar. Find the relationship between, their molar masses., , [Ans. MB = 4MA], , 5., , A 20g chunk of dry ice is placed in an empty 0.75 litre wire bottle tightly, closed what would be the final pressure in the bottle after all CO2 has been, evaporated and temperature reaches to 25°C?, , [Ans. Pressure inside the bottle = P + atm pressure = 14.828 + 1 = 15.828 atm], 6., , A gas at a pressure of 5 atm is heated from 0°C to 546°C and is simultaneously, compressed to one third of its original volume. Find the final pressure of, the gas., , [Ans. 45 atm], , 7., , Calculate the compressibility factor for CO2, if one mole of it occupies 0.4, litre at 300K and 40 atm. Comment on the result., , [Ans. 0.65, since Z < 1, CO2 is more compressible than ideal gas], 8., , Find the pressure of 4 g of O2 and 2 g of H2 confined in a bulb of 1 L at, 0°C. [Ans. 25.215 atm], 5-MARKS QUESTIONS, , 1., , Mention the intermolecular forces present between:, , (i), , H2O and C2H5OH, , (ii), , Cl2 and CCl4, , (iii) He and He atoms, (iv) Na+ ion and H2O, (v), , 84, , HBr and HBr, , Chemistry Class XI
Page 107 :
2. (i) For Dalton’s law of partial pressure derive the expression, , Pgas = Xgas . Ptotal, (ii) A 2L flask contains 1.6 g of methane and 0.5 g of hydrogen at 27 ℃., Calculate the partial pressure of each gas the mixture and calculate the, total pressure., [Ans. PCH = 1.23 atm, PH = 3.079 atm, Ptotal = 4.31 atm], 3., , 4, , 2, , Using van der Waal’s equation calculate the constant ‘a’ when 2 mole of a, gas confined in a 4 L flask exerts a pressure of 11.0 atm at a temperature of, 300K. The value of ‘b’ is 0.05 L mol–1., [Ans. 6.49 atm L2 mol–2], HOTS QUESTIONS, , 1. A mixture of CO and CO2 is found to have density of 1.50 g L–1 at 20 ℃ , and 740 mm pressure. Calculate the composition of mixture., Solution:, Let the mol % of CO in mixture = x, ∴ mol % of CO2 = (100 – x), ∴ Average molecular mass =, ∴, , , , [(x × 28)+ (100 — x) × 24], 100, , [(x × 28)+ (100 — x) × 24] =, dRT, dRT , , Because, M =, 100, , P, , , , , , P , , (x × 28)+ (100 — x) × 24, 293K, =, =, 1.50gL—1 × 0.0821 L atm K —1mol —1 ×, 100, 100 , , ∴ mol % of CO = 43.38 and mol % of CO2 = (100 – x), , , = 100 – 43.38 = 56.62, , 2., , A cylindrical balloon of 21 cm diameter is to be filled up with H2 at NTP, from a cylinder containing the gas at 20 atm at 27°C. The cylinder can hold, 2.82 litre of water at NTP. Calculate the number of balloons that can be, filled up., Solution:, Volume of 1 balloon which has to be filled = 4/3 π (21/2)3, , , = 4851 mL = 4.851 litre, , Let n balloons be filled, then volume of H2 occupied by balloons = 4.851 × n, Also, cylinder will not be empty and it will occupy volume of H2 = 2.82 litre., States of Matter: Gases, Liquids and Solids, , 85
Page 109 :
UNIT TEST, , Time Allowed: 1 hr, Maximum Marks : 20, General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1. If P is the pressure and d is the density of gas, then P and d are related as:, (a) P α 1/d, (b) P α d, [1], 2, 2, (c) P α d , (d) P α 1/d, 2. At which temperature the volume of a gas is expected to be zero., (a) 0°C , (b) 273 K, (c) –273 °C, (d) 273°C, , [1], , 3., , Define Boyle’s temperature., , [1], , 4., , Write van der Waal equation for n mol of gas., , [1], , 5., , Why vegetables are cooked with difficulty at a hill station?, , [1], , 6. A gas occupies 300 ml at 27°C and 730 mm pressure what would, be its volume at STP., , , [2], , 7. Compressibility factor, Z of a gas is given as Z = PV/nRT, [2], (i) What is the value of Z for an ideal gas?, (ii) For real gas, what is the value of Z above Boyle’s temperature?, 8., , Pressure of one gram of an ideal gas A at 27°C is found to be 2 bar. [3], When 2 g of another ideal gas B is introduced in the same flask at, same temperature, the pressure becomes 3 bar. Find the relationship, between their molar masses., 9., , Calculate the total pressure in a mixture of 8 g of dioxygen and, [3], 4 g of dihydrogen confined in a vessel of 1 dm3 at 27°C ., R = 0.083 bar dm3 K–1 mol–1, 10. (a) Critical temperatures of NH3 and SO2 are 405.0 and 430.3 K, , respectively: , [2], (i) Which one is easily liquefiable?, , (ii) Which has higher value of van der Waal constant ‘a’?, (b) Explain the terms: , [3], , (i) Viscosity (ii) Vapour pressure (iii) Boiling point temperature, *****, States of Matter: Gases, Liquids and Solids, , 87
Page 110 :
Chemical, Thermodynamics, FAST TRACK : QUICK REVISION, w System: Specific part of universe in which observations are made., w Surroundings: Everything which surrounds the system., w Types of the System:, Open System: Exchange both matter and energy with the surroundings., For example – Reactant in an open test tube., Closed System: Exchange energy but not matter with the surroundings., For example – Reactants in a closed vessel., Isolated System: Neither exchange energy nor matter with the surroundings., For example – Reactants in a thermos flask., w Thermodynamic Processes:, (i) Isothermal Process: ∆T = 0, (ii) Adiabatic process: ∆q = 0, (iii) Isobaric process: ∆P = 0, (iv) Isochoric process: ∆V = 0, (v) Cyclic process: ∆U = 0, (vi) Reversible process: Process which proceeds infinitely slowly by a, series of equilibrium steps., (vii) Irreversible process: Process which proceeds rapidly and the system, does not have chance to achieve equilibrium., w Extensive Properties: Properties which depend upon the quantity or size, of matter present in the system. For example – mass, volume, internal, energy, enthalpy, heat capacity, work, etc., 88, Chemical, Thermodynamics
Page 111 :
w Intensive Properties: Properties which do not depend upon the quantity, or size of matter present in the system. For example – temperature, density,, pressure, surface tension, viscosity, refractive index, boiling point, melting, point etc., w State Functions: The variables of functions whose value depend only on, the state of a system or they are path independent., For example – pressure (P), volume (V), temperature (T), enthalpy (H),, free energy (G), internal energy (U), entropy (S), amount (n) etc., w Internal Energy: It is the sum of all kind of energies possessed by the, system., w First Law of Thermodynamics: “The energy of an isolated system is, constant.”, Mathematical Form: ∆U = q + w, w Sign Conventions for Heat (q) and Work (w):, (i) W = + ve , if work is done on system, (ii) W = – ve , if work is done by system, (iii) q = + ve , if heat is absorbed by the system, (iv) q = – ve , if heat is evolved by the system, w Work of Expansion/ compression: w = –Pext (Vf – Vi), w Work done in Isothermal Reversible Expansion of an Ideal Gas:, , , wrev = –2.303 nRT log Vf / Vi, , or, , wrev = –2.303 nRT log Pi / Pf, , w Significance of ∆H & ∆U: ∆H = qp and ∆U = qv, w Relation between ∆H & ∆U: ∆H = ∆U + (np – nr)RT for gaseous reaction, (i) ∆H = ∆U if (np – nr) is zero; e.g. H2 (g) + I2 (g) —→ 2 HI(g), (ii) ∆H > ∆U if (np – nr) is positive; e.g. PCl5 (g) —→ PCl3 (g) + Cl2 (g), (iii) ∆H < ∆U if (np – nr) is negative; e.g. N2 (g) + 3H2 (g) —→ 2NH3 (g), w Heat Capacity (C): Amount of heat required to raise the temperature of a, substance by 1°C or 1 K., , q = C ∆T, Chemical Thermodynamics, , 89
Page 112 :
w Specific Heat Capacity (Cs): Amount of heat required to raise the, temperature of 1 g of a substance by 1°C or 1 K., , q = Cs × m × ∆T, w Molar Heat Capacity (Cm): Amount of heat required to raise the, temperature of 1 mole of a substance by 1°C or 1 K., , q = Cm × n × ∆T, w, , Standard State of a Substance: The standard state of a substance at a, specified temperature is its pure form at 1 bar., , w Standard Enthalpy of Formation(∆f Ho): Enthalpy change accompanying, the formation of one mole of a substance from its constituent elements, under standard condition of temperature (normally 298 K) and pressure, (1bar)., • ∆f H0 of an element in standard state is taken as zero., •, •, , Compounds with –ve value of ∆f H0 more stable than their constituents., , ∆rH0 = ∑ai ∆f H0 (products) – ∑bi ∆f H0 (reactants) ; Where ‘a’ and ‘b’, are coefficients of products and reactants in balanced equation., , w Standard Enthalpy of Combustion(∆cH0): Enthalpy change accompanying the complete combustion of one mole of a substance under, standard conditions ( 298 K, 1bar), w Hess’s Law of Constant Heat Summation: The total enthalpy change, of a reaction remains same whether it takes place in one step or in several, steps., w Bond Dissociation Enthalpy: Enthalpy change when one mole of a, gaseous covalent bond is broken to form products in gas phase., For example, Cl2 (g) —→ 2Cl(g); ∆Cl – Cl H0 = 242 kJ mol–1, •, , For diatomic gaseous molecules; Bond enthalpy = Bond dissociation, Enthalpy = Atomization Enthalpy, , •, , For Polyatomic gaseous molecules; Bond Enthalpy = Average of the, bond dissociation enthalpies of the bonds of the same type., , •, , ∆r H0 = ∑∆bond H0 (Reactants) – ∑∆bond H0 (Products), , w Spontaneous Reaction: A reaction which can take place either an its own, or under some initiation., 90, , Chemistry Class XI
Page 113 :
w Entropy(S): It is measure of degree of randomness or disorder of a system., ( q rev )sys DHsys, DS=, =, •, sys, DT, DT, •, , Unit of Entropy = JK–1 mol–1, , w Second Law of Thermodynamics: For all the spontaneous processes, totally entropy change must positive., , , ∆Stotal = ∆Ssys + ∆Ssurr > 0, , w Gibbs Helmholtz Equation for determination of Spontaneity:, , , ∆G = ∆H – T∆S, , (i) If ∆G = –ve, the process is spontaneous, (ii) If ∆G = +ve, the process is non-spontaneous, (iii) If ∆G = 0, the process is in equilibrium, w Relation between Gibbs Energy Change and Equilibrium Constant:, , , ∆Go = –2.303 RT logKc, , w Third Law of Thermodynamics: The entropy of a perfectly crystalline, solid at absolute zero (0 K) is taken to be zero., , Chemical Thermodynamics, , 91
Page 114 :
92, , Chemistry Class XI, , MIND MAP : CHEMICAL THERMODYNAMICS
Page 115 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Which one of the following thermodynamic quantities is not a state, function?, (a) Gibbs free energy, (b) Enthalpy, (c) Entropy, (d) Work, 2., , All of the following have a standard heat of formation value of zero at, 25°C and 1.0 atm except:, (a) N2 (g), (b) Fe(s), (c) Ne (g), (d) H(g), 3., , For the following reaction at 25°C, DH° = +115 kJ and DS° = +125 J/K., Calculate DG° for the reaction at 25℃ :, , SBr4(g) ___→ S(g) + 2Br2(l), (a) +152 kJ, (c) +77.8 kJ., , (b) –56.7 kJ, (d) +37.1 kJ, , 4. Calculate DrH0 for the following reaction at 25°C :, , Fe3O4(s) + CO(g) ___→ 3FeO(s) + CO2(g), DHfo (kJ/mol) –1118, –110.5, –272, –393.5, (a) –263 kJ, (c) 19 kJ., , (b) 54 kJ, (d) –50 kJ, , 5., , A system suffers an increase in internal energy of 80 J and at the same time, has 50 J of work done on it. What is the heat change of the system?, (a) +130 J, (b) +30 J, (c) –130 J, (d) –30 J, 6. The DH0 for the following reaction at 298 K is –36.4 kJ., , 1/2 H2 (g) + 1/2 Br2 (l) ___→ HBr(g), Calculate DU0 at 298 K. The universal gas constant, R, is 8.314 J/mol K., (a) –35.2 kJ, (b) +35.2 kJ, (c) –36.4 kJ, (d) –37.6 kJ., 7., , For which of the following reactions would the Ho for the reaction be, labeled DHf0 ?, (a) Al(s) + 3/2 H2 (g) + 3/2 O2 (g) ___→ Al(OH)3(s), (b) PCl3 (g) + 1/2 O2 (g) ___→ POCl3 (g), Chemical Thermodynamics, , 93
Page 116 :
(c) 1/2 N2O (g) + 1/4 O2 (g) ___→ NO (g), (d) CaO(s) + SO2 (g) ___→ CaSO3(s), , 8. Which statement is ture for reaction? 2H2 (g) + O2 (g) ___→ 2H2O (g), (a) S = +ve, (b) H > U, (c) H < U, (d) H = U, 9., , The heat of combustion of yellow phosphorous is –9.91 KJ and the red, phosphorous is –8.78 KJ. The heat of transition of yellow phosphorous to, red phosphorous is :, (a) –9.91 kJ, (b) –8.78 kJ, (c) –9.34 kJ, (d) –1.13 kJ, 10. Entropy of universe is :, (a) Increasing, (c) Constant, , (b) decreasing, (d) None of these, , 11. Which is state function?, (a) q , (c) q + w (d), , (b) w, None of these, , 12. According to second law of thermodynamics, (a) ∆Stotal = +ve, (b) ∆Stotal = –ve, (c) ∆Ssystem = +ve, (d) ∆Ssystem = –ve, Ans: 1.(d), 2.(d), 3.(c),, 4.(c),, 5.(b),, 8. (a), 9.(d), 10.(c), 11.(d), 12.(a),, , 6.(d), 7.(a),, 13.(c), 14.(a), , FILL IN THE BLANKS, (i), , ……… is a measure of the degree of randomness or disorder of a system., , (ii), , A process which can take place either of its own or under some initiation, is known as ……………….., , (iii) For evaporation of water the sign of ∆H is….…. and sign of ∆S is…..…, (iv) The entropy of a perfectly crystalline solid is zero at ……….., (v), , The heat energy exchanged between the system and surroundings at, constant temperature and pressure is known as……....…, , (vi) ………… is the quantity of heat needed to raise the temperature of one, mole of a substance by 1o, (vii) Cp – Cv = ..............…, 94, , Chemistry Class XI
Page 117 :
(viii) ….......... = ∆H – T∆S., (ix) According to ………. law of thermodynamics, ∆Stotal = + ve., (x), , If ∆H = +ve and ∆S = +ve, the reaction is spontaneous at ……... temperature, , Ans: (i) Entropy, (ii) spontaneous, (iii) +ve, +ve, (v) Enthalpy (vi) molar heat capacity (vii) R, (ix) second, (x) high, , (iv) –273℃, (viii) ∆G, , TRUE AND FALSE TYPE QUESTIONS, Write true or false for following statements:, (i), , For every chemical reaction at equilibrium ∆G0 is zero., , (ii), , Entropy is not a state function because its value depends upon the condition, of temperature and pressure., , (iii) During isothermal expansion of an ideal gas, there is no change in internal, energy., (iv) q and w are not state function but q+w is a state function., (v), , The enthalpy of neutralization of a strong acid by a strong base is always, constant., , (v), , For a spontaneous process ∆Ssystem= +ve., , (vii) The energy of universe is conserved while its entropy is increasing., (viii) Volume is extensive property while temperature is intensive property., (ix) At 0°C the entropy of a perfectly crystalline solid is zero., (x), , Hess’ law is a corollary of the first law of thermodynamics., , Ans: (i) False, (vi) False, , (ii) False, (vii) True, , (iii) True, (iv) True, (viii) True (ix) False, , (v) True, (x) True, , MATCH THE COLUMNS, 1. , , Column I , , Column II, , (i), , State function, , (a), , Pressure, , (ii), , Extensive property, , (b), , Work, , (iii) Intensive property, , (c), , q+w, , (iv) Path function, , (d), , Heat capacity, , Chemical Thermodynamics, , 95
Page 118 :
2., , , Column I Column II, , (i), , ∆H = +ve; ∆S = +ve, , (a), , Spontaneous at all temperatures, , (ii), , ∆H = –ve; ∆S = +ve, , (b), , Non-spontaneous at all temperatures, , (iii) ∆H = +ve; ∆S = –ve, , (c), , Non-spontaneous at high temperature, , (iv) ∆H = –ve; ∆S = –ve, , (d), , Spontaneous at high temperature, , Ans: 1. (i) → (c), (ii) → (d), (iii) → (a), (iv) → (b)., 2. (i) → (d), (ii) → (a), (iii) → (b), (iv) → (c)., ASSERTION AND REASON TYPE QUESTIONS, In the following questions a statement of assertion (A) followed by a statement, of Reason (R) is given. Choose the correct option out of the choices given below, for each question., (i) A and R both are correct, and R is correct explanation of A., (ii) A and R both are correct, but R is not the correct explanation of A., (iii) A is true but R is false., (iv) A and R both are false., 1. Assertion (A): Enthalpy of graphite is lower than that of diamond., Reason (R): Entropy of graphite is greater than that of diamond., 2., , Assertion (A): Enthalpy of formation of H2O(l) is greater than that of, H2O(g)., Reason (R): Enthalpy change is negative for condensation reaction, H2O(g), H2O(l), 3. Assertion (A): ∆H and ∆U are same for the reaction N2(g) + O2(g) ___→ 2NO(g), Reason (R): All the reactants and products are gases., Assertion (A): if both ∆H0 and ∆S0 are positive than the reaction will be, spontaneous at high temperature, Reason (R): All processes with positive entropy change are spontaneous., 4., , 5., , Assertion (A): Enthalpy of formation of HCl is equal to bond energy of, HCl., Reason (R): Enthalpy of formation and bond energy both involve the, formation of one mole of HCl from the elements., Ans: 1. (ii), 96, , 2. (i), , 3. (ii), , Chemistry Class XI, , 4. (iii), , 5. (i)
Page 119 :
ONE WORD ANSWER TYPE QUESTIONS, 1., , ‘w’ amount of work is done by the system and ‘q’ amount of heat is supplied, to the system. What type of system would it be?, , 2., , What is the work done in free expansion of an ideal gas?, , 3., , What is the sign of ∆GO for spontaneous reaction?, , 4., , Write the relation between ∆H and ∆U for H2 (g) + I2 (g) → 2HI (g)., , 5., , Write the SI unit of entropy., , 6., , Name the calorimeter used to measure∆U., , 7., 8., , What is the standard enthalpy of formation of graphite?, What is the sign of DH for H (g) ___→ 2H (g)?, , 9., , If Kc = 1, what will be the value of DG?, , 10., , 2, , An exothermic reaction is spontaneous at all temperature. What is the sign, of S?, , Ans: 1. Closed system 2. W = 0 3. ∆G = –ve 4. ∆H = ∆U, 6. Bomb calorimeter 7. Zero 8. ∆H = –ve 9. Zero, , 5. J K–1 mol–1, 10. ∆S = +ve, , 1-MARK QUESTIONS, 1. Day temp Name the thermodynamic system to which following belong:, (i) Human body, , (ii) Milk in Thermos flask, , (iii) Tea in steel kettle, , 2., , Identify State functions out of the following: Enthalpy, Entropy, Heat,, Temperature, Work, Free energy, , 3., , Give two examples of state functions., , 4., , Write the mathematical statement of first law of thermodynamics., , 5., , Predict the internal energy change for an isolated system?, , 6., , Why ∆H is more significant than ∆U?, , 7., , Write one example each of extensive and intensive properties., , 8., , Write a chemical equation in which ∆H and ∆U are equal., , [Ans. Zero], , 9 Write the relationship between ∆H and ∆U for the reaction:, , C(s)+ O2(g) ___→ CO2(g), 10., , Define standard enthalpy of formation., Chemical Thermodynamics, , 97
Page 120 :
11., , Why is the standard enthalpy of formation of diamond not zero although it, is an element?, , 12. The enthalpy of atomization of CH4 is 1665 kJ mol–1. What is the bond, enthalpy of C – H bond? , [Ans. 416.25 kJ], 13., , Identify the species for which ∆f Hθ = O3, at 298 K; Br2, Cl2, CH4 ., , [Hint: Cl2 (Br2 is liquid at 298K)], 14. For the reaction 2Cl(g) ___→ Cl (g) ; what are the sign of ∆H and ∆S ?, 2, , 15., , For an isolated system ∆U= 0, what will be ∆S ?, , 16., , Why entropy of steam is more than that of water at its boiling point?, , 17., , Out of Diamond and Graphite which has higher entropy?, , 18., , Write an example of endothermic spontaneous reaction., , 19., , State second law of thermodynamics., , 20., , State third law of thermodynamics., , 21., , Which has more entropy? 1 mol H2 O(l) at 25°C or 1 mol H2O(l) at35°C., , 22., , At what temperature the entropy of a perfectly crystalline solid is zero?, , 23., , For a certain reaction ∆Gθ = 0,what is the value of Kc?, , 24., , How can a non spontaneous reaction be made spontaneous?, , 25., , For a reaction both ∆H and ∆S are negative. Under what conditions does, the reaction occur., 2-MARKS QUESTIONS, , 1. In a process 701 J of heat is absorbed by a system and 394 J work is done, by the system. What is the change in internal energy for the process?, [Ans. 307 J], 2., , Neither q nor w is state functions but q + w is a state function. Explain., , 3. Classify the following as extensive or intensive properties : Heat capacity, Density, Temperature, Molar heat capacity., 4., , Derive the relationship between ∆H and ∆U., , 5., , Derive the relationship Cp – Cv = R., , 6. A 1.25g sample of octane (C8H18) is burnt in excess of oxygen in a bomb, calorimeter. The temperature of the calorimeter rises from 294.05 to, 98, , Chemistry Class XI
Page 121 :
300.78K.If heat capacity of the calorimeter is 8.93 kJ K–1. Find the heat, transferred to calorimeter., , [Ans. 0.075 kJ], 7. Show that for an ideal gas, the molar heat capacity under constant volume, conditions is equal to 3/2 R., 8., , Expansion of a gas in vacuum is called free expansion. Calculate the work, done and change in internal energy when 1 mol of an ideal gas expands, isothermally from I L to 5 L into vacuum., , 9., , State and explain Hess’s Law of Constant Heat Summation with a suitable, example., , 10., , Derive the relationship between ∆H and ∆U., Given, N2(g) + 3H2(g) ___→ 2NH3(g); ∆r Hq = –92.4 kJ mol–1;, , What is the standard enthalpy of formation of NH3 gas?, [Ans. –46.2 kJ mol–1], 11., , Calculate the enthalpy change for the reaction:, H2(g) + Br2(g) ___→ 2 HBr(g)., Given the bond enthalpies H2, Br2 and HBr are 435 kJ mol–1, 192 kJ mol–1, and 368 kJ mol–1 respectively. , [Ans. –109 kJ mol–1], 12., , Is the bond dissociation enthalpy of all the four C – H bonds in CH4 same?, Give reason in support of your., , 13., , Define the term entropy. Write its unit. How does entropy of a system, change on increasing temperature?, , 14., , Dissolution of ammonium chloride in water is endothermic but still it, dissolves in water readily. Why?, , 15., , Calculate the entropy change in the surroundings when 1.00 mol of H2O(l), is formed under standard conditions; ∆f Hθ = –286 kJ mol–1., [Ans. 959.7 J K–1 mol–1], , 16., , The enthalpy of vaporization of a liquid is 30 kJ mol–1 and entropy of, vaporization is 75 J K–1 mol–1. Calculate the boiling point of liquid at, 1 atm., , [Ans. 400 K], , 17., , The equilibrium constant for a reaction is 10.What will be the value of, ∆Gθ? R = 8.314J K–1 mol–1, T = 300K., [Ans. –5.527 kJ mol–1], , 18., , Derive the relationship, ∆G = –T∆Stotal for a system., Chemical Thermodynamics, , 99
Page 123 :
9., , Calculate the standard enthalpy of formation of CH3OH(l) from the, following data:, CH3OH (l) + 3/2 O2 (g) ___→ CO2 (g) + 2H2O (l); ∆cHθ = –726 kJ mol–1, C (g) + O (g) ___→ CO (g); ∆ Hθ = –393 kJ mol–1, 2, , 2, , f, , H2(g) + 1/2 O2 (g) ___→ H2O (l); ∆f HO – 286 kJ mol–1, [Ans. –239 kJ mol–1], 10., , For oxidation of iron, 4 Fe(s) + 3 O2(g) →2 Fe2O3(s) entropy change is, –549.4 J K–1 mol–1 at 298 K. In spite of negative entropy change of this, reaction, why is the reaction spontaneous? (∆rHθ for this reaction is –1648, kJ mol–1), [Ans. ∆Stotal = +4980.6 J K–1 mol–1], , 11., , , , , Give reasons:, (i) Evaporation of water is and endothermic process but it is spontaneous., (ii) A real crystal has more entropy than an ideal crystal., (iii) Entropy of universe is increasing., 12. For the reaction at 298 K, 2A + B ___→ C ; ∆H = 400 kJ mol–1, ∆S = 0.2, kJ K–1 mol–1. At what temperature will the reaction become spontaneous, considering ∆H and ∆S to be constant over the temperature range., [Ans. T > 2000 K], , 13., , , , , Reaction X → Y; ∆H = +ve is spontaneous at temperature ‘T’. Determine, (i) Sign of ∆S for this reaction., (ii) Sign of ∆G for Y___→ X, (iii) Sign of ∆G at a temperature < T, 5-MARKS QUESTIONS, , 1., , (a) What is reversible process in Thermodynamics?, (b) Name the thermodynamic processes for which : (i) q = 0 (ii) ∆U = 0, (iii) ∆V = 0 (iv) ∆P = 0, (c) Water decomposes by absorbing 286.2 kJ of electrical energy per, mole. When H2 and O2 combine to form one mole of H2O, 286.2 kJ, of heat is produced. Which thermodynamic law is proved? Write its, statement., , 2., , (a) Although heat is a path function but heat absorbed by the system under, certain specific conditions is independent of path. What are those, conditions? Explain., [Hint: qv = ∆U and qp = ∆H], Chemical Thermodynamics, , 101
Page 124 :
(b) It has been found that 221.4 J is needed to heat 30g of ethanol from, 15℃ to 18℃. Calculate (a) specific heat capacity, and (b) molar heat, capacity of ethanol. [Ans. (a) 2.46 Jg–1 ℃–1, (b) 113.2 J mol–1 ℃–1], 3., , (a), (b), , Differentiate the terms Bond dissociation enthalpy & Bond Enthalpy., Calculate enthalpy change for the process CCl (g) ___→ C(g) + 4Cl(g), 4, , and calculate Bond enthalpy of C – Cl bond in CCl4., , Given: ∆vap Hθ = 30.5 kJ mol–1; ∆f Hθ(CCl4) = –135.5 kJ mol–1;, ∆aHθ(C) = 715 kJ mol–1 and ∆aHθ(Cl2) = 242 kJ mol–1, [Ans. 1304 kJ mol–1, 326 kJ mol–1], 4., , Predict the sign of ∆S for the following changes:, (i) Freezing of water., (ii) C(graphite) ___→ C(diamond), , (iii) H2(g) at 298 k and 1 bar ___→ H2(g) at 298 k and 10 bar, (iv) H (g) + I (g) ___→ 2HI(g), 2, , 2, , (v) 2NaHCO3(s) ___→ Na2CO3(s) + CO2(g) + H2O(g), 5., , (i), , , Define Gibbs Energy. Give its mathematical expression. What is, Gibb‘s energy criteria of Spontaneity., , (ii) For the reaction:, 2A(g) + B (g) → 2D(g), ∆Uθ = –10.5 kJ and ∆Sθ = –44.1 J K–1., Calculate ∆rG° for the reaction, and predict whether the reaction will, occur spontaneously. , [Ans. ∆rGθ = +0.16 kJ, Non-spontaneous], HOTS QUESTIONS, 1., , Does entropy increase or decrease when egg is boiled?, , Ans.:On boiling egg, entropy decreases as due to denaturation, the helical, structure of protein become more complicated and random coiled structure., 2., , 10 g of argon is compressed isothermally and reversibly at a temperature, of 27°C from 10 L to 5 l. Calculate q, w, ∆U and ,∆H., , Solution: q = –2.303 nRT log V2 / V1 = –2.303 × 10/40 mol × 2 Cal K–1, , mol–1 × 300 K × log 5/10 = –103.635 Cal, 102, , Chemistry Class XI
Page 125 :
For isothermal compression ∆U = 0, , , W = ∆U – q = 0 – (–103.635) = +103.635 Cal, , Also when temperature is constant,, , 3., , PV = constant, ∆H = ∆U + ∆(PV) = 0 + 0 = 0, , 1 mole of an ideal gas expand isothermally and reversibly from a pressure, of 10 atm to 1 atm at 300 K. Calculate the height to which an object of 50, kg can be lifted by this expansion., , Solution: w(exp.) = –2.303 nRT, , , log Pi / Pf = –2.303 ×1 mol × 8.314 J K–1mol–1 × 300 K × log 10/1, , , , = 5.74 ×103 J, , Now, mgh = 5.74 × 103 J or 50 kg × 9.81 m s–2 × h = 5.744 ×103 J, ∴ h = 11.7 m, , Chemical Thermodynamics, , 103
Page 126 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , For the reaction 2Cl(g) → Cl2 (g); what are the sign of ∆H and ∆S? [1], , 2., , Write an example of endothermic spontaneous reaction., , [1], , 3. ‘w’ amount of work is done by the system and ‘q’ amount of heat, is supplied to the system. What type of system would it be?, , [1], , 4. In a process 701 J of heat is absorbed by a system and 394 J work, is done by the system. What is the change in internal energy for, the process?, , [2], , 5. State and explain Hess’s Law of Constant Heat Summation with, a suitable example., , [2], , 6. Calculate the number of kJ necessary to raise the temperature of, 60 g of aluminium from 35 to 55°C . Molar heat capacity of, Al is 24 J mol–1 K–1., , [3], , 7. Calculate the standard enthalpy of formation of CH3OH (l) from, the following data:, CH3OH(l) + 3/2 O2 (g) → CO2 (g) + 2H2O (l);, ∆c Hθ = –726 kJ mol–1, C (g) + O2 (g) → CO2 (g); ∆f Hθ= –393 kJ mol–1, H2(g) + ½ O2 (g) → H2O (l); ∆f Hθ = –286 kJ mol–1, 8., , (a) For oxidation of iron, 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s) entropy change, is –549.4 J K–1 mol–1 at 298 K. In spite of negative entropy change of, this reaction, why is the reaction spontaneous? (∆r H° for this reaction is, –1648 kJ mol–1), [2], , (b) For the reaction: 2A (g) + B (g) → 2D (g), ∆Uo = –10.5 kJ and, ∆So = –44.1 J K–1. Calculate ∆rGo for the reaction, and predict whether, the reaction will occur spontaneously., [3], *****, 104, , Chemistry Class XI
Page 128 :
Predicting the direction of reaction :, If, , Qc = Kc ⇒ The reaction is in a state of equilibrium., , Qc > Kc ⇒ The reaction proceeds in reverse direction., Qc < Kc ⇒ The reaction proceeds in forward direction., Ostwald’s dilution law : Degree of dissociation of weak electrolyte,, α=, Ionic Product of water (Kw) = [H3O+] [OH–] = 10–14 at 298K, Le-Chatelier’s Principle : When a system of equilibrium is subjected to, a change in temperature, pressure or concentration, the equilibrium shifts, itself in such a way so as to undo or nullify the effect of change., Outcomes of Le-Chatelier’s Principle, , , Change at equilibrium, , Shift in equilibrium, , , , Increase in temperature, , Endothermic direction, , , , Decrease in temperature, , Exothermic direction, , , , Increase in pressure, , Towards lesser gaseous moles, , , , Decrease in pressure, , Towards greater gaseous moles, , , , Increase in Conc. of reactants, , Forward direction, , , , Increase in Conc. of products, , Reverse direction, , Conjugate Acid or Base : Acid-base pair which differ by H+ ion., , , Species – H+ = Conjugate base, , , , Species + H+ = Conjugate acid, , pH of solution :, , , , pH = –log [H3O+] or [H+] = 10–pH , pOH = –log [OH–], pH + pOH = pKw = 14 at 298K, , Common ion effect : The depression of ionisation of weak electrolyte by, the presence of common ion from a strong electrolyte is called common, ion effect. For example degree of dissociation of NH4OH decreases in the, presence of strong electrolyte NH4Cl., 106, , Chemistry Class XI
Page 129 :
+, Hydrolysis of salts and pH of their solutions : Hydrolysis of salt is, defined as the reaction of cation or anion with water as a result of which, the pH of water changes., 1. Salts of strong and strong bases (e.g., NaCl) do not hydrolyse. The, solution pH will be 7., 2. Salts of weak acids and strong bases (e.g., CH3COONa) hydrolyse,, pH >7 (The anion acts as a base)., X–, , +, , , H2O , , , HX, (Weak acid), , , 3., , pH =, , OH–, , +, , (Weak base), , (pKa + log C), , Salt of strong acids and weak bases (e.g., NH4Cl) hydrolyse, pH < 7., (The cation acts as an acid)., , MOH + H+, M+ + H2O , , , , 4., , pH =, , (pKb + logC), , Salt of weak acids and weak base (e.g., CH3COONH4) hydrolyse. The, cation acts as an acid and anion as a base but whether the solution, is acidic or basic depends upon the relative values of Ka and Kb for, these ions., , MOH + HX, M+ + X– + H2O , , , pH =, , (pKa – pKb), , Buffer solutions : The solutions, which resist the change in pH on dilution, or addition of small amounts of acid or base, are called buffer solutions., Basic buffer : Solution of weak base and its salt with strong acid, For e.g.,, NH4OH + NH4Cl, Acidic buffer : Solution of weak acid and its salt with strong base, For, e.g., CH3COOH + CH3COONa., Henderson Hasselbalch Equation for the pH of Buffer solution—, pH, , = pKa + log, , (for acidic buffer), , pOH = pKa + log, , (for basic buffer), Equilibrium, , 107
Page 131 :
Equilibrium, , 109, , [PA] [PB], , a, , d, , b, , [PC] [PD], , c, , [A] [B], , b, , d, , b, , d, , [A] [B], , a, , [C] [D], , c, , Reaction Quotent, , (, , ), , Le-Chatlier, Principle, , Chemical, Equilibrium, , Non Ionic, Entities, , Effect of Pressure, No effect, On increasing pressure, backward reaction favoured, and vice-versa, ng < 0 On increasing pressure, backward reaction favoured, and vice-versa, , ng = 0, ng > 0, , No effect, On increasing pressure, backward reaction favoured, and vice-versa, On increasing pressure, backward reaction favoured, and vice-versa, , Effect of Inert Gas (N2, Xe, Kr, etc.), If inter gas is added at constant condition then, no effect is observed, If inter gas is added at constant pressure then, at ng = 0 No effect, ng > 0 Forward reaction fovoured, ng < 0 Forward reaction fovoured, , n < 0, , n = 0, n > 0, , Effect of Volume (Opposite ‘P’ Effect), , Effect of Concentration, If reactant concentration increases or, product decreases then forward reaction, forward and vice-versa, , Ionic Equilibrium, , Ionic Entities, , EQUILIBRIUM, , For endothermic reaction H is +, If T increases, forward reaction favoure, and otherwise backward reaction, If T decreases, For Exothermic opposite effect, , K2, , Effect of Temperature, 1, 1, H, R, –, log =, =, 2.303, T, T1, K1, 1, , Q c = Kc Reaction is at equilbrium, Q c < Kc Forward reaction favoured, Q c > Kc Backward reaction fovoured till, new equilibrium is re-establish, , Qc =, , c, , a, , [C] [D], , K p = Kc(R5) and, ng = (c + d) + (a + b), Gaseous component A, B, C & D, , Kc =, , Kc =, , aA + bB cC + dD, , Equilibrium Constant, , MIND MAP : EQUILIBRIUM
Page 132 :
110, , Chemistry Class XI
Page 133 :
MULTIPLE CHOICE QUESTION (MCQ), 1. For the hypothetical reactions, the equilibrium constant (k) values are, given, A, , B : k1 = 2, , B, , C: K2 = 4, , C, , D : K3 = 8, , , , The equilibrium constant (K) for the reaction A, , , , (a) 48, , (b) 24, , (c) 12, , D is, , (d) 64, , 2. The equilibrium constant for the reaction, SO2(g) +, , , 1, O (g), 2 2, , The equilibrium constant for the reaction, , 2SO3(g), , , SO3(g) is 5 × 10–2 atm–1/2, , 2SO2(g) + O2(g) would be, , (a) 100 atm, , (b) 25×10–4 atm, , (c) 400 atm, , (d) 125 ×19-6 atm–3/2, , 3. A(g) + 3B(g), 4C(g) initial concentration of A is equal to that of B. The, equilibrium concentrations of A and C are equal. What is the equilibrium, constant for, 4C(g), , , (a) 4, , A(g) + 3B (g), (b) 1/8, , (c) B, , (d) 16, , 4. The equilibrium reaction that is not affected by volume change at constant, temperature is, (a) H2(g) + Cl2(g), (c) PCl5(g), , 2HCl(g), , PCl3(g) + C12(g), , 5. For the reaction CO(g) + Cl2 (g), equal to, (a) RT, (b) RT, (c) 1/RT, , (b) N2(g) + 3H2(g), , 2NH3(g), , (d) H2(l) + CO2(g), , H2CO3(l), , COCl2(g), the value of Kc/Kp is, (d) 1.0, , 6. At 90°C pure water has Kw = 10–12. The solution with pH value 6.5 is, (a) Acidic, (b) Basic, (c) Amphoteric, (d) Data insufficient, Equilibrium, , 111
Page 134 :
7. 40 ml of 0.1 M NH4OH is mixed with 20 mL of 0.1 M HCl. What is the, pH of the mixture? (pKb of ammonia solution = 4.74), , , (a) 4.74, , (b) 2.26, , (c) 9.26, , (d) 5, , 8. Identify Bronsted Lowry Acids in the reaction, [Al(H2Ol6]3– + HCO3, (X), (Y), , , (a) X, Y, , [Al(H2O)5(OH)]2+ + H2CO3, (P), , (b) Y, P, , (Q), , (c) P, Q, , (d) X, Q, , 9. The pKa of weak acid HA is 4.80 and pKb of a weak base BOH is 4.78., The pH of an aqueous solutions of corresponding salt BA will be, , , (a) 7.01, , (b) 4.79, , (c) 9.22, , (d) 10.0, , 10 If ‘P’ M is the solubility of KAl(SO4)2, then Ksp is equal to, (a) p3, , (b) 4p4, , (c) p4, , (d) 4p3, , TRUE AND FALSE TYPE QUESTIONS, 1. Equilibrium state can be achieved if a reversible reaction is carried out in, closed or open container., 2. For a reaction 2A(g), B (g) Qc > K if ‘A’ is added maintaining, Qc > K, the reaction will move in backward direction., 3. For the reaction at equilibrium, CaCO3, , , CaO(s) + CO2(g), , What CaO(s) is removed reaction moves in forward direction., , 4. For a reaction aA + bB, , cC + dD at eqilibrium Gq = 0 always., , 5. For a reaction at equilibrium H2(g) + Cl2(g), , , K = 4, the value of, , 2HCl(g), , K b [HCl]2, is 1., K f [H 2 ][Cl2 ], , 6. For the electrolyte A2B if Ksp is solubility product then its solubling ‘S’, M is [Ksp]1/3 ÷ 4., 7. HCO–3 is conjugate base of H2CO3., 8. H2O can act as acid as well as base., 9. The pH of buffer solution remain same when any amount of dilution is, done., 112, , Chemistry Class XI
Page 135 :
10. For a salt AB2(s) solution if Ionic product (I.P) > Ksp, then precipitation, will take place., Ans. 1. False, , 2. True, , 3. False, , 4. False, , 5. True, , 6. True, , 7. True, , 8. True, , 9. False, , 10. True, , FILL IN THE BLANKS, 1. At equilibrium rate of forward reaction is always equal to .................., 2. Kp & Kc are ....... for reaction at equilibrium of type H2(g) + Br2(g), 3. If Kc for reaction CH3COOH(l) + C2H5OH, is 4. Then Qc and Kc are ................., , 2HBr(g)., , CH3COOC2H5(l) + H2O(l), , 4. If A+B –70J/mol, D, reaction temperature is increased then reaction, moves in ............... direction., 5. Presence of catalyst will ...... the equilibrium constant., 6. The conjugate acid of H2O is .............., , 7. On dilution, the degree of dissociation of acetic acid will .............., 8. The presence of NH4Cl in NH4OH solution will ............. the degree of, dissociation of NH4OH., 9. If Ionic product (IP) < Ksp for a salt solution of AB, then addition of AB, further ........... lead to precipitation initially., 10. Kp is always equal to Kc if ∆ ng is ............, Ans. 1. rate of backward reaction, 2. equal, 3. equal, 4. forward,, , 5. not change, 6. H3O+, 7. increase, 8. decrease, 9. will not, 10. zero, MATCH THE COLUMNS, 1., Column-I, A) Na(g) + 3H (g), 2, , B) 2N (g) + 2O (g), 2, 2, , C) X(g), D) PC1 (g), 5, , Ans. (A) Q, , Column-II, P) K increases with increase in temp, , 2NH3(g); ∆H = - ve, 4 NO(g) : ∆H = +ve, , R) Pressure has no effect, , 2Y(g) ∆H = +ve, PC13 + Cl2 ; ∆H = +ve, , (B) P, R, , Q) K decreases with increase in temperature, , (C) P, S, , S) Product moles increases due to, addition of inert gast at constant, pressure., , (D) P, S, Equilibrium, , 113
Page 136 :
2., Coloumn-I, , Column-II, , A) Salt of weak acid and weak base, B) Salt of weak Acid and strong Base, C) Salt of strong acid and strong base, D) Salt of strong acid and weak base, , Ans. (A) Q, , (B) P, , (C) S, , P) pH = ½ (pKw + pKa + logc), Q) pH = ½ (pKw + pKa – pkb), , R) pH = ½ (pKw – pKb – logc), S) pH = ½ (pKw), , (D) R, , ASSERTION - REASON TYPE QUESTION, , , A., B., C., D., , Each question contains statement-1 (assertion) and Statement-2 (Reason), Examine the statements carefully and mark the correct answer according, to the instruction given below :, If both the statements are true and statement -2 is the correct explanation, of statement-I, If both the statements are true but statement-2 is not the correct explanation, of statement-I, If statement-I is true and statement-2 is false, If statement-I is false and statement-2 is true., , 1. Statement-1 : The endothermic reactions are favoured at lower temperature, and the exothermic reactions are favoured at higher temperature., Statement-2 : when a system in equilibrium is disturbed by changing the, temperature, it will tend to adjust itself so as to overcome the effect of, change., 2. Statement-1 : The melting point of ice decreases with increase of pressure, Statement-2 : Ice contracts on melting., 3. Statement -1 : The gas phase reaction PCl3(g) + Cl2(g), PCl5(g) shifts, to the right on increasing pressure., Statement-2 : When pressure increase, equilibrium shifts towards more, number of moles., 4. Statement-1 : The physical equilibrium is not static but dynamic in nature., Statement-2: The physical equilibrium is a state in which two opposing, process are proceeding at the same rate., 5. Statement-1 : The catalyst does not after the equilibrium constant. , Statement-2 : Because for the catalysed reaction and uncatalysed reaction, ∆H remains same and equilibrium constant depends on ∆H., 114, , Chemistry Class XI
Page 137 :
6. Statement-1 : If water is heated to 59°C, the pH will increase., Statement-2 : Kw increases with increase in temperature., 7. Statement-1: Addition of HCl(aq.) to CH3COOH (aq.) decrease the, ionisation of CH3COOH (aq.)., Statement-2 : Due to common ion effect H+, ionisation of CH3COOH, decreases., 8. Statement-1: Sparingly soluble salts AB and XY2 with the same solubility, product, will have different solubility., Statement 2: Solubility of sparingly soluble salts depends upon solubility, product., 9. Statement-1 : The ionisation constants of weak diprotic acid are in the, order of Ka1 > Ka2., Statement-2 : Removal of H+ from anion is difficult as compared to neutral, atom., 10. Statement-1 : In a titration of weak acid with strong base, the pH at the, half equivalence point is pKa., Statement-2 : At half equivalence point, it will form acidic buffer at its, maximum capacity where [Acid] = [Salt]., Ans.: 1. D, 2. A, 3. C, 4. A, 5. A, 6. D, 7. A, 8. B, 9. A, 10. A, ONE WORD ANSWER TYPE QUESTIONS, 1. What is sum of pH + pOH at 25ºC? , [Ans. 14], 2. Write the Henderson Hasselbalch equation for acidic buffer, [SALT], , Ans. pH = pka + l0g, [ACID], , 3. How is degree of dissociation related with concentration terms and Ka,, for weak electrolyte. , Ans. α = Ka / c, 4. How NH3 is defined as Lewis base?, [Ans. It contain Lone paid of electrons], 5. How are Kp and Kc related? , [Ans. Kp = Kc (RT)∆n], , 6. How does K affected for endothermic reaction if temperature is increased?, [Ans. K get decreased], 7. What is the effect of catalyst on K? , , [Ans. K remains unaffected], , 8. How is pH scale affected by increasing temperature?, , [Ans. pH scale gets contracted], 9. What is the conjugate base of HCO3– ? , , [Ans. CO32–], , 10. What is the nature of CH3COOH in conc. HCl solution?, [Ans. Bronsted Base], Equilibrium, , 115
Page 138 :
1-MARK QUESTIONS, 1. Define physical equilibrium. Give an example also., 2. Fizz is observed when soda water bottle is opened. Why ?, 3. Justify the statement : ‘Both physical and chemical equilibrium are dynamic, in nature’, 4. State Henry’s law., 5. In a reversible reaction, the two substances are in equilibrium. If the, concentration of each one is reduced to half, then what is the effect on the, equilibrium constant ?, 6. K1 and K2 are equilibrium constant for reactions (1) and (2), (i) N2(g) + O2(g), 2 NO(g), , , (ii) NO(g), , 1/2 N2(g) + 1/2 O2(g), , , , Calculate the relation between K1 and K2., , 7. Write the equilibrium constant expression for the following reaction :, , , 3 Fe(s) + 4 H2O(g), , Fe3O4(s) + 4 H2(g), , 8. Classify the equilibrium as homogeneous or heterogeneous :, CH3COOC2H5(aq.) + H2O(1), 9. Kp =, , CH3COOH(aq.) + C2H5OH (aq.), , (PNH3 ), 3, , (PH2 ) 2 (PN2 ), , 1, , 2, , Write the balanced chemical equation corresponding to the above, expression., 10. Give the direction in which the reaction would proceed if Qc > Kc., 11. Hb(s) + O2(g), , , HbO2(s), , Predict the direction in which equilibrium gets shifted if partial pressure, of O2(g) is lowered., , 12. Discuss the position of equilibrium if the following reaction is carried out, in the presence of catalyst., 2SO2(g) + O2(g), , 2SO3(g), , 13. Which of the following are Lewis acids ?, H2O, BF3, H+, NH4+, 116, , Chemistry Class XI
Page 139 :
14. Write the conjugate acids for the following Bronsted bases., C6H5OH, H2O, 15. Write the conjugate bases for the following Bronsted acids., H2O, CH3COOH., 16. Which of the following are Lewis acids ?, (a) H2O, , (b) AlCl3, , (c) NH4+, , 17. Define Ostwald’s dilution law., 18. SO32– is Bronsted base or acid and why ?, 19. Why pH of our blood remains almost constant at 7.4 though we quite often, eat spicy food ?, 20. pH of black coffee is 5.0 at 25ºC. Is black coffee acidic or basic ?, [Ans. Acidic], 21. What will be the value of (pKa + pKb) at 25ºC., 22. What will be the pH of 1 M KNO3 solutions at 25ºC?, 23. CaCl2(s) + H2O(l), , , CaCl2(aq.) + Heat, , Discuss the solubility of CaCl2 if temperature is increased., , 24. Why does the solubility of CO2 decrease with rise in temperature ?, 25. The solubility of A2 X3 is y mol dm–3. Calculate its solubility product., 26. Write the Ksp expression for Al (OH)3., 27. What is the condition for precipitation of a salt ?, 28. Pridict whether the solution is acidic, basic or natural when NH4NO3, undergo hydrolysis., 29. Explain why pure NaCl precipitates out when HCl gas is passed through, the solution of NaCl ?, 30. Give the Henderson’s Hasselbalch equation for an acidic buffer solution., 31. On which of the factors the equilibrium depend : Temperature, nature of, reactant and product, initial concentration and pressure of the reactants., 32. Arrange the following in increasing acidic strength HCl, HBr, HF, HI, , [Ans. HF < HCl < HBr < HI], , Equilibrium, , 117
Page 141 :
2-MARKS QUESTIONS, 1. The standard Gibbs energy change at 300 k for the reaction 2A, B+, C is 2494. 2 J. At a given temperature, and time. the composition of the, reaction mixture is [A] = ½, [B] = 2, [C] = ½. The reaction proceed in the, (R = 8.314J/K/mo1, = 2.718), [Ans. Reverse direction], 2. The equilibrium constant for, , , N2(g) + O2(g), 2NO(g) is K, then calculate equilibrium constant, for ½N2(g) + ½O2(g), NO(g)., [Ans. √K], , 3. For the reversible reaction N2(g) + 3H2(g), 2NH3(g) at 500°C, the, value of Kp is 1.44×10–5 atn–2. Find the Kc value., [Ans. 1.44 × 10–5 / (0.082 × 773)–2], , , , 4. The equilibrium constant at 298 K for the reaction A + B, C + D is, 100. If the initial concentration of all the four species were 1M each, then, equilibrium concentration of D will be, [Ans. 1.818], 5. For the reaction, , , NH4COO NH2(g), , 2NH3(g) + CO2(g), , , , If equilibrium pressure is 3 atm. Find the value of Kp, , [Ans. 4], , 6. A buffer solution with pH 9 is to be prepared by mixing NH4Cl that should, be added to one litre of 1.0m NH4OH kb 1.8 × 10-5, [Ans. NH4Cl = 1.8 M], 7. Calculate the solubility of silver chloride in water at room temperature if, the Ksp of AgCl is 1.6×10-10., [Ans. 1.26 × 10-5M], 8. Calculate the molar solubility of Ni(OH)2 in 0.10m NaOH. The ionic, product of Ni(OH)2 is 2.0 × 10-15., [Ans. 2.0 × 10-13M], 9. Calculate the pH of 10-8 M HCl solution., , [Ans. 6.96], , 10. How many grams of NaOH must be dissolved in IL of the solution to give, it a pH value of L2?, [Ans. 0.4g], , Equilibrium, , 119
Page 142 :
3-MARKS QUESTIONS, 1. The equilibrium constant for the reaction H2(g) + Br2(g), 2HBr(g) at, 5, 1024 K is 1.6×10 . Find the equilibrium pressure of all gases if 10.0 bar, of HBr is introduced into a sealed container at 1024K., [Ans. 10 bar], 2. For the reaction 2BrCl(g), Br2(g) + Cl2(g) Kc is 32 at 500 K. If initially, pure BrCl is present at a concentration of 3.30 ×10-3 M, what is its molar, concentration in the mixture at equilibrium?, [Ans. 3.0 × 10-4 M], 3. What is the equilibrium constant Kp and Kc for the reaction PCl5(g), PCl3(g) + Cl2(g) if the pressure is 1.0 atm in 8.0L container at equilibrium., , [Ans. Kc = 0.04 Kp = 1.77], 4. The Kp for the reaction, N2O4(g), NO2(g) is 640 mm at 775 K. Calculate, the percentage dissociation of N2O4 at equilibrium pressure of 160mm., At what pressure the dissociation will be 50%., [Ans. 70.7%, P = 480 mm], 5. Show that degree of dissociation (α) for the dissociation of PCl5 into PCl3, 1/ 2, , Kp , and Cl2 at pressure P is given by α =, , P + kp , 6. How much of 0.3M NH4OH should be mixed with 30 mL of 0.2m solution, of NH4Cl to give a buffer solution of pH 10. pkb for NH4OH is 4.75., , , , [Ans. V = 112.5 mL], , 7. Predict whether a precipitate will be formed or not on mixing 20 mL of, 0.001 N NaCl solution with 80 mL of 0.01 M AgNO3 solution. Ksp for, AgCl is 1.5 × 10-10., [Ans. Yes, ppt will formed.], 8. The values of Ksp of two sparingly soluble salts Ni(OH)2 and AgCN are, 2.0 × 10-15 and 6.0 × 10-17 respectively. Which salt is more soluble. Explain, , [Ans. SNi(OH) = 5.8 × 10-5M : S(Ag CN) = 7.8×10-9M . Ni(OH)2, 2, , is more soluble], 9. The ionization constant of propanoic acid is 1.32×10-15. Calculate the, degree of ionization if its solution is 0.05 M. What will be its degree of, ionization if the solution is 0.01 M in HCl solution., , [Ans. 1.62 × 10-2, 1.32 × 10-3], 10. Calculate the pH of a solution obtained by mixing 50ml of 0.2M HCl with, 49.9 mL of 0.2m NaOH solution., [Ans. 3.699], 120, , Chemistry Class XI
Page 143 :
HOTS QUESTIONS, 1. The molar solubility of Cd(OH)2 is 1.84 × 10-5M. Calculate the expected, solubility of Cd(OH)2 in a buffer solution of pH = 12., 2+, —, Ans. Cd(OH) 2 Cd (aq.) + 2OH (aq.), , , , , 10–2, , S, , 2.49 × 10-14 = S(10-2)2, , ∴ S = 2.49 × 10-10M, , 2. An aqueous solution contains an unknown concentration of Ba2+. When 50, ml of a 1M solution of Na2SO4 is added. BaSO4 just begins to precipitate., The final volume is 500ml. The solubility product of BaSO4 is 1×10-10., Find the original concentration., 50 ×1 , —9, 2+ 2— Ba 2+ =, Ans. K=, sp, 10 × 500, Ba SO 4=, , , 500 , , , , Ba2+ = 10–9 M, , , , 10–9 × 500 = 450 × M, , ∴ M = 1.11 × 10–9M, , 3. An aqueous solution contains 0.10 M H2S and 0.20 M HCl. If the, equilibrium constants for the formation of HS– from H2S is 1.0 ×10–7 and, that of S2– from 4S– ions is 1.2×10–13, then find the concentration of S–2, ions in aqueous solution., Ans., , , H2S(aq.), , 2H+, , + S2–, , (0.1 – x), , (2x + 0.29), , x, , Ka = Ka × Ka = 1.2 × 10–20, 1, , , , 1.2 ×, , 10–20, , 2, , =, , ( 0.2 )2 S2— , 0.1, , , [S2–] = 3 × 10–20, , 4. How many litres of water must be added to 1 litre of an aqueous solution, of HCl with a pH of 1 to create an aqueous solution with pH of 2?, Ans. 0.1 × 1 = (1 + v) (0.01), , ⇒ v = 9L, , 5. A certain buffer solution contains equal concentration of X– and HX. The, Kb for X– is 10–10. Find the pH of the buffer ., Ans. ka.kb = 10–14, , ∴=, ka, , , , [x — ], [Hx], , pH = pka + log, , 1, ∴ pH = 4 + log = 4, 1, , 10 —14, =, 10 —4, —10, 10, , ∴ pH = 4, Equilibrium, , 121
Page 144 :
6. The % yield of Ammonia as a function of time in the reaction N2(g) +, 3H2(g), 2NH3(g), DH < O at (P, T) is given below:, , , , If this reaction is conducted at T2 > T1, then plot the % yield of NH3 as a, function of time on same graph, , Ans. Initially on increasing temperature the, rate of reaction increases, however since the, reaction is exothermic therefore % yield of NH3, get decreased overall after a certain interval of, time., , T1, T2, , %, (yield), , Time, , 7. Consider the reaction NH4COONH2(s), 2NH3(g) + CO2(g) at a certain, temperature, the equilibrium pressure of the system is 0.318 atm. Find Kp, of the decomposition of ammonium carbonate., Ans., , , Ptotal = 3P, Kp =, , 4P3, , ∴ P = 0.318/3 = 0.106, = 4.76 × 10–3, , 8. The equilibrium constant for the reaction CO(g) + H2O(g), CO2(g) +, H2(g) is 5. How many moles of CO2 must be added to 1 litre container, already containing 3 moles each of CO and H2O to make 2M equilibrium, concentration of CO?, Ans., t=0, , , , CO + H2O, 3, , 2, , At equilibrium 2, , 2, , , , ∴=, S, , CO2 + H2, x, , 0, , x+1, , 1, , x +1, ⇒=, x 19, 4, , 9. At constant temperature, the equilibrium constant Kp, , , , N2O4, , k p =, , 122, , 2NO2 is given by, , 2, , 4x P, 1— x, , where, P = Pressure and X = Extent of reaction, , Chemistry Class XI
Page 145 :
How does the value of Kp change on following changes, (a) ‘P’ increases, (b) X changes, , (c) ‘P’ decreases, Ans. Kp is equilibrium constant which does not change on changing the, P, x.Kp depends on temperature., 10. When two reactants A and B are mixed to give product 'c' and 'p' the, reaction quotient 'Q' at the initial stages of the reaction will be?, Ans. In the beginning of the reaction Q = 0. As the reaction proceeds in, the forward direction Q starts increasing., , , At chemical equilibrium Q = K, , Equilibrium, , 123
Page 146 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1. What is the pH 10–3 M HCl solution ? , , , (a) 1, , (b) 11, , (c) 3, , (d) 14, , 2. Which one can act as Arrhenius Acid ? , , , (a) NH3, , (b) H2O, , (c) HCl, , [1], [1], , (d) C6H5OH, , 3. Write the conjugate base of CH3COOH + H2., , [1], , 4. Write the relation between Kp and Kc. , , [1], , 5. What is the nature of following reaction , Exothermic or endothermic , A + B – 70J —→ C, , [1], , 6. The pKa of CH3COOH and pKb of NH4OH are 4.76 and 4.75 respectively., Calculate the pH of CH3COONH4. , [2], 7. What is a buffer solution. Calculate the pH of the solution obtained by, adding 4mol of CH3COOH with 3 mol of NaOH in 1 litre container. [2], , , , pKa, CH3COOH = 4.74 log2 = 0.3010 log3 = 0.4771, , 8. Calculate the molar solubility of Ni(OH)2 in 0.1M KOH solution. The Ksp, for Ni(OH)2 is 2.0×10–15. , [3], 9. Kp = 0.04 atm at 899 K for the equilibrium shown below. What is the, equilibrium concentration of 2H6 when it is placed in a flask at 4.0 atm, pressure and allowed to come to equilibrium., [3], C2H6(g), , C2H4(g) + H2(g), , 10. Ionization constant of Benzoic acid is 6.46×10-5 and Ksp for silver benzoate, is 2.5 × 10-13. How many times is silver benzoate more soluble in buffer, of pH 3.19 compared to its solubility in pure water., [H+] = 6.46 ×10–4 , *****, 124, , Chemistry Class XI, , [5]
Page 147 :
Chapter - 8, , Redox, Redox, Reactions, Reactions, , FAST TRACK : QUICK REVISION, Oxidation and Reduction :, Oxidation Reduction, 1. Addition of oxygen, 1. Removal of oxygen, 2. Removal an Hydrogen, 2. Addition of Hydrogen, 3. Addition of an electronegative, 3. Removal of an electronegative, element. element., 4. Removal of an electropositive, 4. Addition of an electropositive, element element., 5. Loss of electron(s), 5. Gain of electron(s), 6. Increase in oxidation number., 6. Decrease in oxidation number., , , Reducing Agent : Donor of electrons., , , , Oxidising Agent : Acceptor of electrons., , , , , , , , , , , , , Redox Reaction : Reactions in which oxidation and reduction takes place, simultaneously., Oxidation Number : It is charge that an atom appears to have in a given, species when the bonding electron are counted towards more electronegative atom., Calculation of Oxidation Number :, (a) Oxidation number of all the elements in their elemental form (in, standard state) is taken as zero. Oxidation number of element in a, molecule Cl2, F2, O2, P4, O3, Fe, H2, N2, C (graphite) is zero., (b) Common Oxidation number of elements of first group is +1. Common, Oxidation number of elements of second group + 2., (c) For ions composed of only one atom, the oxidation number is equal, to the charge on the ion.
Page 148 :
(d) The oxidation number of oxygen in most compounds is – 2. While in, peroxides (e.g., H2O2, Na2O2), each oxygen atom is assigned an, oxidation number of – 1, in super oxides (e.g., KO2, RbO2) each, oxygen atom is assigned an oxidation number of – (½)., , , , (e) In oxygen difluoride (OF2) and dioxygen difluoride (O2F2), the oxygen, is assigned an oxidation number of + 2 and + 1, respectively., , , , (f) The oxidation number of hydrogen is + 1 but in metal hydride its, oxidation no. is – 1., , , , (g) In all its compounds, fluorine has an oxidation number of – 1., , , , (h) The algebraic sum of the oxidation number of all the atoms in a, compound must be zero., , , , (i) In polyatomic ion, the algebraic sum of all the oxidation numbers of, atoms of the ion must equal the charge on the ion., , , , Types of Redox Reactions:, , (i) Combination Reaction :, , , 0, , 0, , –3, , ∆ Mg N (s), 3 Mg (s) + N2 (g) →, 3 2, , (ii) Decomposition Reaction : +1 +5 – 2, , , +2, , , , +1–1, , ∆, 2KClO3(s) →, 2 KC1(s), , (iii) Metal Displacement : + 2 + 6 – 2, , 0, , +2+6–2, , 0, , + 3O2 (g), 0, , CuSO4 (aq) + Zn(s) → ZnSO4 (aq) + Cu (s), (iv) Non-metal displacement : 0, , , +1–2, , +2–2+1, , 0, , Ca (s) + 2 H2O (1) → Ca (OH)2 + H2 (g), , (v) Disproportionation reactions : It is a reaction in which same, element is reduced and oxidized simultaneously., , , 0 , , , , C12 (g) + 2 OH– (aq) → Cl– (aq) + ClO– (aq) + H2O (1), , , , , , 126, , –1, , +1, , Stock Notation : Representing oxidation number of metal in Roman, numerals within parenthesis after the symbol or name of metal in the, molecular formula or name of a compound. For e.g., Stock Notation of, Ferric oxide is Fe2(III)O3 or Iron (III) oxide., Fractional Oxidation Number : When two or more atoms of an element, are present in different oxidation states, then calculated oxidation number, may comes out as fractional due to average of all the different oxidation, states., Chemistry Class XI
Page 149 :
, , In reality no element can have a fractional oxidation state., Balancing of Redox Reactions :, , , , (A) Oxidation number method, , , , (B) Half reaction method, , , , , , , , Electrode Potential (E) : Potential difference between electrode and, electrolytic solution due to charge separation., Standard Electrode Potential (Eθ) : Electrode Potential measured at 298, K and 1M concentration of metal ions (or 1 bar pressure of gas)., Electrochemical Cell : A device in which chemical energy of a spontaneous, redox reaction is converted into electrical energy., , , , Cell diagram: Zn | Zn2+ || Cu2+ | Cu, , , , LHS oxidation,, , , , RHS reduction, , , , Overall reaction, , , , Zn → Zn2+ + 2e–, Cu2+ + 2e– → Cu, Zn(s) + Cu2+ (aq) → Zn2+ (aq) + Cu(s), , Representation of an Electrochemical cell :, ———— Flow of electrons ———→, ←———— Flow of current ———, , , LOAN, , , , , Zn(s) | Zn2+ (aq) || Cu2+(aq) | Cu(s), Left Electrode, Salt Bridge, Oxidation , Anode , Negative , , Right Electrode, Reduction, Cathode, Positive, , Functions of Salt Bridge : (i) To complete inner circuit. (ii) To maintain, electrical neutrality around electrodes. , Redox Reactions, , 127
Page 151 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , 2., , 3., , The oxidation state of Fe in Fe3O4 is, (a) +2, , (b) + 3, , (c), , (d) + 2, + 3, , 8, 3, , The oxidation state of 'S' in KAl(SO4)2 .12H2O is, (a) –2, , (b) – 1, , (c) 2, , (d) + 6, , Oxidation state carbon in C3O2 is, (a), , 4, 3, , (b) 0, , (c) 2, 4., , 5., , 6., , (d) 0, 2, , The reaction S8 + 12OH– —→ 4S2– + 2S2O32– + 6H2O is, (a) Combination reaction, , (b) Decomposition reaction, , (c) Non-metal displacement, , (d) Disproportionation reaction, , E0, , for, , H+/H, , 2, , is, , (a) 0, , (b) +1V, , (c) –1.0V, , (d) –2.0V, , Which one act as strong oxidising agent, K+/K = –2.9 3V, Ag+/Ag = 0.80, Hg2+/Hg = 0.79V, , 7., , (a) K+, , (b) K, , (c) Hg2+, , (d) Ag+, , The coefficient of HCl in balance reaction is, Pb3O4 + HCl —→ PbCl2 + Cl2 + H2O, , 8., , 9., , (a) 1, , (b) 8, , (c) 3, , (d) 4, , Sum of oxidation numbers of all Bromine atoms in Br3O8 is, (a) 6, , (b) 4, , (c) 16, , (d) 20, , In the reaction 6ClO2– —→ 4ClO3– + 2Cl–, Cl– ion is, (a) Oxidised Reduced, , (b) Reduced, , (c) Odixised and, , (d) Neither Oxidised nor reduced, Redox Reactions, , 129
Page 152 :
10., , 'I' can not act as reducing agent in following state, (a) –1, , (b) +1, , (c) +7, , (d) +5, , Ans: 1. (d) 2. (d) 3. (d), , 4. (d) 5. (a) 6. (d) 7. (b) 8. (c) 9. (c) 10. (d), FILL IN THE BLANKS, , (i), (ii), (iii), (iv), (v), (vi), (vii), (viii), (ix), (x), , Oxidation is __________ of electrons., S.H.E. stands for __________., Oxidation state of Oxygen in O2F2 is __________., Disproportionation is a type of __________ reaction., Oxidant is one which __________ electron.., Cl2 + 2OH– —→ ClO– + C1– is a __________ type of reaction., Oxidation state of F is always either ______ or _____ ., Oxidation state of Oxygen in O3 is __________ ., Reducing agent are also called __________., Hydrogen economy is use of Hydrogen as _________., , Ans: (i) loss, (ii) standard hydrogen electrode, (iii) +1, (iv) redox, (v) gain,, (vi) disproportionation, (vii) 0, –1, (viii) zero, (ix) reductant, (x) fuel, , (i), , TRUE AND FALSE TYPE QUESTIONS, In Redox reaction first oxidation take place., , (ii), , Oxidising agents are also called reductant., , (iii) Fluorine cannot have +1 oxidation state., (iv) O2+ has oxidation state of oxygen as +½., (v), , If for the reaction Ca2+ + 2e– —→ Ca(s); EO = –2.87, Then for the reaction 2Ca2+ + 4e– —→ 2Ca(s); EO = 2(–2.87)V, , (vi) Salt bridge is used for enhancing E° values of individual half reaction., (vii) Anode is –ve charged in Galvanic cell., (viii) KCl can be use in salt bridge., (ix) Current flows in galvanic cell from Anode to cathode., (x), , MnO4– is colourless in basic medium., , Ans: (i) False, (vi) False, 130, , (ii) False, (vii) True, , (iii) True, (iv) True, (viii) True (ix) False, , Chemistry Class XI, , (v) False, (x) False
Page 153 :
MATCH THE COLUMNS, Column-I, , 1., , Column-II, , (a) CH4 +2O2 —→ CO2 + 2H2O, , (p) Disproportionation, , (b) Cr2O3 +2A1 —→ Al2O3 + 2Cr, , (q) Non-metal displacement, , (c) Fe +2HCl —→ FeCl2 + H2, , (r) Metal displacement, , Ans. (a) – (s), , (d) – (p), , (d) P4 + 3OH– + 3H2O → PH3 +3H2PO2– (s) Metal displacement, (b) – (r), , (c) – (q), , 2., Column-I, , , Column-II, (Oxidation sate of N), , (a) NO, , (p) + 5, , (b) NO2, , (q) + 3, , (c) NO2–, , (r) + 4, , (d) NO3–, Ans. (a) – (s), , (s) + 2, (b) – (r), , (c) – (q), , (d) – (p), , ASSERTION AND REASON TYPE QUESTIONS, Each question contain statement-1 (Assertion) and statement-2 (Reason), Examine the statements carefully and work the correct answer according, to the instruction given below :, (a), , If both the statements are True and Statement-2 is the correct, explanation of the statement-1, , (b), , If both the statements are True and statement-2 is not the correct, explanation of statement-1, , (c), , If statement-1 is true and statement-2 is False., , (d), , If statement-1 is false and statement-2 is True., , 1., , Statement - 1 :, Statement - 2 :, , In HF, the oxidation state of 'F' is –1, 'F' being most electronegative, will have -1 oxidation in, its compound., , 2., , Statement - 1 :, Statement - 2 :, , Oxygen has zero oxidation state in O2., Element in their elemental form have zero oxidation state., , 3., , Statement - 1 :, Statement - 2 :, , Oxidation state of Oxygen in H2O2 is –1., H2O2 has peroxide linkage., Redox Reactions, , 131
Page 154 :
4., , Statement - 1 :, Statement - 2 :, , For the reaction Zn + Cu2+ —→ Zn2+ + Cu; Ecell is +ve., For standard Hydrogen electrode E° = 0, , 5., , Statement - 1 :, Statement - 2 :, , 2H2O2 —→ 2H2O + O2 is Decomposition reaction, (Redox)., Oxygen has -2 oxidation state in H2O., , 6., , Statement - 1 :, Statement - 2 :, , C + O2 —→ CO2 ; carbon get oxidised., Gain of Hydrogen is reduction., , 7., , Statement - 1 :, Statement - 2 :, , CaCO3 —→ CaO + CO2 is not redox reaction., C, Ca, O do not change their oxidation number in the, reaction., , 8., , Statement - 1 :, Statement - 2 :, , Oxidation also occurs when decrease in electron density, is observed., Oxidation is gain of electro-positive element., , 9., , Statement - 1 :, Statement - 2 :, , Cr2O72– is a self indicator., MnO4– acts as a self indicator., , 10., , Statement - 1 :, Statement - 2 :, , Equivalence point comes first before end point., Equivalence point cannot be obtained even by graphical, method., , Ans: 1. (a) 2. (a) 3. (a), , 4. (b) 5. (d) 6. (b) 7. (a) 8. (c) 9. (d) 10. (d), , ONE WORD ANSWER TYPE QUESTIONS, 1., , What is the oxidation number of S in S8., , 2., , What is the oxidation state of Oxygen in H2O2., , 3., , Name the substance used in salt-bridge., , 4., , Name an indicator which can act as self-indicator., , 5., , When a substance gains electron, it is called :, , 6., , Name the ion which is used for balancing the hydrogen atom in acidic, medium., , 7., , In the reaction 3Mg + N2 ––→ Mg3N2, Nitrogen is oxidised or reduced., , Ans: 1. zero, , 2. 1, , 3. NH4Cl or KCl, , 5. Reduction, , 6. H+, , 7. Reduced, , 132, , Chemistry Class XI, , 4. KMnO4
Page 155 :
1-MARK QUESTIONS, 1. Define oxidation and reduction according to electronic concept., 2. Define oxidation and reduction according to oxidation number., 3. A freshly cut apple is almost white but it turns reddish brown after, sometime. Give reason., 4. Define oxidation number., 5. Write oxidation number of Mn in KMnO4., 6. Write oxidation number of Cr in Cr2O72–., 7. Write Stock notation of MnO2 and AuCl3., 8. Define redox reaction with example., 9. Define disproportionation reaction. Give one example., 10. Define the term redox titration., 11. Name the indicator used in redox titration involving K2Cr2O7 as an, oxidizing agent., 12. At what concentration of Cu2+ (aq.) will electrode potential become equal, to its standard electrode potential ? , [Ans. 1 M], 13. The standard reduction potentials of three metals cations X, Y and Z are, + 0.52, – 3.03 and – 1.18 V respectively. Arrange X, Y and Z in order of, increasing reducing power. , [Ans. X < Z < Y], 14. An electrochemical cell consists of two electrodes i.e., Anode and Cathode., What is the direction of flow of electrons in this cell ?, 15. Why anode is negatively charged in an electrochemical cell?, 16. Out of Zn and Cu vessel one will be more suitable to store 1 M HCl?, , Given, , θ, , = – 0.76 V,, , θ, , [Ans. Cu], , = + 0.34 V., , 15. Is it safe to stir 1 M AgNO3 solution with copper spoon ?, Given, , θ, , = + 0.80 V,, , θ, , = + 0.34 V., , Redox Reactions, , [Ans. No], , 133
Page 156 :
2-MARKS QUESTIONS, 1. Identify oxidant and reductant in the reaction :, I2 (aq) + 2S2O32– (aq) ––→ 2 I– (aq) + S4O62–(aq)., 2. Calculate oxidation number of Fe in Fe3O4 and write a suitable justification, of your answer., 3. Oxidation-reduction reactions are complementary. Explain., 4. Write formula for the following compounds :, , , (i) Mercury (II) chloride, , , , (ii) Nickel (II) sulphate, , , , (iii) Iron (III) sulphate, , , , (iv) Chromium (III) oxide, , 5. Justify that the reaction : H2O(s) + F2 ––→ HF + HOF is a redox reaction., 6. A decomposition reaction may or may not be a redox reaction. Write two, decomposition reactions in support of the statement., 7. Split the reaction 2 K (s) + C12 (g) ––→ 2 KC1 (s) into oxidation and, reduction half reactions., 8. Calculate the oxidation number of underlined elements in following, compounds :, (i) CaO2, , (ii) H2S2O7, , (iii) K2MnO4, , (iv) KI3, , 9. Write the functions of salt bridge in an electrochemical cell., 10. Define the term redox couple. Write the practical application of redox, couple., 11. The standard reduction potentials of two metals A and B are – 0.76 V and, + 0.34 V respectively. An electrochemical cell is formed using electrodes, of these metals., , , (i) Identify the cathode and anode., , , , (ii) Write the direction of flow of electron., , 134, , Chemistry Class XI
Page 157 :
3-MARKS QUESTIONS, 1. Calculate oxidation number of :, , , (i) Cr in Cr2O42–, , (ii), , , , O in KO2, , (iii) Na in Na2O2., , 2. Account for the following :, (i) HNO3 acts as oxidizing agent while HNO2 can act both as reducing, and oxidizing agent., (ii) AgF2 is unstable compound and act as a strong oxidizing agent., , , (iii) Ozone acts as an oxidising agent., , 3. Permanent ion (MnO4–) reacts with sulfur dioxide gas in acidic medium, to produce Mn2+ ion and hydrogen sulphate ion. Write ionic equation and, balance by ion electron method., 4. Balance the following equation by oxidation number method :, P4(s) + OH– (aq) ––→ PH3 + H2PO2– (aq) [Basic Medium], 5. Balance the following equation by ion electron method :, , , C12O7 (g) + H2O2 (1) ––→ ClO2– (aq) + O2 (g) [Basic medium], , 6. Depict the galvanic cell in which the reaction, , , Zn (s) + 2 Ag+ (aq) ––→ Zn2+ (aq) + 2 Ag (s) takes place. Further show :, , , , (i) Which electrode is negatively charged ?, , , , (ii) The carriers of the current in the cell, , , , (iii) Individual reaction at each electrode., , 7. Explain with suitable reasons :, , , (i) Reaction FeSO4 (aq) + Cu (s) ––→ CuSO4 (aq) + Fe does not occur., , , , (ii) Zinc can displace copper from aqueous CuSO4 solution but Ag cannot., , , , (iii) Solution of AgNO3 turns blue when copper rod is immersed in it., , Redox Reactions, , 135
Page 158 :
5-MARKS QUESTIONS, 1. (i) MnO42– undergoes disproportionation reaction in acidic medium but, MnO4– does not. Give reason., (ii) Give one example each of the following redox reactions:, , , (a) Combination reaction, , , , (b) Decomposition reaction, , , , (c) Metal displacement reaction, , 2. Consider the cell reaction of an electrochemical cell : Ni(s) + 2 Ag+(aq) →, Ni2+ (aq) + 2 Ag (s) and answer the following questions :, , , (i) Write anode and cathode half reactions., , , , (ii) Mention the direction of flow of electrons., , , , (iii) How is the electrical neutrality maintained in the solutions of the two, half cells ?, , , , (iv) Write the formula for calculating standard emf of this cell., , , , (v) How does the emf change when the concentration of silver ions is, decreased ?, , 3. Justify the reason that following reactions are redox reactions., (a) CuO (s) + H2 (g) ——→ Cu (s) + H2O (g), (b) Fe2O3 + 3CO (g) ——→ 2 Fe (g) + 3CO2 (g), (c) NH3 (g) 5O2 (g) ——→ 4NO (g) + 5H2O (g), (d) BCl3 (g) + 3 LiAlH4 ——→ B2H6 + LiCl + AlCl3, (e) 2K + F2 ——→ 2KF, [Hints:– CuO is oxidizing agent, H2 is acting as reducing agent because Cu (II), is changing to Cu (0) by gain of e– H2 is getting oxidised to H2O (g), its, oxidations sate is changing from 0 to +1, by loss of electrons., (ii) It is redox reaction: Fe2O3 is getting reduced to fe. CO is getting oxidised, to CO2.], 136, , Chemistry Class XI
Page 160 :
3., , An aqueous solution containing 1M each of Au+3, Cu+2, Ag+, Li+ is being, electrolysed using inert electrodes the value of standard potentials are, E°qAg=, 0.80 V, Eq°Cu 2=, 0.34 V, Eq°Au3=, 1.50 V, Eq°Li=, −3.03V, +, +, +, /Ag, /Li, + Cu, /C4, /Au, , With increasing voltage, find the sequence of deposition of metals on the, cathode., Ans. Only Au3+, Ag+ and Cu2+ will deposit at cathode., Li+ will not deposit at cathode be cause SRP of water is -0.8274V, , 4., , So after Cu2+ ; H2 will evolve at cathode., , Eq for Cl2 (g) + 2l– —→ 2Cl– (aq.) is 1.36 V, then calculate., Eq for 4C1– (aq.) —→ 2Cl2(g) + 4e–, Ans., , 5., , Eq° Cl− /Cl =, − 1.36 Eq is independent of amount of substance, 2, , Why salt bridge is made up of saturated solution of KNO3 in agar–agar., Ans. Velocities of both K+ and NO3– are nearly the same., , 138, , Chemistry Class XI
Page 161 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Identify the oxidised and Reduced species in the following reaction [1], , H2S + Cl2 —→ 2HCl + S, (a) H2S, 2., , (b) Cl2, , (c) Both H2, Cl2, , (d) None of these, , What is the oxidation state of Br in BrO3– ? [1], (a) +1, (b) +3, (c) +4, (d) +5, , 3., Classify the type of reaction in Redox Reaction form : , 3H2O + P4 + 3OH– —→ PH3 + 3H2PO2–, 4., , [1], , What is a redox couple? Give one example., , 5., Identify oxidant in reaction given below : , , CuO(s) + H2 (g) —→ Cu(s) + H2O(g), , [1], , 6., , Assign oxidation number to the underlined elements , PO, H, NaH, OH, PO, MnO, O247O, K, H22 MnO, S2 OH7 4(d), H SO, H24 NaH, P2(b), O4 72 PO, K, HP2 S, (a) NaH 2 PO 4NaH, (c), 44 P, 74 P, 442K, OH, 2 22MnO, 7, 72 4 2K, 2 MnO, 4, 2 S2 O 7 2 2 7, , [2], , 7., , Predict product of electrolysis in following case , - An aqueous solution of CuCl2 with platinum electrodes., , [2], , 8., , Consider the reaction Zn(s) + 2Ag+ (aq.) —→ Zn2+ (aq.) + 2Ag(s), Answer following : , [3], (i), Which electrode is negatively charged ?, (ii), What are carrier of current in the cell ?, (iii) Individual reaction at each electrode., , 9., , Eq values are given : K+/K = –2.93V, Ag+/Ag = 0.80V , [3], 2+, 2+, 3+, Hg /Hg = 0.79V Mg /Mg = –2.37V, Cr /Cr = –0.74V, (i), Which one is strong reducing agent ?, (ii), Which one is strong oxidising agent ?, (iii) Which redox couple is a stronger reducing agent than H+/H2 ?, , 10. Balance the reaction (ion-electron or oxidation number) , [5], –, –, P4(s) + OH (aq.) —→ PH3 (g) + H2PO2 (aq.) [Basic medium], *****, , Redox Reactions, , 139
Page 163 :
(ii) For production of Methanol (CH3OH), (iii) In oxyhydrogen torches, (iv) In a fuel cell., , , Hydrides, , , , (i) Ionic or salt like or saline hydrides are formed with most of the, s-block elements. Significant covalent character is found in LiH, BeH2, and MgH2., , , , (ii) Covalent or Molecular hydrides are formed with most of the p-block, elements. There are further classified as :, (a) Electron deficient hydrides are formed by group 13 elements e.g.,, B2H6. They acts as Lewis acid., (b) Electron Precise hydrides are formed by group 14 elements e.g.,, CH4., (c) Electron rich hydrides have lone pair of electrons on central atoms of, the molecules. Elements of group 15-17 form these types of hydrides., , NH3, HF has high m.p./b.p. due to presence of intermolecular hydrogen, bonding., , , , (iii) Metallic or Non-stoichiometric or Interstitial hydrides are formed, by d and f -block elements. For example La H2.87 or NiH0.6–0.7., Water : (H2O), , Hard water : Hard water contains calcium and magnesium salts in the, form of hydrogencarbonate, chloride and sulphate. Hard water does not, give lathers with soap., Soft water : Water free from soluble salts of calcium and magnesium is, soft water., Types of Hardness :, Temporary hardness is due to presence of calcium or magnesium, hydrogen carbonate in water. Temporary hardness can be removed by :, (i) Boiling, (ii) Clark’s Method, , , Permanent hardness :, , Such hardness is due to presence of calcium or magnesium chlorides and, sulphates., Hydrogen, , 141
Page 164 :
Permanent hardness can be removed by :, (i) Treatment with washing soda, (ii) Calgon’s method, (iii) Ion exchange method., , , , Demineralised or Deionised water : Water free from all soluble mineral , salts is known as demineralised water., Hydrogen Peroxide (H2O2), , Preperation :, , (i) By electrolytic oxidation of acidified sulphate solutions at high current, density., (ii) 2-Ethylanthraquinol, , , H2O2 + (Oxidised product), , Physical Properties, (i) Miscible with water in all proportions., (ii) A 30% of H2O2 solution is marked as ‘100 volume’ hydrogen, peroxide., , , , Chemical Properties :, (i) It acts as an oxidising as well as reducing agent., , (ii) Oxidising action in acidic medium :, 2Fe2+(aq) + 2H+ (aq) + H2O2 (aq) —→ 2Fe3+ (aq) + 2H2O(l), (iii) Reducing action in acidic medium :, 2MnO4– + 6H+ + 5H2O2 —→ 2Mn2+ + 8H2O + SO2, , , Storage of H2O2 :, (i) Stored in wax-linked glass or plastic vessels in dark. Urea can be, added as a stabiliser., (ii) It is kept away from dust because dust can induce explosive, decomposition of the compound., , , , Uses of H2O2 :, , (i) As an antiseptic it is sold in the market name perhydrol., (ii) In synthesis of hydroquinone., (iii) As a bleaching agent., 142, , Chemistry Class XI
Page 165 :
1. Auto–protolysis of water: Water accepts a proton from other water, molecule to from H3O+ and OH– this porous is called auto – protolysis of, water, , H2O(l) + H2O(l) , , H3O+ (aq) + OH– (aq), , Its significance is that water can act as acid as well as base i.e. it is, amphoteric in nature., 2. Hydrogen economy: It is transportation and storage of energy in the form, of liquid or gaseous hydrogen. Advantage of hydrogen economy is that, energy is transmitted in the form of dihydrogen and not as electric power, 3. Hydrogenation: It is a process of converting polyunsaturated oils in edible, fats., Ni, > Vanaspati ghee (fat)., Vegetable oil + H2, 473K, 4. Syngas: It is a mixture of CO and H2 in 1:1 ratio and also known as water, gas or syntnesis gas., 1270 K, C(s) + H2O(g), > CO2 + H2(g), Ni, Carbon , , Carbon monoxide, , 5. Water gas shift reaction., , , CO + H 2 O, , 673 K, >CO 2 + H 2, iron chromate as catalyst, , 6. Fuel-cell:– Fuel cell is a cell in which chemical energy of fuel is converted, into electrical energy., 7. Structure of water: It is bent molecule in gas phase with HOH bond, angle 104.5° and O–H bond length of 95.7 pm as shown if figure, , Hydrogen, , 143
Page 166 :
8. Calgon:– It is sodium polymetaphosphate (NaPO3)n it is used to remove., Permanent hardness of water., 9. De-ionized water:– Pure di-mineralised (ionized water) free from all, soluble mineral matter is obtained by passing water successively through, a cation exchanger (in the H+ form) and an anion exchanger for removal, by cation and anions, , 144, , Chemistry Class XI
Page 167 :
Hydrogen, , 145, , MIND MAP : HYDROGEN
Page 168 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1. What is the strength of 20 volume solution of H2O2?, (a) 5g/L, , (b) 10g/L, , (c) 30g/L, , (d) 60g/L, , 2. The number of H2O molecules which are involve in Hydrozen bonding, in CuSO4.5H2O molecule itself is, (a) H3PO2, , (b) H3PO3, , 3. P4O10 on hydrolysis produces, (a) H3PO2, , (b) H3PO3, , (c) H3PO4, , (d) PH3, , (c) H3PO4, , (d) PH3, , 4. D2O has higher value of following physical parameters than H2O, except, (a) Molecular Mass, , (b) Melting Point, , (c) Density, , (d) Dielectric Constant, , 5. Which one is ionic hydride in nature?, (a) CrH, , (b) NH3, , (c) H2O, , (d) NaH, , (c) CO + H2, , (d) CO + H2CO3, , 6. Syn-gas is a mixture of, (a) CO+N2, , (b) O3, , 7. The electronic conguration of 'D' (Isotope of Hydrogen), (a) 1s2, , (b) 1s22s1, , (c) 1s1, , (d) 1s22s22p1, , (c) 8, , (d) 9, , 8. Which group forms hydride?, (a) 6, , (b) 7, , 9. When MnO4– reacts with H2O2 in basic medium then following species, are involved, except, (a) MnO2, , (b) O2, , (c) OH–, , (d) Mn2+, , 10. Select the incorrect statement for H2O2 structure, (a) It is non planar, (b) O – O bond length is more in gaseous state than in solid phase, (c) Both OH bond are in different plane, (d) O – O – H bond angle in gas phase is more than in solid phase, Ans: 1. (d) 2. (d) 3. (c) 4. (d) 5. (d) 6. (c) 7. (c) 8. (a) 9. (d) 10. (d) , 146, , Chemistry Class XI
Page 169 :
TRUE AND FALSE TYPE QUESTIONSE, 1. H2O2 decomposes slowly on exposure to light., 2. H2O2 on reaction with Pbs convert Pbs into Pb., 3. Chemically calgon is sodium hexametaphosphate Na6P6O18., 4. NH3 is electron rich hydride., 5. Phosphorus form PH5., 6. H2 gas cannot reduce Pb2+ ion., 7. Hydroformylation of olefins yields aldehydes which futher undergoes, reduction to give alcohols., 8. Hydrogenation of vegetable oils using nickel as catalyst gives edible fats., 9. Ice has cage like structure with air spaces., 10. Soft water gives lather with Soap., Ans: 1. True 2. False 3. True 4. True 5. False, 6. False 7. True 8. True 9. True 10. True, FILL IN THE BLANKS, 1. Cation exchange resin contain large organic molecule with _____ group., 2. At atmospheric pressure ice crystallises in __________ for., 3. Due to high _______ of H2O, H2O has a very strong hydrating tendency., 4. Water is present in [Cr(H2O)6]3+.3Cl– in the form of _________., 5. The H-H bond dissociation enthalpy of H2 is _________, is the highest, for a single bond between two atoms of any elements., 6. In the Clark's method for softening compound _________ is used., 7. During photosynthesis H2O is __________., 8. BeH2 and MgH2 are ionic and _________ in nature., 9. When NaH is electrolysed, then _________ is released at anode., 10. Hydrated sodium aluminium silicate is ___________., Ans: 1. SO3H 2. Hexagonal 3. Dielectric 4. Coordinated water, 5. 435.88 kj mol-1 6. Ca(HCO3)2 7. Oxidised 8. Polymeric, 9. H2 10. Zeolite/Permutit, Hydrogen, , 147
Page 170 :
MATCH THE COLUMNS, 1., , 2., , Column -I, , Column-II, , A., , Boiling, , p. CaCO3, , B., , Clark's Method, , q. Mg(OH)2, , C., , Washing soda, , r. NaAISiO4, , D., , Ion-exchange method, , s. NaCl, , Column -I, A., , H2O + NH3, , B., , Column-II, OH + NH4+, , p., , Hydroformylation, , 2H2O + 2Na —→ 2NaOH + H2, , q., , Acid base reaction, , C., , P4O10 + 6H2O —→ 4H3PO4, , r., , Redox Reaction, , D., , 2H2 + CO + RCH = CH2, , s., , Hydrolysis reaction, , , , , , , —→ RCH2CH2CH2O4, Ans. 1. A→ q, B → p, C → s,, 2. A→ q, B → r,, , C → s,, , D→ r, D→ p, , ONE WORD ANSWER TYPE QUESTIONS, 1. Name the gas release when zinc reacts with NaOH., 2. When brine solution is electrolysed then nature of solution will be?, 3. What happens when Al4C3 reacts with D2O?, 4. In which medium H2O2 act as reducing agent?, 5. What is the chemical name of calgon's?, 6. What happens when LiH reacts with Al2C16?, 7. What happens when warm aqueous Barium hydroxide solution is, electrolysed?, 8. What type of particles are emitted by Tritium?, 9. What is the name for the following chemical reaction?, , 148, , CO(g) + H2O(g) —→ CO2(g) + H2(g), Chemistry Class XI
Page 171 :
10. What is the term used to refer “Transportation and storage of energy in, the form of liquid or gaseous dihydrogen”, Ans: 1. H2 2. Basic 3. Al4C3 + 12D2O —→ 3CD4 + 4Al(OD)3, 4. Acidic, Basic , 5. Sodium hexameter phosphate (Na6P6O18), 6. 8LiH + Al2Cl6 —→ 2LiAlH4 + 6 LiCl, 7. H2 gas is produced, 8. β- (beta negative), 9. Water gas shift reaction, 10. Hydrogen economy, ASSERTION AND REASON TYPE QUESTIONS, Each question contain statement-1 (Assertion) and statement-2 (Reason). Examine, the statements carefully and mark the correct answer according to the instruction, given below :, (A) If both the statements are True and statement-2 is the correct explanation of, statement-1, (B) If both the statements are True and statement-2 is not the correct explanation, of statement-1, (C) If statement-1 is true and statement-2 is false, (D) If statement-1 is false and statement-2 is true, 1., , Statement-1, Statement-2, , :, :, , HF form extensive hydrogen bonding., F has highest tendency to form hydrogen bonding., , 2., , Statement-1, Statement-2, , :, :, , MgCl2 solution produces lather with soap., Hard water does not produce lather with soap., , 3., , Statement -1, Statement-2, , :, :, , Density of ice is less than water., Ice has open cage structure., , 4., , Statement-1, Statement-2, , :, :, , Water can act as acid as well as base., Water can accept as well as donate H+ ion., , 5., , Statement-1, Statement-2, , :, :, , KMnO4 act as self indicator., KMnO4 only act as reducing agent., , 6., , Statement-1, , :, , Statement-2, , :, , Washing soda (Na2CO3) is use to remove temporary, hardness., Clark's method is used to remove temporary hardness., Hydrogen, , 149
Page 172 :
7., , In cation exchange process, H+ exchanges for Na+, Ca2+,, Mg2+., In anion exchang process OH– exchanges for anion like, Cl–, HCO3–, SO42-., , Statement-1, , :, , Statement-2, , :, , 8., , Statement-1, Statement-2, , :, :, , When Na reacts with H2O, H2 gas is release., P4O10 on hydrolysis produce H3PO3., , 9., , Statement-1, Statement-2, , :, :, , CH4 is a covalent hydrides., CH4 is dectron precise type hydrides., , 10. Statement-1, Statement-2, , :, :, , H2 gas is use in metallurigical process., H2 gas is use as fuel., , Ans: 1. (a) 2. (d) 3. (a) 4. (a) 5. (c) 6. (d) 7. (b) 8. (c) 9. (a) 10. (b) , 1-MARK QUESTIONS, 1. Name the isotope of hydrogen which is radioactive in nature. [Ans. Tritium], 2. H+ ions does not exist freely and is always associated with other atoms or, molecule. Explain., 3. Give the composition of water gas., , [Ans. CO, H2], , 4. Name the compound whose electrolysis in aqueous state, give high purity, (99.95%) dihydrogen., [Ans. aq Ba(OH)2 solution], 5. Give the main purpose of water gas shift reaction., 6. Write the chemical reaction occuring during coal gasification., 7. Name the element used in fuel cell for generating electricity. [Ans. H2], 8. Give an example of electron deficient covalent hydride., , [Ans. B2H6], , 9. Name the hydrides which have high potential for hydrogen storage., [Ans. Metallic hydrides], 10. Name the groups in d-block elements which do not form metallic hydrides., , , [Ans. 7, 8, 9], , 11. H2 is relatively inert at room temperature. Explain., 12. Complete the reaction :, C(s) + H2O(g), 150, , (A) ___ (g) + (B) ___ (g) ., , Chemistry Class XI, , [Ans. CO, H2]
Page 173 :
13. Name the phenomenon as a reason of which water has unusual boiling, point., [Ans. Extensive hydrogen bonding], 14. Draw structure of water., 15. At atmospheric pressure ices crystallised in the ......... form but at very, low temperature it condenses to ......... form. [Ans. Hexagonal, cubic], 16. Mention the temperature at which density of ice is maximum.[Ans. 4°C], 17. Density of ice is .......... than density of liquid water., , [Ans. Less], , 18. Complete the reaction :, 2H2O(l) + 2Na(s) —→, 19. How many hydrogen-bonded water molecules (s) are associted in, CuSO4.5H2O., [Ans. One], 20. Name the compound used in Clark’s method to remove temporary hardness, of water., [Ans. Lime], 21. Write the chemical formula of “Calgon”., , [Ans. Na4P6O18], , 22. A 30% solution of H2O2 is marketed as ........ volume.[Ans. 100 volume], 23. Draw gas phase structure of H2O2., 24. Name the organic compound whose auto-oxidation is used to produce, H2O2 commercially or industrially., [Ans. 2-Ethylanthraquinol], 25. How is heavy water obtained from ordinary water?, 2-MARKS QUESTIONS, 1. Complete the following reactions :, (i) CO(g) + H2(g), (ii) Zn(s) + NaOH(aq), 2. Among NH3, H2O and HF which would you except to have highest, magnitude of hydrogen bonding and why ?, 3. How do you except the metallic hydrides to be useful for hydrogen storage ?, Explain., 4. How can the production of dihydrogen obtained from “Coal gasification”, be increased ?, Hydrogen, , 151
Page 174 :
5. Write the name of isotopes of hydrogen. What is the mas ratio of these, isotopes ?, 6. Complete the reactions :, (i) CO(g) + 2H2(g), (ii) CH4(g) + H2O(g), 7. Comment on the reactions of dihydrogen with :, (i) Chlorine, (ii) Sodium., 8. Arrange the following :, (i) LiH, NaH, CsH, , (In increasing order of ionic character), , (ii) H—H, D—D, F—F, , (In decreasing order of bond dissociation, enthalpy), 9. List two uses of dihydrogen., 10. Complete the reactions :, (i) H2 + CO + RCH = CH2 —→, , , (ii) H2 + RCH2CH2CHO —→, , 11. Give two reactions to show amphoteric nature of water., 12. Complete the reactions :, (i) 2F2(g) + 2H2O(l) —→, (ii) 6CO2(g) + 12H2O(l) —→, 13. What is the difference between the term hydrolysis and hydration., 14. What do you understand by term ‘autoprotolysis’ of water ? What is its, significance ?, 15. What causes the temporary and permanent harness of water ?, 16. Is demineralised or distill water useful for drinking purposes ? If not, how, can it be made useful ?, 17. Explain the terms :, (i) Hydrogen economy., (ii) Fuel cell., 18. Write chemical reactions to justify that hydrogen peroxide can function, as an oxidising as well as reducing agent., 152, , Chemistry Class XI
Page 175 :
19. Compare the structure of H2O and H2O2., 20. How does H2O2 behaves as a bleaching agent ?, 21. H2O2 acts as an oxidizing as well as reducing agent. Why?, 3-MARKS QUESTIONS, 1. Complete the chemical reactions :, (i) 8LiH + Al2Cl6 —→, (ii) 2LiH + B2H6 —→, 2. What do you understand by : (i) Electron deficient, (ii) Electron precise,, (iii) Electron rich compounds of hydrogen ? Provide justifications with, suitable examples., 3. What do you understand by the term “non-stoichiometric hydrides” ? Do, you expect this type of the hydrides to be formed by alkali metals. Explain, and Justify your answer., 4. Arrange the following :, (i) CaH2, BeH2, TiH2 (in order of increasing electrical conductance), , (ii) NaH, MgH2, H2O (in order of increasing bond dissociation enthalpy), (iii) Li, F, H (in order of increasing ionisation enthalpy), 5. What do you understand by the terms :, (i) Syn gas (ii) Water gas shift reaction (iii) Producer gas., 6. Would gas except the hydrides of N, O and F to have lower boiling point, than the hydrides of their subsequent group members ? Give reasons., 7. Can phosphorous with outer electronic configuration 3s23p3 form PH5 ?, Explain., 8. Why and how the hydrogen is regarded as a fuel of future ? Explain., 9. Write the reactions when dihydrogen reacts with (i) O2 (ii) N2 (iii) Cl2, under specific conditions., 10. Name the hydrides :, (i) Which is non stoichiometric in nature ?, (ii) Which are stoichiometric compounds ?, (iii) Which has electron rich type hydrides ?, Hydrogen, , 153
Page 176 :
11. Complete the reactions :, (i) CaO(s) + H2O(g) —→, , , (ii) AlCl3(g) + H2O(l) —→, (iii) Ca3N2(s) + H2O(l) —→, , 12. Discuss the principle and method of softening of hard water by synthetic, exchange of resin method., 13. What is meant by ‘demineralised’ water and how can it be obtained ?, 14. What properties of water make it useful as a solvent ? What types of, compound can it (i) dissolved (ii) hydrolyse ?, 15. Calculate the strength of 10 volume solution of H2O2., 16. Complete the reactions :, (i) 2Fe2+ (aq) + 2H+(aq) + H2O2(aq) —→, (ii) HOCl + H2O2 —→, (iii) Mn2+ + H2O2 —→, 17. Give three uses of H2O2., 18. Complete the reactions :, (i) CaC2 + 2D2O —→, (ii) SO3 + D2O —→, (iii) Al4C3 + 12D2O —→, 19. Give the limitations of using H2 as a fuel., 20. H2O2 is stored in a wax lined glass or plastic vessels. Explain an equation, showing decomposition of H2O2 on exposure to light., 5-MARKS QUESTIONS, 1. Answer the following :, (a) Name the most abudant form of hydrogen isotope., (b) Name the particles emitted by tritium., , [Ans. 11H], [Ans. β–], , (c) Mixture of CO and H2 is used for preparation ......... . [Ans. Methanol], (d) Name the catalyst used in Haber’s Process for manufacture of NH3(g)., , (e) Name two electron rich hydrides., 154, , Chemistry Class XI, , [Ans. Fe], [Ans. NH3, H2O]
Page 179 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Hydrogen has maximum oxidation state in, (a) NaH (b) MgH2 (c) H2O, , 2., , [1], (d) C & H, , Which one does not cause hardness of water?, (a) MgCl2 (b) CaCl2 (c) MgSO4 (d) AlCl3, , 3., , Give one reaction for preparation of hydrogen gas in laboratory., , [1], , 4., , What causes the hardness of water?, , [1], , 5., , Draw the structure of H2O2., , [1], , 6., , Complete the reaction with balancing, , [2], , (a), , Fe2+ (aq.) + H+(aq.) + H2O2(aq.) —→, , (b), , HOCl + H2O2 —→, , 7., , What is Hydrogen Economy. What are its advantage?, , [2], , 8., , Explain the following, , [3], , (i), , Atomic hydrogen or oxy-hydrogen torch function for cutting, and welding purposes. Why?, , (ii), , CaH2, BeH2 and TiH2 arrange in order of increasing electrical, conductance and give reason., , (iii) Water shows amphoteric behaviour, support by giving, appropriate example., 9., , What are different types of hydrides? Give example., , [3], , 10., , Discuss the principle and method of softening of hard water by, synthetic ion-exchange resins., , [5], , *****, , Hydrogen, , 157
Page 180 :
Chapter - 10, , s-Block, s-Block, Elements, Elements, , FAST TRACK : QUICK REVISION, , , s-block elements consists of group-I (Alkali metals) and group-2 (Alkaline, earth metals)., , , , Group 1st elements — Li, Na, K, Rb, Cs, Fr., , , , Group 2nd elements — Be, Mg, Ca, Sr, Ba, Ra., , , , , , , Atomic radius : Atomic radius of alkali metals are greater than alkaline, earth metals., Hydration enthalpy : Decreases with increases in ionic sizes., Ionic mobility : Smaller the size of ion, more highly it is hydrated and, hence lower is its ionic mobility., , Li+ < Na+ < K+ < Rb+ < Cs+, , , , , , , , , Ionisation enthalpies : 1st I.E. of group 1st is smaller than group 2nd, elements but 2nd I.E. of group 2nd is smaller than group 1st elements., Flame colouration : Due to low I.E., s-block elements and their salts, imparts characteristics colour of oxidising flame (except Be and Mg). Be, and Mg do not show flame colouration because they have small size and, very high ionisation enthalpy., Reducing character : Due to large negative electrode potentials alkali, metals are stronger reducing agent than alkaline earth metal., Reactivity towards air :, , 4Li + O2 —→ 2Li2O (Lithium oxide), , , , , 2Na + O2 —→ Na2O2 (Sodium peroxide), , M + O2 —→ MO2 (M = K, Rb, Cs metal superoxide), , Alkaline earth metals being smaller in size do not from superoxides.
Page 183 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , 2., , 3., , 4., , 5., , 6., , 7., , The alkali metals are low melting. Which of the following alkali metal is, expected to melt if the room temperature rises to 30°C?, (a) Na, , (b) K, , (c) Rb, , (d) Cs, , Alkali metals react with water vigorously to form hydroxides and dihydrogen., Which of the following alkali metals reacts with water least vigorously?, (a) Li, , (b) Na, , (c) K, , (d) Cs, , The reducing power of a metal depends on various factors. Suggest the, factor which makes Li, the strongest reducing agent in aqueous solution., (a) Sublimation enthalpy, , (b) Ionisation enthalpy, , (c) Hydration enthalpy, , (d) Electron-gain enthalpy, , Metal carbonates decompose on heating to give metal oxide and carbon, dioxide. Which of the metal carbonates is most stable thermally?, (a) MgCO3, , (b) CaCO3, , (c) SrCO3, , (d) BaCO3, , Which of the carbonates given below is unstable in air and is kept in CO2, atmosphere to avoid decomposition., (a) BeCO3, , (b) MgCO3, , (c) CaCO3, , (d) BaCO3, , Metals form basic hydroxides. Which of the following metal hydroxide is, the least basic?, (a) Mg(OH)2, , (b) Ca(OH)2, , (c) Sr(OH)2, , (d) Ba(OH)2, , Some of the Group 2 metal halides are cavalent and soluble in organic, solvents. Among the following metal halides, the one which is soluble in, ethanol is, (a) BeCl2, , (b) MgCl2, , (c) CaCl2, , (d) SrCl2, s-Block Elements, , 161
Page 184 :
8., , 9., , The order of decreasing ionisation enthalpy in alkali metals is, (a) Na > Li > K > Rb, , (b) Rb > Na > K > Li, , (c) Li > Na > K > Rb, , (d) K > Li > Na > Rb, , The solubility of metal halides depends on their nature, lattice enthalpy, and hydration enthalpy of the individual ions. Amongst fluorides of alkali, metals, the lowest solubility of LiF in water is due to, (a) Ionic nature of lithium fluoride, (b) High Lattice enthalpy, (c) High hydration enthalpy of lithium atom, (d) Low ionisation enthalpy of lithium atom, , 10., , Amphoteric hydroxides react with both alkalies and acids. Which of the, following Group 2 metal hydroxides is soluble in sodium hydroxide?, (a) Be(OH)2, , (b) Mg(OH)2, , (c) Ba(OH)2, , (d) Ca(OH)2, , ASSERTION-REASON TYPE QUESTIONS, The question given below contains statement -1 (Assertion) and Statement-2, (Reason) Each question has four choice (a), (b), (c) and (d) out of which, only one is correct. Choice the correct option as under., (a) Statement-1 is true, statement-2 is true., , Statement-2 is a correct explanation for statement-1., (b) Statement-1 is true, statement-2 is true ;, , Statement-2 is not a correct explanation of statement-1., (c) Statement -1 is true, statement-2 is false., (d) Statement-1 is false, statement-2 is true., 1., , Statement-1 : Sodium metal is softer than potassium metal., Statement-2 : Metallic bonding in Potassium is weaker than in Sodium., , 2., , Statement-1 : Be(OH)2 is soluble in HCl and NaOH., Statement-2 : Be(OH)2 is amphoteric in nature., , 3., , 162, , Statement-1 : Metallic character of alkali metals increases on going down, , a group from top to bottom., Chemistry Class XI
Page 185 :
Statement-2 : Ionisation enthalpy of alkali metals increases on going down, , from top to bottom., 4., , Statement-1 : Super oxides of alkali metals are diamagnetic., Statement-2 : Super oxides contain the ion O2-which has one unpaired, electron., , 5., , Statement-1 : Alkali metals do not impart colour to the flame., Statment-2 :, , 6., , Statement-1 : Sodium cannot be obtained by chemical reduction of its ore., Statment-2 :, , 7., , Their ionization enthalpies are very low., Sodium is one of the strongest reducing agent., , Statement-1 : Beryllium hydroxide becomes soluble in excess alkali, , forming beryllate ion [Be(OH)4]2–., Statment-2 :, , Beryllium ion has greater tendency to form complexes., FILL IN THE BLANKS, , 1., , In the synthesis of sodium carbonate, the recovery of ammonia is done, by treating NH4Cl with Ca(OH)2. The by product obtained in this process, is .................., (a) NaCl, (b) NaOH, (c) CaCl2, (d) NaHCO3, , 2., , When sodium is dissolved in liquid ammonia, a solution of deep blue colour, is obtained. The colour of the solution is due to..............., (a) Sodium ion, (b) Ammoniated electron, (c) Sodium amide, (d) Ammoniated sodium ion, , 3., , By adding gypsum to cement..............., (a) Setting time of cement becomes less., (b) Setting time of cement increases, (c) Colour of cement becomes light, (d) Shining surface is obtain., , 4., , A substance which gives crimson red flame and breaks on heating to give, oxygen and a brown gas is, (a) Magnesium nitrate, (b) Calcium nitrate, (c) Barium nitrate, (d) Strontium nitrate, s-Block Elements, , 163
Page 186 :
5., , The hydration energy of Mg2+ is greater than that of............, (a) Al3+, (b) Be2+, (c) Na+, (d) Mg3+, , 6., , The active constituent of bleaching power is .........., (a) Ca(OCl)2, (b) Ca(OCl)Cl, (c) Ca(ClO2)2, (d) Ca(ClO2)Cl, , 7., , KO2 is used in oxygen cylinder is space and submarines because it.........., (a) Absorbs CO2 and increases O2 content, (b) Eliminates moisture, (c) Produces ozone, (d) None of the above, , 8., , A metal M readily forms water soluble sulphate MSO4, water insoluble, hydrozide and oxide MO which becomes inert on heating. The hydroxide, is soluble in NaOH. The metal M oxide M is ................., (a) Be, (b) Ca, (c) Mg, (d) Sr, , 9., , Photo electric effect is maximum in..............., (a) Cs, (b) K, (c) Na, (d) Li, , 10., , Fill in the blanks with proper option given below for the following statement., "All the halides of alkaline earth metals with exception of ............. are ionic, in nature.", (a) Barium halide, (b) Strontium halide, (c) Beryllium halide, , 11., , (d) Calcium halide, , Flame test is not given by ..............., (a) Be, , (b) Sr, , (c) K, , (d) Ca, , MATCH THE COLUMNS, In the following questions more than one option of column I and II may be, correlated., Column-I, (i) Li, (ii) Na, (iii) Ca, (iv) Ba, , 1., , 164, , (a), (b), (c), (d), (e), , Chemistry Class XI, , Column-II, Insoluble sulphate, Strongest monoacidic base, Most negative E° value among alkali metals., Insoluble oxalate, 6s2 outer electronic configuration
Page 187 :
2., , Column-I, (i) CaCO3, (a), (ii) Ca(OH)2, (b), , (iii) CaO, (c), (iv) CaSO4, (d), , Column-II, Dentistry, ornamental work, Manufacture of sodium carbonate from, caustic soda, Manufacture of high quality paper, Used in white washing., , 3., , Column-I, (i) Cs, (ii) Na, (iii) K, (iv) Ca, (v) Sr, (vi) Ba, , (a), (b), (c), (d), (e), (f), , Column-II, Apple green, Violet, Brick red, Yellow, Crimson red, Blue, , (a), (b), (c), (d), , Column-II, Photo electric cells, Coolant in nuclear reactors, SO2 absorber, Detergent, , 4., (a), (b), (c), (d), , Column-I, NaOH, Na2CO3, Liquid Na, Caesium, , 1-MARK QUESTIONS, 1. What is the oxidation state of K in KO2 ?, 2. Why are group I element called alkali metals ?, 3. Potassium carbonate cannot be prepared by solvay process. Why ?, 4. LiCl is soluble in organic solvent. Why ?, 5. Why are group I elements called alkali metals ?, 6. Alkali metals are strong reducing agents. Why ?, 7. Why do alkali metals give characteristics flame colouration ?, 8. Arrange the following in order of increasing covalent character : MCl,, MBr, MF, MI (where M = Alkali metal) [Ans. MF < MCl < MBr < MI], 9. Alkali metals can not be obtained by chemical reduction method. Explain., 10. Why is sodium metal kept under kerosene oil ?, s-Block Elements, , 165
Page 188 :
11. Why Be and Mg do not give characteristics colour to the flame ?, 12. Arrange the alkaline earth metal carbonate in the decreasing order of, thermal stability., 13. Why do alkaline earth metals not form any superoxide ?, 14. Why gypsum is added to cement ?, 15. How plaster of paris is obtained from gypsum ?, 16. BeO is insoluble in water but BeSO4 is soluble in water ? Why ?, 17. Why second I.E. of group II elements is less than group I elements ?, 18. What is quick lime ? How is it prepared ?, 19. Why does Be show similarities with Al ?, 20. Name the alkaline earth metal hydroxide which is amphoteric., 2-MARKS QUESTIONS, 1. Why are alkali metals soft and have low melting points ?, 2. Write any four similarities between Li and Mg., 3. Why are potassium and caesium rather than Lithium used in photoelectric, cells ? , 4. Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3 at, higher temperature ? , 5. Among the alkali metals which has :, (i) Highest melting point., (ii) Most electropositive character, (iii) Lowest size of ion., , , (v) Strongest reducing character., , [Ans. (i) Li (ii) Cs (iii) Li (iv) Li], , 6. Why does the solubility of alkali earth metal carbonates and sulphates, decrease down the group ? , 7. Draw the structure of BeCl2 in (i) Vapour phase (ii) Solid state., 8. When CO2 gas is passed in lime water it turns milky but in case of excess, CO2 milkiness disappears. Support the statement by giving suitable, reaction equations., 9. (i) Eθ for M2+ (aq) + 2e– —→ M(s) (where M = Ca, Sr, Ba) is nearly, constant. , 166, , Chemistry Class XI
Page 189 :
(ii) What is dead burnt plaster ? How is it obtained from gypsum?, , 10. Write two important uses of (i) Limestone (ii) Quick lime., 3-MARKS QUESTIONS, 1., , , , , Assign reason for the following :, (i) Compounds of lithium are generally covalent., (ii) Alkali metals are strong reducing agent., (iii) LiCl is more covalent than NaCl., , 2. Discuss the various reactions that occur in Solvay process., 3., , , , , Explain why ?, (i) Lithium salts are commonly hydrated., (ii) Sodium peroxide is widely used as oxidising agent., (iii) Sodium wire is used to remove moisture from benzene but can’t be, used for drying alcohol., , 4. Sodium hydroxide is generally prepared by electrolysis of brine solution, in the Castner-Kellner cell :, (i) Write the reactions that occur in the cell., (ii) Write any two uses of NaOH., 5., , , , , Explain with suitable reasons :, (a) A solution of Na2CO3 is alkaline., (b) Alkali metals are prepared by electrolysis of their fused chlorides., (c) Sodium is found to be more useful than potassium ?, , 6. Arrange the following in order of property mentioned against each :, (i) BaCl2, MgCl2, BeCl2, CaCl2 (Increasing ionic character), (ii) Mg(OH)2, Sr(OH)2, Ba(OH)2, Ca(OH)2 (Increasing solubility in water), (iii) BeO, MgO, BaO, CaO (Increasing basic strength), 7., , , , , What happens when :, (i) Mg is burnt in air., (ii) Quick lime is heated with silica., (iii) Chlorine is heated with slaked lime., , 8. Write the raw material required for the manufacture of portland cement ?, Why gypsum is added into it ?, 9. (i) Why alkaline earth metals cannot be obtained by reduction of their, oxides ?, s-Block Elements, , 167
Page 190 :
(ii) Why the elements of group 2 are known as alkaline earth metals ?, , 10. (i) Alkaline earth metals forms ionic salt having bivalent cations. Explain., Why ?, , , (ii) A piece of magnesium ribbon continues to burn in SO2. Why ?, 5-MARKS QUESTIONS, , 1., , , , , , , Explain the following observation :, (a) LiI is more soluble than KI in ethanol., (b) Sodium reacts with water less vigorously than potassium., (c) LiF is insoluble in water., (d) The mobilities of the alkali metal ions in aqueous solution are, Li+ < Na+ < K+ < Rb+ < Cs+., (e) Lithium is the only alkali metal to form a nitride directly., , 2. Complete the following reaction equations :, (i) BeCl2 + LiAlH4 —→, (ii) CaO + SiO2 —→, (iii) Ca(OH)2 + Cl2 —→, (iv) CaO + P4O10 —→, (v) Ca(OH)2 + CO2 —→, 3. Compare the solubility and thermal stability of the following :, , , Compounds of the alkali metals with those of alkaline earth metals, (a) nitrates (b) carbonates (c) sulphates., , 4. Explain the significance of Sodium (Na), Potassium (K), Magnesium (Mg), and Calcium(Ca) in biological fluids., 5. Explain the significance of Sodium Potassium, Magnesium and Calcium, biological fluids., 6. (i) A solutions of Na2CO3 is alkaline why?, (ii) BeO insoluble but BeSO4 in soluble in water. Why?, (iii) Lithium salts are commonly hydrated and those of other alkali metal, ions are usually anhydrous give reasons., (iv) What is the importance of cement?, (v) What happen when quick lime is heated with silica?, , 168, , Chemistry Class XI
Page 191 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Photoelectric effect is maximum in , (a) Cs, , 2., , (b) K, , (c) Na, , (d) Li, , Flame test is not shown by , (a) Be, , (b) Sr, , (c) K, , [1], [1], , (d) Ca, , 3., , Oxidation state of K in KO2 is _____________., , [1], , 4., , LiCl is soluble in organic solvent. Why? , , [1], , 5., , Why is sodium kept under kerosene? , , [1], , 6., , Write only four similarities in properties of Li and Mg., , [2], , 7., , Write two important uses of CaO and CaCO3., , [2], , 8., , Discuss the various reactions that occur in solvay process., , [3], , 9., , What happens when :– , , [3], , 10., , (a), , Mg is burnt in air., , (b), , Quick lime is heated with silica., , (c), , Chlorine is heated with slaked lime., , Complete the following chemical reactions : , (a), (b), (c), , [5], , CaO + SiO2 –—→, , Ca(OH)2 + CO2 –—→, , (d), , 2Mg(NO3)2 –—→, D, 3Mg + N –—→, , (e), , NH4HCO3 + NaCl –—→, , 2, , *****, , s-Block Elements, , 169
Page 192 :
Chapter - 11, , p-Block, p-Block, Elements, Elements, , FAST TRACK : QUICK REVISION, General outer Electronic configuration : ns2np1–6., Inert Pair Effect:, Reluctance of ns2 electrons of valence shell to participate in bond formation, is termed as inert pair effect., It arises due to poor or insufficient shielding of ns2 electrons by intervening, d- or f-electrons & hence increases down the group., Causes of Anomalous Behaviour of First Element in groups of p-Block:, (i) Very small size, (ii) Unavailability of vacant d-orbital, (iii) Tendency to form pp – pp multiple bonds., Group No-13 Elements: (B, Al, Ga, In, Tl, Nh), , , General Electronic Configuration: ns2 np1, , , , Atomic radius: B < Ga < Al < In <TI, rGa < rAl due to ineffective shielding of valence electrons by intervening, 3d-electrons in Ga., , , , Ionization Enthalpies: B > Tl > Ga > Al > In, , , , Electronegativity: B > Tl > In > Ga > Al, , , , Oxidation States: B (+3), Al (+3), Ga (+3, +1), In (+3, +1), Tl (+1, +3), Tl (+1) is more stable than Tl (+3) due to inert pair effect., , , , , , Nature of Compounds: Compounds of group 13 elements are electron, deficient i.e. Lewis Acid and hence used as industrial catalyst e.g. BF3, AlCl3., Oxides:, , , , B2O3, , Acidic, , Al2O3, Ga2O3, Amphoteric, , ln2O3, Basic, , Tl2O, , Strongly Basic
Page 193 :
, , , , , , , , , Halides: MX3 type, Electron deficient (Lewis acid), AICI3 exist as dimer, Borax: Na2B4O7.10H2O. On heating it form transparent glassy bead, consisting of NaBO2 + B2O3., Boric acid: H3BO3, It acts as a Lewis acid by accepting electron pair from, OH– ions of water., Diborane: B2H6, Colourless & toxic gas, acts as Lewis acid due to having, electron deficient 3c-2e– bonds. Obtained by treating BF3 with LiAIH4 or, NaH, Also obtained by treating NaBH4 with l2., Borazine: B3N3H6, It is isostructural with benzene and hence known as inorganic benzene. Prepared by heating B2H6 withNH3, , Group -14 Elements: (C, Si, Ge, Sn, Pb,Fl), General Electronic Configuration: ns2 np2, Atomic radius: C < Si < Ge < Sn < Pb, lonisation Enthalpy: LiHx : C > Si > Ge > Sn < Pb, Oxidation States: C (+4), Si (+4), Ge (+4, +2), Sn (+4, +2), Pb (+4, +2), Pb (+2) is more stable than Pb (+4) due to inert pair effect., Oxides: Form di oxides (MO2) & mono oxides (MO)., PbO2 is powerfull oxidizing agent because Pb stabilizes in +2 oxidation state, due to inert pair effect. CO2 is gas while SiO2 is network solid because C has, ability to form pp — pp multiple bonds., Halides: Form tetra halides (MX4) & dihalides (MX2)., Tetra halides are more covalent due to greater polarizing power of cation., CCI4 is not hydrolysed with water as C has no vacant d-orbital to accept, electron pair from water., Catenation: C >> Si > Ge ≈ Sn >> Pb, Allotrops of carbon: Diamond (sp3), Graphite (sp2), Fullerenes (sp2), Silicones: Silicones are synthetic organosilicon compounds containing, R2SiO repeating units. Silicones are water repellent, heat resistant, chemically inert, electrical insulators, resistant to oxidation., Silicates: Silicates are compounds in which anions are derived from, Si–o–si– tetrahedral units., Zeolites: Zeolites are 3D silicates in which some of the Si atoms are replaced, by Al3+ ions and negative charge is balanced by cations such as Na+, K+,, Ca2+ etc., ZSM-5 is used in petrochemical industries to convert methanol into petrol., p-Block Elements, , 171
Page 194 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1. The element which exists in liquid state for a wide range of temperature, and can be used for measuring high temperature is, (i), , B, , (ii), , Al, , (iii), , Ca, , (iv), , Ga, , 2. Which of the following is Lewis acid?, (i), , AlCl3, , (ii), , MgCl2, , (iii), , CaCl2, , (iv), , BaCl2, , 3. The geometry of a complex species can be understood from the knowledge, of type of hybridisation of orbitals of central atom. The hybridisation of, orbitals of central atom in [Be(OH4]– and the geometry of the complex, are respectively, (i), , sp3, tetrahedral, , (ii), , sp3, square planar, , (iii), , sp3d2, octahedral, , (iv), , dsp2, square planar, , 4. Which of the following oxides is acidic in nature?, (i), , B2O3, , (ii), , Al2O3, , (iii), , Ga2O3, , (iv), , In2O3, , 5. The exhibition of highest co-ordination number depends on the avilability, of vacant orbitals in the central atom. Which of the following elements is, not likely to act as central atom in MF63-?, (i), , B, , (ii), , Al, , (iii), , Ga, , (iv), , In, , 6. Boric acid is an acid because its molecule, (i), , Contains replaceable H+ ion, , (ii), , Gives up a proton, , (iii), , Accepts OH– from water releasing proton, , (iv), , Combines with proton from water molecule, , 7. Catenation i.e., linking of similar atoms depends on size and electronic, configuration of atoms. The tendency of catenation in Group 14 elements, follows the order:, , 172, , (i), , C > Si > Ge > Sn, , (ii), , C >> Si > Ge = Sn, , (iii), , Si > C > Sn > Ge, , (iv), , Ge > Sn > Si > c, , Chemistry Class XI
Page 195 :
8. Silicon has a strong tendency to form polymers like sillicones. The chain, length of silicone plymer can be controlled by adding, (i), , MeSiCl3, , (ii), , Me2SiCl2, , (iii), , Me3SiCl, , (iv), , Me4Si, , 9. Ionisation enthalpy (∆1H1 kJ mol-1) for the elements of Group 13 follows, the order, (i), , B > Al > Ga > In > T1, , (ii), , B < Al < Ga < In < T1, , (iii), , B < Al > Ga < T1, , (iv), , B > Al < Ga > In < T1, , 10. In the structure of diborane, (i), , All hydrogen atoms lie in one plane and boron atoms lie in a plane, perpendicular to this plane., , (ii), , 2 boron atoms and 4 terminal hydrogen atoms lie in the same plane, and 2 bridging hydrogen atoms lie in the perpendicular plane., , (iii) 4 bridging hydrogen atoms and boron atoms lie in one plane and, two terminal hydrogen atoms lie in a plane perpendicular to this, plane., (iv) All the atoms are in the same plane., 11. A compound X, of boron reacts with NH3 on heating to give another, compound Y which is called inorganic benzene. The compound X, can be prepared by treating BF3 with Lithium aluminum hydride. The, compounds X and Y are represented by the formulas., (i), , B2H6, B3N3H6, , (ii), , B2O3, B3 N3 H6, , (iii), , BF3, B3N3H6, , (iv), , B3N3H6, B2H6, , 12. Quartz is extensively used as a piezoelectric material, it contains ............, (i), , Pb, , (ii), , Si, , (iii), , Ti, , (iv), , Sn, , 13. The most commonly used reducing agents is, (i), , AlCl3, , (ii), , PbCl2, , (iii), , SnCl4, , (iv), , SnCl2, , 14. Dry ice is, (i), , Solid NH3, , (ii), , Solid SO2, , (iii), , Solid CO2, , (iv), , Solid N2, p-Block Elements, , 173
Page 196 :
15. Cement, the important building material is a mixture of oxides of several, elements. Besides calcium, iron and sulphur, oxides of elements of which, of the group(s) are present in the mixture?, (i), , Group 2, , (ii), , Groups 2, 13 and 14, , (iii), , Groups 2 and 13, , (iv), , Groups 2 and 14, , MATCH THE COLUMNS, In the following questions more than one correlation is possible between, options of Column I and Column II. Make as many correlation as you can, Column I, , 1., , Column II, , (i), , BF4, , (a) Oxidation state of central atom is +4, , (ii), , AlCl3, , (b) Strong oxidishing agent, , (iii), , SnO, , (c) Lewis acid, , (iv), , PbO2, , (d) Can be further oxidised, , , , (e) Tetrahedral shape, , Column I, , 2., , Column II, , (i), , Diborane, , (a) Used as a flux for soldering metals, , (ii), , Galluim, , (b) Crystalline form of silica, , (iii), , Borax, , (c) Banana bonds, , (iv) Aluminosilicate, (d) Low melting, high boiling, useful for, , measuring high temperature, (v), , (e) Used as catalyst in petrochemical industries, , Column I, , 3., , 174, , Quartz, , Column II, , (i), , Boron in [B(OH)4]–, , (a), , Sp2, , (ii), , Aluminium in [Al(H2O)6]3+, , (b), , Sp3, , (iii), , Boron in B2H6, , (c), , Sp3d2, , (iv), , Carbon in Buckminsterfullerene, , (v), , Silicon in SiO44–, , (vi), , Germanium in [GeCl6]2–, , Chemistry Class XI
Page 197 :
ASSERTION-REASON TYPE QUESTIONS, In the following questions a statement of Assertion (A) followed by a, statement of Reason (R) is given. Choose the correct option out of the choices, given below each question, 1., , Assertion (A), , :, , If aluminium atoms replace a few silicon atoms in, three dimensional network of silicon dioxide, the, overall structure acquires a negative charge, , Reason (R), , :, , Aluminium is trivalent while silicon is tetravalent., , (i), , Both A and R are correct and R is the correct explanation of A., , (ii) Both A and R are correct but R is not the correct explanation of A., (iii) Both A and R are not correct, (iv) A is not correct but R is correct., 2., , Assertion (A), , :, , Silicon is water repelling in nature., , Reason (R), , :, , Silicon is organosilicon polymers, which have, (–R2SiO–) as repeating unit, , (i), , A and R both are correct and R is the correct explanation of A., , (ii) Both A and R are correct but R is not the correct explanation of A, (iii) A and R both are not true., (iv) A is not true but R is true., 1-MARK QUESTIONS, 1. Mention two important ores of boron., 2. Name the elements of group 13 which forms only covalent compounds., 3. Why the atomic radius of gallium is less than that of Al ?, 4. Why does Boron form electron deficient compounds ?, 5. Boron does not exist as B3+ ion. Why ?, 6. Why the trihalide of group 13 elements fume in moist air ?, 7. Aluminum form [AlF6]3– but boron does not form [BF6]3–., 8. Why boric acid is a monobasic acid ?, 9. White fumes appear around the bottle of anhydrous AlCl3. Give reason., 10. AlCl3 exist as dimer while BCl3 exist as monomer, why ?, p-Block Elements, , 175
Page 198 :
11. Mention the type of hybridization of Boron in B2H6., , [Ans. sp3], , 12. Write the formula of inorganic benzene. , , 13. Why aluminum utensils should not be kept in water overnight., 14. Explain what happens when boric acid is heated., 15. BCl3 exists but BH3 does not. Explain., 16. Why SnCl4 is more covalent than SnCl2 ?, 17. Why PbCl4 is good oxidising agent ?, 18. What are germanes and plumbanes ?, 19. Give one example of zeolite., 20. Mention the type of hybridization of carbon in diamond and graphite., 21. Why CCl4 is insoluble in water but SiCl4 is soluble in water? Explain., 22. Give two uses of silicones., 23. Why graphite is used as lubricant ? , 24. Lead (Pb) do not form PbI4. Why ?, 25. CO2 is gas while SiO2 is solid at room temperature. Explain why ?, 26. Explain why silicon shows a higher covalency than carbon?, 27. Out of carbon and silicon which can form multiple bonds and why ?, 28. Write the formula of dry ice., 29. Mention the basic building unit of all silicates., 30. Graphite is a good conductor of electricity, but diamond is not. Why ?, 2-MARKS QUESTIONS, 1. Draw the structure of diborane., 2. What happens when :, , , (a) Borax is heated strongly., , , , (b) Boric acid is added to water., , 3. Write balanced chemical equations for :, (a) BF3 + LiH —→, (b) B2H6 + NH3 —→, 176, , Chemistry Class XI
Page 199 :
4. Write chemical reactions to justify amphoteric nature of Al., 5. Suggest reason why the B-F bond length in BF3 and BF4– differ., 6. Give reason for the following :, (i) BF3 act as weak Lewis acid., , , (ii) Boron cannot show covalency more than four., , 7. How can you explain higher stability of BCl3 as compared to TlCl3?, 8. Give reason for the following :, , , (i) Aluminium alloys are used to make aircraft body., , , , (ii) Aluminium wire is used to make transmission cables., , 9. Describe the shapes of BF3 and BH4–. Assign the hybridization of boron, in these species. , 10. Explain the chemistry of borax bead test., 11. [SiF6]2– is known whereas [SiCl6]2– not. Give reason., 12. Hydrolysis of SiCl4 take place but of CCl4 does not. Why ?, 13. Account for the following :, (a) CO2 is gas while SiO2 is solid at room temperature., (b) Solid CO2 is known as dry ice., 14. Elemental silicon does not form graphite like structure as carbon does., Give reason., 15. Suggest a reason as to why CO is poisonous?, 16. How is excessive content of CO2 responsible for global warming ?, 17. What is allotropy ? Name two elements which exhibit allotropy., 18. Write equations for the production of water gas and producer gas from, coke., 19. Define zeolite. Name the zeolite which converts alcohols directly into, gasoline., 20. Arrange the hybrides of group 14 elements in increasing order of :, (a) Thermal stability, , , (b) Reducing power., , p-Block Elements, , 177
Page 200 :
3-MARKS QUESTIONS, 1. Give reasons of the following :, , , (i) In diborane, two B – H – B bonds are different from common covalent, bonds., , , , (ii) Aluminium metal shows amphoteric behaviour., , , , (iii) Quartz is used to develop extremely accurate clocks., , 2. A certain salt X gives the following results :, , , (i) Its aqueous solution is alkaline to litmus., , , , (ii) It swells up to a glassy material Y on strong heating., , , , (iii) When conc. H2SO4 is added to a hot solution of X, white crystal of, an acid Z separates out. Write equations for all the above reactions, and identify X, Y and Z., , 3. Write balanced chemical equation for :, (i) B2H6 + H2O —→, , , (ii) Al + NaOH —→, , , , (iii) NaOH + B2H6 —→, , 4. List two important properties in which boron differs from the rest of the, members of group. Mention the main reasons for the difference., 5. What are electron deficient compounds? Are BCl3 and SiCl4 electron, deficient species ? Explain. , 6. Select the member(s) of group 14 that :, , , (i) Forms the most acidic dioxide., , , , (ii) Is commonly found in + 2 oxidation state., , , , (iii) Used as semiconductor., , 7. What are allotropes ? Sketch the structure of two allotropes of carbon, namely diamond and graphite., 8. Give suitable reasons for the following :, (a) CO2 turns lime water milky, but if passed for a long time, the solution, become transparent again., , , (b) Graphite is a good conductor of electricity but diamond is insulator., , , , (c) Lead (IV) chloride is highly unstable towards heat., , 178, , Chemistry Class XI
Page 201 :
9. (i) Write the resonance structure of CO32– and HCO3–., , , (ii) Write the name of thermodynamically most stable form of carbon., , 10. (i) Explain why is there a phenomenal decreases in ionisation enthalpy, from carbon to silicon ? , , , (ii) Write an industrial application of silicones., 5-MARKS QUESTIONS, , 1. When metal X is treated with NaOH, a white precipitate ‘A’ is obtained,, which is soluble in excess of NaOH to give soluble complex (B). Compound, ‘A’ is soluble in dilute HCl to form compound ‘C’. The compound ‘A’, when heated strongly gives ‘D’, which is used to extract metal. Identify, X, A, B, C and D. Write suitable equations to support their identities., 2. (i) If B-Cl bond has dipole moment explain why BCl3 molecules has, zero dipole moment., , , (ii) A mixture of dil. NaOH and aluminium pieces is used to open drain., Give reason., , , , (iii) Aluminium wire is used to make transmission cables. Why ?, , 3. (i) Identify the compounds X and Y in the following reactions :, (a), , Na2B4O7 + 2HCl + 5H2O → 2NaCl + X, , (b), , X, , HBO2, , Y., , , , (ii) Write the name of group 13 element which is used to measure high, temperature., , , , (iii) Why in case of thallium + 1 oxidation state is more stable than + 3?, , 4. Compare the general trend in the following properties of the elements of, group 13 and 14 :, , , (a) Atomic size, (b) Ionisation enthalpy, (c) Metallic character,, (d) Oxidation states, (e) Nature of halides., , p-Block Elements, , 179
Page 202 :
5. Name the following :, , , (a) The crystalline form of silica used in modern radio and T.V., broadcasting and mobile radio communication., , , , (b) The oxides of carbon which form a complex with haemoglobin 300, times more faster than oxygen., , , , (c) The allotrope of carbon which has ∆f Hθ = 0., , , , (d) A type of polymer is semiorganic in nature., , , , (e) Two man made silicates., , 6. Explain the formation of (i) water gas (ii) producer gas. Give their uses., What happens when CO2 is passed through limewater?, , , (i) for short duration, , , , (ii) for long duration., , 180, , Chemistry Class XI
Page 203 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Which of the following is Lewis acid? , (a) AlCl3, , 2., , (b) MgCl2, , [1], , (c) CaCl2, , (d) BaCl2, , Dry ice is , (a) Solid CO2, , (b) Solid SO2, , (c) Solid N2, , [1], (d) Solid NH3, , 3., , Chemical formula of diborane is ___________., , [1], , 4., , Write an example of shape relative catalyst. , , [1], , 5., , Allotrope of carbon with sp3 hybridisation state is _________?, , [1], , 6., , Complete the following chemical equations : , , [2], , (a), (b), , B2H6 + NH3 –—→, , BF3 + LiH –—→, , 7., , Write the chemical reactions involved in borax bead test., , [2], , 8., , What are allotrope? Sketch the structure of two allotrope of, carbon namely diamond and graphite., , [3], , 9., , Compare the properties of the elements of group-13 and 14, , [3], , 10., , (a), , Atomic size, , (b), , Ionisation enthalpy, , (c), , Oxidation state, , (a), , Explain the formation of (i) water gas (ii) producer gas, , (b), , Identify the compound X and Y in the following reactions, , , , (c), , [5], , (i) Na2B4O7 + 2HCl + 5H2O –—→ 2NaCl + X, 370 K HBO ––—→, >370 K Y, (ii) X ––—→, 2, , Write two important applications of silicons., *****, p-Block Elements, , 181
Page 204 :
3, , SP –S, σ bond, , H, , Organic, Chemistry:, Organic, Chemistry, :, Some, Basic, Some, Basic, Principles And, Chapter - 12, Principles, and, Techniques, Techniques, H, , C, C, , H, , on, , ugati, , rconj, , Hype, , C, , H, , H, , FAST TRACK : QUICK REVISION, , ORGANIC CHEMISTRY, It deals with the study of hydrocarbons (compounds of carbon and hydrogen, elements) and their derivatives., Some organic compounds may also contain nitrogen, oxygen, sulphur,, phosphorus, halogens, etc., Berzelius, proposed that a 'vital force' was responsible for the formation of, organic compounds., This was rejected by F. Wohler who synthesised first organic compound urea, from an inorganic compound., , , , , , NH4CNO, , Ammonium cyanate, , , , , , Urea, , Acetic acid was synthesised by Kolbe and methane by Berthelot., Types of hybridisation of C-atom :, Hybridisation, sp3, sp2, sp, , , , NH2CONH2, , Structure, Tetrahedral, Trigonal, Linear, , Bond angle, 109°28', 120°, 180°, , Examples, Ethane, Methane, Ethene, Propene, Ethyne, Propyne, , Reasons for existence of large number of organic compounds:, Catenation : The property of atoms of an element to link with one another, forming chains of identical atoms is called catenation. Carbon exhibits, catenation to the maximum extent., Isomerism : It is the property by virtue of which two or more compounds, have the same molecular formula but different physical or chemical, properties.
Page 205 :
, , , , Formation of multiple bonds : Because of its small size carbon atom, is capable of forming multiple bonds with other atoms and this gives a, variety of compounds., CLASSIFICATION OF ORGANIC COMPOUNDS, , H, (Pysrole), , CLASSIFICATION OF CARBON ATOMS, 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 quarterly or 4° carbon atom., Functional Group : The atom e.g., –Cl, –Br, etc., or group of atoms, e.g., –COOH, –CHO, which is responsible for the chemical properties of, the molecule, is called functional group., , , Organic Chemistry: Some Basic Principles and Techniques, , 183
Page 206 :
, , Homologous Series : The series in which the molecular formula of, adjacent members differ by a – CH2 unit, is called homologous series and, the individual members are called homologous, e.g., The homologous, series of alkene group is, C2H4, C3H6, C4H8, C5H10, , }, , difference of —CH2 unit or 14 unit mass, , 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, , CnH2n+2, , Alkenes, , CnH2n, , Alkynes, , CnH2n–2, , Alcohol and ether, , CnH2n+2O, , Aldehyde and ketone, , CnH2nO, , Acid and ester, , CnH2nO2, , 3. All the members can be prepared by almost similar methods., 4. With increase in the molecular weight of a series, the physical, properties vary gradually., , Representation of Organic Compounds :, Organic compounds can be represented by the following ways:, (i) Complete Structural Formula : All the bonds present between any, two atoms are shown clearly. e.g.,, , H H H H, , H C C C C H, , , H Cl H, , 184, , H, , Chemistry Class XI
Page 207 :
(ii) Condensed Formula : All the bonds are not shown clearly. e.g.,, CH3CHCH2CH3, Cl, CH3CH(CI)CH2CH3, , (iii) Bond Line Formula : Every fold and free terminal represents a carbon, and lines represent the bond. e.g.,, Cl, CH3 C CH CH2CH3, , CH3, , CH3, , , CH2 COOH, , OH, , IUPAC Nomenclature of Organic Compounds : Following rules are, used to write the IUPAC name of an organic compound., , Rule 1. : 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.,, , Word Root for Carbon Chain, Chain length, C1, C2, C3, C4, C5, C6, , Word root, MethEthPropButPentHex-, , Chain length, C7, C8, C9, C10, C11, C12, , Word root, Hept, Oct, Non, Dec, Undec, Dodec, , Organic Chemistry: Some Basic Principles and Techniques, , 185
Page 209 :
Nomenclature of substituted benzene compounds :, , , , ISOMERISM, Structural isomerism, Stereo isomerism, Same molecular formula but, Same molecular and structural, different structures, formula but different configuration, Types , e.g., Geometrical isomerism, 1. Chain Isomerism, (cis-trans isomerism), , e.g., Pentane and , H3C, CH3, C , C, , 2-Methylbutane , 2. Position Isomerism, H, H, , e.g., But-1-ene, Cis.But-2-ene, , But-2-ene, CH3, H, 3. Functional Isomerism, C, C, , e.g., Propanal & Propanone, H, CH3, , Ethanol & Methoxymethane, 4. Metamerism, Trans.But-2-ene, , e.g., Pentan-2-one and, , Pentan-3-one, , Organic Chemistry: Some Basic Principles and Techniques, , 187
Page 210 :
Fission of a Covalent Bond :, (i) 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, are called free radicals. Generally,, homolytic fission takes place in non-polar covalent molecules in the, presence of sunlight or high temperature., , , Sunlight, , {, , A — B ––––––→ A* + B*, free radicals, , Sunlight, , Cl2 ––––––→ 2Cl*, Free radicals are highly reactive, neutral and electron deficient species., (ii) Heterolytic Fission : The covalent bond breaks in such a fashion that, the shared pair of electrons goes with one of the fragments., –→, , more electronegative, , A — B ––––––→ A+, , electrophile, , +, , B–, , nucleophile, , –→, , less electronegative, , A — B ––––––→ A–, , +, , B+, , nucleophile electrophile, , Heterolytic fission generally takes place in polar covalent molecules, but in non-polar molecules, it takes place in the presence of catalyst, like AiCl3 (anhy.), FeCl3 (anhy.) etc., Attacking Reagents :, These are of two types, (i) Electrophiles or Electrophilic Reagents, These are electron deficient species, i.e., behave as Lewis acids., +, e.g., Cl+, NO2, CH3CO+ etc., BF3, ZnCl2 (anhydrous), FeCl3 (anhydrous), AlCl3 (anhydrous), (ii) Nucleophiles or Nucleophilic Reagents, These are negatively charged or neutral molecules with unshared, electron pair., —, °°, °°, e.g., OH, CN–, RNH, 2, NH3, Reaction Intermediates :, (i) Free radicals : These are the product of homolysis and contain, an odd electron. These are highly reactive planar species with sp2, hybridisation., , , 188, , Chemistry Class XI
Page 211 :
Their order of stability is, , °, , °, , °, , (C6H5)3C > (C6H5)2 CH > C6H5CH2, , °, °, > CH2 = CH –– CH, 2 > 3° > 2° > 1° > CH2 = CH, (ii) Carbocations : These are the product of heterolysis and contain a, carbon bearing positive charge. These are electron deficient species., These are also polar chemical species i.e., sp2 hybridised with an, empty p-orbital., empty p-orbital, , , C, , , , Stability order of carbocation is, +, , +, , +, , (C6H5)3C > (C6H5)2 CH > C6H5CH2, , +, , +, , > CH2 = CH –– CH2 > 3° > 2° > 1° > CH2 = CH, (iii) Carbanions : These are the product of heterolysis and contain a carbon, bearing negative charge and 8 electrons in its valence shell., These have pyramidal shape with sp3 hybridised carbon (having one, lone pair) order of stability of carbanions is, –, , –, , –, , (C6H5)3C > (C6H5)2 CH > C6H5CH2, –, , > CH3 > 1° > 2° > 3° carbanions, Electron Displacement in Covalent Bond, 1. Inductive Effect : If shared pair is more shifted towards more, electronegative atom, the less electronegative atom acquires slight, positive charge and more electronegative atom acquires partial, negative charge,, , , +d, , –d, , e.g., CH3 →— Cl, , , 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 (–l) while, that having, smaller electron affinity than hydrogen are said to have, electron releasing or positive inductive effect (+l)., + dd, , +d, , –d, , + ddd, , + dd, , +d, , e.g., CH3 →— CH2 →— Cl, , –d, , CH3 →— CH2 →— CH2 →— Cl, , 1° alkyl halide, Organic Chemistry: Some Basic Principles and Techniques, , 189
Page 212 :
Cl has –l 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 > – NH2 > – C6H5 > – H, , , , , , , , , Order of groups producing +l effect is, 3° alkyl group > 2° alkyl group > 1° alkyl group > – CH3 > – H, , Applications of Inductive Effect, (i) Presence of groups showing +I effect increases the stability of, carbocation while presence of groups showing –I effect decreases, their stability., (ii) Strength of acid increases with the attachment of group showing –I, effect and decreases with the attachment of group showing +I effect., (iii) Presence of +I showing groups increases the basic strength of amines., , 2., , , , Electromeric Effect : 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., It may be of +E type (when displacement of electron pair is away, from the atom of group) or of –E type (when displacement is towards, the atom or group)., H, , H, C, , e.g.,, , H, , Reagent, , C, H, , H, , H, , + –, , C, , C, H, , H, +, , E, C, , O, , Reagent, , C, , –, , O, , Nu–, , Hyper-conjugation : 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, H+, e.g.,, –, CH2, CH2, CH2, CH, CH2, 3., , This effect is also called no bond resonance or Baker Nathan effect., 190, , Chemistry Class XI
Page 213 :
Applications of Hyper-conjugation, , , Stability of alkenes : More the number of a-hydrogen atoms, more, stable is the alkene., , , CH3, , , , , , CH3, , , , H3C, , C, , , , , , > CH3CH, C , CH3, , C, , H2, , CH3, , , , > CH3, C , CH3, , CH, , , , CH3, , CH, , Stability of Carbocation : Greater the number of alkyl groups, attached to positively charged carbon atom, the greater is the stability., +, , +, , +, , e.g., (CH3)2CH > CH3 — CH > CH3, 4., , Resonance Effect : When 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., , , , , , Conditions for resonance, (i) The arrangement of atoms must be identical in all the formula., (ii) The energy content of all the canonical forms must be nearly, same., (iii) Each canonical of p electrons. This effect may be of +R type or, –R type., , , , Positive Resonance Effect (+R), Electron donating groups with respect to conjugated 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, –NH2, NHCOR, etc., °°, , NH2, , +, , +, , +, , NH2, , NH2, , NH2, , -, , , , -, , 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, –NO2, etc., Organic Chemistry: Some Basic Principles and Techniques, , 191
Page 214 :
H, , C, , O, , H, , C, , O-, , H, , C, , O-, , +, , H, , O-, , C, +, , +, , , Methods of Purification of Organic Compounds, , Method, Crystallization, , Sublimation, , Distillation, , – Fractional, Distillation, , – Steam, Distillation, , Differential, Extraction, , 192, , Principle, Applications, Different solubilities of a given organic • Crystallization of sugar, compound and its impurities in the same, (containing an impurity of, solvent., common salt) is achieved by, shaking the impure solid with, hot ethanol at 348K (sugar, dissolves whereas common, salt remains insoluble)., Some solid substances change from solid • Iodine from sodium chloride, to vapour state without passing through, (as iodine sublimes readily, liquid state. Sublimable compounds, leaving behind sodium, get separated from non-sublimable, chloride)., impurities., • C a m p h o r, n a p h t a l e n e ,, anthracence, benzoic Acid,, etc. are purified., It is used to separate, • Hexane (b.p. 342K) and, • Volatile liquids from non-volatile, toluene (b.p. 384K), impurities., • Chloroform (b.p. 334K) and, • Liquids having sufficient difference in, aniline (b.p. 457K), their boiling points., If the difference in boiling points of two • Crude oil in petroleum, liquids is not much, this method is used., industry is separated into, various useful fractions such, as gasoline, kerosene oil,, diesel oil, lubricating oil, etc., This method is used to separate substances • Aniline is separated from, which are (i) steam volatile, (ii) immiscible, aniline water mixture., with water, (iii) posses a vapour pressure • Essential oils, turpentine oil,, of 10-15 mm Hg and (iv) contain nono-nitrophenol, bromobenzene, volatile impurities., nitrobenenze, etc. can be, purified., By shaking an aqueous solution of an • Benzoic acid can be extracted, organic compound with an organic, from its water solution using, solvent in which the organic compound is, benzene., more soluble than in water. The organic, solvent and the aqueous solution should, be immiscible with each other so that they, can form two distinct layers which can, be separated by using separating funnel., , Chemistry Class XI
Page 215 :
Chromatography, , – Adsorption, Chromatography, – Column, Chromatography, – Thin Layer, Chromatography, – Partition, Chromatography, – Paper, Chromatography, , Differential movement of individual • Widely used for separation, components of a mixture through a, purification, identification, stationary phase under the influence of a, and characterization of the, mobile phase., components of a mixture,, whether coloured or, colourless., Differential adsorption of the various, components of a mixture on a suitable, adsorbent such as silica get or alumina., The mixture is passed through adsorbent • Mixture of naphthalene and, packed in glass tube., benzophenone., The mixture is passed over adsorbent on • Amino acids can be detected, a thin glass plate., by spraying the plate with, ninhydrin solution., Differential partitioning of components of, a mixture between stationary and mobile, phases., A special quality paper known as • For separation of sugars and, chromatography paper is used. It contains, amino acids., water trapped in it, which acts as the, stationary phase., , Types of Chromatography, Column Chromatography, Thin Layer Chromatography, High Performance Liquid Chromatography (HPLC), Gas Liquid Chromatography (GLC), Partition or Paper Chromatography, Element, Carbon, , Detection, , Confirmatory Test, , Mobile / Stationary Phase, Liquid / Solid, Liquid / Solid, Liquid / Solid, Gas / Solid, Liquid / Solid, Reactions, , D, 2CuO + C ––→, 2Cu + CO2 CO 2 gas turns lime CO2 + Ca(OH)2 –→ CaCO3↓ + H2O, Lime water Milkiness, water milky., , D, Hydrogen CuO + 2H ––→, Cu + H2O Water droplets appear CuSO4 + 5H2O –→ CuSO4.5H2O, Blue, on the cooler part of White, the ignition tube and, also turns anhydrous, CuSO4 blue., , Nitrogen, , Lassaigne's extract (L.E.), D, Na + C + N ––→, NaCN, (L.E.), , L.E. + FeSO4 + NaOH, FeSO4 + 2NaOH –→ Fe(OH)2 + Na2SO4, boil and cool + FeCl3 + Fe(OH) + 6NaCN –→, 2, conc. HCl. Gives blue, Na4[Fe(CN)6] + 2NaOH, or green colour., 3Na4[Fe(CN)6] + 4FeCl3 –→, Fe4[Fe(CN)6]3 + 12NaCl, Prussian blue, , Organic Chemistry: Some Basic Principles and Techniques, , 193
Page 219 :
MIND MAP : ORGANIC CHEMISTRY, , Organic Chemistry: Some Basic Principles and Techniques, , 197
Page 220 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Homolytic fission of C-C bond in ethane gives an intermediate in which, carbon is:, a. sp3 hybridised , b. sp2 hybridised, c. sp-hybridised , d. sp3d- hybridized, , 2., , The kind of delocalization involving sigma bond in conjugation with pi, electrons is called:, a. Inductive effect , b. Hyperconjugation effect , c. Electromeric effect , d. Mesomeric effect, , 3. Which organic species has only one type of hybridized carbon?, , ⊕, a. CH2 = C = CH2 , b. CH3 – CH – CH3, c. CH3 – C = CH , , ⊕, , d. CH2 = CH – CH2, , 4., , Which of the following can act as an electrophile?, a. CN–, , b. OH–, c. H2O, , d. BF3, , 5., , Which of the following is correct about the species: (CH3)3 – C+, a. It is planar , b. Its C+ is sp2 hybridised, c. A nucleophile can attack on its C+ d. All of these, , 6., , Which of the following has all the effects namely Inductive, Mesomeric and, Hyperconjugative ?, a. CH3Cl , b. CH3CH = CH2, c. CH3CH = CHCOCH2Cl, d. CH2 = CH – CH = CH2, , 7., , The most stable free radical among the following is:, •, •, •, a. C6H5CH2CH2 b. C6H5CHCH3 c. CH3CH2, , •, d. CH3CHCH3, , 8., , Isomers of a compound must have :, a. Same physical properties, c. Same structural properties, , 9., , The type of isomerism not found in alkenes is :, a. Chain isomerism , b. Geometrical isomerism, c. Metamerism , d.Position isomerism, , 198, , Chemistry Class XI, , b. Same chemical properties, d. Same molecular weight
Page 221 :
10. Which of the following species have six p conjugated electrons?, +, , b. CH2 = CH – CH = CH – CH2–, , a., , c., , d. All of these, N, , 11. The correct decreasing order of priority for the functional groups of organic, compounds in the IUPAC system of nomenclature is:, a. –COOH, –SO3H, –CONH2, –CHO, b. –SO3H, –COOH, –CONH2, –CHO, c. –CHO, –COOH, –SO3H, –CONH2, d. –CONH2, –CHO, –SO3H, –COOH, 12. The IUPAC name of CH3 – CH = CH – C ≡ CH is:, a. pent-3-en-1-yne , b. pent-3-en-4-yne, c. pent-2-en-4-yne , d. pent-2-en-3-yne, 13. Different structures generated due to rotation about C-C axis of an organic, molecule are example of:, a. Geometrical isomerism, b. Conformational isomerism, c. Optical isomerism, d. Structural isomerism, 14. Which of the following process is not used for the preparation of solid, impurities?, a. Distillation , b. Sublimation, c. Crystallisation , d. Vapouristaion, 15. Quantitative measurement of nitrogen in an organic compound is done by, the method:, a. Berthelot method, b. Lassaigne method, c. Carius method , d. Kjehldahl method, ANSWERS, 1. a, 2. b, 11. a 12. a, , 3. d, 13. b, , 4. d, 14. d, , 5. d 6. c, 15. a, , 7. b, , 8. d, , 9. c, , 10. d, , FILL IN THE BLANKS, 1., 2., , The CH4 molecule has ____________ structure., The property of carbon responsible for the large number of carbon compounds, is called ____________., 3. A triple bond between two carbon atoms is composed of one _________ and, _________ bonds., Organic Chemistry: Some Basic Principles and Techniques, , 199
Page 222 :
4., 5., 6., 7., 8., 9., 10., , An organic compound which decomposes below its boiling point can be, purified by ____________., The central atom of CH2 = C = CH2 is __________ hybridized., There is a difference of _________ mass units between two consecutive, members of a homologous series., Geomerical isomerism happens due to _________ around p bond., Electrophiles are the species which attack the regions of _________ electron, density., Hyperconjugation effect is also known as ___________ resonance., In Duma’s method, the nitrogen present in an organic compound is set free, as ____________., , ANSWERS, 1. Tetrahedral 2. Catenation, 6. 14 7. Restricted rotation, , 3. s , two p 4. Vacuum distillation 5. sp, 8. high, 9. No-bond, 10. Nitrogen, , TRUE AND FALSE TYPE QUESTIONS, 1., 2., 3., 4., 5., 6., 7., 8., 9., , In homologous series all the members have the same physical properties., IUPAC name of CH3CN is Methanenitrile., Cis-trans isomers have different dipole moments., Ethanol and methoxymethane are position isomers., A free radical is a species with an unpaired valence electron., Acetylene is a linear molecule., Resonance brings down the stability of molecule., Inductive effect is observed in p bond in presence of attacking reagent., The percentage of carbon and hydrogen are estimated simultaneously in an, organic compound by Liebig method., 10. Chromatography is the method used to separate and purify compounds when, present in small amounts., ANSWERS, 1. F 2. F 3. T, , 4. F, , 5. T, , 6. T, , 7. F, , 8. F, , 9. T, , 10. T, , ASSERTION REASON TYPE QUESTIONS, The questions given below are Assertion (A) and Reason (R). Use the, following key to select the correct answer., (a) If both assertion and reason are correct and reason is correct explanation for, assertion., 200, , Chemistry Class XI
Page 223 :
(b) If both assertion and reason are correct but reason is not correct explanation, for assertion., (c) If reason is correct but assertion is incorrect., (d) If both assertion and reason are incorrect., 1., , Assertion: But-1-ene and 2-Methylprop-1-ene are position isomers., Reason: Position isomers have same molecular formula but different, arrangement of carbon atoms., , 2., , Assertion: All the carbon atoms of But-2-ene lie in one plane., Reason: All the carbon atoms in But-2-ene are sp2 hybridized., , 3., , Assertion: Alkanes having more than three carbon atoms exhibit chain, isomerism., Reason: All carbon atoms in alkanes are sp-hybridised., , 4., , Assertion: In CH2 = C = CH2, all the carbon atoms are sp2 hybridised., Reason: All the hydrogen atoms lie in one plane., , 5., , Assertion: Butane and 2-Methylbutane are homologues., Reason: Butane is a straight chain alkane while 2-Methylbutane is branched, chain alkane., , 6., , Assertion: Tertiary carbocations are generally formed more easily than, primary carbocations., Reason: Hyperconjugation as well as inductive effect due to additional alkyl, groups stabilize tertiary carbocations., , 7., , Assertion: Alkyl carbanions like ammonia have pyramidal shape., Reason: The carbon atom carrying negative charge has an octet of electrons, Assertion: Carbocations are planar in nature., Reason: Carbocations are sp2 Hybridised., , 8., 9., , Assertion: IUPAC name of compound CH3CH = CH – CHO is But-2-enal., Reason: Functional group gets preference over multiple in IUPAC name of, a compound., , 10. Assertion: Compounds with difference in their boiling points by about 30°C, can be separated by simple distillation., Reason: All liquid mixture can be separated by distillation method., ANSWERS, 1. d 2. c 3. c, , 4. d, , 5. b, , 6. a, , 7.b, , 8. a, , 9. a, , 10. c, , Organic Chemistry: Some Basic Principles and Techniques, , 201
Page 224 :
MATCH THE COLUMNS, Match the statements (a,b,c,d) in column I with the statements (I,ii,iii,iv) in, column II., 1., Column I, Column II, a. Leibig method, i. N2, b. Dumas method, ii. AgX, c. Kjehldahl method, iii. CO2 and H2O, d. Carius method, iv. NH3, Column I, a. Nonbenzenoid aromatic compound, b. Catenation, , c. Free radical, , d. sp-hybridised carbon atom, 2., , Column II, i. 50% s character, ii. Species containing single, unpaired nonbonding electrons, iii. Chain-forming property of, an element, iv. Tropolone, , ANSWERS, 1. a. iiii b. iv c. i d. ii, 2. a. iv b. iii c. ii d. i, ONE WORD ANSWER TYPE QUESTIONS, 1, 2., 3., , Write the formula of next higher homologue of C2H5OH., , Mention the hybridisation of underlined carbon in CH3C ≡ N., , What type of isomerism is shown by Pentane and 2-Methylbutane?, , 4., , Nucleophiles are Lewis acids or Lewis bases?, , 5., , What type of bond fission results in the formation of free radicals?, , 6 . What is the number of electrons present in the outermost shell of carbon in, the methyl radical?, 7., , What is the other name for no-bond resonance?, , 8., , What is the name of the Prussian blue coloured compound formed in, Lassaigne’s test for nitrogen in an organic compound?, , 9., , SO3 is an electrophile or nucleophile in sulphonation reaction of benzene?, , 10. Name suitable technique of separation of the components from a mixture of, calcium sulphate and camphor., 202, , Chemistry Class XI
Page 226 :
17. Identify electrophilic centre in CH3CHO., , 18. What is state oh hybridization of positively charged carbon atom in, carbocation?, 19. What is the effect of introducing an alkyl group on the stability of carbocation?, 20. Out of Benzyl and ethyl carbocation which is more stable and why?, 21. Arrange the following in increasing order of acidic strength:, ClCH2COOH, CH3CH2COOH, ClCH2CH2COOH, , 22. Name two solvents which are commonly used to dissolve organic solids., 23. Name the technique that can be used for purification of iodine that contains, traces of NaCl., 24. A liquid (10 mL) has three components A, B, C. which technique is suitable, to sparate A,B, C from such a small amount of mixture?, 25. Name one commonly used adsorbent in column chromatography., 26. Under what condition do we use fractional distillation?, 27. A liquid compound starts decomposing well before its boiling point under, normal pressure. How will you purify it?, 28. Which elements are normally not detected in an organic compound?, 29. For which type of compounds Kjehldahl’s method is not useful?, 30. How do you precipitate sulphur in Carius method?, 31. Which method is used to estimate carbon and hydrogen?, 32. What do we notice in Lassaigne’s test if the compound contains both nitrogen, and sulphur?, 2-MARKS QUESTION, 1., , How will you account for the presence of large number of organic, compounds?, , 2., , Draw the structural formulae of the following compounds:, (i) Ethoxypropane , (ii) But-1-en-3-yne, (iii) 3,4,4,-Trimethylhex-1-yne, (iv) sec-butyl alcohol, (v) But-2-enoic acid, , 3., , How is alkyl group represented? Give the structure and the names of the, alkyl groups which originate from (i) n-Butane (ii) isobutene, , 204, , Chemistry Class XI
Page 227 :
4., , Give IUPAC name of the following compounds:, (i) C6H5 CH2 CH2OH , (ii) (CH3)2 CH2 CH2 CHO, (iii) CH2 = CH – C ≡ N, (iv) CH3 – CH – C – CH – CH3, |, || |, , Br O CH3, (v) CH3 – CH – CH = C – CH2 – COOH, |, |, , OH, OH3, 5., , What is functional isomerism? Give two examples., , 6., , Distinguish between position isomerism and functional isomerism., , 7., , What is metamerism? Give example., , 8., , How are free radicals formed?, , 9., , What is the effect of introducing an alkyl group on the stability of a free, radical?, , 10. Give two examples each of the groups exerting –I and + I effect when, attached to a chain of carbon atoms., 11. A tertiary butyl carbocation is is more stable than isobutyl carbocation., Justify., 11. What do you understand by +R and –R effect?, 12. Define hyperconjugation., 13. What is the difference between inductive and electromeric effect?, 14. All electrophiles are Lewis acids while nucleophile are Lewis bases. Explain., 15. What is the purpose of filtration through hot water funnel?, 16. What precautions are necessary while purifying an organic solid with the, help of crystallization process?, 17. Discuss the principle of steam distillation., 18. Discuss the role of fractionating column in fractional distillation., 19. How will you prepare Lassaigne’s extract? Name the elements which can be, detected from this extract?, 20. Why do we boil Lassaigne’s extract with conc. HNO3 while detecting, halogens in an organic compound?, Organic Chemistry: Some Basic Principles and Techniques, , 205
Page 228 :
3-MARKS QUESTIONS, 1., , Discuss the orbital structure of ethene., , 2., , Define (i) Functional group (ii) Homologous series., , 3., , What do you understand by 1°, 2°, 3° and 4° carbon? Write one example, having atleast one carbon of each type., , 4., , Why stability of carbocations follows the order: tertiary>secondary>primary?, , 5., , What are the various conditions essential for resonance?, , 6., , Write resonance structures of CH2 = CH – CHO. Indicate relative stability of, the contributing structures., , 7., , Inductive effect is of permanent nature while electromeric effect is only, temporary. Explain., , 8., , What is chromatography? Name different types of chromatographic, processes., , 9., , You are given a mixture of methanol and acetone. Discuss the process which, you will employ to separate them., , 10. Explain the reason for the fusion of an organic compound with metallic, sodium for testing nitrogen, sulphur and halogens., 5-MARK QUESTIONS, 1., , What are free radicals? Justify the stability of the aliphatic primary, secondary, and tertiary free radicals., , 2., , What is a carbanion? How is it formed? Discuss relative stability of primary,, secondary and tertiary carbanion., , 3., , Arrange the following in the order of property indicated against each set:, – C6H5, – NO2, – COOH, – I, – F, – CH3, – C2H5 ( In the increasing, order of –I effect) , +, +, +, (ii) CH3CH2CH2CH2 , (CH3)3C , CH3CH2CH2CHCH3 (In the order of, increasing stability), , (i), , (iii) – Cl, – CONH2, – CHO (In the increasing priority order if present in, same molecule), , 206, , Chemistry Class XI
Page 229 :
4., , Draw the resonance strutuctures for the following compounds. Show the, electron shift using curved arrow notation., (i), , C6H5NO2, , (ii) CH3CH = CHCHO, (iii) C6H5OH, (iv) C6H5CH2+, (v) CH3CH = CHCH2+, 5., , Suggest a method to separate the constituents from the following mixture:, (i), , Mixture of two miscible liquids, , (ii) A mixture of oil and water, (iii) A mixture of plant pigments, (iv) A mixture of solid benzoic acid and sodium chloride, (v) o-Nitrophenol and p-Nitrophenol present in the mixture., 6., , 0.378g of an organic compound containing carbon and hydrogen was, subjected to combustion by Leibig’s method, the CO2 and H2O formed were, passed through potash bulbs and anhydrous CaCl2 tube. At the end of the, experiment, the increase in the respective weights were 0.264g and 0.162g., Calculate the percentage of carbon and hydrogen., (Ans: C = 19.05% , H = 4.76%), , Organic Chemistry: Some Basic Principles and Techniques, , 207
Page 230 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Write bond line formula for the following compound: , , [1], , HOCH2CH2CH2CH(CH3)CH(CH3)COOH, 2., , Write IUPAC name of the following compound: , , [1], , CH3 – CH – C – CH – CH3, |, ||, |, NO2 O CH3, 3., , The central atom of compound CH2 = C = CH2 is ______ hybridized. [1], , 4., , There is a difference of _____________ mass units between two, consecutive members of a homologous series., , 5 Which of the following has all the effects namely :, Inductive, Mesomeric and Hyperconjugative ?, , [1], [1], , (a). CH3Cl (b). CH3CH = CH2, (c). CH3CH = CHCOCH2Cl , 6., , (d). CH2 = CH – CH = CH2, , (i) What type of isomerism is exhibited by the following pair of, compounds?, , , CH3CH2CHO and CH3 – C – CH3, ||, O, , (ii) Give one example each of nucleophile and electrophile., 7., , (i) Arrange the following in increasing order of stability:, –, (CH3)3C– , CH3 – CH – CH3, CH3CH2–, , , , , , , (ii) Differentiate between inductive and electromeric effect., , 208, , Chemistry Class XI, , [1]
Page 231 :
8., , (i), , When do we use hot water funnel for filtration?, , (ii) How will you separate a mixture bof two organic compounds which, have different solubilities in the same solvent?, (iii) An organic liquid decomposes below its boiling point. How will you, purify it?, 9., , Draw the resonating structures of (a) Phenol (b) Benzaldehyde., , 10. Arrange the following in the order of property indicated against each set:, (i) –C6H5, –NO2, –COOH, –I, –F, –CH3, –C2H5, (In the increasing order of –I effect), +, (ii) CH3CH2CH2CH2 , (CH3)3, CH3CH2CH2CHCH3, (In the order of increasing stability), +, , C+,, , (iii) –COOH , –CONH2, –CHO, (In the increasing priority order if present in same molecule), (iv) HCOOH, CH3COOH, ClCH2COOH, (Increasing order of acidic strength), (v) O2NCH2CH2O– , CH3CH2O–, (species having greater stability), *****, , Organic Chemistry: Some Basic Principles and Techniques, , 209
Page 242 :
AROMATIC HYDROCARBONS, These hydrocarbon are also known as arenes. The parent member of the family, aromatic hydrocarbons is benzene., Aromatic compounds containing benzene ring are known as benzenoids., Structure of benzene : Hexagonal ring of carbon atoms with alternate single and, double bonds. Each carbon atom is sp2 hybridised. Planar ring, bond angle 120°., All C-C bond lengths are equal due to complete delocalisation of π electrons., H, , H, , H, , H, , H, , H, , Formation of C-C and C-H , Sigma skeleton of, sigma bonds benzene molecule, Sideways, overlap, , Sideways, overlap, , HUCKEL'S RULE, , •, , Huckel's rule, (based on calculations) : a planar cyclic molecule with, alternating double and single bonds has aromatic stability if it has (4n +2p), electrons (n is 0, 1, 2, 3, 4), , •, , For n = 1 : 4n+2 = 6; benzene is stable and electrons are delocalized., Benzene, Three double bonds;, six π electrons, , 220, , Chemistry Class XI
Page 243 :
, , 1., , METHODS OF PREPARATION, Cyclic polymerisation of ethyne, 3C2H2, , 2., , Red hot fe tube, 873K, , Decarboxylation of aromatic acids, COONa, , + NaOH, 3., , CaO, ∆, , + Na2CO3, , Reduction of phenol, OH, Zn, ∆, , + ZnO, , Physical Properties of Benzene :, (i) Aromatic hydrocarbons are non-polar molecules and are usually, colourless liquids or solids with a characteristic aroma., (ii) Aromatic hydrocarbons are immiscible with water but readily miscible, with organic solvents., (iii) Aromatic compounds burn with sooty flame., Chemical Reactions of Benzene :, (i) Benzene gives electrophile substitution reactions., (ii) According to experimental evidences, electrophile substitution reaction, involve following three steps :, • Generation of electrophilie, • Formation of carbocation intermediate., • Removal of proton from the carbocation intermediate., , Hydrocarbons, , 221
Page 246 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Which of the following has zero dipole moment?, (a.) cis-But-2-ene, (b) trans-But-2-ene, (c) But-1-ene, (d) 2-Methylprop-1-ene, , 2., , Bond length of (I) ethane, (II) ethene, (III) Acetylene, (IV) Benzene follows, the order:, (a) I > II > III > IV, (b) I > II > IV > III, (c) I > IV > II > III, (d) III > IV > II > I, , 3., , The methyl group in benzene ring is:, (a) Ortho directing, (b) Ortho and meta directing, (c) Para directing, (d) Ortho and para directing, , 4., , The dihedral angle in the staggered conformation of C2H6, (a) 120°, (b) 60°, (c) 0°, (d) 90°, , 5., , On heating C2H2 in red hot tube copper tube, the compound formed is:, (a) Ethylene, (b) Benzene, (c) Ethane, (d) Methane, , 6., , Action of acetylene on dilute H2SO4 gives:, (a) Acetic acid, (b) Acetone, (c) Acetaldehyde, (d) Ethyl alcohol, , 7., , Which of the following compounds will exhibit cis-trans (geometrical), isomerism?, (a) Butanol, (b) 2-Butyne, (c) 2-Butenol, (d) 2-Butene, , 8., , Hydrolysis of ozonide of But-1-ene gives, (a) Ethylene only, (b) Acetaldehyde and formaldehyde, (c) Propionaldehyde and formaldehyde, (d) Acetaldehyde only, , 9., , Reaction of hydrogen bromide with propene in the absence of a peroxide, is a/an, (a) free radical reaction, (b) nucleophilic substitution, (c) electrophilic addition, (d) nucleophilic substitution, , 224, , Chemistry Class XI
Page 247 :
10., , Among the following compounds, the one which is most reactive towards, electrophilic nitration is:, (a) Benzoic acid, (b) Nitrobenzene, (c) Toluene, (d) Benzene, , ANSWERS: 1.b, , 2.c, , 3.d, , 4.b, , 5.b, , 6.c, , 7.d, , 8.c, , 9.c, , 10.c, , FILL IN THE BLANKS, 1., , Alkanes mainly undergo _____________ reaction., , 2., , Halogenation of alkanes does not occur in ____________., , 3., , The H – C – H bond angle in ethene is __________., , 4., , The addition of HBr to an unsymmetrical alkene takes place in accordance, with ___________ rule., , 5., , Baeyer’s reagent is used for testing ___________., , 6., , Benzene favours ___________ substitution reaction., , 7., , The Dipole moment of Benzene is ___________., , 8., , The nitro group in the benzene nucleus is ________ directing. It __________, the reactivity of the benzene ring., , 9., , Melting point and boiling point increase as the molar masses _______., , 10., , The reaction of solid calcium carbide with water produces __________, a, flammable gas., , ANSWERS : 1. Substitution, 2. Dark, 3. 120°, , 5. Unsaturation 6. electrophilic 7. Zero, , 9. Increase, 10. Ethyne, , 4. Markownikov’s, 8. Meta, decreases, , TRUE AND FALSE TYPE QUESTIONS, 1., 2., 3., 4., , Alkanes mainly undergo substitution reactions using the free-radical, mechanism., The decreasing order of boiling points among the isomeric pentanes is, neo > iso > n., The acidic character of three types of hydrocarbons follows the order, alkanes > alkenes > alkynes., The peroxide effect is observed only in addition of HBr, and not with HCl, and HI., Hydrocarbons, , 225
Page 248 :
5., , Wurtz reaction is suitable for the preparation of both symmetrical and, unsymmetrical alkanes., 6., For a compound to be aromatic it must have (4n + 2)π electrons., 7., Benzene has planar structure., 8., The benzene molecule has two different carbon-carbon bond lengths,, corresponding to alternate single and double bonds., 9., In Friedel-Crafts reaction, AlCl3 is an electrophile., 10. An electron-donating substituent in benzene ring gives a meta product., ANSWERS: 1. T 2. F, , 3. F, , 4. T 5. F, , 6. T 7.T 8. F, , 9. F, , 10. F, , MATCH THE COLUMNS, Match the statements (a,b,c,d) in column I with the statements (i, ii, iii, iv) in, column II., 1., Column I, Column II, , a. C2H6 , i. Electrophilic addition, , b. C2H4 , ii. Electrophilic substitution, , c. C2H2 , iii. Free radical substitution, , d. C6H6 , iv. Free radical addition, 2., , , , , , Column I, a. Alkanes , b. Alkenes , c. Alkynes , d. Arenes , , ANSWERS: 1. a. → iii, 2. a. → i, , Column II, i. Saturated nature, ii. Ozonolysis, iii. Geometrical isomerism, iv. Aromatic character, , b. → i, b. → ii, iii, , c. → i, c. → ii, , d. → ii, d. → i, iv, , ASSERTION-REASON TYPE QUESTIONS, Type 1. The questions given below consist of Assertion(A) and Reason (R). Use, the following key to select correct answer., (a) If both assertion and reason are correct and reason is correct explanation, for assertion., (b) If both assertion and reason are correct but reason is not correct explanation, for assertion., (c) If assertion is correct but a reason is incorrect., (d) If assertion and reason both are incorrect., 226, , Chemistry Class XI
Page 249 :
1., , Assertion: The IUPAC name of CH3CH = CH – C ≡ CH is pent-3-en1-yne and not pent-2-en-4-yne., Reason: While deciding the locants of double and triple Bonds, lowest sum, rule is always followed., , 2., , Assertion: Tropylium cation, is aromatic in character., Reason: The only property which decides the aromatic character is its planar, nature., , 3., , Assertion: Friedel-craft reaction between benzene and acetic anhydride, in the presence of anhydrous AlCl3 yields acetophenone and not polysubstituted products., Reason: Acetophenone formed poisons the catalyst preventing further, reaction., , 4., , Assertion: But-1-ene on reacting with HBr in the presence of peroxide,, products 1-bromobutane., Reason: It involves the formation of a primary free radical., , 5., , Assertion: Alkanes with more than three carbon atoms exhibit chain, isomerism., Reason: Branching of the carbon atom chain is necessary for exhibiting, chain isomerism., , 6., , Assertion: Benzene reacts with chlorine in the form of light to form BHC., Reason: BHC is also called gammexane or 666., , 7., , Assertion: All the hydrogen atoms in CH2 = C = CH2 lie in one plane., Reason: All the carbon atoms in it are sp2 hybridised., , 8., , Assertion: Propene reacts with HBr in the presence of benzoyl peroxide to, yield 2-bromopropane., Reason: In the presence of peroxide, the addition of HBr to propene follows, ionic mechanism., , 9., , Assertion: Benzene does not decolourise bromine water., Reason: Benzene is stabilised by resonance due to delocalisation of π, electrons., , 10. Assertion: Acidity of C-H bond decreases in the order:, HC ≡ CH > H2C = CH2 > H3C – CH3, Reason: Greater the percentage s-character, more is the acidity of C – H bond., ANSWERS: 1.a, , 2.c, , 3.c, , 4.c, , 5.a, , 6.b, , 7.c, , 8.d, , 9.a, , Hydrocarbons, , 10.a, 227
Page 250 :
ONE WORD TYPE QUESTIONS, 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., , What is the state of hybridisation of Carbon atoms in alkanes?, What is self linking property of atoms called?, What is the general formula of alkenes?, What is the other name for Geometrical isomerism?, Which out of Ethane, Ethene and Ethyne has longest C-C bond?, What is the number of bonds in But-3-en-1-yne?, Name the product formed when Propyne is treated with aqueous H2SO4 in, the presence of dil.HgSO4., What is C – C – C bond angle in benzene?, Name the product formed when Benzene reacts with CH3Cl in the presence, of anhydrous aluminium chloride., – COOH is ortho, para directing or Meta directing group?, 1-MARK QUESTIONS, , 1., , Name the chain isomer of C5H12 which has tertiary carbon atom., , 2., , Give the IUPAC name of the lowest molecular weight alkane that contains, a quaternary carbon., , 3., , Write the reaction involved in Kolbe’s electrolytic method to prepare ethane., , 4., , Define term decarboxylation., , 5., , Why dry ether and not water is used as a solvent in the preparation of alkane, by Wurtz reaction?, , 6., , Sodium salt of which carboxylic acid will be needed for the preparation of, propane by decarboxylation method?, , 7., , Complete the following reaction:, dry ether, CH3Cl + Na, , 8., , Amongst the following which one has the maximum boiling point?, n-Pentane, iso-pentane, neo-pentane., , 9., , Define the term conformation., , 10., , Write IUPAC name of CH3CH = CHCH2CH = CCH2CH = CH2, , CH2CH3, , 228, , Chemistry Class XI
Page 251 :
11., , Draw the cis and trans isomers of CHCl = CHCl., , 12., , What happens when 2-Bromobutane is being treated with alc. KOH?, , 13., , Name the reagents used to carry out the following conversions:, CH3 – CH = CH2 → CH3CH(OH)CH2OH, , 14., , Complete the following reaction :, CH3 – CH = CH2 + HBr, , Organic peroxide, , 15., , An alkene A on ozonolysis gives a mixture of ethanol and pentan-3-one., Write IUPAC name of element., , 16., , When alkyne is treated with bromine water then what will be the colour of, the product?, , 17., , Why alkynes do not exhibit geometrical isomerism?, , 18., , Complete the following reaction:, (i) CH3C ≡ CH, , H2O, Hg2+/H+, , (ii) CaC2 + 2H2O, , ?, , ___________ + __________, , 19., , How will you convert ethyne to benzene?, , 20., , Write chemical equation for combustion reaction of Hexyne., , 21., , Write IUPAC name of C6H5 – CH2 – CH2 – CH = CH2., , 22., , Why is benzene extraordinarily stable although it contains three double, bonds?, , 23., , Write chemical reaction to exemplify Friedel-Crafts alkylation of benzene., , 24., , What is the nature of substitution in benzene?, , 25., , Why, , 26., , C-C bond length in benzene is intermediate between C – C and C = C. Why?, , 27., , Starting from benzene,how would you synthesize m- Bromonitrobenzene., , 28., , Give one example each of o, p-directing group and m-directing group., , 29., , Complete the reaction:, , is not aromatic?, , C6H6 + CH3COCl, , Anhy. AlCl3, , 30. Write the electrophile which is involved in the nitration of benzene., , Hydrocarbons, , 229
Page 252 :
2-MARKS QUESTIONS, 1., , What effect does branching have on the boiling point of an alkane and why?, , 2., , What is the difference between isomers and conformers?, , 3., , Is it possible to isolate pure staggered ethane or pure eclipsed ethane at room, temperature? Give reason., , 4., , Draw Newman projection formula for conformations of ethane., , 5., , How will you convert methyl bromide to ethane?, , 6., , Wurtz reaction cannot be used for the preparation of unsymmetrical alkanes?, Give reason., , 7., , How can ethene be prepared from (i) Ethanol (ii) Ethyl bromide?, , 8., , Melting point of cis-But-2-ene is lower than that of trans-But-2-ene. Give, reason., , 9., , Draw the structures of cis and trans Hex-2-ene., , 10., , Explain with the help of equation : Ozonolysis of propene., , 11., , Give a chemical test to distinguish between ethene and ethane., , 12., , What do you understand by peroxide effect (Kharasch effect)?, , 11., , What factor determines the stability of alkene?, , 14., , Arrange the following alkenes in decreasing order of stability :, , 15., , CH3 – CH = CH – CH3, CH2 = CH2, CH3 – CH = CH2, , Complete the reaction:, (i), , + HBr → ?, , (ii), , Zn, + O3 CH COOH, 3, , ? + ?, , 16., , An alkene on treatment with HBr in presence of peroxide can generate two, types of free radicals CH3 – C• – CH2-Br and CH3 – C(CH3) – CH2•, , , , , CH3, Br, Predict the final product of the reaction and give reason., (Hint: Stability of free radicals), 17. What happens when But-2-ene reacts with acidified potassium permanganate, solution?, 230, , Chemistry Class XI
Page 253 :
18., , You are provided with But-2-yne, how will you convert it into:, (i) cis-But-2-ene, (ii), , trans-But-2-ene, , 19., , An alkene C4H8 reacts with HBr both in the presence and absence of peroxide, to give the same product. Identify the alkene., , 20., , Arrange ethane, ethene and ethyne in the order of increasing acidity., , 21., , Identify A and B in the following reaction:, A, , 22., , Na, , CH ≡ CH, , Red hot iron tube, , B, , 873K, , Write the structures of the products A and B of the following reactions:, Na, , (i), , HC ≡ CH, , A, , (ii), , BrH2C – CH2Br, , CH3Br, , Alc.KOH, , B, A, , NaNH2, , B, , 23., , Give a chemical test to distinguish between ethyne and ethene., , 24., , Out of benzene and toluene ,which will undergo nitration easily and why?, , 25., , Why does presence of a nitro group make the benzene ring less reactive in, comparison to the unsubstituted benzene ring? Explain., , 26., , What happens when Chlorine is passed through benzene in the presence of, sunlight and absence of halogen carrier?, 3-MARKS QUESTIONS, , 1., , Write the structures and name of products obtained in the reaction of sodium, with a mixture of 1-Iodo-2-methylpropane and 2-Iodopropane., , 2., , State Markownikov’s rule. Using this rule, write the reaction of propene, with (i) HCl & (ii) H2O., , 3., , Complete the following reactions:, Alc.KOH, , (i), , CH3CH2Br, , (ii), , CH3CH = CH2 + O3, , (iii) CH2 = CH2 +H2O + [O], 4., , Zn/H2O, Dil.KMnO4, , (i), , Write the structure of 3, 4-Dimethylhept-3-ene., , (ii), , Name the compounds obtained by ozonolysis of 3-Methylpent-2-ene., , Hydrocarbons, , 231
Page 254 :
5., , Complete the following reactions:, (i), , CH ≡ CH, , (ii), , CH ≡ CH, , NaNH2,CH3Br, H2O,HgSO4/H2SO4, , (iii) CH3C ≡ CH + H2, , Pt, , ?, ?, ?, , H2, , ?, , 6., , Write the mechanism of nitration of benzene., , 7., , Arrange in the order of decreasing relative reactivity with an electrophile, and explain:, Toluene, p-Nitrotoluene, 1, 4-Dinitrobenzene, , 8., , What is meant by delocalization of π electrons? How does it affect stability, of benzene?, , 9., , What are the conditions for a compound/species to be aromatic according, to Huckel’s rule?, , 10., , How will you convert benzene into, (i) Acetophenone, (ii) m- Chloronitrobenzene?, 5-MARKS QUESTIONS, , 1., , Define isomerism. Write all the structural isomers of hexane(C6H14) and, arrange them in increasing order of boiling points., , 2., , Write short note on (i) Wurtz reaction (ii) Kolbe’s electrolysis (iii) Ozonolysis, , 3., , Alkenes show geometrical isomerism while alkanes do not. Give a suitable, explanation., , 4., , An alkene ‘A’ of molecular mass ‘28u’ on treatment with bromine gives, a product ‘B’. The Compound ‘B’ on further dehalogenation with zinc, gives back ‘A’. Give the structures of ‘A’ and ‘B’ and also the sequence of, reactions., , 5., , An organic compound ‘A’ with formula C4H9Br on treatment with KOH(alc.), gave two isomeric compounds ‘B’ and ‘C’ with formula C4H8. Ozonolysis of, ‘B’ gave only one product CH3CHO while ’C’ gave two different products., Identify A, B and C., , 6., , How will you convert Ethyne into (i) 1, 1, 2, 2-Tetrachloroethane (ii) Ethene, (iii) Ethanal (iv) Benzene (v) Sodium ethynide, , 7., , Discuss the structure of benzene with an emphasis on resonance and orbital, pictures., , 232, , Chemistry Class XI
Page 255 :
UNIT TEST, Time Allowed: 1 hr, , Maximum Marks : 20, , General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , Amongst the following which one has the maximum boiling point, and why? n-Pentane , iso-pentane, neo-pentane, , [1], , 2., , What is the number of σ and π bonds in But-3-en-1-yne? , , [1], , 3., , Action of acetylene on dilute H2SO4/dil.HgSO4 gives: , [1], (a) Acetic acid (b) Acetone (c) Acetaldehyde (d) Ethyl alcohol, , 4., , An alkene A on ozonolysis gives a mixture of ethanal and , pentan-3-one. Write IUPAC name of element., , [1], , 5., , The nitro group in the benzene nucleus is ______ directing. , It ________the reactivity of the benzene ring., , [1], , 6., , Arrange the following alkenes in decreasing order of stability and, give reason., CH3 – CH = CH – CH3, CH2 = CH2, CH3 – CH = CH2, , [1], , 7., , (i) Give a chemical test to distinguish between ethyne and ethene. [2], (ii) Melting point of cis-But-2-ene is lower than that of trans-But-2-ene., Give reason., , 8., , Complete the following reactions: , (i) CH3CH2Br, , Alc.KOH, , (ii) CH3CH = CH2 + O3, (iii) CH2 = CH2 +H2O + [O], , [3], , Zn/H2O, Dil.KMnO4, , 9., (i) What are the conditions for a compound/species to be aromatic [3], , according to Huckel’s rule?, (ii) How will you convert Benzene to acetophenone?, 10. (i), , , An alkene ‘A’ of molecular mass ‘28u’ on treatment with, [5], bromine gives a product ‘B’. The Compound ‘B’ on further, dehalogenation with zinc gives back ‘A’. Give the structures, , of ‘A’ and ‘B’ and also the sequence of reactions., (ii) Why is benzene extraordinarily stable although it contains three, double bonds?, (iii) How can we convert ethyne into benzene?, ****, Hydrocarbons, , 233
Page 256 :
3, , SP –S, σ bond, , H, , H, C, , C, H, , H, , on, , ugati, , rconj, , Hype, , C, H, , Chapter - 14, , Environmental, Environmental, Chemistry, Chemistry, , FAST TRACK : QUICK REVISION, ► Environmental pollution: Environmental pollution is the effect of, undesirable changes in our surroundings that have harmful effects on plants,, animals and human beings. A substance which causes pollution is known, as pollutant. Pollutants can be degradable and non-degradable., ► Atmospheric pollution: Any undesirable changes in their atmosphere, which adversely effect living beings is called air pollution. Air pollution is, generally limited to troposphere and stratosphere., Ozone is present in stratosphere and prevents UV radiations of sun from, reaching the earth’s surface., ► Tropospheric pollution: It is due to gaseous and particulate pollutants., 1., , Gaseous air pollutants:, Oxides of sulphur: Major sources of oxides of sulphur (mainly SO2) are, burning of fossil fuels containing sulphur. Sulphur dioxide is converted to, sulphur trioxide in presence of particulat matter., , 2SO2+O2 → 2SO3, Sulphur dioxide is a corrosive gas which produces acid rain that causes, damage and destruction of vegetation and degradation of soils, building, materials and watercourses. SO2 in ambient air is also associated with asthma, and chronic bronchitis. It also causes irritation to eyes., ● Oxides of nitrogen: Major sources of nitrogen oxides are high, temperature combustion processes, oxidation of nitrogen in the air and, fuel respectively, denitrifying bacteria, etc., , N2 + O2 → 2NO, 2NO + O2 → 2NO2, NO + O3 → NO2 + O2
Page 257 :
Finally, these gases are converted into nitric acid (HNO3) which comes, down to the surface of the earth in the form of acid rain., — NO2 is a respiratory irritant,, — The oxides produce eye irritation, injury to liver and kidneys., ●, , Hydrocarbons: They are majorly produced naturally (e.g. marsh gas), as well as due to incomplete combustion of automobile fuel., — Hydrocarbons are carcinogenic, these harm plants., ●, , Oxides of carbon: two major pollutants are oxides of carbon i.e.,, carbon monoxide and carbon dioxide., , ●, , Carbon monoxide: Carbon monoxide (CO) is a toxic gas which is, emitted into atmosphere by incomplete combustion of coal and firewood, and by oxidation of hydrocarbons and other organic compounds., CO may reduce the oxygen carrying capacity of the blood by, combining with haemoglobin to produce carboxyhaemoglobin, This, oxygen deficiency results in headache weak eyesight, choking and, cardiovascular disorders., , , , ●, , , , , Carbon dioxide: CO2 is released into atmosphere by respiration, burning of fossil fuels, forest fire decomposition of limestone in cement, industry, etc., — It is a greenhouse gas, the concentration of which is constantly raising., — In excess it causes headache and nausea., , ►, , Greenhouse effect and global warming: The greenhouse effect is the, process in which the emission of infrared radiation by the atmosphere warms, the Earth surface., ● Greenhouse gases include carbon dioxide, methane, ozone, chlorofluorocarbons (CFCs) and water vapour., ● Earth absorbs energy from sunlight entering the atmosphere and emit, energy out to space in form of infrared rays. The outgoing radiation, emitted by the surface is in the absorption range of many atmospheric, gases, including carbon dioxide, methane, and water vapour. These, radiations are thus locked in the earth's atmosphere. This results in, the steady increase in the temperature of the earth resulting in global, warming., ► Acid rain: Rainwater normally has a pH of 5.6 due to dissolution of CO2, present in the atmosphere., , CO2 + H2O = H2CO3 = H+ + HCO-3, Environmental Chemistry, , 235
Page 258 :
●, , When the pH Falls below 5.6, the rain water becomes acidic, It is, caused due to presence of acidic gases into the atmosphere the common, ones are sulphur dioxide and nitrogen oxides which are changed into, sulphuric acid and nitric acid by combining with oxygen and water., 2SO2 + O2 + 2H2O → 2H2SO4, 4NO2 + O2 + 2H2O → 4HNO3, ● Harmful effects of acid rain: It is causes extensive damage to buildings, and statues made by marble, limestone due to the reaction,, CaCO3 + H2SO4 → CaSO4 + CO2 + H2O, , — It is toxic to vegetation and aquatic life., , — It corrodes water pipes resulting in the leaching of the heavy metals, such as Fe, Pb, and Cu into the drinking water which have toxic effects., 2., , 236, , Particulate pollutants: Particulate pollutants are small solid particles and, liquid droplets suspended in air., Smoke: it consists of solid or mixture of solid and liquid particles formed, by combustion of organic matter. e.g., cigarette smoke, oil smoke, smoke, from fossil fuel etc., Dust: It consists of fine particles produced during crushing and grinding of, solid materials. Common dust particulate emission include cement, fly ash,, silica dust, from Industries, dust storm, ground limestone, etc., Mist: These are formed by particles of spray liquids and condensation of, sepals in air. For example, sulphuric acid, mist herbicide or insecticide that, Miss their targets and travel through air from mist., Fumes: These are produced by condensation of vapours. For example, metal, fumes, metallurgical fumes and alkali fumes., Smog: The word smog has its origin from smoke and fog. It is a major air, pollutant., Classical smog, , Photochemical smog, , Also called as London smog., , Also called as Los Angeles smog., , Form due to oxides of sulphur., , Formed due to oxides of Nitrogen., , Contains primary pollutants., , Content secondary pollutants., , Causes bronchitis and problem, in lungs., , Causes irritation in Eyes., , It is reducing in nature., , It is oxidising in nature., , Chemistry Class XI
Page 260 :
●, , , , Ozone depletion by oxides of Nitrogen:, Nitrous oxide is quite inert, in the stratosphere it is photochemically, converted into more reactive nitric oxide., , , , NO + O3 —→ NO2 + O2, , , , hv, O2 —→, O+O, , , , NO2 + O —→ NO + O2, , , , Thus NO is regenerated in chain reaction., , ●, , Effects of ozone depletion:, , With the depletion of Ozone layer, more UV radiation filters into, troposphere., — UV radiations leads to ageing of skin, cataract, Sunburn, skin cancer,, killing of many phyotplanktons, damage to fish productivity, etc., Water pollution: Water pollution may be defined as any change in its, physical, chemical, biological properties or contamination with foreign, materials that can adversely affect human beings or reduce its utility for the, intended use., Major water pollutants and their sources:, , ●, , 238, , Pollutants, , Major sources, , natural waste, , Leaching of minerals slits from soil erosion falling, of organic matter from bank,etc., , organic Chemicals, , Pesticides, surfactants, detergents, Industrial waste, , metals, , Nuclear power plants, mining, metal plating, industries., , man-made wastes, , Sewage domestic waste, soaps and detergents,, waste from animal sheds and slaughter houses,, run off from agricultural fields, industrial wastes,, oil pollution., , Eutrophication: The process in which nutrient enriched water bodies, support a dense plant population, which kills animal life by depriving, it of Oxygen and results in subsequent loss of biodiversity is known, as eutrophication., , Chemistry Class XI
Page 261 :
●, , BOD: The amount of oxygen required by bacteria to break down the, organic matter present in a certain volume of a sample of water, is, called Biochemical Oxygen Demand (BOD), , International standards for drinking water:, , ►, , Element, , Permissible limit, , Effect of excess amount, , Fluoride, , 1 ppm or 1mg dm-3, , Over 10 ppm causes harmful effect, to bones and teeth., , Lead, , 50ppb, , Excess amount can damage kidney,, liver reproductive system, etc., , Nitrate, , 50ppm, , Excess amount can cause blue baby, syndrome., , Sulphate, , 500ppm, , Excess can cause laxative effects., , Soil pollution: Soil pollution is the addition of such chemical substances (in, an indefinite proportion) which deteriorates the quality, texture and mineral, content of the soil and disturbs the biological balance of the organisms in, it and has little effect on the plant growth., Some major soil pollutants and their sources:, Pollutants, Industrial wastes, , Major sources, Waste products from paper, sugar, chemical, Industries dumped into the soil., Agricultural wastes, Chemical such as fertilizers pesticides extra used, for killing insects fungi and weeds., Soil conditioners, Used to protect soil fertility but contains several, toxic metals like Pb, As, Hg, Cd, etc, Farm wastes, Wet slurry, faecal wastes are seeped into the soil., Radioactive pollutants Dumping of nuclear waste into the soil., ►, , Remedial measures:, ● Forestation should be done to check the spread of desert., , — Use of chemical fertilizers should be minimised., , — Recycling, digestion and incineration of urban waste and organic waste, should be done., , — The industrial effluents should not be allowed to discharge into fields., , — The fertility of the soil can be improved by soil rotation and mixed, farming., Environmental Chemistry, , 239
Page 262 :
►, , Control of environmental pollution:, Waste management: Environmental pollution can be controlled to a certain, extent by managing the waste disposal in a proper way., ● Recycling: A large amount of disposed waste materials can be reduced by, recycling the waste., , Thus, it reduces the landfill and converts waste into usable products., , ●, , ►, , Green chemistry: Green Chemistry may be defined as a strategy to design chemical, process and products that reduces or eliminate the use and generation of hazardous, substances., ● It is an alternative tool for reducing pollution. Green Chemistry includes, concepts such as waste minimization, solvent selection, atom utilisation,, intensive processing and alternative synthetic routes from sustainable, resources., ● Green chemistry in day-to-day life:, , — Dry cleaning of clothes: Tetra chloroethene (Cl2C = CCl2) was earlier, used as solvent for dry cleaning. The compound contaminates the, ground water and is also a suspected carcinogen., , The process using this compound is now being replaced by a process,, where liquefied carbon dioxide, with suitable present is used., , — Bleaching of paper: Chlorine gas was used earlier for bleaching paper., These days, hydrogen peroxide (H2O2) with suitable catalyst, which, promotes the bleaching action of hydrogen peroxide, is used., , 240, , Chemistry Class XI
Page 263 :
Environmental Chemistry, , 241, , Degradable, , Nondegradable, , Pollutants, , Environmental Pollution, , Soil Pollution, , Water, Pollution, , Chlorofluorocarbons, Oxides of nitrogen etc., , Ozone layer depletion, , Stratospheric, Pollution, , Air Pollution, , Particulate, Pollutants, , e.g., NO2NO3, , e.g., SO2SO3, e.g., CO, CO2, , Oxides, of C, e.g., CH4, , Hydrocarbons, , Smog, , e.g. Chemicals such as fertilizers, pesticides., e.g. Wet slurow, fecal wastes., , Agricultural Waste, Farm Wastes, , Soil conditioners, , e.g. those containing toxic metals like Pb, As,, Hg, Cd etc., , Radioactive pollutants e.g. Dumping of nuclear waste into the soil., , e.g. Waste from paper, sugar industry., , e.g. Sewage domestic waste, industrial wastes., , Man-made Waste, Industrial Waste, , e.g. Nuclear power plants, mining., , e.g. Pesticides, detergents., , Organic Chemicals, Metals, , e.g. Leaching of mineral slits from soil erosion., , Natural Waste, , Classical, Photo chemical, • Reducing, • Oxidising, • Landon smog • Los angles smog, , Fumes, , Mist, , Dust, , • Greenhouse effect & Global warming, • Acid rain, , Oxides, of N, , Gaseous air, Pollutants, , Oxides, of S, , Tropospheric, , Smoke, , MIND MAP : ENVIRONMENTAL CHEMISTRY
Page 264 :
MULTIPLE CHOICE QUESTIONS (MCQ), 1., , Which of the following is not the consequence of global warming?, (a) Increase in average temperature of Earth., (b) Melting of Himalayan glaciers, (c) Rise in sea level, (d) Eutrophication, , 2., , Which of the following statement is incorrect?, (a) Oxidize of Nitrogen in atmosphere can cause depletion of Ozone, layer, (b) Ozone absorbs infrared rays, (c) Depletion of O2 is due to its chemical reaction with halo alkanes, (d) None of these, , 3., , Which of the following are the hazardous pollutants present in automobile, exhaust gases?, (i) N2, (ii) CO, (iii) CH4, (iv) Oxides of nitrogen, (a) ii and iii, (b) i and ii, (c) ii and iv, (d) i and iii, , 4., , Which of the following gas causes green house effect to maximum extent?, (a) CH4 , (b), Water vapour, (c) N2O , (d), CO2, , 5., , The lowest region of atmosphere is?, (a) Stratosphere, , (c) Mesosphere, , , (b), (d), , Troposphere, Hydrosphere, , Classical smog occurs in place of, (a) Excess of NO2 , (c) Cool humid climate , , (b), (d), , Warm dry climate, All of these, , 6., , 7., , When huge amount of sewage is dumped in a river, the BOD, (a) Will increase (b) Will remain unchanged, (c) Will in decrease (d) May increase or decrease, , 8., , Which of the following practices will not come under Green chemistry?, (a) Use of CO2 as solvent instead of Cl2, (b) Use of H2O2 instead of Cl2 for bleaching, (c) Synthesis of ethanal from ethane in one step, (d) Use of tetrachloroethene as a solvent for dry cleaning, , 242, , Chemistry Class XI
Page 265 :
9., , Eutrophication causes reduction in, (a) Dissolved salts (b) Dissolved oxygen, (c) Nutrients , (d) All of these, , 10., , SO2 and NO2 cause pollution by increasing, (a) Acidity , (b) Alkalinity, (c) Buffer action (d) Both (a) and (c), , ANSWERS: 1.d, , 2.b, , 3.c, , 4.d, , 5.b, , 6.c, , 7.a, , 8.d, , 9.d, , 10. a., , FILL IN THE BLANKS, 1., , Three substances normally considered as primary pollutant are ____, ____,, and _____., , 2., , Sulphur dioxide is mainly produced by the burning of ________., , 3., , BOD stands for __________., , 4., , The single plant nutrient mainly responsible for eutrophication is ______., , 5., , The lowest layer of atmosphere is the_______., , 6., , A crucially important species formed by oxygen in stratosphere is _____., , 7., , _______ is a greenhouse gas., , 8., , A major class of organic halides that are thought to pose a threat to, stratospheric ozone are _______., , 9., , The component that distinguishes classical smog from photochemical smog, is _____., , 10., , Carbon dioxide traps heat in the atmosphere. This is called the ______., Answers : 1. CO, NO 2 , SO 2 2. Coal 3. Biochemical oxygen, demand 4. Phosphate 5. Troposphere 6. Ozone 7. Carbon dioxide 8., Chlorofluorocarbons 9. Sulphur dioxide 10. Greenhouse effect, TRUE AND FALSE TYPE QUESTIONS, , 1., , The troposphere is the region above the stratosphere., , 2., , Dust, mist, fumes, smoke and smog are particulate pollutants., , 3., , Carboxyhaemoglobin is less stable than oxyhaemoglobin., , 4., , Ozone occurs naturally in the troposphere., Environmental Chemistry, , 243
Page 266 :
5., , Plants such as Pinus, Juniparus, Pyrus and Vitis metabolize nitrogen oxides., , 6., , Clean water should have BOD of 17 ppm or more., , 7., , Photochemical smog is a mixture of oxidising pollutants., , 8., , The exhaust from jet aeroplanes contains nitric oxide, which can destroy, the ozone layer., , 9., , PAN is one of the constituents of photochemical smog., , 10., , DDT is non-biodegradable and persistent., Answers : 1. F 2. T 3. F 4. F 5. T 6. F 7. T 8. T 9. T 10. T, MATCH THE COLUMNS, , Match the column:, 1., , Column I, , Column II, , a. CO2, i., , b. CO, ii., , c. O3, iii., , a gas produced by the partial combustion of, many fuels, a gas that occurs naturally in the atmosphere, and which is needed for photosynthesis, a dangerous gaseous pollutant with, corrosive properties formed by combustion, of fossil fuels., iv. an allotrope of oxygen found in the upper, atmosphere, , d. SO2, 2., , Match the pollutants (a, b, c, d) in column I with the effects (i, ii, iii, iv), in column II., Column I, , Column II, , a., b., c., d., , i. BOD level of water increases, ii. Acid rain, iii. Global warming, iv. Photochemical oxidant, , Phosphate fertilisers in water, Methane in air, PAN, Nitrogen oxides in air, , ANSWERS: 1. a. ii, 2. a. i, , 244, , b. i, b. iii, , Chemistry Class XI, , c. iv, c. iv, , d. iii, d. ii
Page 267 :
ASSERTION-REASON TYPE QUESTIONS, In the following questions a statement of Assertion (A) followed by reason(R) is, given. Use the following key to select correct answer., (a) Both Assertion and Reason are correct and Reason is the correct, explanation of Assertion., (b) Both Assertion and Reason are correct but Reason is not the correct, explanation of Assertion., (c) Both Assertion and Reason are incorrect., (d) Assertion is not correct but Reason is correct., 1., , Assertion: The pH of acid rain is less than 5.6., Reason: Carbon dioxide present in the atmosphere dissolves in rain water, and forms carbonic acid., , 2., , Assertion: Photochemical smog is oxidizing in nature., Reason : Photochemical smog contains NO2 and O3, which are formed, during the sequence of reactions., , 3., , Assertion: If BOD level of water in a reservoir is less than 5ppm, it is highly, polluted., Reason: High biological oxygen demand means low activity of bacteria in, water., Assertion: Ozone is destroyed by solar radiation in upper atmosphere., Reason: Thinning of the ozone layer allows excessive UV radiations to, reach the surface of earth., Assertion: Carbondioxide is an of the important greenhouse gas., Reason: It is largely produced by respiratory function of animals and plants., , 4., , 5., , ANSWERS : 1. b, , 2. a, , 3. c 4. d 5. b, , ONE WORD TYPE QUESTIONS, 1., , Name the gas which reacts with haemoglobin in blood., , 2., , In which part of atmosphere is ozone layer present?, , 3., , Besides CO2 name one other green house gas., , 4., , Which acid is most abundant in acid rain?, , 5., , Name the gas whose release was responsible for Bhopal gas tragedy., Environmental Chemistry, , 245
Page 268 :
6., , What is the nature of photochemical smog?, , 7., , Write full form of BOD., , 8., , What is the lowest region of the atmosphere which extends upto a height, of 10 km from sea level?, , 9., , Name the gas which is produced by the incomplete combustion of gasoline., , 10., , What does CFC stand for?, 1-MARK QUESTIONS, , 1., , Name two gaseous pollutants., , 2., , What is the size range of particulates?, , 3., , What are primary pollutants?, , 4., , Name two greenhouse gases., , 5., , What is the composition of photochemical smog?, , 6., , What is the composition of classical smog?, , 7., , Which are the compounds responsible for ozone layerdepletion?, , 8., , Name the pollutants which has affected Taj Mahal., , 9., , Name two strong acids present in acid rain., , 10., , What is PAN?, , 11., , Name two sources of phosphate pollution., , 12., , When a huge amount of sewage is dumped into a river, what will be the, effect on BOD?, , 13., , How is NO formed in atmosphere?, , 14., , In which season the depletion of ozone on Antarctica takes place and when, is it replenished?, , 15., , Define acid rain., 2-MARKS QUESTIONS, , 1., , 246, , Explain giving reason: The presence of CO reduces the amount of, haemoglobin available in the blood for carrying oxygen to body cells., Chemistry Class XI
Page 269 :
2., , Oxygen plays a key role in the troposphere while ozone in stratosphere., Explain., , 3., , What is meant by Eutrophication?, , 4., , Define BOD., , 5., , What is the importance of measuring BOD of a water body?, , 6., , Why does water with excessive algae growth become polluted?, , 7., , A person was using water supplied by municipality. Due to shortage of water,, he started using underground water, he felt laxative effect. What could be, the cause?, , 8., , What do you understand by the term Green chemistry?, , 9., , Give two examples each of biodegradable and non-biodegradable waste., , 10., , List few ways to control photochemical smog., 3-MARKS QUESTIONS, , 1., , Give three harmful effects of oxides of sulphur., , 2., , What is Global warming? What is its cause?, , 3., , What is photochemical smog and what are its harmful effects?, , 4., , How is classical smog different from photochemical smog?, , 5., , State briefly the reactions causing ozone layer depletion in the stratosphere., , 6., , How does rain water get contaminated with acidic impurities?, , 7., , Discuss the harmful effects of acid rain., , 8., , Suggest any four methods for waste management., 5-MARKS QUESTIONS, , 1., , What is Green house effect? How is it responsible for global warming?, , 2., , How can you apply green chemistry in for the following?, (i), , To control photochemical smog, , (ii), , To avoid use of halogenated solvents in dry cleaning, , (iii) To reduce the use of detergents, (iv) To reduce the consumption of petrol and diesel., Environmental Chemistry, , 247
Page 270 :
UNIT TEST, , Time Allowed: 1 hr, Maximum Marks : 20, General Instructions:, (i) All questions are compulsory., (ii) Maximum marks carried by each question are indicated against it., 1., , The lowest region of atmosphere is , (a) Stratosphere, , (b) Troposphere, (c) Mesosphere, , (d) Hydrosphere, , [1], , 2., , Classical smog occurs in place of , (a) Excess of NO2 , (b) Warm dry climate, (c) Cool humid climate , (d) All of these, , [1], , 3., , Name two Greenhouse gases. , , [1], , 4., , A major class of organic halides that are thought to pose a threat, [1], to stratospheric ozone are ___________., The single plant nutrient responsible for eutrophication is , [1], _____________., Explain giving reason: The presence of CO reduces the amount of, [2], haemoglobin available in the blood for carrying oxygen to body cells., , 5., 6., 7., , How is classical smog different from photochemical smog? , , [2], , 8., , Define BOD. What is the importance of measuring BOD of a , water body?, , [3], , 9., , How does rain water get contaminated with acidic impurities?, Write one harmful effect of acid rain., , [3], , 10., , How can you apply green chemistry for the following? , (i) To control photochemical smog, (ii) To avoid use of halogenated solvents in dry cleaning, (iii) To reduce the use of detergents, (iv) To reduce the consumption of petrol and diesel., , [5], , ****, , 248, , Chemistry Class XI
Page 271 :
SAMPLE PAPER - I, Time Allowed: 1 hr, , SUB : CHEMISTRY, CLASS - XI, , Maximum Marks : 70, , General Instructions:, • All question are compulsory, •, •, •, •, •, , Q 1 to 20 are very short answer objective type and each carries 1 mark each., Q 21 to 27 are short answer question and carry 2 marks each., Q 28 to 34 are also short answer question and carry 3 marks each., Q 35 to 37 are long answer questions and carry 5 marks each., There is no overall choice. However internal choice have been provided in some, questions., • Use of log tables if necessary. Use of calculators is not allowed., , 1. What are the oxygen moles in 0.5 mol of CaCO3 ?, (a) 1 mol , (b) 0.2 mol, (c) 1.5 mol, , , , (d) 3.0 mol, , 2. What is the unit of wave number (v) ?, 3. The general configuration of ‘f’ block is, (a) (n-1) f 1-14 nd0-1 ns2, , (b), , (n-1)f0-1 nd2 ns2, , (c) (n-2) f1-14 (n-1) d0-1 ns2, , (d), , (n-2) f1-14 (n-1)d0-2 ns0-1, , 4. The shape of IBr–2 is, (a) Tetrahedral, (c) Linear, , (b), (d), , Planar, V-shape, , 5. What is the pressure of the gas in tube, , , 6. Arrange the following in order of decreasing boiling point : Be, Mg, Ca, Sr, 7. ∆f H0 for Graphite is ___________ ., 8. Nature of NaH is ___________ ., , Sample Paper, , 249
Page 272 :
Q.9 - Q.10 Assertion-Reason Type Questions, Each question contains statements-1 (Assertion) and Statement-2 (Reason), Examine the statements carefully and mark the correct answer according to, the instruction given below:, A. If both the statements are true and statement-2 is the correct explaination, of statement-1., B. If both the statements are true but statement-2 is not the correct explanation, of statement-1., C. If statement-1 is true and statement-2 is false., D. If statement-1 is false and statement-2 is true., 9. Statement-1 For reaction A + B, C, K = 4 on addition of catalyst K, becomes more than 4., Statement-2 Catalyst only helps to attain the equilibrium faster from either, end of reaction., 10. Statement-1 Cl2 + 2OH–, ClO– + Cl– is a disproportion reaction., Statement-2 In disproportionation, the same element get oxidised as well, as reduce., 11. Complete the reaction, H2(g) + Pd2+ (aq.), , OR, CO(g) + H2O(g) 673K, , Catalyst, , 12. Why ammoniacal solution of alkali metal is blue in colour?, 13. What is a producer gas?, 14. Write the IUPAC name of following, NO2, , , , OR, Cl, , CH3, , 15. What does B.O.D. stands for?, 16. Calculate number of atoms in 52u of He., 17. Which series of lines of the hydrogen spectrum lie in the visible region?, 18. Write the name of element with highest electron gain enthalpy., , 250, , Chemistry Class XI
Page 273 :
19. Draw the shape of ClF3., OR, Draw the shape of SF6., 20. What is the unit of ‘a’ in van der Waal's equation?, 21. (i) What are the number of waves made by a Bohr electron in an orbit of, maximum magnetic quantum number 3?, (ii) If kinetic energy of a particle is doubled. What will happen to de Broglie, wavelength as compared to previous de Broglie wavelength., 22. (i) Why PbCl2 is more stable than PbCl4?, (ii) Why Electron gain enthalpy of Mg is positive?, OR, (i) Second I.E. (Ionisation Enthalpy) is always more than first Ionisation, energy., (ii) Why first electron gain enthalpy of sulphur is more negative than, oxygen., 23. Balance the following reaction by (ion-electron or oxidation number method), Cl2O7(g) + H2O2 (aq.) → ClO2– (aq.) + O2 (g) + H+ (Acidic medium), 24. (i) What is the difference between hydrolysis and hydration?, (ii) Arrange the following in order of increasing electrical conductance, CaH2, BeH2 and TeH2., 25. A sample of 0.5g of an organic compound was treated according to Kjeldahl's, method. The ammonia evolved was absorbed in 50 ml of 0.5 M H2SO4. The, residual acid requirede 60 mL of 0.5 solution of NaOH for neutralisation., Find the percentage composition of nitrogen in the compound., 26. (i), , Out of benzene, m-dinitrobenzene and toluene, which will undergo, nitration most easily and why?, (ii) What effect does branching of an alkane chain has on its boiling point?, , 27. (i) What is Eutrophication?, (ii) What is the action of F– on enamel present on the surface of teeth?, OR, (i) What is the upper limit concentration of lead in drinking water?, (ii) What is smog? Classify them as reducing smog or oxidising smog., Sample Paper, , 251
Page 274 :
28. A crystalline salt on being rendered anhydrous loses 45.6% of its weight., The percentage composition of the anhydrous salt is, Al = 10.50%, K= 15.1%, S= 24.96%, O=49.92%, Find the simplest formula of the anhydrous and crystalline salt., (Atomic Mass, hv : K= 39, Al = 27, S = 32, O = 16)., 29. Explain following with example :, (i) Aufbau's Rule (ii) Hund's Rule (iii) Pauli's Exclusion Principle, OR, An ion with mass number 81 contains 31.7% more neutrons as compared, to protons. Assign the atomic symbol., 30. Explain the bonding in SF6 using hybridisation concept and define what is, hybridisation., OR, On the basis of molecular orbital theory find the bond order, molecular, orbital configuration and magnetic nature of O2+., 31. Derive van der Waal's equation :, , , an 2 , nRT, P + 2 (v − nb) =, , v, , , , , , 32. Explain Born Haber cycle with by considering example of formation of, MgCl2 as given in the chemical reaction, , Mg(s) + Cl2(g) → MgCl2(s), 33. Give suitable reasons :, (i), , A solution of Na2CO3 is alkaline why?, , (ii) Beo insoluble but BeSO4 soluble in water why?, (iii) Lithium salts are commonly hydrated as compare to other alkali metal, ions. Why?, 34. Arrange following in order of increasing stability, (a), (b), , 252, , (CH 3 )3 C+, , CH2, , CH2, , NO2, , OCH3, , Chemistry Class XI, , CH2, , +, , CH2, , CH3
Page 275 :
•, , (c) CH3CH2,, , •, , CH3,, , •, , CH2–CH= CH2,, , •, , CH = CH2, , OR, (i) What is ambident nucleophile? Mention one example., (ii) Distinguish between homolytic and hetrolytic bond cleavage., (iii) Which one is stronger acid and why, , , 35. (a) What is a buffer solution? Give example., (b) What is common ion effect?, (c) Define Le-Chatlier principle and explain effect of following :, (i) Change of concentration (ii) Change of pressure, OR, (a) Find out Kc for following reaction, 2NOCl(g) 2NO(g) + Cl2(g) ; Kp = 1.8×10-4 at 500K, (b) Kp = 0.04 atm at 899K. What is the equilibrium concentration of C2H6, where it is placed in a flask at 4.0 atm pressure and allow to come to, equilibrium, C2H6 C2H4(g) + H2(g), (c) What is the unit of Kp for the following chemical reaction?, 2NH3(g) N2(g) + 3H2(g), 36. (i), , Show with the help of chemical reaction that Al shows amphoteric, behaviour., , (ii) Draw the structure of (a) B2H6 (b) Boric acid., (iii) Write the formula of Borax., OR, (i) Explain Lewis acid strength, , BF3 < BCl3 < BBr3 < BI3, , Sample Paper, , 253
Page 276 :
(ii) What are silicones? Give reaction for formation of chain silicones., (iii) Why CO is poisionous in nature?, 37. (i), , Explain with the help of mechanism, , , , NO2, Con. HNO3, Con H2SO4, , (ii) Draw the Newman structure of (a) 2-Methyl butane, , (b) 1-Methyl prop-1-ene, (iii) Calculate total number of s and p bond(s) in, , , (i), , OR, Explain Kolbe's electrolysis with mechanism., , (ii) State Huckel Rule's., , , Check whether, , is an aromatic or non aromatic, anti-aromatic., , (iii) Write the product, , ****, , 254, , Chemistry Class XI
Page 277 :
SAMPLE PAPER - II, Time Allowed: 1 hr, , SUB : CHEMISTRY, CLASS - XI, , Maximum Marks : 70, , General Instructions:, • All question are compulsory, •, •, •, •, •, , Q 1 to 20 are very short answer objective type and each carries 1 mark each., Q 21 to 27 are short answer question and carry 2 marks each., Q 28 to 34 are also short answer question and carry 3 marks each., Q 35 to 37 are long answer questions and carry 5 marks each., There is no overall choice. However internal choice have been provided in some, questions., • Use of log tables if necessary. Use of calculators is not allowed., , 1., 2., , SECTION-A, The number of nodal planes in px orbitals is, (a) 1, (b) 2 , (c) 3 , , (d) 0, , Which of the following has smallest bond angle?, (a) H2O, (b) H2S , (c) NH3 , , (d) SO2, , 3., , For a reaction to be spontaneous at all the temperature:, (a) ∆G –ve, ∆H +ve, ∆S +ve, (b) ∆G +ve, ∆H -ve, ∆S +ve, (c) ∆G –ve, ∆H -ve, ∆S - ve, (d) ∆G –ve, ∆H -ve, ∆S +ve, , 4., , Which is is most strongly hydrated?, (a) Li+, (b) Na+, (c) K+, , (d) Rb+, , Which of the following has largest ionic radii?, (a) Na+, (b) Mg2+, (c) F–, , (d) O2–, , 5., 6., , When carbon is bonded to four other atoms or groups it uses ________, hybrid orbitals., , 7., , Surface tension ____________ with increase in temperature., , 8., , The second electron gain enthalpy is ________., , Sample Paper, , 255
Page 278 :
Directions for Question No. 9 and 10 : A statement of assertion (A), followed by a statement of reason (R) is given. Choose the correct option, out of the choices given below for each question:, (a) A and R both are correct and R is the correct explanation of A., (b) A and R both are correct but R is not the correct explanation of A., (c) A is true but R is false., (d) A and R both are false., 9., , Assertion: The entropy of ice is less than that of water., Reason: Ice has a cage like structure., , 10, , Assertion: London forces are much more stronger between Xenon atoms, than between Helium atoms., Reason: Xenon atom is bigger than Helium atom., , 11., , Write empirical formula of CH3COOH and K2CO3, Or, Define mole fraction., , 12., , Mention the quantum number which determines the energy of electron in, the H-atom., Or, How many unpaired electrons are there in Ni2+ ion? (Given : Z =28), , 13., , State the condition for the formation of precipitate., Or, Write the conjugate acid and conjugate base of HSO4-., , 14., 15., 16., , 17., , Using VSEPR theory draw the shape of XeF4 molecule., , Write IUPAC name of CH2 = CH – CH(OH)C ≡ CH., , In a reaction between an oxidant and a reductant which will give up, electrons and which will accept electrons?, Or, Calculate oxidation number of Cr in K2Cr2O7 and Mn in KMnO4., Elements of which group form electron precise hydrides?, Or, Which part of periodic table is known as hydride gap?, , 18., , State the reason of using certain alkali metals in photoelectric cells., Or, Name those alkaline earth metals which do not impart colour to the flame., , 19., , Mention the compounds which are responsible for ozone layer depletion., , 20., , Cis But-2-ene has lower melting point that trans But-2-ene. Give reason., , 256, , Chemistry Class XI
Page 279 :
SECTION: B, 21. Balance the following redox reaction in acidic medium by ion electron, method., Zn(aq.) + NO3– (aq.) → Zn2+ (aq.) + N2O (g) + H2O, 22., , (i) Mg2+ ion is smaller than O2-ion, although both are isoelectronic. Give, reason., (ii) Write IUPAC name and symbol for the element with atomic no. 120., , 23., , (i) Mention the number of radial nodes in 6s orbitals., (ii) Write electronic configuration of Fe2+ ion. (Given, Z = 26), Or, Calculate the wavelength of a ball of mass 0.1kg moving with a velocity of, 10ms-1. (Given, h = 6.626 × 10–34 Js), , 24., , Describe on one method to remove permanent hardness of water., Or, Give one chemical reaction each to show that hydrogen peroxide can act as, oxidising as well as reducing agent., , 25., , Write a short note on Greenhouse effect and global warming., Or, State the point of differences between Classical and photochemical smog., , 26., , (i) Stability of carbocations follows the order 3° > 2° > °1. Explain this, order of stability of carbocations., (ii) In what manner is Electromeric effect different from Inductive effect?, , 27., , (i) Mention the reason of not using Wurtz reaction for the preparation of, unsymmetrical alkanes from alkyl halides., (ii) How will you convert Benzene to p-Nitrobromobenzene?, SECTION-C, , 28., , The density of 3M solution of NaCl is 1.25g/mL. Calculate the molality of, the solution. (Given: Atomic masses: Na=23u , Cl=35.5u), Or, Calculate the molarity of nitric acid (HNO3) in a sample having a density, 1.41g/mL and mass percent of nitric acid in it being 69%. (Atomic mass:, N=14u, H=1u, O=16u), Sample Paper, , 257
Page 280 :
29., , (i) The ball hit with a hockey by a player does not form a wave. State, reason., (ii) Write the possible values of ‘m’ for an electron with l=2., (iii) Chromium has configuration 3d54s1 and not 3d44s2.Explain., , 30., , (i) Explain non linear shape H2S and non-planar shape of PCl3 using, VSEPR theory., (ii) Can we have a diatomic molecule with its ground state molecular, orbitals full with electrons. Give reason for your answer., , 31., , Calculate enthalpy change for the reaction:, CH4(g) + 2O2(g) → CO2 (g) + 2H2O (l), The enthalpy of formation of CH4(g) ,CO2(g) and H2O(l) are -74.8kJmol-1,, -393.5 kJmol-1 and 285.8kJmol-1 respectively., Or, Calculate the bond enthalpy of Cl-Cl bond from the following data:, CH4(g) + Cl2(g) → CH3Cl (l) + HCl ∆ H = -100.3kJmol-1, Given: bond enthalpies of C – H, C – Cl and H – Cl bonds are 413, 326, and 431 kJmol-1 respectively., , 32., , A neon-dioxygen mixture contains 70.6 g dioxygen and 167.5 g neon. If, pressure of the mixture of gases in the cylinder is 25 bar, what is the partial, pressure of dioxygen and neon in the mixture? (Atomic mass: O = 16u,, Ne = 20u), , 33., , (i) Compounds of beryllium are much more covalent than other group, 2 elements. Give reason., (ii) Why does the solubility of alkaline earth metal carbonates and, sulphates in water decrease down the group?, (iii) When a metal of group 1 is dissolved in liquid ammonia a blue solution, is obtained initially. How do you account for the blue colour of the, solution?, (i) State the necessary compound to be aromatic according to Huckel’s, rule., (iii) Explain why alkyl groups act as electron donors when attached to a, π system., Or, (i) Draw the resonance structures of Phenol., (ii) Suggest a method used to purify the liquids which have high boiling, points and decompose below their boiling points., , 34., , 258, , Chemistry Class XI
Page 281 :
35., , (i), (ii), (iii), (iv), (v), (i), (ii), (iii), (iv), (v), , 36., , (i), (ii), (iii), , 37., , (i), (ii), (iii), (i), , (ii), , , SECTION-D, Boron trihalides(BX3) act as Lewis acids. Why?, Conc. HNO3 can be transported in aluminium containers. Give reason., Pb(IV) is less stable tha Pb(II). Give reason., Gallium has higher ionisation enthalpy than aluminium. Why?, What do you understand by diagonal relationship?, Or, Why CCl4 is resistant to hydrolysis but SiCl4 is readily hydrolysed?, Explain why there is a decrease in ionisation enthalpy from carbon to, silicon?, Boron does not form B3+ ion. Give reason., How can you explain greater stability of BCl3 as compared to TlCl3?, Define diagonal relationship between elements in modern period, table., Explain common ion effect with example., The concentration of hydrogen ion in a sample of soft drink is 4 x 10-3, M. Calculate its pH., What is the effect of removal of CH3OH on the equilibrium of the, reaction, 2H2(g) + CO(g) CH3OH(g)., Or, Calculate H3O+ ion concentration of a water sample having pH = 6.78., Define buffer solutions., State Lewis definition of acids and bases. Give one example of each., An alkene A on ozonolysis gives a mixture of propanal and pentan-3one. Write the structural formula of A., Complete the following reactions:, organic peroxide, (a) CH3CH=CH2 + HBr, Dry Ether, , (b) CH3CH2Br + Na, (iii) Write a short note on Friedel Crafts alkylation., , Or, (i) Why eclipsed form and staggered form of ethane cannot be isolated at, room temperature?, (ii) State Markovnikov’s rule., (iii) Which out of Ethene or Ethyne is more acidic and why?, (iv) What happens with 2-Bromobutane is being treated with KOH, (alcoholic)?, ****, Sample Paper, , 259
Page 282 :
SAMPLE PAPER - III, Time Allowed: 1 hr, , SUB : CHEMISTRY, CLASS - XI, , Maximum Marks : 70, , General Instructions:, • All question are compulsory, •, •, •, •, •, , Q 1 to 20 are very short answer objective type and each carries 1 mark each., Q 21 to 27 are short answer question and carry 2 marks each., Q 28 to 34 are also short answer question and carry 3 marks each., Q 35 to 37 are long answer questions and carry 5 marks each., There is no overall choice. However internal choice have been provided in some, questions., • Use of log tables if necessary. Use of calculators is not allowed., , 1., , Which of the following d-orbital has double disc (body shooter shape), (a) dxy, (b) dz2, (c) dx2 – y2, (d) dyz, , 2., , Among the following, the compound that contains, ionic, covalent and Coordinate linkage is, (a) NH4Cl, (b) NH3, (c) NaCl, (d) CO2, , 3., , Which of the following is a state function, (a) q (b) w, (c) q + w, (d) None of these, , 4., , Which of the following alkali metal ion has highest ionic mobility, (a) Li+, (b) Na+, (c) k+, (d) Cs+, , 5., , The correct order of electron gain enthalpy with negative sign of F, Cl, Br, and I having atomic number 9, 17, 35 and 53 respectively is, (a) I > Br > Ci > F, (b) F > Cl > Br > I, (c) Cl > F > Br > I, (d) Br > I > Cl > F, , 6., , Arrange the following carbonations in order of their increasing stability, (CH3)3C+, CH3CH2+, (CH3)2CH+, CH3+, , 7., , The IUPAC name and symbol of element with Z = 120 is _________., , 8., , Direction for Question No. 9 to 10 : A statement of assertion (A) followed, by a statement of Reason (R) is given., (i) A and R both are correct, and R is correct explanation of A., (ii) A and R both are correct, but R is not correct explanation of A., (iii) A is true but R is false., (iv) A and R both are false., , 260, , Chemistry Class XI
Page 283 :
9., , Assertion (A) : Enthalpy of graphite is lower than that of diamond., Reason (R) : Enthalpy of graphite is greater than that of diamond., , 10., , Assertion (A) : Lower the critical temperature of the gas; more easily can, it be liqufied., Reason (R) : Critical temperature is the temperature above which a gas, cannot be liquefied depending upon the pressure., , 11., , If ten volumes of dihydrogen gas react with five volumes of dioxygen gas,, how much volume of water vapour would be produced?, OR, Calculate the number of atoms in 32.0 u of He., , 12., , Why are alkali metals used in photoelectric cells?, OR, Write electronic configuration of Cr3+ ion. (Atomic No. of Cr = 24), , 13., , Draw the shape of ClF3 molecule according to VSEPR theory?, , 14., , Write the conjugate acid and conjugate base of H2O., OR, Write the relation between solubility and solubility product of Cr2(SO4)3., , 15., , Consider the given standard reduction potentials of following elements A,, B, C & D and arrange them in order of their increasing reducing power., A = –3.71V, B = –0.76V, C = +0.34 V, D = +0.80 V, OR, , 16., , Write the cause of temporary and permanent hardness of water., , 17., , Why do magnesium and beryllium not import colour to the flame in the, flame test?, , 18., , Write IUPAC name of CH3 – CO – CH2 – CHO., , 19., , Out of Cis-But-2-ene and Trans-but-2-ene which has greater boiling point, and why?, , 20., , Define Biochemical oxygen demand., , 21., , (i) What is the lowest value of n that allows 'g' orbitals to exist?, (ii) Why 4s orbital is filled before 3d?, OR, Calculate wave number for the longest wavelength transition in the Balmer, Series of hydrogen atom., Sample Paper, , 261
Page 284 :
22., , Explain why?, (i) DiH1 of 'N' is more than that of 'O'., (ii) A cation is smaller than parent atom., , 23., , Balance the following redox reaction in acidic medium by ion electron, method., Cr2O72–(aq.) + SO2(g) → Cr3+(aq.) + SO42–(aq.), 24., , Write chemical reactions to justify that H2O2 can act as an oxidising as well, as reducing agent., OR, (i) What is water gast shift reaction?, (ii) What do you mean by 20 vol. H2O2?, , 25., , In sulphur estimate, 0.157 g of an organic cmpound gave 0.4813 g of, barium sulphate. What is the percentage of sulphur in the compound?, , 26., , Write chemical equations to covert:, (i) Ethyne to Ethanal, (ii) Benzene to m-Nitrotoluene, , 27., , Define smog. How is classical smog different from photochemical smog?, OR, Explain the following terms:, (a) Green house effect, (b) Green chemistry, , 28., , Calcium carbonate reacts with aqueous HCl according to the reaction:, CaCO3(s) + 2HCl(aq.) → CaCl2(aq.) + CO2(g) + H2O(l), What mass of CaCO3 is required to react completely with 25 mL of 0.75, M HCl?, , 29., , (i) State Hund's rule of maximum multiplicity of electrons., (ii) The mass of an electron is 9.1 × 10–31 kg. If its K.E. 3.0 × 10–25 J,, , calculate its wavelength., , 30., , N2 is diamagnetic while O2 is paramagnetic. Explain on the basis of, molecular orbital theory., OR, Explain the structure of PCl5 according to hybridization. Why all P – Cl, bonds., , 262, , Chemistry Class XI
Page 285 :
31., , What will be the pressure exerted by a mixture of 3.2 g of methane and, 4.4 g of carbon dioxide contained in 9 dm2 flask at 27°C., OR, Calculate the compressibility factor for CO2, if one mole of it occupies 0.4, litre at 300K and 40 atm. Comment on the result., , 32., , The combustion of 1 mol of benzene takes place at 298K. After combustion, CO2 and H2O are formed and 3267 kJ mol–1, DfHO(H2O) = –393 kJ mol–1., OR, For the reaction : 2A(g) + B(g) → 2D(g), DUO = –10.5 kJ and DS° = –44.1, J K–1. Calculate DG° for the reaction, and predict whether the reaction will, occur spontaneously., , 33., , Complete the following reaction equations:, D, (i) Li(NO3)2 →, D, (ii) BeCl2 + LiAlH4 →, D, (iii) Ca(OH)2 + Cl2 →, , 34., , (i), , 35., , (i) State Le Chatelier's principle., (ii) Calculate the pH of 10–8 M HCl., (iii) A sample of HI (g) is placed in flask at a pressure of 0.2 atm. At, equalibrium the partial pressure of HI (g) is 0.04 atm. What is the Kp, for given equilibrium?, , Out of NO2 – CH2 – O and CH3 – CH2 – O– which is more stable, and why?, (ii) Why is it necessary to prepare Lassaigne extract for detection of N, S, and halogens?, (iii) Define the term hyperconjugation., , , , 2HI (g), , H2(g) + I2(g), OR, , (i), , Define common ion effect., , (ii) Write the relationship between Kp and Kc for the reaction:, N2(g) + 3H2(g), , 2NH3(g), , (iii) Equal volume of 0.002 M solutions of sodium iodate and cupric, chlorate are mixed together. Will it lead to precipitation of copper, iodate? (For cupric iodate Ksp = 7.4 × 10–8), , Sample Paper, , 263
Page 286 :
36., , (i), , Draw the structure of Diborane indicating electron precise and, electron deficient bonds., , (ii), , , , , Give reason for the following :, (a) PbCl4 is powerful oxidising agent., (b) Fullerenes are the purest allotropes of carbon., (c) N – N bond dissociation enthalpy is less than P – P bond, , dissociation enthalpy., , (i), , , , OR, What happens when (give chemical equation) :, (a) Borax is heated strongly., (b) BF3 is treated with LiH., , (ii), , , , , Give reason for the following :, (a) NaBiO3 is good oxidising agent., (b) Graphite acts as a good lubricant., (c) Boric and acid is a weak acid., , 37., , Propanal and pentan-3-one are the ozonolysis product of an alkene., What is the structural formula and IUPAC name of alkene?, , (i), , (ii) Give the main products of the reactions:, Anhydrous AlCl3, , , , (a) C6H6 + CH3Cl, , , , (b) CH3Cl + Na, , , , (c) CH3 – CHCl – CH2 – CH3 + KOH(alc.) →, , (i), , , , OR, Give chemical euqation for each of the following :, (a) Decarboxylation, (b) Friedel Craft acetylation, , Dry ether, , (ii) Addition of HBr to propene yields 2-Bromopropane, while, in the presence of benzoyl peroxide, the same reaction yields, 1-Bromopropane. Explain and give mechanism., ****, , 264, , Chemistry Class XI
Page 287 :
SAMPLE PAPER - IV, Time Allowed: 1 hr, , SUB : CHEMISTRY, CLASS - XI, , Maximum Marks : 70, , General Instructions:, • All question are compulsory, •, •, •, •, •, , Q 1 to 20 are very short answer objective type and each carries 1 mark each., Q 21 to 27 are short answer question and carry 2 marks each., Q 28 to 34 are also short answer question and carry 3 marks each., Q 35 to 37 are long answer questions and carry 5 marks each., There is no overall choice. However internal choice have been provided in some, questions., • Use of log tables if necessary. Use of calculators is not allowed., , 1., , SECTION-A, Number of matamers possible for molecular formula C4H10 are _______., OR, Functional isomer of CH3CH2CHO is ___________., , 2., , Among the following, the least thermally stable is ?, (a) K2CO3, (b) Li2CO3, (c) Na2CO3 , (d) Rb2CO3, , 3., , Van der waals constant is a maximum for, (a) He, (b) Ne, (c) Ar , (d) Kr, , 4., , Orbital which is not possible, (a) 2p , (c) 3s , , (b) 3d, (d) 3f, , 5., , Which of the following is paramagnetic, (a) CO , (b) O–2, (c) N2 , (d) NO+, , 6., , Which of the following is not correct?, (a) DG is zero for a reversible reaction., (b) DG is positive for a spontaneous reaction., (c) DG is negative for a spontaneous reaction., (d) DG is positive for a non-spontaneous reaction., Sample Paper, , 265
Page 288 :
Direction for Question No. 7 and 8 :, (i) If both assertion & reason are true and the reason is the correct, explanation of the assertion., (ii) If both assertion & reason are true but the reason is the correct, explanation of the assertion., (iii) If assertion is true statement but reason is false., (iv) If both assertion and reason are false statements., 7., , Assertion : Number of orbitals in 3rd shell is 9., Reason : Number of orbitals for a particular value of n = n2., , 8., , Assertion : Ionic radius of Na+ is smaller than Na., Reason : Effective nuclear charge of Na+ is higher than Na., , 9., , What is the IUPAC name of picric acid., , 10., , Why noble gases have positive electron gain enthalpy?, , 11., , How many molecules of SO2 are present in 11.2 L at STP?, OR, Calculate the number of atoms in 35 g of Li (Atomic mass of Li = 7 u)., , 12., , For an isolated system, DU = 0, what will be DS ?, OR, Write the statement of third law of thermodynamics., , 13., , Calculate the number of sigma and pie bonds in C2H2?, , 14., , Give the relation between Ka and Kb., OR, Write the conjugate base of H2CO3., , 15., , Write the oxidation number of Cr in K2Cr2O7., OR, Write the stock notation MnO2., , 16., , Give an example of electron deficient covalent hydride., OR, Name the isotope of hydrogen which is radioactive in nature., , 17., , Potassium carbonate cannot be prepared by solvay process. Why?, , 18., , Define the Boyle temperature or Boyle point., , 19., , Out of staggered and eclipsed form which is more stable and why?, , 20., , What is the meaning of the term eutrophication with regards to water, pollution., , 266, , Chemistry Class XI
Page 289 :
SECTION-B, 21., , Explain why :, (a) The three electron present in 2p subshell of nitrogen remain upaired., (b) Cr has configuration 3d5 4s1 and not 3d4 4s2., OR, Calculate the radius of Bohr's fifth orbit for hydrogen atom., , 22. (a), , (b), , , Show by a chemical reaction with water that Na2O is a basic oxide, and Cl2O7 is an acidic oxide., Name a species that will be isoelectronic with each of the following, atoms or ions, (i) F– (ii) Ca2+, , 23. Balance the following redox reaction in acidic medium, MnO4– + H+ + Fe2+ → Mn2+ + H2O + Fe3+., 24., , What do you understand by the terms :, (i) Syn gas, (ii) Hydrogen economy, OR, What causes the temporary and permanent harness of water?, , 25., , 0.40 g of an organic compound gave 0.3 g of silver bromide of Carius, method. Find the percentage of bromine in the compound. [Atomic mass, of Ag & Br are 105 and 80 u], , 26., , Propanal and pentan-3-one ate the ozonolysis product of an alkene. What, is the structural formula of alkene?, OR, Convert the following :, (a) 1-Bromopropane to 2-Bromopropane, (b) Ethanol to Glycol, , 27., , Explain the following terms :, (a) Acid Rain, (b) Global warming, OR, What are the reactions involved for ozone layer depletion in the stratosphere?, (a) Green house effect, (b) Green chemistry, , 28., , In a compound CxHyOz, the mass % of C and H is 6 : 1 and the amount, of oxygen present is equal to the half of the oxygen required to react, completely CxHy. Find the empirical formula of the compound., Sample Paper, , 267
Page 290 :
29., , When light with a wavelength of 400 nm falls on the surface of sodium,, electrons with a kinetic energy of 1.05 × 105 J mol–1 are emitted., (a) What is the minimum energy needed to remove on electron from, , sodium?, (b) What is the maximum wavelength of light that will cause a, , photoelectrons to be emitted?, , 30., , (a), (b), (a), , (b), , Describe the hybridisation in case of C2H2., Which out of NH3 and NF3 has higher dipole moment and why?, OR, Use molecular orbital theory to predict why the He2 molecule does, not exist?, Compare the stability of O2 and O2+ on the basis of molecular theory., , 31., , Pressure of one gram of an ideal gas A at 27°C is found to be 2 bar. When, 2g of another gas (ideal) B is introduced in the same flask at the same, temperature the pressure become 3 bar. Find a relationship between their, molecular masses., OR, Explain the following terms :, (a) Dalton's law of partial pressure, (b) Surface tension, (c) Coefficient of viscosity, , 32., , The standard enthalpy of combustion of Surcose (C12H32O11) at 298 K, producing CO2(g) and H2O(l) is –5200.7 kJ mol–1. If DfH° of CO2(g) and, H2O(l) are –393.0 kJ mol–1 and –286 kJ mol–1., OR, Explain the First law of thermodynamics and how can you prove the, following relation :, DH = DU + P DV from the first law of the thermodynamics (DU = q + w)?, , 33., , Assign reason for the following :, (a) Potassium carbonate cannot be prepared by solvay process., (b) Be and Mg do not give characteristics colour to the flame., (c) Alkali metals are strong reducing agent., , 34., , Explain the resonance effect and draw the resonance structures of, CH2 = CH – CHO. Indicate the relative stability of the contributing, structures., , 268, , Chemistry Class XI
Page 291 :
35., , (a), , (b), , (c), (a), (b), , , 36., , (a), (b), , (a), (b), (c), 37., , (a), (b), , , (a), (b), , (c), , SECTION-D, Addition of HBr to propene yields-2-bromopropane, while, in the presence of benzoylperoxide, the same reaction yields, 1-bromopropane. Explain and give tis mechanism., Identify A, B, C & D, , Give a chemical test between ethen and ethane., OR, Out of benzene and toluene, which will undergo nitration more easily, and why?, Explain the following :, (i) Friedal - Craft reaction, (ii) Wurtz reaction, What is solubility product? How is it different from ionic product?, Equal volume of 0.02 M solutions of sodium iodate and cupric, chlorate are mixed together. Will it lead to precipitation of copper, iodate? (For cupric iodate Ksp = 7.4 × 10–8)., OR, Define Le-Chatelier principle., Explain ionic product of water. What is the effect of temperature on, ionic product of water?, Calculate the pH of 10–10 M NaOH solution., Draw the structure of diborane., Explain the following reactions :, (i) Silicon is heated with methyl chloride at high temperature in the, presence of Cu., (ii) Hydrate alumina is treated with aqueous NaOH solution., OR, What are silicons. If the starting material for the manufacture of, silicons is RSiCl3, write the structure of the product formed., Complete the following reactions :, (i) B2H6 + NH3 →, (ii) H3BO3 + H2O →, Explain Inert pair effect., ****, Sample Paper, , 269
