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m=) gant, , 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., , STAND ALONE MCQs, , , , Q. 1. Which of the following is not true about the ionic, solids?, (A) Bigger ions form the close packed structure., (B) Smaller ions occupy either the tetrahedral or, the octahedral voids depending upon their, size., (C) Occupation of all the voids is not necessary., (D) The fraction of octahedral or tetrahedral voids, occupied depends upon the radii of the ions, occupying the voids., Ans. Option (B) is correct., Explanation: In ionic solids, smaller ions occupy, , the voids, and this depends on stoichiometry of, the compounds not on the radius of ions, , , , Q. 2. Solid A is very hard electrical insulator in solid, as well as in mollen slate and mells al an extremely, high temperature. What lype of solid is it?, , (A) Ionic solid (B) Molecular solid, (©) Covalent solid (D) Metallic solid, , Ans. Option (C) is correct., , Explanation: Covalent solids are generally hard,, act as insulators and melting points of such solids, are extremely high., , Q. 3. Which of the following is a network solid?, , (A) SO, (solid) (B) 1,, (©) Diamond (D) H,0 (ice), , Ans. Option (C) is correct., , , , , , ete aeete |, , , , Explanation: A network solid consists of a network, atoms of same or different elements connected, to each other by covalent bonds. So, diamond is, a network solid as it contains network of carbon, atoms ., , Q. 4. Graphite cannot be classified as, (A) Conducting solid (B) Network solid, (C) Covalent solid (D) Ionic solid, Ans. Option (D) is correct., Explanation: Graphite is a conducting solid,, network or covalent solid but it cannot be, classified as ionic solid., Q. 5. Which of the following statements is not true about, amorphous solids?, (A) On heating they may become crystalline at, certain temperature., (B) ‘They may become crystalline on keeping, for, long time., (C) Amorphous solids can be moulded by heating., (D) They are anisotropic in nature., Ans. Option (D) is correct., , Explanation: Amorphous solids are isotropic in, nature, ie., there is no long-range order, and, arrangement is irregular along all the directions., , Q. 6. Which of the following is an amorphous solid?, , (A) Graphite (G) (B) Quartz glass (SiO), (©) Chrome alum (D) Silicon carbide (SiC), Ans. Option (B) is correct.

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Explanation: Quartz. glass (SiO) isan amorphous, solid as it has no long-range order., , Q. 7. The sharp melling, point of crystalline solids is due, to, (A) a regular arrangement of constituent particles, observed over a short distance in the crystal, lattice., a regular arrangement of constituent particles, observed over a long distance in the crystal, lattice., , same arrangement of constituent particles in, different directions, , different arrangements of constituent particles, in different directions., Ans. Option (B) is correct., Explanation: ‘The sharp melting point of, crystalline solids is due to a regular arrangement, , of constituent particles observed over a long, distance in the crystal lattice., , Q.8.Which of the following conditions favours the, existence of a substance in the solid state?, , (A) High temperature, (B) Low temperature, (©) High thermal energy, , (B), , (©), , (D), , (D) Weak cohesive forces, Ans. Option (B) is correct., , Explanation: At low temperature substance, exists in solid state. It is due to the decrease in, molecular movement which leads to strong, cohesive force, that is, the force which tightly, holds the constituent particles together., , Q. 9. A compound is formed by two elements M and, N. The element N forms ccp lattice and atoms of M, occupy two atoms an Mercury 1/3" of tetrahedral, voids, What is the formula of the compound, (A) MN, (B) M)N3, (C) M3Ny (D) MN;, , Ans. Option (B) is correct., , , , Explanation: Suppose the atoms N in the cep = a, No. of tetrahedral voids = 3a, , No. of atoms M = 2a :a=2:3, , Hence compound as M;: N3, Q.10. Silver crystallises in Lec. lattice. It edge length, of the unit cells is 4.07 x 10% cm density and is, 10.52 cmv. Calculate the atomic mass of silver., (A) 144 g/mol (B) 125 g/mol, (©) 106.6 g/mol (D) 213 g/mol, Ans. Option (C) is correct., , , , Explanation:, , _ Z2xM, @ RN,, ma2*Na xa, , Z, , 3, , 10.5 x 6.022 x 10 x(4.07 x10)’ gem, , = 106.6 gmol”, , Q.11. The correct order of the packing efficiency in, different types of unit cells is, (A) fec < lec < simple cubic, (B) fee > bee > simple cubic, (©) fee < bec > simple cubic, (D) bee < fev = simple cubic, , Ans. Option (B) is correct., , Explanation: ‘The correct order of the packing, efficiency in different types of unit cells is given, , , , , , , , , , below:, Unit Cell Packing efficiency, fec 74%, bee 68%, Simple cubic 52.4%, , , , , , , , , , feo > bec > simple cubic, (BD) Q. 12. The total number of tetrahedral voids in the, face centred unit cell is, , (A)6, (c)10, , Ans. Option (B) is correct., , (B) 8, (D) 12, , Explanation: The total number of tetrahedral, voids in the face centred unit cell is 8., , Q. 13. The lattice site in a pure crystal cannot be occupied, by ‘, (A) Molecule, (C) Electron, Ans. Option (C) is correct., , (B) Ion, (D) Atom, , Explanation: Bach point in a lattice is known, as lattice point which can be either atom,, molecule or ion. It is joined together by a, straight line to bring, out geometry of lattice in, pure crystal constituents. They are arranged in, fixed stoichiometric ratio. Hence, existences of free, , electrons are not possible., , (AD) Q. 14. Which of the following statements is not true, about the hexagonal close packing?, , (A) The coordination number is 12., (B) Ithas 74% packing efficiency., (C) Tetrahedral voids of the second layer are, covered by the spheres of the third layer., (D) In this arrangement spheres of the fourth layer, are exactly aligned with those of the first layer, Ans. Option (D) is correct.

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Explanation: Hexagonal close packing (hep), can be arranged by two layers A and B one, over another which can be diagrammatically, represented as:, , In the above figure the first layer and fourth are, not exactly aligned. Thus, statement (D) is not, correct while other statements, i.e., (A), (B) and, (C) are true., , Q.15. In which of the following structures coordination, number for cations and anionsin the packed structure, will be same?, , (A) Cl ion form fcc lattice and Na* ions occupy all, octahedral voids of the unit cell., , Ca?* jons form fcc lattice and F- ions occupy all, , the eight tetrahedral voids of the unit cell., , O* ions form fcc lattice and Na* ions occupy, , all the eight tetrahedral voids of the unit cell., , S? ions form fec lattice and Zn’* ions go into, , alternate tetrahedral voids of the unit cell., , Ans. Option (A) is correct., , (B), (c), , (D), , Explanation: NaC\ unit cell has a fee structure of, CF ions, and Na* ions occupy octahedral voids., ‘The radius ratio of 0.524 for NaCl suggests an, octahedral void., Q.16. What is the coordination number in a square close, packed structure in two dimensions?, (A) 2 (B) 3, (C) 4 (D) 6, Ans. Option (C) is correct., Explanation: In square close packing in two, dimensions each sphere is in contact with four, of its neighbours. Thus, its coordination number, is 4., Q.17. The crystal showing, defect is:, , , , “@ 08-06, 090-0, 0000, , °@ 000, ©-0-0-0, , OOOO, veo eo, , o-0-0-@, OO ®-©, , ICBSE, SQP 2020-21], , , , Ans. Option (A) is correct., , Explanation: The Frenkel defect is formed when, an atom or smaller ion (usually cation) leaves its, place in the crystal lattice, creating a vacancy,, and becomes an interstitial by lodging in a, nearby location., (Al) Q. 18. Which stoichiometric defect does not change, the density of the crystal?, (A) Frenkel defect (B) Schottky defect, (C) Interstitial defect (D) F-centres, Ans. Option (A) is correct., , Explanation: In Frenkel defect, one of the ion, is missing from its lattice site and occupies an, interstitial site. So, density of the crystal does, not change., , (A) Q. 19. Which of the following defects is also known as, , dislocation defect?, , (A) Frenkel defect, , (B) Schottky defect, , (C) Non-stoichiometric defect, , (D) Simple interstitial defect, Ans. Option (A) is correct., , Explanation: Frenkel defect is also known as, dislocation defect because in this defect one of, the ion is missing from its lattice site and occupies, an interstitial site., , Q. 20. Interstitial compounds are formed when small, aloms are dropped under the curved lattice, of metals. Whether the following is not the, characteristics property of interstitial compounds?, (A) They have high melting points in to pure, , metals, (B) They are very hard, (C) They retain metallic conductivity, (D) They are chemically very reactive

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Ans. Option (D) is correct., , Explanation: Interstitial compounds are usually, non-stoichiometric and arc neither typically ionic, nor covalent, Hence, interstitial compounds are, chemically inert., , , , Q. 21. Examine the given defective crystal, At B At B At, BO B At B, At BAT 0 AT, BAY BOAT BO, , , , Directions: In the fallowing questions, A statement, of Assertion (A) is followed by a statement of, Reason (R). Mark the correct choice as., , (A) Both Aand Rare true and Ris the correct explanation, of A, , (B) Both A and R are true but R is NOT the correct, explanation of A, , (C) Ais true but R is false, , (D) Ais false and Ris True, , Q. 1. Assertion (A): Most of the solids possess high, melting point., Reason (R): They have strong intermolecular forces, of attraction., Ans. Option (A) is correct., Explanation: Most of the solids possess high, melting point due to the presence of intermolecular, forces of attraction between their particles., , , , Q. 2. Assertion (A): Amorphous solids possess a longrange order in the arrangement of their particles., Reason (R): The formation of amorphous solids, involves very rapid cooling., , Ans. Option (D) is correct., , Explanation: Amorphous solids do not possess, a long-range order in the arrangement of their, particles because their formation involves rapid, cooling., , , , Q. 3. Assertion (A): Crystalline solids are anisotropic, in nature., Reason (R): Some of their physical properties show, same electrical and optical properties in different, directions in the same crystal., , Ans. Option (C) is correct., , Explanation: Crystalline solids are anisotropic, in nature as some of their physical properties, show different electrical and optical properties, in different directions in the same crystal., , ASSERTION AND REASON BASED MCQs, , How is the density of the crystal affected by, this defect?, (A) Density increases, (B) Density decreases, (C) No effect on density, (D) Density first increases then decreases, Ans. Option (B) is correct., , Explanation: The given defective crystal shows, that there is missing of one cation and one anion, from their lattice positions which is Schottky, defect. Due to missing of ions, density of the, crystal decreases., , POW Farr, , , , (AD) @ 4. Assertion (A): Graphite is a good conductor, of electricity; however, diamond belongs to the, category of insulators., , Reason (R): Graphite is soft in nature, on the other, hand diamond is very hard and brittle., Ans. Option (B) is correct., , Explanation: Diamond is a bad conductor of, electricity because all valence electrons of carbon, are involved in bonding. In graphite, however, 3 out of 4 valence electrons are involved in, bonding and the fourth electron remains free, between adjacent layers which makes it a good, conductor. Graphite is soft because parallel layers, are held together by week vander Waals forces., However, diamond is hard due to compact threedimensional network of bonding., , Q. 5. Assertion (A): Total number of octahedral voids, present in unit cell of cubic packing including the, one that is present at the body centre is four., Reason (R): Besides the body centre these is one, octahedral void present at the centre of each of the, 4 faces of the unit cell and each of which is shared, between two adjacent unit cells., , Ans. Option (C) is correct., , Explanation: Total number of octahedral voids, present in unit cell of cubic packing including, the one ie., present at the body centre, is four., , Q.6. Assertion (A): A two dimensional arrangement, where each sphere is in contact with four of its, neighbour and has a 2-D coordination number 4 is, square close packing arrangement., , Reason (R): In such arrangement, if centres of, the neighbouring spheres are joined, a square is, formed., , Ans. Option (A) is correct., , Explanation: In square close packing arrangement, in two dimension, each sphere is in contact with, 4 spheres and if the centres of neighbouring, spheres are joined a square is formed.

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Q. 7. Assertion (A): The packing efficiency of simple, cubic lattice is 52.4%, Reason (R): The number of atoms per unit cell is 2., Ans. Option (C) is correct., , Explanation: For simple cubic lattice a = 2r, Number of atoms per unit cell = 1, {Al10.8. Assertion (A): The packing efficiency is maximum, for the fee structure., Reason (R): The coordination number is 12 in fec, structure., Ans, Option (B) is correct,, , Explanation: Both cep and hep are highly efficient, lattice; in terms of packing. The packing efficiency, of both types of close packed structure is 74%, ie,, 74% of the space in hep and cep is filled. The hep, and cep structures are equally efficient; in terms, of packing. The packing efficiency of simple cubic, lattice is 52.4% and the packing efficiency of bodycentred cubic lattice (bec) is 68%., , CASE-BASED MCQs, , , , I. Read the passage given below and answer the, following questions:, , All real structures are three dimensional structures., They can be obtained by stacking two dimensional, layers one above the other while placing the second, square close packed layer above the first we follow, the same rule that was followed when one row, was placed adjacent to the other. The second layer, is placed over the first layer such that the spheres, of the upper layer are exactly above there of the, first layer. In his arrangement spheres of both the, layers are perfectly aligned horizontally as well as, vertically. A metallic element crystallise into a lattice, having a ABC ABC pattern and packing of spheres, leaves out voids in the lattice., , Q.1.What type of structure is formed by this, , arrangement?, (A) cep (B) hep, (©) ccpfice (D) none of the above, , Ans. Option (C) is correct., , , , Q.2.Name the non-stoichiometric point defect responsible for colour in alkali metal halides., (A) Frenkel defect, (B) Interstitial defect, (C) Schottky defect, (D) F-centres, Ans. Option (D) is correct., Q. 3. What is the total volume of atoms in a face centred, cubic unit cell of a metal? (r is atomic radius)., (A) 163 25, (B) x, (C) 24/3 mr?, (D) 122°, , (AD) Q. 9. Assertion (A): Density of the crystal decreases in, , Frenkel defect., Reason (R): In this defect, one of the ion is missing, from lattice position and occupies interstitial site., , Ans. Option (A) is correct,, , Explanation: Density of the crystal does not decreases in Frenkel defectasnoionis missing from, the crystal., , Q.10. Assertion (A): Schottky defect arises when a, , non-ionic solid is heated., Reason (R): It happens because some of the lattice, sites are vacant in the crystal., , Ans. Option (D) is correct., , Explanation: Vacancy defect arises when a, non-ionic solid is heated. It happens because, some of the lattice sites are vacant in the crystal., , , , Ans. Option (A) is correct., , Explanation:, Number of atoms per unit cell in fec = 4, -. Total volume of atoms present in fee unit cell, , 16 i, , , , =4xtnp =, 3, , Q. 4. Which of the following statements not true for the, , amorphous and crystalline solids?, , (A) Amorphous solids are isotropic and crystalline, solids are anisotropic., , (B) Amorphous solids are short range order and, crystalline solids are long range order., , (C) Amorphous solids melt at characteristic, temperature while crystalline solids melt over, a range of temperature., , (D) Amorphous solids have irregular shape and, crystalline solids have a geometrical shape., , Ans. Option (C) is correct., , Explanation: Crystalline solids meltat characteristic, temperature while amorphous solids melt over a, range of temperature., , OR, , Which of the following statements is not true for, , unit cell?, , (A) Each cubic unit cell has 8 atoms on ils corners, the total number of atoms in one unit cell is 1., , (B) A unit cell is characterized by its dimensions, along the three edges a, b,c, , (C) Each body centred cube cell has 2 atoms in one, unit cell