133 CHAPTER THE SOLID STATE 1. The ability of a substances to assume two or more crystalline structures is called [1990] Isomerism Polymorphism Isomorphism Amorphism 2. Most crystals show good cleavage because their atoms, ions or molecules are [1991] weakly bonded together strongly bonded together spherically symmetrical arranged in planes. 3. [1991] 4. The number of atoms contained in a fcc unit cell of a monoatomic substance is [1993] 1 2 4 6 5. In the fluorite structure, the coordination number of Ca 2+ ion is: [1993] 4 6 8 3 6. On doping Ge metal with a little of In or Ga, one gets [1993] p-type semi conductor n-tpe semi conductor insulator rectifier 7. In graphite electrons are: [1993] localised on each carbon atom spread out between the sheets localised on every third carbon atom present in antibonding orbital. 8. The pure crystalline substance on being heated gradually first forms a turbid liquid at constant temperature and still at higher temperature turbidity completely disappears. The behaviour is a characteristic of substance forming. [1993] Allotropic crystals Liquid crystals Isomeric crystals Isomorphous crystals. 9. When electrons are trapped into the crystal in anion vacancy, the defect is known as: [1994] Schottky defect Frenkel defect Stoichiometric defect F-centres 10. Asolid with high electrical and thermal conductivity from the following is [1994] Si Li NaCl Ice 11. The edge length of a centred unit cubic cell is 508 pm. If the radius of the cation is 100 pm, the radius of the anion is [1996] 288 pm 398 pm 154 pm 618 pm 12. The intermetallic compound LiAg crystallizes in a cubic lattice in which both lithium and silver atoms have coordination
134 number of eight. To what crystal class does the unit cell belong? [1997] Simple cubic Face-centred cubic Body-centred cubic None 13. For two ionic solids CaOand KI, identify the wrong statement amongst the following: [1997] The lattice energy of CaOis much large than that of KI KIis more soluble in water KIhas higher melting point CaOhas higher melting point 14. Schottky defect in crystals is observed when [1998] an ion leaves its normal site and occupies an interstitial site unequal number of cations and anions are missing from the lattice density of the crystal is increased equal number of cations and anions are missing from the lattice 15. [1998] 16. In the solid state, MgOhas the same structure as that of sodium chloride. The number of oxygens surrounding each magnesium in MgOis [1999] 6 1 2 4 17. Acompound is formed by elements Aand B. The crystalline cubic structure has the Aatoms at the corners of the cube and Batoms at the body centre. The simplest formula of the compound is [2000] AB A6B AB6 A8B4 18. When molten zinc is converted into solid state, it acquires HCPstructure. The number of nearest neighbours will be [2001] 6 12 8 4 19. The pyknometric density of sodium chloride crystal is 2.165 10 3 kg m 3 while its X-ray density is 2.178 10 3 kg m 3. The fraction of unoccupied sites in sodium chloride crystal is [2003] 5.96 10 3 5.96 5.96 10 2 5.96 10 1 20. Acompound formed by elements Xand Ycrystallizes in a cubic structure in which the Xatoms are at the corners of a cube and the Yatoms are at the face centres. The formula of the compound is [2004] XY3 X3Y XY XY2 21. In face-centred cubic lattice, a unit cell is shared equally by how many unit cells? [2005] 2 4 6 8 22. The appearance of colour in solid alkali metal halides is generally due to [2006] Schottky defect Frenkel defect Interstitial positions F-centres
135 23. CsBr crystallises in a body centered cubic lattice. The unit cell length is 436.6 pm. Given that the atomic mass of Cs = 133 and that of Br = 80 amu and Avogadro number being 6.02 10 23 mol 1, the density of CsBr is [2006] 0.425 g/cm3 8.25 g/cm3 4.25 g/cm3 42.5 g/cm3 24. If NaCl is doped with 10 4 mol% of SrCl2, the concentration of cation vacancies will be (NA= 6.02 10 23 mol 1 ) [2007] 6.02 10 16 mol 1 6.02 10 17 mol 1 6.02 10 14 mol 1 6.02 10 15 mol 1 25. Which of the folloiwng anions is present in the chain structure of silicates? [2007] (Si2O5 2 ) n (SiO3 2 ) n SiO4 4 Si2O7 6 26. The fraction of total volume occupied by the atoms present in a simple cube is [2007] 27. If a stands for the edge length of the cubic systems: simple cubic, body centred cubic and face centred cubic, then the ratio of radii of the spheres in these systems will be respectively, [2008] 28. Percentage of free space in a body centred cubic unit cell is: [2008] 30% 32% 34% 28% 29. With which one of the following elements silicon should be doped so as to give p-type of semiconductor? [2008] Germanium Arsenic Selenium Boron 30. Lithium metal crystallises in a body centred cubic crystal. If the length of the side of the unit cell of lithium is 351 pm, the atomic radius of the lithium will be: [2009] 151.8 pm 75.5 pm 300.5 pm 240.8 pm 31. Copper crystallises in a face-centred cubic lattice with a unit cell length of 361 pm. What is the radius of copper atom in pm? [2009] 157 181 108 128 32. AB; crystallizes in a body centred cubic lattice with edge length equal to 387 pm. The distance between two oppositely charged ions in the lattice is: [2010] 335 pm 250 pm 200 pm 300 pm 33. Among the following which one has the highest cation to anion size ratio? [2010] NaF CsI CsF LiF
136 34. Asolid compound XYhas NaCl structure. If the radius of the cation is 100 pm, the radius of the anion (Y ) will be: [2011] 275.1 pm 322.5 pm 241.5 pm 165.7 pm 35. Ametal crystallizes with a face-centered cubic lattice. The edge length of the unit cell is 408 pm. The diameter of the metal atom is: [2012] 288 pm 408 pm 144 pm 204 pm 8 6 1 4 1. 2. 3. 4. 36. The number of octahedral void per atom present in a cubic close-packed structure is: [2012] 1 3 2 4 37. Structure of a mixed oxide is cubic closepacked (c.c.p). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal Aand the octahedral voids are occupied by a monovalent metal B. The formula of the oxide is: [2012] ABO2 A2BO2 A2B3O4 AB2O2 38. Ametal has a lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g cm -3. The molar mass of the metal is: (NAAvogadro s constant = 6.02 10 23 mol -1 ) [2013] 30 g mol -1 27 g mol -1 20 g mol -1 40 g mol -1 39. The number of carbon atoms per unit cell of diamond unit cell is: [2013] 5. 6. 7. 8. 9.
137 17. 10. 11. 18. 12. 19. 13. 14. 20. 15. 21. 16.
138 25. 26. 22. 27. 23. 24. 28.
139 29. 36. 37. 30. 31. 38. 32. 33. 39. 34. 35.