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4., , il., , 12., , 13., , MM,, , 15., , 16., , 17., , Which of the following statement is not true about amorphous solids? INCE,, (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., , The sharp melting point of crystalline solids is due to 5 INCERTy,, (a) a regular arrangement of constituent particles observed over a short distance in the Crystal laig :, (6) a regular arrangement of constituent particles observed over a long distance in the Crystal lattice, (c) same arrangement of constituent particles in different directions., , (d) different arrangement of constituent particles in different directions., , Which one of the following is a covalent crystal?, , (a) Rock salt (b) Ice (ec) Quartz (d) Dry ice, , Which of the following solids is not an electrical conductor?, , (i) Mgis) (ii) TiO(s) (iii) TAs) (i) H,O(s), , (a) (0) only (b) (ii) only (c) (iii) and (iv), The number of atoms in a face centred cubic unit cell is, , (a) 2 (b) 4 ()5 (d) 6, , In a face centred cubic lattice, atom A occupies the corner positions and atom B occupies the fiy, , centre positions. If one atom of B is missing from one of the face centred points, the formuta of ih, compound is:, , , , (d) (ii), (iii) and (iv), , (a) AB, (6) AB, (c) A:Bs (@) AB, ‘The total number of tetrahedral voids in the face centred unit cell is ,, (a) 6 (6) 8 (©) 10 (d) 12 ;, , IfZ is the number of atoms in the unit cell that represents the closest packing sequence—ABC ABC, the number of tetrahedral voids in the unit cell is equal to, , (az (b) 2z oF wz |, In which pair most efficient packing is present?, , (a) hep and bee (b) hep and cep, , (c) bee and ccp (d) bce and simple cubic cell, , ‘The fraction of the total volume occupied by the atoms present in a simple cube is, , (a) #/4 (b) x6 (c) 1/32) (d) wh4V2), , A metallic crystal has the bec type staking pattern, What percentage of volume of this lattice is emptt, space?, , (a) 68% (b) 32% (c) 26% (d) 74%, , A solid compound XY has NaC! structure. If the radius of the cation is 100 pm, the radius of tht, anion (Y>) will be, , (@) 2153.1 pa (b) 322.5 pm (©) 241.5 pm (d) 165.7 pm__, , AB crystallizes in a body centred cubic lattice with edge length ‘a’ equal to 387 pm. The distance, between two oppositely charged ions in the lattice is ; we, (a) 250 pm (6) 200 pm (c) 300 pm (d) 335 pm, Ifa stands for the edge length of the cubic systems: simple cubic, body centred cubic and face centred, cubic, then the ratio of the radius of the spheres in these systems will be respectively, , 1 1, , 8 ie (b) ~a:V3a:—=a, (a) an alee 2 5, (oO 1, Sgialy (d) la :3a:V2a, , 2° 2 2, , A, , In, Sei