21773.In which of the following crystals alternate tetrahedral voids are occupied?
NaCl
ZnS
CaF2
Na2O
21774.Volume occupied by single CsCl ion pair in a crystal is 7.014 × 10–23 cm3. The smallest Cs – Cs internuclear distance is equal to length of the side of the cube corresponding to volume of one CsCl ion pair. The smallest Cs to Cs internuclear distance is nearly
4.4 Å
4.3 Å
4 Å
4.5 Å
21775.The white ZnO turns yellow on heating because of
Frenkel defect
Metal excess defect
Metal deficiency defect
Schottky defect
21777.A metal has a fcc 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 ofthe metal is (NA = Avogadro's constant = 6.02 × 1023 mol–1)
40 g mol–1
30 g mol–1
27 g mol–1
20 g mol–1
21778.The ionic radii of Rb+ and I– are 1.46 Å and 2.16 Å respectively. The most probable type of structure exhibited by it is
NaCl type
ZnS type
CsCl type
CaF2 type
21781.In a face–centered cubic lattice, a unit cell is shared equally by how many unit cells?
2
4
6
8
21782.A compound is formed by elements A and B. This crystallizes in the cubic structure where A atoms are at the corners of the cube and B atoms are at the body centres. The simplest formula of the compound is
AB
AB6
A6B
A8B4
21783.The crystal system of a compound with unit cell dimensions, a = 0.387, b = 0.387 and c = 0.504 nm and α = β = 90° and γ = 120° is
cubic
hexagonal
orthorhombic
rhombohedral
21784.The radius ratio in CsCl is 0.93. The expected lattice structure is
octahedral
square planar
tetrahedral
body centred cubic
21785.The unit cell of a binary alloy composed of A and B metals, has a ccp structure with A atoms occupying the corners and B atoms occupying the centres of each face of the cube. If during the crystallization of this alloy, in the unit cell, two A atoms are missing, the overall composition per unit cell is
AB6
AB4
AB8
AB24