A compound is formed by cation C and anion A. The anions form hexagonal close packed (hcp) lattice and the cations occupy 75 % of octahedral voids. The formula of the compound is:

1. ${\mathrm{C}}_3{\mathrm{A}}_4$

2. ${\mathrm{C}}_2{\mathrm{A}}_3$

3. ${\mathrm{C}}_3{\mathrm{A}}_2$

4. ${\mathrm{C}}_4{\mathrm{A}}_3$

The formula of nickel oxide with metal deficiency defect in its crystal is $N{i}_{0.98}O$. The crystal contains ${\mathrm{Ni}}^{2+} \mathrm{and} {\mathrm{Ni}}^{3+}$ ions. The fraction of nickel existing as $N{i}^{2+}$ ions in the crystal is-

1. 0.96

2. 0.04

3. 0.50

4. 0.31

An element has a body-centered cubic (BCC) structure with a cell edge of 288 pm. The atomic radius is:

1. $\frac{\sqrt{2}}{4}\times 288$ pm

2. $\frac{4}{\sqrt{3}}\times 288$ pm

3. $\frac{4}{\sqrt{2}}\times 288$ pm

4. $\frac{\sqrt{3}}{4}\times 288$ pm

A compounds that can show both, Frenkel as well as Schottky defects is -

1. AgBr

2. AgI

3. NaCl

4. ZnS

The number of tetrahedral and octahedral voids in hexagonal primitive unit cell are respectively:

1. 2, 1

2. 12, 6

3. 8, 4

4. 6, 12

The correct option for the number of body centred unit cells in all 14 types of Bravais lattice unit cells is :

1. 2

2. 3

3. 7

4. 5

A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because:

Which statements among the following is not correct?