Which is the incorrect statement?

(1) _{${\mathrm{Fe}}_{0.95}\mathrm{O}$} has non-stoichiometric metal deficiency defect

(2) Density decreases in case of crystals with Schottky's defect

(3) NaCI(s) is insulator, silicon is semiconductor, silver is conductor, quartz is piezoelectric crystal

(4) Frenkel defect is favoured in those ionic compounds in which sizes of cation and anions are almost equal

In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion (Ca²⁺) and fluoride ion (F^-) are

(1) 4 and 2                   

(2) 6 and 6

(3) 8 and 4                   

(4) 4 and 8

The ionic radii of A⁺ and B^- ions are 0.98 x 10^-10 m and 1.81 x10^-10 m.  The coordination

number of each ion in AB is.

1. 4

2. 8

3. 2

4. 6

The correct statement regarding defects in the crystalline solid is

1. Schottky defects have no effect on the density of crystalline solids

2. Frenkel defects decreases the density of crystalline solids

3. Frenkel defcct is a dislocation defect

4. Frenkel defect is found in halides of alkaline metals

The vacant space in bcc lattice cell is ;

1. 26%

2. 48%

3. 23%

4. 32%

if a is the length of the side of a cube, the distance between the body centered atom and

one corner atom in the cube will be :-

1. $\frac{2}{\sqrt{3}}a$

2. $\frac{4}{\sqrt{3}}a$

3. $\frac{\sqrt{3}}{4}a$

4. $\frac{\sqrt{3}}{2}a$

Percentage of free space in a body centered cubic unit cell is

(1) 30%                       

(2) 32%

(3) 34%                       

(4) 28%

With which one of the following elements silicon should be doped so as to give p-type of semiconductor?
(1) Germanium

(2) Arsenic

(3) Selenium

(4) Boron

A compound forms hcp structure. The total number of voids in 0.5 mol will be- 

1. 9.033$\times$10²³

2. 6.011$\times$10²³

3. 5.023$\times$10²³

4. 7.033$\times$10²³

Iron exhibits bcc structure at room temperature. Above 900 °C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900 °C is:

(Molar mass and atomic radii of iron remain constant with temperature) 

1. $\frac{\sqrt{3}}{\sqrt{2}}$

2. $\frac{4\sqrt{3}}{3\sqrt{2}}$

3. $\frac{3\sqrt{3}}{4\sqrt{2}}$

4. $\frac{1}{2}$