Select the correct option based on statements below:

Assertion (A):	Due to Frenkel defect, the density of the crystalline solid decreases.
Reason (R):	In Frenkel defect cation and anion leave the crystal.

 

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	Both (A) and (R) are false.

The crystal with a metal deficiency defect is - 

1. NaCl 

2. FeO

3. ZnO 

4. KCl

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

The electrical conductivity of semiconductors increases with a rise in temperature because:

Select the correct option based on statements below:

If an element (at. Wt. = 50) crystallises in fcc lattice, with a = 0.50 nm, then the density of unit cell if it contains 0.25 % Schottky defect is -

(Use $N_A=6\times {10}^{23}$) 

1. 2.0 g/cc

2. 2.66 g/cc

3. 3.06 g/cc

4. None of the above.

An element occurring in the bcc structure has $12.08\times {10}^{23}$ unit cells. The total number of atoms of the element in these cells will be:

1. $24.16\times {10}^{23}$

2. $36.18\times {10}^{23}$

3. $6.04\times {10}^{23}$

4. $12.08\times {10}^{23}$

Select the correct option based on statements below:

The packing efficiency of the face-centered cubic unit cell is:
(assuming that the atoms are touching each other)

1. 52.40 %

2. 68.04 %

3. 74 %

4. 79.06 %

Silver crystallizes in fcc lattice. If the edge length of the cell is 4.07 × 10⁻⁸ cm and density is 10.5 g cm⁻³, the atomic mass of silver is -

1. 120.31 g ${\mathrm{mol}}^{-1}$

2. 107.9 g ${\mathrm{mol}}^{-1}$

3. 207.60 g ${\mathrm{mol}}^{-1}$

4. 138.52 g ${\mathrm{mol}}^{-1}$