81.

The property of crystalline solid is not

• anisotropic

• isotropic

• hardness

• denseness

Due to Frenkel defect, the density of the ionic solids

• does not change

• decreases

• increases

• may increase or decrease

The dimensions of a unit cell of a crystal are a = 0.397, b = 0.387, c = 0.504 and α = β = 90°, γ = 120° the crystal system is

• cubic

• hexagonal

• orthorhombic

• rhombohedral

Sodium atom crystallizes in bcc lattice with cell edge a = 4.29 Å, the radius of sodium atom is

• 18.6 Å

• 1.86 Å

• 0.186 Å

• 37.2 Å

Which is mismatched for NaCl crystal ?

• $\frac{{\mathrm{r}}^{+}}{{\mathrm{r}}^{-}}= 0.414 \mathrm{to} 0.732$

• Coordination number = 6.6

• Edge of unit cell =(r⁺ + r^-)

• Crystal structure = fcc

The structure of ionic compound A⁺B identical to NaCl. If the edge lenght is 400pm and cation radius is 75pm, the radius of anion will be

• 100 pm

• 125 pm

• 250 pm

• 325 pm

The length of unit cell edge of a body-centred cubic metal crystal is 352 pm. The radius of metal atom is

• 162.4 pm

• 152.4 pm

• 142.4 pm

• 156.pm

If NaCl is doped with 10^-3 mol% of SrCl₂, the number of cation vacancies will be

• 6.023 × 10¹⁸

• 1 × 10^-3

• 6 × 10¹²

• 6.023 × 10²³

Match List I with List II and select the correct answer using the given codes.

• A    B    C    D

  2    3    4    1

• A   B   C   D

  1   4   3    2

• A   B   C   D

  3   2    1   4

• A   B   C    D

  4   1    2    3

The vacant space in bcc unit cell is

• 10%

• 23%

• 32%

• 46%