41.

A binary solid has a primitive cubical structure with B^- ions constituting the lattice points and A⁺ ions· occupying 25% of its tetrahedral holes. The molecular formula of the crystal is

• A₂B

• AB₃

• AB₂

• A₂B₃

Which one of the following has a different crystal lattice from those of the rest?

• Ag

• V

• Cu

• Pt

The lattice energy of NaCl is 788 kJ mol^-1. This means that 788 kJ of energy is required

• to separate one mole of solid NaCl into one mole of Na (g) and one mole of Cl (g) to infinite distance

• to separate one mole of solid NaCl into one mole of Na⁺ (g) and one mole of Cl^- (g) to infinite distance

• to convert one mole of solid NaCl into one mole of gaseous NaCl

• to convert one mole of gaseous NaCl into one mole of solid NaCl

Which one of the following metals has a different lattice from those of the others?

• Fe

• Co

• Ni

• Cu

In face centred cubic unit cell, what is the volume occupied?

• $\frac{4}{3}{\mathrm{\pi r}}^3$

• $\frac{8}{3}{\mathrm{\pi r}}^3$

• $\frac{16}{3}{\mathrm{\pi r}}^3$

• $\frac{64{\mathrm{r}}^3}{3\sqrt{3}}$

A solid compound contains X, Y and Z atoms in a cubic lattice with X atom occupying the comers. Y atoms in the body centred positions and Z atoms at the centres of faces of the unit cell. What is the empirical formula of the compound?

• XYZ

• X₂Y₂Z₃

• XYZ₃

• XY₂Z₃

KCl crystallises in the same type of lattice as does NaCl. Given that r_Na⁺/ r_Cl^-= 0.55 and r_K⁺/r_Cl^-= =0.74. Calculate the ratio of the side of the unit cell for KCl to that of NaCl. 

• 1.123

• 0.0891

• 1.414

• 0.414

The cubic unit cell of Al (molar mass 27 g mol^-1) has an edge length of 405 pm. Its denstiy is 2.7g cm^-3. The cubic unit cell is

• face centred

• body centred

• primitive

• edge centred

Density of a crystal remains unchanged as a result of:

• ionic defect

• Schottky defect

• Frenkel defect

• crystal defect

High purity Si and Ge for semiconductor properties can be obtained by :

• calcination

• roasting

• zone refining

• thermic process