Solid State

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 (assuming molar mass and atomic radii of iron remains constant with temperature) is

1. 3 2
2. 4 33 2
3. 3 34 2
4. 12

Which is the incorrect statement?

1. Density decreases in case of crystals with Schottky defect.
2. NaCl(s) is insulator, silicon is semi conductor, silver is conductor, quartz is piezoelectric crystal.
3. Frenkel defect is favoured in those ionic compounds in which sizes of cation and anions are almost equal
4. FeO0.98 has non-stoichiometric metal deficiency defect.

Lithium has a bcc structure. Its density is 530 kg m-3 and its atomic mass is 6.94 g mol-1. Calculate the edge length of a unit cell of lithium metal. (NA = 6.02 1023 mol-1)

1. 527 pm
2. 264 pm
3. 154 pm
4. 352 pm

The ionic radii of A+ and B- ions are 0.98 10-10 m and 1.81 10-10 m. The coordination number of each ion in AB is

1. 8
2. 2
3. 6
4. 4

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 vacant space in bcc lattice unit cell is

1. 48%
2. 23%
3. 32%
4. 26%

The correct statement regarding defects in crystalline solids is

1. Frenkel defects decrease the density of crystalline solids
2. Frenkel defect is a dislocation defect
3. Frenkel defect is found in halides of alkali metals
4. Schottky defects have no effect on the density of crystalline solids

A given metal crystallises out with a cubic structure having edge length of 361 pm. If there are four metal atoms in one unit cell, what is the radius of one atom?

1. 80 pm
2. 108 pm
3. 40 pm
4. 127 pm

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. 2 3a
2. 4 3a
3. 34a
4. 32a

A metal has a fcc lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g cm-3. The molar mass of the metal is (NA Avogadro's constant = 6.02 1023 mol-1)

1. 27 g mol-1
2. 20 g mol-1
3. 40 g mol-1
4. 30 g mol-1