Schottky defect occurs mainly in electrovalent compounds where :

1. Positive ions have large sizes.

2. Negative ions have small sizes.

3. Positive and negative ions are of similar size.

4. Positive ions are big and negative ions are small.

Ice crystallizes in a hexagonal lattice having the volume of the unit cell as $132\times {10}^{-24}$ $c{m}^3$. If the density is 0.92 g/cm³ at a given temperature, then the number of H₂O molecules per unit cell is : 

1. 1

2. 2

3. 3

4. 4

AB crystallizes in a body-centred cubic lattice with edge length a equal to 387 pm. The distance between two oppositely charged ions in the lattice will be : 

1. 250 pm

2. 200 pm

3. 300 pm

4. 335 pm

In which of the following crystals are alternate tetrahedral voids occupied:

1. NaCl

2. ZnS

3. CaF₂

4. Na₂O

An element (atomic mass = 100 g/mole) having a BCC structure has a unit cell edge of 400 pm. The density of the element is :
1. 2.14 g/cm³
2. 5.20 g/cm³
3. 7.28 g/cm³
4. 10.37 g/cm³

Oxygen atoms form fcc unit cells with 'A' atoms occupying all tetrahedral voids and 'B' atoms occupying all octahedral voids. If atoms are removed from two of the body diagonals then the formula of the resultant compound formed is: 

1. A₄B₄O₇

2. A₈B₆O₇

3. A₈B₈O₇

4. A₆B₈O₆

A metallic element exists as a cubic lattice. Each edge of the unit cell is 2.88 Å. The density of the metal is 7.20 g cm^–3.  The number of unit cells, that will be present in 100 gm of the metal is: 

1. 5.82 × 10²³

2. 16.33 × 10²³

3. 7.49 × 10²⁴

4. 6.9 × 10²⁴

The incorrect statement among the following is:

Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. Density of iron is 7.87 g cm^-3. The value of  Avogadro's number based on this data will be -

(Atomic mass of Fe = 56.0 u)

1. 6.04 x 10²³ mol^-1

2. 12.08 x 10²⁴ mol^-1

3. 6 x 10²² mol^-1

4. 6 x 10^-23 mol^-1

TiO₂ is a well-known example of:

1. Triclinic system.

2. Tetragonal system.

3. Monoclinic system.

4. None of the above.