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 . 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:
1. | The fraction of the total volume occupied by the atoms in a primitive cell is 0.48. |
2. | Molecular solids are generally volatile. |
3. | The number of carbon atoms in a unit cell of diamond is 8. |
4. | The number of Bravais lattices in which a crystal can be categorized is 14. |
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.