A solid has a definite size and shape which does not change its state without any external condition. In solids, particles are very close to each other due to strong intermolecular force which keeps their particles in a fixed position. Due to this factor solids are hard and rigid and cannot be compressed. When the atoms are forced to come closer, the intermolecular force becomes repulsive. With an increase in thermal energy, the kinetic energy of the molecules increases resulting in the conversion of solid into a liquid.
1. How many unit cells are divided equally in a face-centred cubic lattice?
2. A crystalline solid:
- changes abruptly from solid to liquid when heated.
- has no definite melting point.
- undergoes deformation of its geometry easily
- has irregular 3-dimensional arrangements.
3. In a simple cubic, body-centred cubic and face-centred cubic structure, the ratio of the number of atoms present is respectively
4. Na and Mg crystallize in crystals of bcc and fcc form respectively and then the amount of Na and Mg atoms present in their respective crystal unit cells is:
- 4 and 2
- 9 and 14
- 14 and 9
- 2 and 4
5. Ferrous oxide has a cubic structure and each unit cell edge is 5.0Ao. Assuming the oxide density is 4.0g / cm3, the amount of Fe2+ and O2- ions in each unit cell will then be
- four Fe2+ and four O2-
- two Fe2+ and four O2-
- four Fe2+ and two O2-
- three Fe2+ and three O2-
6. Each of the following solids shows the Frenkel defect except
7. Schottky defect in a crystal is observed when
- The ion leaves its normal position and occupies an interstitial location
- the unequal number of cation and anions are missing from the lattice
- the density of the crystal increases.
- an equal number of cations and anions are missing from the lattice.
8. Copper crystalline in FCC with a unit cell length of 361pm. What is the radius of a copper atom?
9. The total no of voids in 0.5 mol of a compound forming hexagonal close-packed structure are:
- 6.022 × 1023
- 3.011 × 1023
- 9.033 × 1023
- 4.516 × 1023
10. For the orthorhombic system, axial ratios are a ≠ b ≠ c and the axial angles are:
- α = β = γ ≠ 90o
- α ≠ β ≠ γ ≠ 90o
- α = β = γ = 90o
- α ≠ β ≠ γ = 90o
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