Chemistry Class Twelve

# Solid State

## NCERT Exercise Solution (part 2)

Question – 1.7 - How will you distinguish between the following pairs of terms:

(i) Hexagonal close-packing and cubic close-packing?

(ii) Crystal lattice and unit cell?

(iii) Tetrahedral void and octahedral void?

Solution:

(i) Hexagonal close-packing and cubic close-packing?

(ii) Crystal lattice and unit cell

(iii) Tetrahedral void and octahedral void

Question – 1. 8 - How many lattice points are there in one unit cell of each of the following lattice?

(i) Face-centred cubic

(ii) Face-centred tetragonal

(iii) Body-centred

Solution:

(i) One unit cell of a face-centered cubic has 8 lattice points are corners and 6 lattice points at faces, total 14 lattice points.

(ii) One unit cell of face-centered tetragonal has 8 lattice points are corners and 6 lattice points at faces, total 14 lattice points.

(iii) One unit cell of body centered has 8 lattice points are corners and 1 lattice points at faces, total 9 lattice points.

Question – 1.9 - Explain

(i) The basis of similarities and differences between metallic and ionic crystals.

(ii) Ionic solids are hard and brittle.

Solution:

(ii) In ionic solids, constituent particles are held together with strong electrostatic force of attraction along with their fixed position. The fixed position of ions and strong electrostatic force of attraction make ionic solids hard and brittle.

Question – 1.10 - Calculate the efficiency of packing in case of a metal crystal for

(i) simple cubic

(ii) body-centred cubic

(iii) face-centred cubic (with the assumptions that atoms are touching each other).

Solution:

(i) Simple cubic:

Let the side of a simple cubic lattice is ‘a’ and radius of atom present in it is ‘r’.

Since, edges of atoms touch each other, therefore, a = 2r (for simple cubic lattice)

(ii) body-centred cubic

(iii) face-centered cubic

Previous            Next
Solid State - Introduction
Solid State - Crystal Lattice
Solid State - Close Packing Structure
Solid State - Efficiency of Close Packing Structure - 1
Solid State - Efficiency of Close Packing Structure - 2
Solid State - Imperfections in Solids - Crystal Defects
Solid State - Electrical and Magnetic Properties
Solid State - NCERT In Text Solution 1
Solid State - NCERT In Text Solution 2
Solid State - NCERT In Text Solution 3
Solid State - NCERT Exercise Solution (Part 1)
Solid State - NCERT Exercise Solution (Part 3)
Solid State - NCERT Exercise Solution (Part 4)
Solid State - NCERT Exercise Solution (Part 5)

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