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The Solid State

Question 113
CBSEENCH12005461
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How will you distinguish between the following pairs of terms:
Crystal lattice and unit cell?

Solution
Question 114
CBSEENCH12005462
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How will you distinguish between the following pairs of terms:
Tetrahedral void and octahedral void?

Solution
Question 115
CBSEENCH12005463
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How many lattice points are there in one unit cell of each of the following lattice?
(i) face centered cubic
(ii) face centered tetragonal
(iii) body centered.

Solution

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 116
CBSEENCH12005464
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Explain the basis of similarities and differences between metallic and ionic crystals.

Solution
The similarities and differences between metallic and ionic crystals are described as below:

Characteristics

Ionic crystals

Metallic crystals

1.

Constituent particles

cations (positive ions) and anions (negative ions)

Positive ions and mobile electrons.

2.

Binding forces

Strong electrostatic forces (electro valent bonding)

Electrical attraction between positive ions and mobile electrons (metallic bonding)

3.

Physical properties

Hard and brittle; high m.p. and b.p. good conductors of heat and electricity in molten state and aqueous solution, high heat of fusion.

Hard but malleable, high m.p., very good conductors of heat and electricity in solid and molten state, moderate heats of fusion.

 

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