The Solid State

Question 221
CBSEENCH12005569

Which solid is likely to be the best material for converting sunlight into electricity?

Solution

Potassium, rubidium.

Question 222
CBSEENCH12005570

In an alloy of gold and cadmium, gold crystallizes in cubic structure occupying the corners only and cadmium fits into the face centre voids. What is quantitative composition of the alloy?

Solution

In an alloy of gold and cadmium, gold crystallizes in cubic structure occupying the corners only and cadmium fits into the face centre voids.

Number of gold atoms     =1/8 x 8 =1Au

Number of candium atoms =1/2 x 6 =3Cd

Hence, quantitative composition on = AuCd3

Question 223
CBSEENCH12005571

What is the difference between glass and quartz, though both contain SiO44– units?

Solution

Both naturally-occurring and artificial quartz crystal contains at least ninety-nine percent silicone dioxide, while cut glass crystal only possesses at most eighty percent silicone dioxide. 

Question 224
CBSEENCH12005572

What is the effect of Frenkel defect on electrical conductivity of the solid?

Solution

Compounds having frenkel defect conduct electricity to a small extent. When electric field is applied, an ion moves from its lattice site to occupy a hole, it creates a new hole. In this way, a hole moves from one end to the other. Thus, it conducts electricity across the crystal. Due to the presence of holes, stability (or the lattice energy) of the crystal decreases.

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