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**Q.1. Which of the following compounds is likely to show both Frenkel and Schottky defects in its crystalline form? (2020)****(1) AgBr****(2) CsCl****(3) KBr****(4) ZnS****Ans. **(1)

In AgBr, there in not very large difference between the size of the cation and anion, thus, it will show both Frenkel and Schottky defect in crystalline form.**Q.2. At 100°C, copper (Cu) has FCC unit cell structure with cell edge length of x Å. What is the approximate density of Cu (in g cm ^{-3}) at this temperature?[Atomic Mass of Cu = 63.55 u] (2019)(1) 205/x^{3}(2) 105/x^{3}(3) 211/x^{3}(4) 422/x^{3}Ans.** (4)

We know that,

Given that: Z = 4(fcc)

M= 63.5 g

N

a =

After putting the values, we get

(2) Hexagonal

(3) Monoclinic

(4) Tetragonal

Ans.

For triclinic crystal

a ≠ b ≠ c Edge lengths

α ≠ β ≠ γ Axial angle

(1) hep lattice - A, 2/3 Tetrahedral voids - B

(2) hep lattice - A, 1/3 Tetrahedral voids - B

(3) hep lattice - B, 2/3 Tetrahedral voids - A

(4) hep lattice - B, 1/3 Tetrahedral voids - A

Ans.

Here, A

Thus, hep has six atoms so, ‘B’ forms hep lattice and ‘A’ is present in tetrahedral void.

Total tetrahedral voids = 12

∴ Fraction of tetrahedral voids occupied by A = 4/12 = 1/3

[Avogadro constant ≈ 6 x 10

(2) 0.0216 kg mol

(3) 0.0305 kg mol

(4) 0.4320 kg mol

Ans.

M = 305.4 x 10

(Edge length is represented by ‘a’) (2019)

(1) 0.027 a

(2) 0.047 a

(3) 0.134 a

(4) 0.067 a

Ans.

For BCC

∴ Empty space at edge = a - 2R

∴

(1) A

(2) AB

(3) A

(4) A

Ans.

(1) 45%

(2) 75%

(3) 90%

(4) 65%

Ans.

Volume occupied by atoms in solid 2

Relationship between body diagonal and radius of atom (r),

6r = √3 a

(1) √2a

(2) a

(3) a/2

(4) 3/2 a

Ans.

In FCC, tetrahedral voids are located on the body diagonal at a distance of √3a/4 from the corner. Together they form a smaller cube of edge length a/2. Therefore, distance between centres of two nearest tetrahedral voids in the lattice is also a/2.

(1) 8 : 1 : 6

(2) 1 : 2 : 4

(3) 4 : 2 : 1

(4) 4 : 2 : 3

Ans.

(1) 1.0 pm

(2) 2.0 pm

(3) 0.1 nm

(4) 2.0 nm

Ans.

No. of surfactant molecules = 6 × 10

Let edge length = a cm

Total surface area of surfactant = 6 × 10

(1) Schottky defect

(2) Vacancy defect

(3) Frenkel defect

(4) Metal deficiency defect

Ans.

In Frenkel defect, smaller ion displaces from its actual lattice site into the interstitial sites.

(1)

(2)

(3)

(4)

Ans.

Basic knowledge of Antiferromagnetic

(1) 2a

(2) 2√2a

(3) √2a

(4) a/√2

Ans.

In FCC, one of the face is like

By ΔABC,

2a

Distance of closest approach = 2r = a/√2

(1) TiO

(2) CrO

(3) VO

(4) MnO

Ans.

CrO

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