Solid State Chemistry Solved Objective Questions

**Que 1. Experimentally it was found that a metal oxide has the formula M _{0.98}O_{1}. M is present as M^{2+} and M^{3+} in its oxide. Fraction of metal which exists as M^{3+} would be **

a. 7.01% b. 4.08% c. 6.05% d. 5.08%

**Ans 1.**(b)

**Explanation:**Ratio of the numbers of M atoms to the number of O atoms is

M : O = 0.98 : 1 = 98 : 100

Total +ve charge = Total -ve charge

Because, oxide is neutral

Let, number of M

^{2+}ions = x

So, number of M

^{3+}ions = 98 – x

On equating the charge, we get

2x + 3(98 – x) = -2 (100) (Charge on O atoms) = -200

-x + 294 = 200

x = 94

Number of M

^{2+}ions = 94

Number of M

^{3+}ions = 4

Hence, percentage of M that exists as M

^{3+}= (4/98) × 100 = 4.08 %

**Que 2. ****How many unit cells are present in a cube-shaped ideal crystal of NaCl of mass 1 g? **

a. 5.14 × 10^{21}

b. 1.28 × 10^{21}

c. 1.771 × 10^{21}

d. 2.57 × 10^{21}

**Ans 2.** (d)

**Explanation:** Mass of the unit cell = Number of formula units in unit cell x mass of each formula unit = 4 × 58.5 g mol^{-1}

Solid State Chemistry Solved Objective Questions

**Que 3. ****Which of the following crystals have 6:6 coordination? **

(a) MnO (b) NH_{4}I (c) ZnS (d) None of these

**Ans 3.** (b)

**Explanation:** NH_{4}I = 6:6 MnO = 4:4 ZnS = 4:4

**Que 4.** **A compound contains two types of atoms: X and Y. It crystallizes in a cubic lattice with atoms X at the corners of the unit cell and atoms Y at the body centres. The simplest possible formula of this compound is:**

(a) XY (b) X_{2}Y_{2} (c) XY_{6} (d) X_{8}Y

**Ans 4.** (a)

**Explanation:** X:Y (8 × 1/8):1(1/1) = 1:1 Therefore, the formula is XY.

**Que 5. The number of atoms per unit cell in a BCC, an FCC, and a simple cubic cell is respectively: **

(a) 1, 4, 2 (b) 2, 4, 1 (c) 4, 1, 2 (d) 4, 2, 2

**Ans 5.** (b)

Solid State Chemistry Solved Objective Questions

**Que 6. The edge length of the unit cell of NaCl crystal lattice is 552 pm. If the ionic radius of sodium ion is 95 pm. What is the ionic radius of chloride ions? **

(a) 181 pm (b) 190 pm (c) 276 pm (d) 368 pm

**Ans 6.** (a)

**Explanation:** The edge length of unit cell of NaCl = 552 pm

The ionic radius of sodium ion = 95 pm

The ionic radius of Cl^{–} ion = (552/2) – 95

276 – 95 = 181 pm

**Que 7. The density of solid argon is 1.65 g/mL at –233°C. If the argon atom is assumed to be a sphere of radius 1.54 × 10 ^{–8} cm, what percentage of solid argon is apparently empty space? (Atomic wt. of Ar = 40) **

(a) 32% (b) 52% (c) 62% (d) 72%

**Ans 7**. (c)

**Explanation:**

Solid State Chemistry Solved Objective Questions

**Que 8. A solid has 3 types of atoms namely X, Y, and Z. X forms an FCC lattice with Y atoms occupying all the tetrahedral voids and Z atoms occupying half the octahedral voids. The formula of the solid is **

(a) XYZ (b) X_{2}Y_{4}Z (c) X_{4}YZ_{2} (d) X_{4}Y_{2}Z

**Ans 8.** (b)

**Explanation:** X (FCC) = 8 × 1/8 = 1, that is, 1

Y (tetrahedral voids) = 2,

that is, 2 Z (octahedral voids) = 1, that is, ½

X : Y : Z = 1 : 2 : 1/2 = 2 : 4 : 1

= X_{2}Y_{4}Z

**Que 9. Amorphous substances show: **

(1) Short and long-range order

(2) Short-range order

(3) Long-range order

(4) Have no sharp melting point

(a) (1) and (2) are correct (b) (2) and (4) are correct

(c) (2), (3) and (4) are correct (d) (1) and (4) are correct

**Ans 9.** (b)

**Que 10. Na _{2}O has an antifluorite structure. In Na_{2}O, the coordination number of Na^{+} and O^{2–} are respectively: **

(a) 4, 4 (b) 6, 6 (c) 4, 8 (d) 8, 8

**Ans 10.**(c)

**Explanation:**Antifluorite structures like Li

_{2}O, Na

_{2}O, K

_{2}O, Rb

_{2}O, Rb

_{2}S, Na

_{2}S possess 4:8 coordination.

Solid State Chemistry Solved Objective Questions