This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Phases and Components – 1”.

1. What is the number of phases and components present in the following reaction?

MgCO_{3} ⟶ MgO +CO_{2} (Gas)

a) 3, 2

b) 1, 3

c) 2, 3

d) 1, 2

View Answer

Explanation: Since we have two solids and one gaseous component in the above reaction, we have 3 phases. Also since under equilibrium, the gaseous component may evaporate, we have only two components.

2. What is the number of phases and components in the following reaction?

NH_{4}Cl ⟶ NH_{3} (Gas) + HCl (Gas)

a) 1, 2

b) 2, 1

c) 3, 1

d) 3, 2

View Answer

Explanation: Since we have one solid component and two gaseous components (n gaseous components contribute to one phase and n solid components contribute to n phases), we have 2 phases. Since the gaseous components may evaporate, we have only one component.

3. What is the number of phases and components in an aqueous solution of glucose?

a) 2, 1

b) 3, 2

c) 1, 3

d) 1, 2

View Answer

Explanation: Since we have a solid mixed in a liquid, we have two components. Since the above solution is homogeneous, we have only one phase.

4. What is the number of phases and components in the following reaction?

Fe + H_{2}O (Gas) ⟶ FeO + H_{2} (Gas)

a) 3, 3

b) 2, 3

c) 1, 3

d) 2, 2

View Answer

Explanation: Here we have two solids and two gases, so the number of phases is two. Also the number of species is 4 (i.e N=4) and the number of reactions is one (i.e E=1). Therefore, the number of components is C = N-E = 4-1 = 3.

5. What is the number of components in a nonreactive system of KCl-NaCl-H_{2}O?

a) 1

b) 2

c) 3

d) 4

View Answer

Explanation: Since it is a nonreactive system, we should also take the ions into consideration (sodium ions, potassium ions, chlorine ions) and also the individual components (NaCl, KCl, H

_{2}0). Hence N=6. Also E=3. Therefore the number of components are C = N-E = 6-3 = 3.

6. What is the number of components present in a reactive system of NaCl-KBr-H_{2}0?

a) 1

b) 2

c) 3

d) 4

View Answer

Explanation: Since it is a reactive system, we have N=9 (taking all the ions into consideration along with individual species) and also we have E=5 (considering all the neutral reactions). Therefore C = N – E = 9-5 = 4.

7. What is the degree of freedom for a water system?

a) 1

b) 2

c) 4

d) 0

View Answer

Explanation: We know that the number of phases and components in a water system is 3 and 1 respectively. Since it is a one component system, F = C-P+2 = 1-3+2 = 0.

8. Calculate the degree of freedom for the following reaction.

CaCO_{3} ⟶ CaO + CO_{2} (Gas)

a) 1

b) 2

c) 3

d) 0

View Answer

Explanation: We know that the number of phases and components in the above reaction is 3 and 2 respectively. Since it is a one component system, F = C-P+2 = 2-3+2 = 1.

9. Calculate the degree of freedom for the following reaction.

NaCl (Solid) ⟶ NaCl (Liquid) + H_{2}0 (Gas)

a) 2

b) 3

c) 1

d) 0

View Answer

Explanation: We know that the number of phases and components in the above reaction is 3 and 2 respectively. Since it is a one component system, F = C-P+2 = 2-3+2 = 1.

10. Calculate the degree of freedom for an aqueous solution of glucose.

a) 1

b) 2

c) 4

d) 3

View Answer

Explanation: We know that the number of phases and components in the above reaction is 1 and 2 respectively. Since it is a one component system, F = C-P+2 = 2-1+2 = 3.

11. Calculate the degree of freedom for the following reaction.

N_{2}O_{4} (Gas) ⟶ 2NO_{2} (Gas)

a) 1

b) 2

c) 3

d) 0

View Answer

Explanation: We know that the number of phases and components in the above reaction is 1 and 1 respectively. Since it is a one component system, F = C-P+2 = 1-1+2 = 2.

12. Calculate the degree of freedom for a saturated solution of sodium chloride.

a) 0

b) 1

c) 3

d) 2

View Answer

Explanation: We know that the number of phases and components in the above reaction is 2 and 2 respectively. Since it is a one-component system, F = C-P+2 = 2-2+2 = 2.

**Sanfoundry Global Education & Learning Series – Engineering Chemistry.**

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