## Engineering Chemistry MCQ (Phases and Components)

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Phases and Components – 1

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

**MgCO3 ⟶ MgO +CO2 (Gas)**

a) 3, 2

b) 1, 3

c) 2, 3

d) 1, 2

Answer: a

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?**

**NH4Cl ⟶ NH3 (Gas) + HCl (Gas)**

a) 1, 2

b) 2, 1

c) 3, 1

d) 3, 2

Answer: b

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

Answer: d

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 + H2O (Gas) ⟶ FeO + H2 (Gas)**

a) 3, 3

b) 2, 3

c) 1, 3

d) 2, 2

Answer: a

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-H2O?a) 1**

b) 2

c) 3

d) 4

Answer: c

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, H20). 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-H20?a) 1**

b) 2

c) 3

d) 4

Answer: d

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

Answer: d

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.**

CaCO3 ⟶ CaO + CO2 (Gas)

a) 1

b) 2

c) 3

d) 0

Answer: a

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) + H20 (Gas)

a) 2

b) 3

c) 1

d) 0

Answer: c

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

Answer: d

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.**

N2O4 (Gas) ⟶ 2NO2 (Gas)

a) 1

b) 2

c) 3

d) 0

Answer: b

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

Answer: d

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.