## Engineering Chemistry MCQ (One Component System)

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One Component System

**1. With respect to one component system, what is the mixture present at the triple point?**

a) Water

b) Ice

c) Water vapor

d) Water, ice, vapor

Answer: d

Explanation: Since at the triple point, all the states of water are in equilibrium, all the

three states will stay together. At this point where the three phases exist is invariant where F=0.

**2. Which of the following statements is incorrect about the triple point?**

a) The point at which the solid, liquid and gaseous phases for a substance co-exist

b) The triple point exists for a substance at a specific temperature and pressure

c) The triple point exists at a single temperature and is not related with pressure

d) The system must be closed so that no vapor can escape

Answer: c

Explanation: The triple point for a pure substance occurs in a closed system at a

particular temperature and pressure (i.e. one cannot be varied with the other). Hence the triple point is dependent on both the factors.

**3. What does a horizontal arrest in a cooling system refer to?**

a) Continuous cooling

b) Invariant reaction

c) Variant reaction

d) Bi variant reaction

Answer: b

Explanation: Horizontal arrest refers to the equilibrium state of the system where

the degree of freedom is 0 (as all the phases co-exist) and hence this state is

referred to as invariant reaction (unique point).

**4. Calculate the degree of freedom for sublimation curve.**

a) Does not exist

b) 1

c) 0

d) 2

Answer a

Explanation: Since in the sublimation curve, super cooled liquid exists along with

Vapor and liquid states, this condition will not be applicable to normal Gibbs

formula which states F = C-P+2.

**5. Calculate the number of phases at the sublimation curve.**

a) 2

b) 3

c) 4

d) 0

Answer: c

Explanation: Since in a sublimation state, all the phases exist together (solid, liquid,

vapor and super cooled liquid), they contribute to individual species and hence the

number of phases is four.

**6. Under what condition is one component system converted to two component systems?**

a) Decrease the temperature

b) Add a miscible liquid

c) Add an immiscible liquid

d) Decrease the pressure

Answer: b

Explanation: We know that two immiscible liquids form a heterogeneous mixture.

Similarly, if a miscible liquid is added to the one component system, then under

high temperature and pressure, it can be converted into two component systems.

**7. Under what condition is two component systems converted to one component system?**

a) Decrease the temperature

b) Add a miscible liquid

c) Add an immiscible liquid

d) Decrease the pressure

Answer: c

Explanation: We know that two miscible liquids form a homogeneous mixture.

Similarly, if an immiscible liquid is added to the two component systems, then under

high temperature and pressure, it can be converted into one component system.

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

**CH4 ⟶ CO2 (gas) + 2H20**

a) 2

b) 3

c) 4

d) 6

Answer: a

Explanation: The number of components in this system is three. Also the number of

phase in this reaction is three. Therefore the degree of freedom is given by F = CP+2. Therefore F=2.

**9. Calculate the degree of freedom for decomposition of potassium permanganate.**

a) 3

b) 2

c) 1

d) 0

Answer: b

Explanation: In this reaction, the number of phases is 3 (solid, liquid, gas). The

number of components is also 3. Therefore the degree of freedom is given by F = CP+2. Therefore F=2.

**10. Calculate the degree of freedom for decomposition of charcoal.**

a) 1

b) 2

c) 3

d) 0

Answer: c

Explanation: In this reaction, the number of phases is 2 and the number of

components is 3. Hence the degree of freedom is given by F=C-P+2. Therefore here

the degree of freedom is F=3-2+2=3.