# Chemical Engineering Questions and Answers – Application of the Energy Balance to Closed Systems

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This set of Chemical Engineering Aptitude Test focuses on “Application of the Energy Balance to Closed Systems”.

1. What is the energy balance of a closed system?
a) Matter in the system is constant
b) Energy in the system is constant
c) Neither energy nor matter is constant
d) Both of energy and matter are constant

Explanation: For closed system energy balance, matter in the system is constant.

2. What is the heat transferred to the system, if a change in internal energy is 10 J?
a) 0
b) -10 J
c) 10 J
d) Cannot be determined

Explanation: Q = ∆U = 10 J.

3. What is the heat transferred to the system, if change in enthalpy is 15 J and change in volume is 2 m3 at 5 Pa?
a) 5 J
b) 8 J
c) 10 J
d) 12 J

Explanation: Q = ∆H – P∆V = 15 – 5*2 = 5 J.

4. What is the heat transferred to the system, if a change in enthalpy is 25 J and change in pressure is 5 Pa at volume 3 m3?
a) 5 J
b) 10 J
c) 15 J
d) 20 J

Explanation: Q = ∆H – V∆P = 25 – 3*5 = 10 J.

5. What is the heat transferred to the system, if change in enthalpy is 30 J and pressure, volume changed from 8 Pa, 5 m3 to 4 Pa, 12 m3?
a) 12 J
b) 15 J
c) 18 J
d) 22 J

Explanation: Q = ∆H – V∆P = 30 – (4*12 – 8*5) = 22 J.

6. The specific volume of SO2 is 10 m3/Kg, at 5 Pa, H = 100 J/Kg and at 10 Pa, H = 250 J/Kg, what is the heat transferred to the system?
a) 100 J/Kg
b) 150 J/Kg
c) 250 J/Kg
d) 350 J/Kg

Explanation: Q = ∆H – V∆P = (250 – 100) – 10(10 – 5) = 100 J/Kg.

7. The specific volume of a gas is 5 m3/Kg, at 10 Pa, H = 50 J/Kg and at 20 Pa, H = 100 J/Kg, what is the heat transferred to the system?
a) 0
b) 50 J/Kg
c) 100 J/Kg
d) 150 J/Kg

Explanation: Q = ∆H – V∆P = (100 – 50) – 5(20 – 10) = 0.

8. The specific volume of a gas is 5 m3/Kg, at 25 Pa, H = 40 J/Kg and at 40 Pa, H = 90 J/Kg, what is the heat transferred to the system?
a) -5 J/Kg
b) 5 J/Kg
c) -25 J/Kg
d) 25 J/Kg

Explanation: Q = ∆H – V∆P = (90 – 40) – 5(40 – 25) = -25 J/Kg.

9. The specific volume of a gas is 2 m3/Kg, at 12 Pa, H = 30 J/Kg and at 15 Pa, H = 45 J/Kg, what is the heat transferred to the system?
a) 6 J/Kg
b) 9 J/Kg
c) 12 J/Kg
d) 15 J/Kg

Explanation: Q = ∆H – V∆P = (45 – 30) – 2(15 – 12) = 15 – 6 = 9 J/Kg.

10. The specific volume of a gas is 3 m3/Kg, at 6 Pa, H = 4 J/Kg and at 9 Pa, H = 14 J/Kg, what is the heat transferred to the system?
a) 0
b) 1 J/Kg
c) 5 J/Kg
d) 25 J/Kg