Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) on “Internal Energy and Energy Conversion Concept”.

1. What is the change in internal energy for a process which has final and initial states are exactly similar?

a) Positive

b) Negative

c) Zero

d) Cannot say

Answer: c

Clarification: Since internal energy is a state function, change in internal energy for the process will be zero.

2. What is the change in internal energy of 2 mole of air (C_{v} = 2.1 X 10^{4} J/mole^{o}C), if its temperature changes from 10^{o}C to 20^{o}C?

a) 420 kJ

b) 540 kJ

c) 840 kJ

d) 1050 kJ

Answer: a

Clarification: Change in internal energy = 2*(2.1 X 104)*(20 – 10) = 420 kJ.

3. What is the change in internal energy of 1 mole of air ((C_{v} = 2.1 X 10^{4} J/mole^{o}C), if its temperature changes from 10^{o}C to 5^{o}C?

a) 84 kJ

b) 105 kJ

c) – 84 kJ

d) – 105 kJ

Answer: d

Clarification: Change in internal energy = 1*(2.1 X 104)*(5 – 10) = – 105 kJ.

4. Ratio of change in internal energy of a substance from 4^{o}C to T and from T to 10^{o}C is 2, what is T?

a) 5^{o}C

b) 6^{o}C

c) 7^{o}C

d) 8^{o}C

Answer: d

Clarification: 2 = (T – 4)/(10 – T), => T = 8^{o}C.

5. Ratio of change in internal energy of a substance from 15^{o}C to T and from T to 10^{o}C is – 2, what is T?

a) 5^{o}C

b) 15^{o}C

c) 20^{o}C

d) 30^{o}C

Answer: a

Clarification: – 2 = (T – 15)/(10 – T), => T = 5^{o}C.

6. Total energy of the universe is always ______

a) Increasing

b) Decreasing

c) Constant

d) Cannot say

Answer: c

Clarification: According to the law of conservation of energy, the total energy of the universe is always constant.

7. A stone has initial potential and kinetic energy as 10 J and 5 J respectively if the final potential energy of the stone is 15 J what is its final kinetic energy?

a) 0

b) 5 J

c) 10 J

d) 15 J

Answer: a

Clarification: Law of conservation of energy, 10 + 5 = 15 + KE, => KE = 0.

8. A stone has initial potential and kinetic energy as 5 J and 20 J respectively if the final kinetic energy of the stone is 15 J what is its final potential energy?

a) 0

b) 10 J

c) 15 J

d) 25 J

Answer: b

Clarification: 5 + 20 = 15 + PE, => PE = 10 J.

9. A stone has initial potential, kinetic and internal energy 4 J, 15 J and 20 J respectively, if the final kinetic energy and potential energy of the stone is 5 J and 10 J respectively, what is the final internal energy?

a) 15 J

b) 20 J

c) 24 J

d) 32 J

Answer: c

Clarification: Final internal energy = 4 + 15 + 20 – 5 – 10 = 24 J.

10. A stone has initial potential, kinetic and internal energy 7 J, 10 J and 2x J respectively, if the final kinetic energy, potential energy and internal energy are 5 J, 21 J and x respectively, what is the final internal energy?

a) 2 J

b) 4 J

c) 5 J

d) 9 J

Answer: d

Clarification: 7 + 10 + 2x = 5 + 21 + x, => x = 9 J.