1. Q20.1
Metal box at 0°C
Metal box at 0°C
Which statement about these two thermodynamic processes is correct?
A. Both are reversible.
B. Both are irreversible.
C. The upper one is reversible and the lower one is irreversible.
D. The upper one is irreversible and the lower one is reversible.
Ice at 0°C
Liquid water at 0°C
Metal box at 70°C
Metal box at 40°C
Ice at 0°C
Liquid water at 40°C

2. A20.1
Metal box at 0°C
Metal box at 0°C
Which statement about these two thermodynamic processes is correct?
A. Both are reversible.
B. Both are irreversible.
C. The upper one is reversible and the lower one is irreversible.
D. The upper one is irreversible and the lower one is reversible.
Ice at 0°C
Liquid water at 0°C
Metal box at 70°C
Metal box at 40°C
Ice at 0°C
Liquid water at 40°C

3. Q20.2
An ideal gas is taken around the cycle shown in this pV–diagram, from a to b to c and back to a. Process b  c is isothermal. Which of the processes in this cycle could be reversible?
A. a  b
B. b  c
C. c  a
D. two or more of A., B., and C.
E. none of A., B., or C.

4. A20.2
An ideal gas is taken around the cycle shown in this pV–diagram, from a to b to c and back to a. Process b  c is isothermal. Which of the processes in this cycle could be reversible?
A. a  b
B. b  c
C. c  a
D. two or more of A., B., and C.
E. none of A., B., or C.

5. Q20.3
An ideal gas is taken around the cycle shown in this pV–diagram, from a to c to b and back to a. Process c  b is adiabatic. Which of the processes in this cycle could be reversible?
A. a  c
B. c  b
C. b  a
D. two or more of A., B., and C.
E. none of A., B., or C.

6. A20.3
An ideal gas is taken around the cycle shown in this pV–diagram, from a to c to b and back to a. Process c  b is adiabatic. Which of the processes in this cycle could be reversible?
A. a  c
B. c  b
C. b  a
D. two or more of A., B., and C.
E. none of A., B., or C.

8. During one cycle, an automobile engine takes in 12,000 J of heat and discards 9000 J of heat. What is the efficiency of this engine?
A. 400%
B. 133%
C. 75%
D. 33%
E. 25%

9. A20.4
During one cycle, an automobile engine takes in 12,000 J of heat and discards 9000 J of heat. What is the efficiency of this engine?
A. 400%
B. 133%
C. 75%
D. 33%
E. 25%

10. Q20.5
During one cycle, an automobile engine with an efficiency of 20% takes in 10,000 J of heat. How much work does the engine do per cycle?
A J
B J
C J
D J
E. 400 J

11. A20.5
During one cycle, an automobile engine with an efficiency of 20% takes in 10,000 J of heat. How much work does the engine do per cycle?
A J
B J
C J
D J
E. 400 J

12. A Carnot engine takes heat in from a reservoir at 400 K and discards heat to a reservoir at 300 K.
If the engine does 12,000 J of work per cycle, how much heat does it take in per cycle?
A. 48,000 J
B. 24,000 J
C. 16,000 J
D J
E. none of the above

13. Q20.6
A copper pot at room temperature is filled with room-temperature water. Imagine a process whereby the water spontaneously freezes and the pot becomes hot. Why is such a process impossible?
A. It violates the first law of thermodynamics.
B. It violates the second law of thermodynamics.
C. It violates both the first and second laws of thermodynamics.
D. none of the above

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15. A20.6
A copper pot at room temperature is filled with room-temperature water. Imagine a process whereby the water spontaneously freezes and the pot becomes hot. Why is such a process impossible?
A. It violates the first law of thermodynamics.
B. It violates the second law of thermodynamics.
C. It violates both the first and second laws of thermodynamics.
D. none of the above

16. A20.7
A Carnot engine takes heat in from a reservoir at 400 K and discards heat to a reservoir at 300 K.
If the engine does 12,000 J of work per cycle, how much heat does it take in per cycle?
A. 48,000 J
B. 24,000 J
C. 16,000 J
D J
E. none of the above

17. Q20.8
Metal box at 70°C
Metal box at 40°C
You put an ice cube at 0°C inside a large metal box at 70°C. The ice melts and the entropy of the ice increases. Which statement is correct?
Ice at 0°C
Liquid water at 40°C
A. Entropy of the metal box is unchanged; total entropy increases.
B. Entropy of the metal box decreases; total entropy decreases.
C. Entropy of the metal box decreases; total entropy is unchanged.
D. Entropy of the metal box decreases; total entropy increases.
E. none of the above

18. Metal box at 70°C Metal box at 40°C
You put an ice cube at 0°C inside a large metal box at 70°C. The ice melts and the entropy of the ice increases. Which statement is correct?
Ice at 0°C
Liquid water at 40°C
A. Entropy of the metal box is unchanged; total entropy increases.
B. Entropy of the metal box decreases; total entropy decreases.
C. Entropy of the metal box decreases; total entropy is unchanged.
D. Entropy of the metal box decreases; total entropy increases.
E. Entropy of the metal box increases; total entropy increases.