Ch 15 Practice Test
1. Complete the following statement: The first law of thermodynamics states that
A) heat is a form of energy.
B) entropy is a function of state.
C) the entropy of the universe is increasing.
D) the change in the internal energy of a system is given by Q W.
E) no engine can be more efficient than a Carnot engine operating between the same two temperatures.
2. Enclosed beneath the moveable piston in the figure is 4.8 moles of a monatomic ideal gas. The gas performs
work on the piston as 2300 J of heat are added from the surroundings. During the process, the temperature of
the gas decreases by 45 K. How much work does the gas perform?
3. A system containing an ideal gas at a constant pressure of 1.22  105 Pa gains 2140 J of heat. During the
process, the internal energy of the system increases by 2320 J. What is the change in volume of the gas?
A) +1.48  103 m3 B) 1.48  103 m3 C) +3.66  103 m3 D) 3.66  103 m3 E) zero m3
4. Heat is added to a sample of an ideal monatomic gas. Which one of the following statements is necessarily true?
A) The gas must expand.
B) The gas must do work.
C) The type of change that will occur depends on the conditions of the gas when the heat was added.
D) The gas must change phase.
E) The temperature of the gas must increase.
5. In one stage of a reversible process, the temperature of an ideal gas remains constant as its volume is decreased.
Which one of the following statements concerning this situation is true?
A) The process is adiabatic.
B) The pressure of the gas decreases in this process.
C) Heat flows out of the gas and into the surroundings.
D) The gas does "positive" work on its surroundings.
E) The average kinetic energy of the gas molecules increases.
6. A fixed amount of ideal gas is compressed adiabatically. Which entry in the table below correctly depicts the
sign of the work done, the change in the internal energy, and the heat exchanged with the environment?
work done change in internal energy
heat exchanged
A) positive
negative
zero
B) negative
zero
positive
C) negative
negative
zero
D) positive
positive
zero
E) negative
positive
zero
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7. Draw a diagram of each of the four special thermal processes. For each process, write down the equation for work
done.
Use the following to answer questions 8-11:
An ideal monatomic gas originally in state A is taken reversibly to state B along the straight-line path shown in the
pressure-volume graph.
8. How much work was done by the gas?
A) zero calories B) +12 C) 110 cal D) +110 cal E) +122 cal
9. What is the change in the internal energy of the gas for this process?
A) zero B) +12 cal C) 110 cal D) +110 cal E) +122 cal
10. How much heat was exchanged during this process?
A) 110 cal B) 12 cal C) zero D) +122 cal E) +232 cal
11. Suppose that the same gas is originally in state A as described above, but its volume is increased isothermally
until a new volume of 3.0 liters is reached. Which one of the following statements for this isothermal process is
false?
A) The change in the internal energy is zero.
B) The final state of the system will still be B.
C) The work done will be smaller for the isothermal process.
D) The heat added will be smaller for the isothermal process.
E) The heat added for the isothermal process will be equal to the work done.
12. An engine is used to lift a 2700 kg truck to a height of 3.0 m at constant speed. In the lifting process, the engine
received 3.3  105 J of heat from the fuel burned in its interior. What is the efficiency of the engine?
A) 0.19 B) 0.24 C) 0.29 D) 0.34 E) 0.39
13. A heat engine operates in a Carnot cycle between reservoirs of temperatures 1000 K and 400 K. It is found to
discharge 20 J of heat per cycle to the cold reservoir. What is the work output per cycle?
A) 10 J B) 20 J C) 30 J D) 40 J E) 50 J
14. A Carnot heat engine is to be designed with an efficiency of 85%. If the low temperature reservoir is 25 °C,
what is the temperature of the "hot" reservoir?
A) 45 °C B) 430 °C C) 850 °C D) 1300 °C E) 1700 °C
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Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
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14.
D
A
B
C
C
E
D
E
E
B
B
C
E
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