PES 2130 General Physics III
Practice Exam 2
1. An inflexible container is sealed with a sample of an ideal gas inside at 1 atmosphere of
pressure [1 atm = 1.013x105 Pa]. What must the temperature be to double the pressure inside?
2. A calorimeter is constructed using an insulated container and 500 grams of water [specific heat
of water is 4186 J/(K·kg)] initially at 20o C. A 100 gram ingot of copper [specific heat of 387
J/(K·kg)] initially at 300o C is placed into the calorimeter and the system is allowed to reach
thermal equilibrium. Assume heat loss to the insulated container, thermometer, and steam is
negligible. Find the final temperature after equilibrium is reached.
3. Identify the isobaric, isothermal, isochoric, and adiabatic
processes in the diagram to the right. (For process B, there is
no heat exchange.)
4. Under 1 atm of pressure (1 atm = 1.013x105 Pa), how much
heat is absorbed by a 200 gram block of frozen ethyl alcohol (initially at its freezing point) to
convert it entirely to vapor (at its vaporization point)?
Melting point of liquid ethyl alcohol at 1 atm.
Boiling point of liquid ethyl alcohol at 1 atm.
Latent heat of fusion for ethyl alcohol
Latent heat of vaporization for ethyl alcohol
Specific heat of liquid ethyl alcohol
R. Gist
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159 K
351 K
109 kJ/kg
879 kJ/kg
2.4 kJ/(kg K)
Ver A, Rev. 4
PES 2130 General Physics III
Practice Exam 2
5. A 0.08 mole sample of a monatomic ideal gas with molar heat capacity Cv=12.47 J/(mol∙K) is
allowed to expand at a constant pressure of 2.0 atmospheres from a volume of 1 liter to a
volume of 1.1 liters. How much work did the gas do during this compression? The
temperature rises from 31.6o C to 62.1o C during this process. How much heat flowed into or
out of the ideal gas? [1 atm = 1.013x105 Pa, R=8.315 J/(mol K), 1 L = 10-3 m3]
6. A particular heat engine operates between two temperatures, 100 o C and 300o C. Each engine
cycle takes 0.1 seconds to complete. During each cycle, 120 J is transferred out of the hot
reservoir and 100 J is transferred into the cold reservoir. What is the efficiency of this heat
engine? What power is generated by this engine? What is the efficiency of a perfect (Carnot)
engine operating between these two reservoirs?
7. A heat pump is running as a refrigerator. It is found that for each cycle, 10 J of heat are
extracted from the cold reservoir and 15 J of heat enter the hot reservoir. What is the
coefficient of performance of this heat pump?
8. A 3 mol sample of an ideal gas at 20o C contained in a .25 L jar. The jar is then connected to a
1 L evacuated chamber (by a tube of negligible volume) and allowed to expand into the
chamber with a negligible temperature change. How much has the entropy of the universe
changed in this process? How much potential work is forever lost? [possible processes on
exam: isothermal & isobaric phase change, free expansion of ideal gas, or heat transfer from
one reservoir to another]
9. How much longer will a slot in a copper plate be if it is 2 cm at 20o C after the plate is heated
to 1000o C [Coefficient of linear thermal expansion for copper is 17x10-6 1/K]?
10. A bunker wall is constructed of concrete, an air gap, and an inner layer of steel. The concrete
wall is 8 cm thick [thermal conductivity of concrete is 0.15 W/(m∙K)]. The inner wall is 1 cm
thick and made of steel [thermal conductivity=46 W/(m∙K)]. The air gap between the two
walls is 1 cm wide [thermal conductivity of still air at 27o C is 0.026 W/(m∙K)]. What is the
rate of heat loss through an area 4 meters by 1 meter if the interior temperature is 27o C and the
exterior temperature is 0o C?
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Ver A, Rev. 4