Question 1

A heat engine with an efficiency of 30.0% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir?

Accepted Answer

A)   5830 J
B)   8330 J
C)   750 J
D)   1350 J
E)   7080 JF) B) and E)
G) A) and E)

Question 2

The temperature inside a Carnot refrigerator placed in a kitchen at 22.0°C is 2.0°C. The heat extracted from the refrigerator is 89 MJ/h. What power is needed to operate this refrigerator?

Accepted Answer

A)   1.7 kW
B)   1.8 kW
C)   1.5 kW
D)   1.9 kW
E)   1.6 kWF) B) and C)
G) B) and E)

Question 3

A heat engine performs the reversible cycle abca with 9.0 moles of an ideal gas, as shown in the figure. Path ca is an adiabatic process. The temperatures at points a and b are 300 K and 500 K, respectively. The volume at point c is 0.20 m3. The adiabatic constant of the gas is 1.60. The thermal efficiency of this engine is closest to 3. The adiabatic constant of the gas is 1.60. The thermal efficiency of this engine is closest to   A)  0.070. B)  0.10. C)  0.13. D)  0.16. E)  0.19." class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   0.070.
B)   0.10.
C)   0.13.
D)   0.16.
E)   0.19.F) A) and B)
G) A) and C)

Question 4

What is the maximum theoretical efficiency possible for a heat engine operating between a reservoir in which ice and water coexist, and a reservoir in which water and steam coexist? The pressure is constant at 1.0 atmosphere for both reservoirs.

Accepted Answer

A)   27%
B)   45%
C)   73%
D)   17%E) A) and B)
F) B) and C) A

Question 5

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt, causing no appreciable change in the temperature of the bath water. Which one of the following statements is true?

Accepted Answer

A)   The entropy gained by the ice cube is equal to the entropy lost by the water.
B)   The entropy lost by the ice cube is equal to the entropy gained by the water.
C)   The net entropy change of the system (ice plus water)  is zero because no heat was added to the system.
D)   The entropy of the system (ice plus water)  increases because the process is irreversible.
E)   The entropy of the water does not change because its temperature did not change.F) A) and E)
G) B) and D)

Question 6

According to the second law of thermodynamics, the entropy of any system always increases.

Accepted Answer

A) True 
 B)False

Question 7

A Carnot engine operates between reservoirs at 550K and 300K, discarding 1500 J of heat in each cycle.
(a) What is the engine's efficiency?
(b) How much heat is supplied to the engine by the hot reservoir in each cycle?

Accepted Answer

(a) 45.5% ...

Question 8

A Carnot cycle engine operates between a low temperature reservoir at 20°C and a high temperature reservoir at 800°C. If the engine is required to output 20.0 kJ of work per cycle, how much heat must the high temperature reservoir transfer to the engine during each cycle?

Accepted Answer

A)   27.5 kJ
B)   73.2 kJ
C)   39.2 kJ
D)   800 kJ
E)   20.5 kJF) A) and B)
G) D) and E)

Question 9

A Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C. How much energy does it need to remove 2000 J of heat from the interior of the house?

Accepted Answer

A)   105 J
B)   130 J
C)   780 J
D)   520 J
E)   340 JF) B) and E)
G) A) and B)

Question 10

Is it possible to transfer heat from a hot reservoir to a cold reservoir?

Accepted Answer

A)   No; this is forbidden by the second law of thermodynamics.
B)   Yes; this will happen naturally.
C)   Yes, but work will have to be done.
D)   Theoretically yes, but it hasn't been accomplished yet.E) B) and C)
F) A) and B)

Question 11

The compressor in a certain Carnot refrigerator performs 480 J of work to remove 150 J of heat from the interior of the refrigerator. How much heat must the coils behind the refrigerator discharge into the kitchen?

Accepted Answer

A)   110 J
B)   150 J
C)   330 J
D)   480 J
E)   630 JF) D) and E)
G) B) and D)

Question 12

A brass rod, 75.0 cm long and having a cross-sectional area of 2.50 cm2, conducts heat from a large furnace at 375°C into a very large cold water bath at 10.0°C without losing any heat at the lateral surface of the rod. Steady state has been established, and the thermal conductivity of brass is 109 W/m∙K. The rate at which the entropy of the system (furnace plus water)  is changing is closest to

Accepted Answer

A)   2.05 × 10-2 W/K.
B)   2.64 × 10-2 W/K.
C)   3.54 × 10-2 W/K.
D)   4.69 × 10-2 W/K.
E)   6.74 × 10-2 W/K.F) D) and E)
G) B) and E)

Question 13

An automobile engine takes in 4000 J of heat and performs 1100 J of mechanical work in each cycle.
(a) Calculate the engine's efficiency.
(b) How much heat is "wasted" in each cycle?

Accepted Answer

(a) 27.5% ...

Question 14

A 2.00-kg block of ice at 0.00°C is dropped into a very large lake at 25.0°C and completely melts. For water, the heat of fusion is 3.35 × 105 J/kg, the heat of vaporization is 2.25 × 105 J/kg, and the specific heat is 4190 J/kg∙K. The net change in entropy of the system consisting of the ice and the lake due to this melting process is closest to

Accepted Answer

A)   2.45 × 103 J/K.
B)   2.24 × 103 J/K.
C)   2.06 × 102 J/K.
D)   -2.45 × 103 J/K.
E)   -2.06 × 102 J/K.F) A) and E)
G) All of the above

Question 15

A Carnot refrigerator takes heat from water at 0°C and rejects heat to a room at 12°C. Suppose that 92.0 grams of water at 0°C are converted to ice at 0°C by the refrigerator. Calculate the mechanical energy that must be supplied to the refrigerator. The heat of fusion of water is 3.34 × 105 J/kg.

Accepted Answer

1350 J

Question 16

At atmospheric pressure, 45 moles of liquid helium are vaporized at its boiling point of 4.22 K. The heat of vaporization of helium, at atmospheric pressure, is 2.09 × 104 J/kg, and the atomic weight of helium is 4.00 g/mol. The change in the entropy of the helium, as it vaporizes, is closest to

Accepted Answer

A)   890 J/K.
B)   14,000 J/K.
C)   18,000 J/K.
D)   -9400 J/K.
E)   -14,000 J/K.F) B) and C)
G) A) and D) A

Question 17

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into a room per cycle. How much work is required in each cycle?

Accepted Answer

A)   4 kJ
B)   20 kJ
C)   22 kJ
D)   24 kJ
E)   44 kJF) B) and C)
G) A) and E)

Question 18

A 2.0-kg block of aluminum at 50°C is dropped into 5.0 kg of water at 20°C and the temperature is allowed to stabilize. What is the total change in entropy during this process, assuming no heat is exchanged with the environment? The specific heat of aluminum is 910 J/(kg∙K)  and the specific heat of water is 4190 J/(kg∙K) .

Accepted Answer

A)   8.2 J/K
B)   10 J/K
C)   3.3 × 10-2 J/K
D)   3.8 × 10-3 J/K
E)   2.4 × 10-3 J/KF) B) and D)
G) C) and D)

Question 19

The entropy of an isolated system must be conserved, so it never changes.

Accepted Answer

A) True 
 B)False

Question 20

A 2.00 kg piece of lead at 40.0°C is placed in a very large quantity of water at 10.0°C, and thermal equilibrium is eventually reached. Calculate the TOTAL change in entropy that occurs during this process. The specific heat of lead is 130 J/(kg∙K) .

Accepted Answer

A)   190 J/K
B)   100 J/K
C)   6.6 J/K
D)   6.2 J/K
E)   1.4 J/KF) A) and D)
G) All of the above

Exam 19: Heat Engines and Refrigerators

A heat engine with an efficiency of 30.0% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir?

Correct Answer
verified

The temperature inside a Carnot refrigerator placed in a kitchen at 22.0°C is 2.0°C. The heat extracted from the refrigerator is 89 MJ/h. What power is needed to operate this refrigerator?

Correct Answer
verified

Correct Answer
verified

What is the maximum theoretical efficiency possible for a heat engine operating between a reservoir in which ice and water coexist, and a reservoir in which water and steam coexist? The pressure is constant at 1.0 atmosphere for both reservoirs.

Correct Answer
verified
A

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt, causing no appreciable change in the temperature of the bath water. Which one of the following statements is true?

Correct Answer
verified

According to the second law of thermodynamics, the entropy of any system always increases.

Correct Answer
verified

A Carnot engine operates between reservoirs at 550K and 300K, discarding 1500 J of heat in each cycle. (a) What is the engine's efficiency? (b) How much heat is supplied to the engine by the hot reservoir in each cycle?

Correct Answer
verified
(a) 45.5% ...
View Answer

A Carnot cycle engine operates between a low temperature reservoir at 20°C and a high temperature reservoir at 800°C. If the engine is required to output 20.0 kJ of work per cycle, how much heat must the high temperature reservoir transfer to the engine during each cycle?

Correct Answer
verified

A Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C. How much energy does it need to remove 2000 J of heat from the interior of the house?

Correct Answer
verified

Is it possible to transfer heat from a hot reservoir to a cold reservoir?

Correct Answer
verified

The compressor in a certain Carnot refrigerator performs 480 J of work to remove 150 J of heat from the interior of the refrigerator. How much heat must the coils behind the refrigerator discharge into the kitchen?

Correct Answer
verified

Correct Answer
verified

An automobile engine takes in 4000 J of heat and performs 1100 J of mechanical work in each cycle. (a) Calculate the engine's efficiency. (b) How much heat is "wasted" in each cycle?

Correct Answer
verified
(a) 27.5% ...
View Answer

Correct Answer
verified

Correct Answer
verified
1350 J

At atmospheric pressure, 45 moles of liquid helium are vaporized at its boiling point of 4.22 K. The heat of vaporization of helium, at atmospheric pressure, is 2.09 × 10⁴ J/kg, and the atomic weight of helium is 4.00 g/mol. The change in the entropy of the helium, as it vaporizes, is closest to

Correct Answer
verified
A

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into a room per cycle. How much work is required in each cycle?

Correct Answer
verified

Correct Answer
verified

The entropy of an isolated system must be conserved, so it never changes.

Correct Answer
verified

A 2.00 kg piece of lead at 40.0°C is placed in a very large quantity of water at 10.0°C, and thermal equilibrium is eventually reached. Calculate the TOTAL change in entropy that occurs during this process. The specific heat of lead is 130 J/(kg∙K) .

Correct Answer
verified

Exam 19: Heat Engines and Refrigerators

A heat engine with an efficiency of 30.0% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir?

Correct AnswerverifiedShow Answer

The temperature inside a Carnot refrigerator placed in a kitchen at 22.0°C is 2.0°C. The heat extracted from the refrigerator is 89 MJ/h. What power is needed to operate this refrigerator?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

What is the maximum theoretical efficiency possible for a heat engine operating between a reservoir in which ice and water coexist, and a reservoir in which water and steam coexist? The pressure is constant at 1.0 atmosphere for both reservoirs.

Correct AnswerverifiedA

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt, causing no appreciable change in the temperature of the bath water. Which one of the following statements is true?

Correct AnswerverifiedShow Answer

According to the second law of thermodynamics, the entropy of any system always increases.

Correct AnswerverifiedShow Answer

A Carnot engine operates between reservoirs at 550K and 300K, discarding 1500 J of heat in each cycle. (a) What is the engine's efficiency? (b) How much heat is supplied to the engine by the hot reservoir in each cycle?

Correct Answerverified(a) 45.5% ...View AnswerShow Answer

A Carnot cycle engine operates between a low temperature reservoir at 20°C and a high temperature reservoir at 800°C. If the engine is required to output 20.0 kJ of work per cycle, how much heat must the high temperature reservoir transfer to the engine during each cycle?

Correct AnswerverifiedShow Answer

A Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C. How much energy does it need to remove 2000 J of heat from the interior of the house?

Correct AnswerverifiedShow Answer

Is it possible to transfer heat from a hot reservoir to a cold reservoir?

Correct AnswerverifiedShow Answer

The compressor in a certain Carnot refrigerator performs 480 J of work to remove 150 J of heat from the interior of the refrigerator. How much heat must the coils behind the refrigerator discharge into the kitchen?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

An automobile engine takes in 4000 J of heat and performs 1100 J of mechanical work in each cycle. (a) Calculate the engine's efficiency. (b) How much heat is "wasted" in each cycle?

Correct Answerverified(a) 27.5% ...View AnswerShow Answer

Correct AnswerverifiedShow Answer

Correct Answerverified1350 J

At atmospheric pressure, 45 moles of liquid helium are vaporized at its boiling point of 4.22 K. The heat of vaporization of helium, at atmospheric pressure, is 2.09 × 104 J/kg, and the atomic weight of helium is 4.00 g/mol. The change in the entropy of the helium, as it vaporizes, is closest to

Correct AnswerverifiedA

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into a room per cycle. How much work is required in each cycle?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The entropy of an isolated system must be conserved, so it never changes.

Correct AnswerverifiedShow Answer

A 2.00 kg piece of lead at 40.0°C is placed in a very large quantity of water at 10.0°C, and thermal equilibrium is eventually reached. Calculate the TOTAL change in entropy that occurs during this process. The specific heat of lead is 130 J/(kg∙K) .

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
A

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
(a) 45.5% ...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
(a) 27.5% ...
View Answer

Correct Answer
verified

Correct Answer
verified
1350 J

At atmospheric pressure, 45 moles of liquid helium are vaporized at its boiling point of 4.22 K. The heat of vaporization of helium, at atmospheric pressure, is 2.09 × 10⁴ J/kg, and the atomic weight of helium is 4.00 g/mol. The change in the entropy of the helium, as it vaporizes, is closest to

Correct Answer
verified
A

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified