Chapter 15

Question 1

In an isothermal process, there is no change in ________

Answer 1

temperature

Question 2

A gas is expanded to twice its original volume with no change in its temperature. This process is ________

Answer 2

isothermal

Question 3

An ideal gas is compressed to one-half its original volume during an isothermal process. The final pressure of the gas ________

Answer 3

increases to twice its original value

Question 4

A gas is quickly compressed in an isolated environment. During the event, the gas exchanged no heat with its surroundings. This process is ________

Answer 4

adiabatic

Question 5

The process shown on the PV diagram is an ________

Answer 5

isobaric expansion

Question 6

When water freezes, the entropy of the water ________

Answer 6

decreases

Question 7

During an isothermal process, 5.0 J of heat is removed from an ideal gas. What is the change in internal energy of the gas?

Answer 7

zero

Question 8

During an isothermal process, 5.0 J of heat is removed from an ideal gas. What is the work done by the gas in the process?

Answer 8

-5.0 J

Question 9

An ideal gas undergoes an adiabatic process while doing 25 J of work. What is the change in internal energy?

Answer 9

-25 J

Question 10

A heat engine receives 7000 J of heat and loses 3000 J in each cycle. What is the efficiency?

Answer 10

57%

Question 11

A heat engine has an efficiency of 35.0% and receives 150 J of heat per cycle. How much work does it perform in each cycle?

Answer 11

52.5 J

Question 12

What is the Carnot efficiency of an engine which operates between 450 K and 310 K?

Answer 12

31%

Question 13

What is the maximum theoretical efficiency possible for an engine operating between 100°C and 400°C?

Answer 13

45%

Question 14

What is the change in entropy when 50 grams of ice melt at 0°C?

Answer 14

60.9 J/K

Question 15

What is the change in entropy when 100 g of water at 10°C is mixed with 100 g of water at 40°C?

Answer 15

1.0 J/K

Question 16

What is the change in entropy when 1 kg of water at 0°C is mixed with 3 kg of water at 20°C?

Answer 16

7.7 J/K

Question 17

1.0 kg of steam at 100°C condenses to water at 100°C. What is the change in entropy in the process?

Answer 17

-6.1 x 10^3 J/K

Question 18

On a very hot day, could you cool your kitchen by leaving the refrigerator door open?

Answer 18

No, the refrigerator would exhaust more heat into the room than it takes out of the room.

Question 19

In the closed thermodynamic cycle shown in the PV diagram, the total work done by the gas during a complete cycle is:

Answer 19

postive

clockwise closed cycle = positive total work
counter-clockwise closed cycle = negative total work

Question 20

Answer 20

Question 21

A heat engine exhausts 7800 J of heat while performing 2600 J of useful work. What is the efficiency of this engine?

Answer 21

Question 22

Which of the following is the best example of a reversible process?

Answer 22

A block of metal surrounded by water at a slightly higher temperature slowly heats up.

• a reversible process is carried out slow enough that is could be considered a series of equilibrium states

Question 23

A Carnot engine’s operating temperatures are 210°C and 45°C. The engine’s power output is 950 W. Calculate the rate of heat output.

Answer 23

Question 24

Answer 24

an irreversible heat engine

*efficiency is smaller than the Carnot engine efficiency so it must be an irreversible heat engine

Question 25

A restaurant refrigerator has a coefficient of performance of 5.0. If the temperature in the kitchen outside the refrigerator is 32°C, what is the lowest temperature that could be obtained inside the refrigerator if it were ideal? | * Coefficient of performance (COP)

Answer 25

Question 26

What is the COP of a Carnot heat pump used to remove heat from ice at 0.0°C and add heat to a room at 20.0°C?

Answer 26

14.7 293 K/20 K = 14.7

Question 27

Totoal change in entropy for a reversible process is:

Answer 27

zero

Question 28

If 0.45 kg of water at 100°C is changed by a reversible process to steam at 100°C, determine the change in entropy of (a) the water, (b) the surroundings, and (c) the universe as a whole. (d) How would your answer differ if the process were irreversible?

Answer 28

Question 29

The second law of thermodynamics leads us to conclude that:

Answer 29

disorder in the universe is increasing with the passage of time.

Question 30

If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other

Answer 30

Zeroth Law

Question 31

The change in internal energy of a system equals the heat that flows into or out of it minus the work done by the system (conservation of energy)

Answer 31

First Law

Question 32

For any real process, the entropy of any isolated system always increases

Answer 32

Second Law

Question 33

The entropy of a system approaches a constant minimum value as the temperature approaches absolute zero.

Answer 33

Third Law *absolute zero is impossible to reach through real processes