Deck 18: The Laws of Thermodynamics

Question 1

The entropy of the universe remains constant during a reversible adiabatic change.

Answer 1

True

Question 2

Neither heat nor work are state functions.

Answer 2

True

Question 3

In the first law of thermodynamics, Q is the heat gained by the system, that is, Q is positive if the system gains heat.

Answer 3

True

Question 4

On a hot day, you open the refrigerator and experience a refreshing feeling when the cool air comes in contact with your body. You think to yourself "I think that I'll just keep the refrigerator door open and stand in front of the refrigerator all day today to stay cool. I might even bring a chair." Will this work?
Explain why or why not.

Question 5

State the Second Law of Thermodynamics.

Question 6

Internal energy is a state function.

Question 7

If a thermometer measures the temperature of two objects as being equal, you can conclude that the objects will be in thermal equilibrium if they are brought into thermal contact.

Question 8

Which has the larger entropy:
a gas that occupies only half of a container, with the other half a vacuum, or the same gas occupying the entire container?

Question 9

State the Zeroth Law of Thermodynamics.

Question 10

If a thermometer measures the temperature of two objects as being equal, you can conclude that if the objects are placed in thermal contact, no heat will flow between them.

Question 11

The entropy of the surroundings remains constant during an adiabatic change even if the change is irreversible.

Question 12

State the Third Law of Thermodynamics

Question 13

State the First Law of Thermodynamics.

Question 14

The pressure falls more rapidly in a quasi-static, adiabatic process than along an isotherm when the volume of the gas is increased.

Question 15

All reversible engines operating between the same two temperatures have the same efficiency.

Question 16

Entropy is a state function.

Question 17

In the first law of thermodynamics, W is the work done on the system, that is, W is positive if work is done on the system.

Question 18

The entropy of a system remains constant during an adiabatic change even if the change is irreversible.

Question 19

Order in one part of the universe can only be produced at the expense of disorder in another part.

Question 20

A Diesel engine uses adiabatic heating to ignite the fuel.

Question 21

For an ideal monatomic gas,

A) C_p = C_v.
B) C_p > C_v.
C) C_p < C_v.
D) More information is needed to answer this question.

Question 22

FIGURE 18-1
An ideal monatomic gas undergoes the reversible expansion shown in the Figure 18-1, where V₂ = 5V₁ and P₂ = 3P₁. How much heat is gained by the gas in this process, in terms of the initial pressure and volume?

A) 14 P₁V₁
B) 7 P₁V₁
C) 21 P₁V₁
D) 15 P₁V₁
E) 29 P₁V₁

Question 23

A monatomic ideal gas is compressed isothermically to one-third of its initial volume. The resulting pressure will be

A) three times as large as the initial value.
B) less than three times as large as the initial value.
C) more than three times as large as the initial value.
D) equal to the initial value.
E) impossible to predict on the basis of this data.

Question 24

The molar specific heat is the amount of heat required to raise the temperature of what amount of matter by one unit of temperature?

A) one tooth
B) one unit of mass of a material
C) one mole of a substance
D) two moles of a substance
E) one molecule of a substance

Question 25

FIGURE 18-1
An ideal monatomic gas undergoes the reversible expansion shown in Figure 18-1, where V₂ = 5V₁ and P₂ = 3P₁. What is the change in internal energy of the gas in this process, in terms of the initial pressure and volume?

A) 7 P₁V₁
B) 14 P₁V₁
C) 21 P₁V₁
D) 15 P₁V₁
E) 29 P₁V₁

Question 26

When objects at different temperatures are brought into thermal contact with one another, the resulting spontaneous flow of heat proceeds from the object with the higher

A) thermal conductivity to the one with the lower thermal conductivity.
B) specific heat to the one with the lower specific heat.
C) heat capacity to the one with the lower capacity.
D) temperature to the one with the lower temperature.
E) impossible to predict on the basis of this data.

Question 27

In a given reversible process, the temperature of an ideal gas is kept constant as the gas is compressed to a smaller volume. Select the true statement from among the following:

A) The gas must absorb heat from its surroundings.
B) The gas must release heat to its surroundings.
C) The pressure of the gas also stays constant.
D) The process is adiabatic.
E) It is impossible to predict on the basis of this data.

Question 28

When a gas expands adiabatically,

A) the internal energy of the gas decreases.
B) the internal energy of the gas increases.
C) there is no work done by the gas.
D) work is done on the gas.
E) heat flows out of the system.

Question 29

From the following statements regarding the ratio of the molar specific heat at constant pressure to the molar specific heat at constant volume, C_p/C_v, the only correct one for an ideal monatomic gas is

A) = 1.
B) > 1.
C) < 1.
D) C_p/C_v is sometimes more than 1, sometimes less than 1, but never equal to 1.
E) C_p/C_v is sometimes more than 1, sometimes equal to 1, but never less than 1.

Question 30

An ideal monatomic gas undergoes a reversible expansion to 1.5 times its original volume. In which of these processes does the gas perform the most work?

A) at constant pressure
B) if the pressure increases in proportion to the volume
C) if the pressure decreases in proportion to the volume
D) at constant temperature
E) adiabatically

Question 31

A monatomic ideal gas is compressed isobarically to one-third of its initial volume. The resulting pressure will be

A) three times as large as the initial value.
B) equal to the initial value.
C) more than three times as large as the initial value.
D) equal to the initial value..
E) impossible to predict on the basis of this data.

Question 32

An ideal monatomic gas undergoes a reversible expansion to 1.5 times its original volume. In which of these processes does the gas have the largest loss of internal energy?

A) at constant pressure
B) if the pressure increases in proportion to the volume
C) if the pressure decreases in proportion to the volume
D) at constant temperature
E) adiabatically

Question 33

Two identical samples of a monatomic gas are initially at pressure P and occupy volume V. You perform two experiments which will both lead to the gas samples being compressed to final volumes one-third as large as their initial volumes. In one of the experiments you make the gas undergo an isothermal compression. In the second you make the gas undergo an adiabatic compression. It is correct to say that:

A) The isothermal compression leads to a higher final pressure than the adiabatic compression and the gas exchanges heat with its surroundings.
B) The adiabatic compression leads to a higher final pressure than the isothermal compression and the gas does not exchange heat with its surroundings.
C) The isothermal compression leads to a lower final pressure than the isothermal compression and the gas does not exchange heat with its surroundings.
D) The adiabatic compression leads to a lower final pressure than the isothermal compression and the gas exchanges heat with its surroundings.
E) It is impossible to predict on the basis of this data.

Question 34

What is meant by "the heat death of the universe"?

A) The universe will end in a giant inferno.
B) The universe will reach thermal equilibrium.
C) Some day the sun will explode and we will all burn.
D) Some day the sun will cease to provide electromagnetic radiation.
E) The radiation from the stars will continuously heat up the universe.

Question 35

A monatomic ideal gas is compressed adiabatically to one-third of its initial volume. The resulting pressure will be

A) three times as large as the initial value.
B) less than three times as large as the initial value.
C) more than three times as large as the initial value.
D) equal to the initial value.
E) impossible to predict on the basis of this data.

Question 36

For water at 2°C,

A) C_p = C_v.
B) C_p > C_v.
C) C_p < C_v.
D) More information is needed to answer this question.

Question 37

An ideal monatomic gas undergoes a reversible expansion to 1.5 times its original volume. In which of these processes does the gas perform the least amount of work?

A) at constant pressure
B) if the pressure increases in proportion to the volume
C) if the pressure decreases in proportion to the volume
D) at constant temperature
E) adiabatically

Question 38

If a system undergoes a reversible process,

A) it must be possible to restore the system to its original state.
B) it must be possible to restore the surroundings to their original state.
C) it must be possible to restore both the system and the surroundings to their original states.
D) it is impossible to restore either the the system or the surroundings to their original states.
E) the system must not interact with its surroundings.

Question 39

An ideal monatomic gas undergoes an isothermal expansion. It is correct to affirm that its entropy

A) decreases.
B) remains unchanged.
C) increases.
D) cannot be predicted with the data given.

Question 40

A certain gas is compressed adiabatically. The amount of work done on the gas is 800 J. What is the change in the internal energy of the gas?

A) 800 J
B) -800 J
C) 400 J
D) 0 J
E) More information is needed to answer this question.

Question 41

1.50 moles of an ideal monatomic gas are initially at a temperature of 317 K. If the gas gains 2730 J of heat and performs 780 J of work, what is its final temperature?

A) 359 K
B) 421 K
C) 526 K
D) 687 K
E) 756 K

Question 42

A refrigerator has a COP of 2.5. If it removes 7.7 MJ of heat in 25. minutes,
(a) what is the minimum power motor to operate the refrigerator?
(b) what is its efficiency if it were a reversible engine?

Question 43

What is the change in entropy of the lead when 2.0 kg of molten lead solidifies?
[Data:
L_v = 207. kcal/kg at 1744.°C; L_f = 5.9 kcal/kg at 328.°C]

Question 44

FIGURE 18-3
An ideal gas undergoes the process a→b→c→a shown in Figure 18-3. P_a = P_c = 240 kPa, V_b = V_c = 40 L, V_a = 15 L, and P_b = 400 kPa. How much heat is gained by the system in this process?

A) 1000 J
B) 1500 J
C) 2000 J
D) 2500 J
E) 3000 J

Question 45

A heat engine absorbs 64 kcal of heat each cycle and exhausts 42 kcal.
(a) Calculate the efficiency each cycle.
(b) Calculate the work done each cycle.

Question 46

Which of the following is a statement of the third law of thermodynamics?

A) If two objects are in equilibrium with a third, then they are in thermal equilibrium with one another.
B) The entropy of the universe cannot decrease.
C) The entropy of the universe cannot increase.
D) All reversible engines operating between the same two temperatures have the same efficiency.
E) It is impossible to lower the temperature of an object to absolute zero in a finite number of steps.

Question 47

FIGURE 18-3
An ideal gas undergoes the process a→b→c→a shown in Figure 18-3. P_a = P_c = 360.0 kPa, V_b = V_c = 68.00 L, V_a = 35.00 L, and P_b = 560.0 kPa. How much work is done by the system in this process?

A) 2300 J
B) 3300 J
C) 2800 J
D) 3800 J
E) 3000 J

Question 48

FIGURE 18-3
An ideal gas undergoes the process a→b→c→a shown in Figure 18-3. The heat gained in process a→b is 546 J, while in process b→c the system loses 62 J. In process a→b the system performs 310 J of work, while in process c→a work is done on the system in the amount of 223 J. How much heat is gained by the system in process c→a?

A) - 397 J
B) - 62 J
C) 223 J
D) 18 J
E) - 236 J

Question 49

One of the most efficient engines built so far has the following characteristics:
combustion chamber temperature = 1900°C; exhaust temperature = 430°C. 7.0 × 10⁹ cal of fuel produces
1.4 × 10¹⁰ J of work in one hour. What is the power output, in hp, of this engine?

Question 50

A reversible engine takes in 555. Joules per second and exhausts 482. watts.
(a) How much power does it produce?
(b) What is its efficiency?
(c) If operated in reverse as a refrigerator, what would be its COP?

Question 51

FIGURE 18-2
Referring to Figure 18-2, a substance carried from point A to B absorbs 50. J and finds its internal energy has increased by 20. J. Going from B to C the internal energy decreases by 5. Joules.
(a) How much work was done from A to B?
(b) How much heat was absorbed from B to C?
(c) How much work was done going from B to C?

Question 52

An engine on each cycle takes in 40. Joules, does 10. Joules of work, and expels 30. J of heat. What is its efficiency?

Question 53

What is the change of entropy of water (L_f = 0.333 MJ/kg, L_v = 2.26 MJ/kg) when 450. grams of water:
(a) changes from liquid to steam?
(b) changes from ice to liquid?

Question 54

One of the most efficient engines built so far has the following characteristics:
combustion chamber temperature = 1900°C, exhaust temperature = 430°C, 7.0 × 10⁹ cal of fuel produces 1.4 × 10¹⁰ J of work in one hour.
(a) What is the actual efficiency of this engine?
(b) What is the Carnot efficiency of the engine?
(c) What is the power output, in hp, of this engine?

Question 55

An athlete doing push-ups performs 650 kJ of work and loses 425 kJ of heat. What is the change in the internal energy of the athlete?

A) -225 kJ
B) -1075 kJ
C) 1075 kJ
D) 225 kJ
E) 276 kJ

Question 56

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

Question 57

If the efficiency of a reversible engine is 28.%,
(a) what is its COP operated as a refrigerator?
(b) what is its COP operated as a heat pump?

Question 58

An inventor tries to sell you his new engine which takes in 40. Joules of heat at 87°C on each cycle, expels 30. Joules at 27°C, and does 10. Joules of work. Why are you not fooled, and can have him prosecuted as a fraud?

Question 59

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

Question 60

A gas expands from an initial volume of 30.0 L to a final volume of 65.0 L at a constant pressure of 110 kPa. How much work is done by the gas?

A) 3.85 kJ
B) 10.4 kJ
C) 3850 kJ
D) 10.4 MJ
E) 3.85 MJ

Question 61

An expandable container holds 2.30 mole of He gas with an initial pressure of 770 kPa and an initial volume of 2.10 L. The gas expands isothermally to a final pressure of 350 kPa. How much heat is gained by the gas in this process?

A) 1280 J
B) 792 J
C) 685 J
D) 1370 J
E) 1700 J

Question 62

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

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

Question 63

A monatomic ideal gas with an initial pressure of 500 kPa and an initial volume of 1.80 L expands isothermally to a final volume of 5.20 L. How much work is done on the gas in this process?

A) 955 J
B) 900 J
C) 875 J
D) 1570 J
E) 1700 J

Question 64

700 J of heat are added to 12 moles of an ideal monatomic gas at constant volume. What is the change in temperature?

A) 4.7 K
B) 5.2 K
C) 5.8 J
D) 6.8 K
E) 9.3 K

Question 65

A certain ideal gas has a molar specific heat at constant volume C_v = 7R/5. What is its molar specific heat at constant pressure?

A) 12R/5
B) 7R/3
C) 12R/7
D) 12R/5.
E) 4R

Question 66

A monatomic ideal gas expands adiabatically from an initial volume of 72 L and an initial temperature of 350 K until its temperature falls to 290 K. What is the final volume of the gas?

A) 95 L
B) 98 L
C) 101 L
D) 104 L
E) 142 L

Question 67

20.0 L of a monatomic ideal gas at a pressure of 100 kPa expand adiabatically until the volume doubles. What is the pressure in the gas at that point?

A) 31.5 kPa
B) 50.0 kPa
C) 200 kPa
D) 317 kPa
E) 400 kPa

Question 68

A certain ideal gas has a value of γ = 4/3. What is its molar specific heat at constant pressure?

A) 5R/2
B) 2R
C) 3R
D) 7R/2
E) 4R

Question 69

A monatomic ideal gas at an initial temperature of 390 K is compressed adiabatically from an initial volume of 120 L to a final volume of 40.0 L. What is the final temperature of the gas?

A) 124 K
B) 811 K
C) 610 K
D) 775 K
E) 820 K

Question 70

4.00 moles of a monatomic ideal gas at a temperature of 340 K are compressed adiabatically from an initial volume of 70.0 L to a final volume of 30.0 L. What is the final pressure in the gas?

A) 663 kPa
B) 581 kPa
C) 106 kPa
D) 42.1 MPa
E) 2.17 MPa

Question 71

A gas expands from an initial volume of 0.040 m³ and an initial pressure of 210 kPa to a final volume of 0.065 m³ while its temperature is kept constant. How much work is done by the system?

A) 3.7 kJ
B) 4.1 kJ
C) 5.3 kJ
D) 5.6 kJ
E) 7.9 kJ

Question 72

A certain engine extracts 1300 J of heat from a hot temperature reservoir and discharges 700 J of heat to a cold temperature reservoir. What is the efficiency of this engine?

A) 46%
B) 54%
C) 86%
D) 27%
E) 13%

Question 73

2.50 moles of a monatomic ideal gas expand adiabatically from an initial temperature of 300 K and an initial volume of 80.0 L to a final volume of 150 L. What is the final temperature of the gas?

A) 840 K
B) 563 K
C) 426 K
D) 287 K
E) 197 K

Question 74

How much heat is required to raise the temperature of 2 moles of an ideal monatomic gas by 10 C° at constant volume?

A) 249 J
B) 416 J
C) 208 J
D) 200 J
E) 125 J

Question 75

How much heat is required to increase the temperature of 1.70 moles of an ideal monatomic gas by 23.0 K at constant pressure?

A) 812 J
B) 346 J
C) 751 J
D) 391 J
E) 290 J

Question 76

A gas expands from an initial volume of 0.040 m³ to a final volume of 0.085 m³ while its pressure increases linearly with the volume (so that the process follows a straight-line path in a P-V diagram) from 110 kPa to 225 kPa. How much work is done by the system?

A) 5.2 kJ
B) 7.5 kJ
C) 7.8 kJ
D) 11 kJ
E) 12 kJ

Question 77

A 40.0-L container is divided into two equal parts by a rubber membrane. One half of the container has 1.50 moles of an ideal monatomic gas at 250 K, and the other half is a vacuum. The container is well insulated, so there is no exchange of heat with the surroundings. The membrane breaks, and eventually the gas reaches a new equilibrium condition occupying the entire volume. What is the final temperature of the gas?

A) 100 K
B) 125 K
C) 157 K
D) 180 K
E) 250 K

Question 78

A gas expands at constant temperature from an initial volume of 0.040 m³ and an initial pressure of 210 kPa until its pressure drops to 135 kPa. How much work is done by the system?

A) 3.0 kJ
B) 3.7 kJ
C) 4.1 kJ
D) 5.6 kJ
E) 7.9 kJ

Question 79

3.0 moles of gas expand from an initial volume of 0.040 m³ to a final volume of 0.085 m³ while the temperature of the gas is kept fixed at 300 K. How much work is done by the system?

A) 5.6 kJ
B) 6.6 kJ
C) 7.6 kJ
D) 8.6 kJ
E) 14 kJ

Question 80

A reversible engine operating between 500 K and 300 K has the same efficiency as a reversible engine operating between 400 K and what lower temperature?

A) 200 K
B) 220 K
C) 240 K
D) 260 K
E) 280 K