Deck 15: Thermodynamics

Question 1

1.00 mol of oxygen gas (O₂) is heated at a constant pressure of 1.00 atm from 10.0°C to 25.0°C. How much heat is absorbed by the gas?

A) 389 J
B) 544 J
C) 436 J
D) 288 J

Answer 1

436 J

Question 2

1.00 mol of oxygen gas (O₂) is heated at constant pressure of 1.00 atm from 10.0°C to 25.0°C. What is the work done by the gas during this expansion?

A) 159 J
B) 125 J
C) 102 J
D) 172 J

Answer 2

125 J

Question 3

10 joules of heat are transferred to a sample of ideal gas at constant pressure. As a result, the internal energy of the gas

A) increases by 10 J
B) increases by less than 10 J
C) increases by more than 10 J
D) remains unchanged.

Answer 3

increases by less than 10 J

Question 4

If 30 kJ of heat flows into a system and the internal energy increases by 15 kJ, then what is the work done by the system?

A) +85 kJ
B) +65 kJ
C) −65 kJ
D) +15 kJ
E) −15 kJ

Question 5

An ideal gas is in contact with a heat reservoir so that it remains at a constant temperature of 300.0 K. The gas is compressed from 24.0 L to 14.0 L. The mechanical device that operates the piston to compress the gas expends 5.00 kJ of energy. How much heat flows between from the heat reservoir to the gas?

A) −3.0 kJ
B) −5.1 kJ
C) −2.0 kJ
D) −5.0 kJ

Question 6

A toy steam engine has a mass of 1.00 kg. The toy starts from rest and reaches a velocity of 4.00 m/s in a time of 3.00 seconds while covering a distance of 4.50 meters. During that time the toy takes in 30 J of heat. What is the change in the internal energy of the toy?

A) −52.0 J
B) +52.0 J
C) −22 J
D) +22 J

Question 7

In the first law of thermodynamics (ΔU = Q + W), the variables Q and W stand for

A) the heat flow out of the system and the work done on the system.
B) the heat flow out of the system and the work done by the system.
C) the heat flow into the system and the work done by the system.
D) the heat flow into the system and the work done on the system.

Question 8

The internal energy of a system increases by 500 J while 610 J of work are performed on it. What was the heat flow into the system?

A) −1,110 J
B) 1,110 J
C) −110 J
D) 110 J

Question 9

If 30 kJ of heat flows out of a system and 15 kJ of work is done by the system, then what is the change in internal energy?

A) 85 kJ
B) 45 kJ
C) −45 kJ
D) 15 kJ
E) −15 kJ

Question 10

On a PV diagram where pressure is in atmospheres and V is in liters the area is measured in liter-atmospheres. What is the number of Joules in 1.00 liter-atmosphere?

A) 101.3
B) 83.1
C) 65.2
D) 22.4
E) 15.7

Question 11

When an ideal gas is compressed isothermally

A) the internal energy of the gas does not change.
B) the work done on the gas is zero.
C) heat flows into the gas.
D) the temperature of the gas increases.

Question 12

If 50 kJ of heat flows into a system and 35 kJ of work is done by the system, then what is the change in internal energy?

A) 85 kJ
B) 70 kJ
C) 65 kJ
D) 15 kJ
E) 10 kJ

Question 13

Using 0.0200 mol of an ideal monatomic gas, an isochoric process from state A (230 kPa, 1.0 L) to B (98 kPa, 1.0 L) results in what change in internal energy?

A) −200 J
B) +200 J
C) −375 J
D) +375 J

Question 14

1.00 mol of oxygen gas (O₂) is heated at constant pressure of 1.00 atm from 10.0°C to 25.0°C. From the first law, calculate the change of internal energy of the gas in this process.

A) 312 J
B) 291 J
C) 365 J
D) 155 J

Question 15

A system performs 800 J of work while taking in 500 J of heat. What is the change in internal energy of the system?

A) not possible.
B) 300 J
C) −300 J
D) 1,300 J
E) −1,300 J

Question 16

What physical quantity is represented by the area under a curve on a PV diagram where pressure is in Pa and volume is in m³?

A) Area in meters²
B) Work in Joules
C) Heat in Watts
D) Heat in Joules
E) Work in Calories

Question 17

When an ideal gas adiabatically expands

A) the temperature of the gas changes.
B) the internal energy of the gas does not change.
C) work is not done on or by the gas.
D) no heat is given off or taken in by the gas.

Question 18

A kilogram of water (c = 4.186 kJ/kg °C) is stirred using a 400−watt device for 5 minutes. At the end of this time the temperature of the water has increased by 15°C. How much heat was lost to the surroundings?

A) 90.1 kJ
B) 57.2 kJ
C) 82.6 kJ
D) 38.9 kJ

Question 19

1.00 mol of oxygen gas (O₂) is heated at constant pressure of 1.00 atm from 10.0°C to 25.0°C. What is the change of volume of the gas in this process?

A) 1.23 L
B) 0.86 L
C) 1.88 L
D) 2.09 L

Question 20

A monatomic ideal gas at 27°C undergoes an isobaric process from state A to B, followed by an isochoric process from state B to C. What is the total work done by the gas in these two processes? (A = 2 atm, 1 L; B = 2 atm, 2 L; C = 1 atm, 2 L)

A) 203 J
B) 231 J
C) 187 J
D) 195 J

Question 21

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

A) zero
B) 2.5 J
C) 5.0 J
D) 10 J

Question 22

A heat pump uses 100 J of work to output 150 J of heat at some temperature. What is the coefficient of performance for the heat pump?

A) 1.0
B) 1.5
C) 2.0
D) 2.5
E) 3.0

Question 23

A heat pump uses 100 J of work to output heat at some temperature. If the heat pump withdraws 60 J of heat from the lower temperature reservoir, then what is the coefficient of performance for the heat pump?

A) 1.6
B) 2.0
C) 2.4
D) 2.8

Question 24

A refrigerator uses 40.0 J of work to extract 90.0 J from a heat reservoir at 0.00°C. What is the coefficient of performance for the refrigerator?

A) 1.60
B) 2.05
C) 2.25
D) 2.85

Question 25

A heat pump uses 100 J of work to output 150 J of heat at some temperature. What is the heat that is withdrawn from some lower temperature?

A) 90 J
B) 75 J
C) 50 J
D) 25 J

Question 26

A engine goes through a cyclic process. During the cyclic process the engine does 600 J of work and has a heat output of 2,400 J. What is the efficiency of the engine?

A) 10%
B) 20%
C) 35%
D) 55%
E) 62%

Question 27

A heat engine has an efficiency of 25.0% and a power output of 600 W. What is the rate of heat input?

A) 1.8 kW.
B) 2.0 kW.
C) 2.4 kW.
D) 3.0 kW.

Question 28

A engine goes through a cyclic process. During the cyclic process the engine takes in 3,200 J of heat and has a heat output of 2,400 J. What is the efficiency of the engine?

A) 10%
B) 15%
C) 25%
D) 40%
E) 52%

Question 29

A very efficient engine has the following characteristics-combustion = 1,900°C, exhaust = 430°C, 5.0 × 10⁶ cal of fuel produces 1.4 × 10⁷ J of work in one hour. What is the output in hp? (1 hp = 745.7 W)

A) 5.2 hp
B) 8.1 hp
C) 7.3 hp
D) 6.3 hp

Question 30

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

A) zero
B) −5.0 J
C) +5.0 J
D) None of these choices are correct.

Question 31

An engine takes in 150 J of energy from a 400 K thermal source. If the engine discharges energy into a thermal reservoir at 150 K, then what is the maximum amount of work one can get out of the engine?

A) 93.8 J
B) 84.2 J
C) 28.5 J
D) 168 J

Question 32

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?

A) zero
B) 52.5 J
C) 97.5 J
D) 150 J

Question 33

In an isochoric process, the internal energy of a system decreases by 50 J. What is the work done on the system?

A) zero
B) +50 J
C) −50 J
D) None of these choices are correct.

Question 34

An engine delivers 40.0 J of work while it takes in energy from a 400 K thermal source. If the engine discharges energy into a thermal reservoir at 200 K, then what is the least amount of heat needed to run the engine?

A) 55.0 J
B) 65.0 J
C) 80.0 J
D) 110 J

Question 35

When the first law of thermodynamics is applied to an ideal gas that is taken through an isothermal process

A) ΔU = 0.
B) W = 0.
C) Q = 0.
D) None of these choices are correct.

Question 36

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

A) zero
B) 52.5 J
C) 97.5 J
D) 150 J

Question 37

In an isochoric process, the internal energy of a system decreases by 50 J. What is the heat flow to the system?

A) zero
B) +50 J
C) −50 J
D) none of the above

Question 38

A heat pump uses 200 J of work to output 300 J of heat into a heat reservoir at 200 K. What is the coefficient of performance for the heat pump?

A) 1.0
B) 1.5
C) 2.5
D) 2.8

Question 39

10 joules of heat are transferred to a sample of ideal gas at constant volume. As a result, the internal energy of the gas

A) increases by 10 J
B) increases by less than 10 J
C) increases by more than 10 J
D) remains unchanged.

Question 40

A refrigerator uses 40 J of work to extract heat from a heat reservoir at 0.00°C. If the coefficient of performance of the refrigerator is 2.1, then how much heat is extracted from the heat reservoir at 0.00°C?

A) 48 J
B) 65 J
C) 84 J
D) 90 J

Question 41

It can be shown that the change in entropy in heating or cooling a sample is given by the relation ΔS = mc ln (T_F/T_i), where m is the mass of the sample, c is the specific heat of the sample, and T_F and T_i are the final and initial temperatures, respectively. What is the change in entropy when 20.0 grams of aluminum with a specific heat of 0.900 J/g K is heated from 10.0°C to 60.0°C?

A) +2.93 J/K
B) +2.50 J/K
C) 0 J/K
D) −2.93 J/K

Question 42

According to the second law of thermodynamics, for any process that may occur within an isolated system, which answer applies?

A) entropy remains constant
B) entropy increases (or stays the same)
C) entropy decreases (or stays the same)
D) depends on the rate of change of the process

Question 43

120 J of heat flows by thermal conduction from 100°C to 0.00°C. What is the net change in entropy for this process?

A) 0.034 J/K
B) 0.118 J/K
C) 0.201 J/K
D) 0.338 J/K

Question 44

2.00 moles of an ideal gas freely expands from 1.50 liters to 4.00 liters. The change in entropy in the expansion is

A) 5.80 J/K
B) 8.50 J/K
C) 16.3 J/K
D) 18.7 J/K

Question 45

When 2.000 kg of water evaporates, 22.60 × 10⁵ J/kg of heat are needed. What is the entropy change of the water in the boiling process?

A) 12,120 J/K
B) 8,566 J/K
C) 6,750 J/K
D) 5,844 J/K

Question 46

A refrigerator uses 40.0 J of work to extract heat from a heat reservoir at 0.00°C. If the coefficient of performance of the refrigerator is 2.10, then how much heat is discharged out of the refrigerator at a higher temperature?

A) 52.0 J
B) 66.0 J
C) 86.0 J
D) 124 J

Question 47

1.50 moles of an ideal gas freely expands from 1.00 liter to 4.50 liters. The change in entropy of the gas in the expansion is

A) 5.80 J/K
B) 8.50 J/K
C) 16.3 J/K
D) 18.7 J/K

Question 48

A heat pump takes in 60.0 J of energy from a 250 K thermal reservoir outside a house and discharges heat energy into a 350 K thermal reservoir inside a house. What is the minimum amount of work needed to make the pump work?

A) 17.2 J
B) 24.0 J
C) 52.0 J
D) 65.0 J

Question 49

It can be shown that the change in entropy in heating or cooling a sample is given by the relation ΔS = mc ln (T_F/T_i), where m is the mass of the sample, c is the specific heat of the sample, and T_F and T_i are the final and initial temperatures, respectively. What is the change in entropy when 10.0 grams of lead with a specific heat of 0.452 J/g K is heated from 10.0°C to 50.0°C?

A) 0.45 J/K
B) 0.60 J/K
C) 0.90 J/K
D) 0.30 J/K

Question 50

It can be shown that the change in entropy in heating or cooling a sample is given by the relation ΔS = mc ln (T_F/T_i), where m is the mass of the sample, c is the specific heat of the sample, and T_F and T_i are the final and initial temperatures, respectively. What is the change in entropy when 20.0 grams of aluminum with a specific heat of 0.900 J/g K is cooled from 60.0°C to 10.0°C?

A) +2.93 J/K
B) +2.50 J/K
C) 0.00 J/K
D) −2.93 J/K

Question 51

A refrigerator extracts 65 J of heat from a heat reservoir at 0.00°C. If the coefficient of performance of the refrigerator is 2.5, then how much work is needed to run the refrigerator?

A) 26 J
B) 48 J
C) 75 J
D) 90 J

Question 52

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

A) 4 kJ
B) 20 kJ
C) 24 kJ
D) 44 kJ

Question 53

One mole of an ideal gas freely expands from 1.00 liter to 2.00 liters. The change in entropy of the gas in the expansion is

A) 5.80 J/K
B) 8.50 J/K
C) 16.3 J/K
D) 18.7 J/K

Question 54

A container of ideal gas at 0°C and 1 atm undergoes an isothermal expansion, and its entropy changes by 3.7 J/K. How much work does it do?

A) zero
B) 1.0 × 10³ J
C) −1.0 × 10³ J
D) None of these choices are correct.

Question 55

A heat pump takes in energy from a 250 K thermal reservoir outside a house and discharges 140 J of energy into a 350 K thermal reservoir inside a house. What is the minimum amount of work needed to make the pump work?

A) 67 J
B) 50 J
C) 40 J
D) 37 J

Question 56

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and rejects 24 kJ into the room per cycle. What is the coefficient of performance?

A) 0.17
B) 0.2
C) 1.2
D) 5
E) 6

Question 57

When water freezes, the entropy of the water

A) increases.
B) decreases.
C) does not change.
D) depending on other factors could increase or decrease.

Question 58

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

A) 25%.
B) 45%.
C) 55%.
D) 75%.

Question 59

When 1.000 kg of ice melts, 33.00 × 10⁴ J/kg of heat are needed. What is the entropy change of the ice in the melting process?

A) 758.0 J/K
B) 1,209 J/K
C) 1,684 J/K
D) 2,316 J/K

Question 60

A refrigerator extracts 65.0 J of heat from a heat reservoir at 0.00°C. If the coefficient of performance of the refrigerator is 2.50, then how much heat is discharged out of the refrigerator?

A) 125 J
B) 91.0 J
C) 75.0 J
D) 55.0 J

Question 61

A heat pump is used to heat a house in Minnesota in the winter and has half the ideal coefficient of performance for a reversible heat pump. If the outside air temperature is −15°C and the indoor temperature desired is 20°C, what is its coefficient of performance under these conditions?

A) 3.7
B) 1.1
C) 2.0
D) 4.2

Question 62

A friend tells you that he knows of a situation in which heat is passed from one body to another body with a higher temperature. He explains that he thinks the 2nd law of thermodynamics must have been violated. Is he correct?

A) No. If the temperature difference is small enough, heat can spontaneously flow from the cooler to the hotter body.
B) Yes. Heat cannot pass from a cooler body to a hotter body.
C) No. He forgot that if external work is done on the system this is possible.
D) No. The cooler body can give up energy to the hotter body by radioactivity or another natural process.

Question 63

100 coins are tossed randomly onto a table. The macrostate is defined as the number of heads that appear after the toss. A microstate is a specification of the outcome of each individual coin. What is the value for the number of heads that has the greatest number of possible microstates?

A) 95
B) 75
C) 60
D) 50

Question 64

An engineer uses a river (minimum temperature of 4°C) to cool his electrical plant, which heats water with a boiler operating at 220°C. His boiler uses 420 kW of energy to heat water to steam. What is the maximum power output under ideal circumstances?

A) 230 kW
B) 184 kW
C) 330 kW
D) 416 kW

Question 65

A system in a certain macrostate has 1.2 × 10³ microstates. Through some process, the system changes the number of microstates to 3 × 10⁴. What is the change in entropy for the process?

A) 1.1 × 10⁻²³ J/K
B) 2.1 × 10⁻²³ J/K
C) 4.4 × 10⁻²³ J/K
D) 5.6 × 10⁻²³ J/K

Question 66

An ideal, reversible refrigerator keeps food in the freezer portion at −15°C and dumps excess heat into the kitchen, whose temperature is 20°C. What is the refrigerator's coefficient of performance under these conditions?

A) 7.4
B) 4.0
C) 8.4
D) 2.1

Question 67

An engineer wants to use a river (minimum temperature of 4°C) to cool his electrical plant, which heats water with a boiler operating at 220°C. If he wishes to produce 185 kW of power using this plant, what is the minimum power he must supply to his boiler if it is maximally efficient?

A) 233 kW
B) 187 kW
C) 332 kW
D) 422 kW

Question 68

A refrigerator keeps food in the freezer portion at −15°C and dumps excess heat into the kitchen, whose temperature is 22°C. If the refrigerator has half the coefficient of performance of an ideal reversible refrigerator, and if its motor consumes 250 W of power, what is the rate of heat flow out of the freezer portion of the refrigerator?

A) 340 W
B) 870 W
C) 1,100 W
D) 630 W

Question 69

For a system undergoing an adiabatic process,

A) Q = ΔU
B) Q = −ΔU
C) Q = −W
D) Q = 0
E) Q = W

Question 70

A friend tells you that he knows of a situation in which bowl of ice sitting by itself on a table in a room whose air temperature is 20°C gives up heat to the surrounding air. What's wrong with this concept?

A) It would violate the 0^th law of thermodynamics
B) It would violate the 1^st law of thermodynamics
C) It would violate the 2^nd law of thermodynamics
D) It would violate the 3^rd law of thermodynamics

Question 71

Four coins are tossed randomly onto a table. The macrostate is defined as the number of heads showing, which can be 0, 1, 2, 3, or 4. A microstate is a specification of the outcome of each individual coin. What value for the number of heads has the greatest number of possible microstates?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 72

An engineer uses a river (which averages 4°C) to cool his electrical plant, which heats water with a boiler operating at 750°C. What's the maximal performance (in terms of efficiency) theoretically possible for this electrical plant?

A) 64%
B) 36%
C) 27%
D) 73%

Question 73

For an ideal gas undergoing an isothermal expansion, the work done on the gas is

A) May be either, depending on the temperature
B) Positive
C) Zero
D) Negative

Question 74

On a PV diagram, for a curve representing an isothermal compression of an ideal gas, what is the relationship between the initial P value and the final P value?

A) The initial is greater than the final.
B) The initial is less than the final.
C) They may be either-it depends on the temperature of the process.
D) They may be the same.

Question 75

An ideal reversible heat pump is used to heat a house in Minnesota in the winter. If the outside air temperature is −15°C and the indoor temperature desired is 20°C, what is the expected coefficient of performance for the heat pump under these conditions?

A) 2.1
B) 8.4
C) 7.4
D) 4.0

Question 76

A system in a certain macrostate has 2 × 10²³ microstates. Through some process, the system changes the number of microstates to 3 × 10²³. What is the change in entropy for the process?

A) 2.5 × 10²³ J/K
B) 1.2 × 10¹³ J/K
C) 4.2 × 10⁻¹⁰ J/K
D) 5.6 × 10⁻²⁴ J/K

Question 77

A heat pump is used to heat a house in Minnesota in the winter and has half the ideal coefficient of performance for a reversible heat pump. If the outside air temperature is −15°C and the indoor temperature desired is 20°C, and if it inputs work at a rate of 1,250 W, what is the rate of heat flow into the house?

A) 5,230 W
B) 1,100 W
C) 625 W
D) 300 W

Question 78

Two coins are tossed randomly onto a table. The macrostate is defined as the number of heads showing, which can be 0, 1, or 2. A microstate is a specification of the outcome of each individual coin. What value for the number of heads has the greatest number of possible microstates?

A) 0
B) 1
C) 2

Question 79

For a system undergoing an isothermal process,

A) Q = −ΔU
B) Q = 0
C) Q = ΔU
D) Q = −W
E) Q = W

Question 80

A refrigerator keeps food in the freezer portion at −15°C and dumps excess heat into the kitchen, whose temperature is 20°C. If the refrigerator has half the coefficient of performance of an ideal reversible refrigerator, what is the refrigerator's coefficient of performance under these conditions?

A) 1.1
B) 4.2
C) 2.0
D) 3.7