Deck 21: Thermodynamics

Question 1

The perpetual motion machine of the first kind is

A) a device that extracts thermal energy from a heat source and converts it into mechanical energy.
B) a device that supplies endless output of work without input of fuel.
C) a Carnot engine.
D) none of the above.

Answer 1

a device that supplies endless output of work without input of fuel.

Question 2

The perpetual motion machine of the second kind is

A) a device that extracts thermal energy from a heat source and converts it into mechanical energy.
B) a device that supplies endless output of work without input of fuel.
C) a Carnot engine.
D) none of the above.

Answer 2

a device that extracts thermal energy from a heat source and converts it into mechanical energy.

Question 3

The metric unit associated with the amount of heat transferred, Q, is

A) watt.
B) Btu.
C) joule.
D) newton.

Answer 3

joule.

Question 4

The metric unit associated with entropy is

A) joule/kelvin.
B) joule.
C) joule·kelvin.
D) kelvin/joule.

Question 5

During an adiabatic process

A) Q is greater than zero.
B) Q is less than zero.
C) Q is equal to zero.
D) all of the above are possible.

Question 6

During an adiabatic process the work done by the system is

A) greater than zero.
B) less than zero.
C) equal to zero.
D) any of the above.

Question 7

During an adiabatic process the change in the temperature of the system is

A) greater than zero.
B) less than zero.
C) equal to zero.
D) any of the above.

Question 8

During an expanding process 140 J of heat is added to a system and 150 J of work is done by the system. The change in the internal energy of the system is

A) 10 J.
B) -10 J.
C) 150 J.
D) -290 J.

Question 9

During an expanding process 140 J of heat is removed from a system and 150 J of work is done by the system. The change in the internal energy of the system is

A) 10 J.
B) -10 J.
C) 150 J.
D) -290 J.

Question 10

A gas at a temperature T₁ undergoes an isothermal free expansion. The First Law of Thermodynamics tells us that the change in the internal energy of the gas

A) increases.
B) decreases.
C) depends on the temperature T₁.
D) None of the above answers is correct.

Question 11

A heat engine produces a power output of 1.5 * 10⁵ W when it receives 50.0 MJ of heat per minute. The efficiency of the engine is

A) 0.18.
B) 0.30.
C) 0.03.
D) 0.003.

Question 12

The efficiency of a heat engine is 0.20 when it is expelling 4.0 $\times$ 10⁸ J of heat. The work that the engine is producing is

A) 1.0 $\times$ 10⁸ J.
B) 5.0 $\times$ 10⁸ J.
C) 8.0 $\times$ 10⁷ J.
D) 2.0 $\times$ 10⁸ J.

Question 13

One-quarter of the energy a heat engine receives is expelled as waste. The theoretical efficiency of this system

A) is 0.25.
B) is 0.50.
C) is 0.75.
D) cannot be determined from the information given.

Question 14

The graph here represents a p-V diagram where the x axis is the volume in units of 10^-3 m³ and the y axis is the pressure in units of 10⁵ N/m². The work done by the gas as it expands from (p₁, V₁) to (p₂, V₂) along the path indicated is

A) 30 kJ.
B) 10 kJ
C) -30 kJ.
D) 10 kJ.

Question 15

The graph here represents a p-V diagram where the x axis is the volume in units of 10^-3 m³ and the y axis is the pressure in units of 10⁵ N/m². The work done by the gas as it contracts from (p₂, V₂) to (p₁, V₁) along the path indicated is

A) 30 kJ.
B) 10 kJ
C) -30 kJ.
D) 10 kJ.

Question 16

The graph here represents a p-V diagram where the x axis is the volume in units of 10^-3 m³ and the y axis is the pressure in units of 10⁵ N/m². The work done by the ideal gas as it follows the path sequence (p₁,V₁) to (p₂,V₂) to (p₃,V₃) to (p₁,V₁) along the lines indicated

A) is 0 J.
B) is 10 kJ.
C) is -10 kJ.
D) cannot be determined from the given information.

Question 17

The graph here represents a p-V diagram where the x axis is the volume in units of 10^-3 m³ and the y axis is the pressure in units of 10⁵ N/m². The work done by the ideal gas as it follows the path sequence A to B to C to D back to A along the lines indicated is

A) 80 kJ.
B) -80 kJ.
C) 20 kJ.
D) -20 kJ.

Question 18

Given a cyclic process on a p-V diagram, the area enclosed by the paths is

A) the change in the internal energy.
B) the work done by the system.
C) the net exchanged heat.
D) none of the above.

Question 19

In an adiabatic expansion of an ideal gas, 150 J of work is performed on the surroundings. The change in the internal energy of the gas is

A) 0 J.
B) 150 J.
C) -150 J.
D) unknown; not enough information is given to answer the question.

Question 20

In an adiabatic expansion of an ideal gas, 150 J of work is performed on the surroundings. The heat added or removed from the gas is

A) 0 J.
B) 150 J.
C) -150 J.
D) unknown; not enough information is given to answer the question.

Question 21

During an isothermal process involving an ideal gas, 150 J of heat is removed from the system. The change in the internal energy of the gas is

A) 0 J.
B) 150 J.
C) -150 J.
D) unknown; not enough information is given to answer the question.

Question 22

During an isothermal process involving an ideal gas, 150 J of heat is removed from the system. The work done by the gas is

A) 0 J.
B) 150 J.
C) -150 J.
D) unknown; not enough information is given to answer the question.

Question 23

A heat engine has an efficiency of 0.25 when it receives 250 J of heat. The amount of work done by the engine is

A) 0 J.
B) 63 J.
C) 190 J.
D) 250 J.

Question 24

A heat engine has an efficiency of 0.25 when it receives 250 J of heat. The amount of heat exhausted by the engine is

A) 0 J.
B) 63 J.
C) 190 J.
D) 250 J.

Question 25

For each 150 Btu a heat engine absorbs, the system exhausts 64 Btu. The efficiency of the engine is

A) 0.43.
B) 0.57.
C) 1.3.
D) 2.3.

Question 26

For each 150 Btu a heat engine absorbs, the system exhausts 64 Btu. The amount of work done by the engine for each 150 Btu absorbed is

A) 0 Btu.
B) 64 Btu.
C) 86 Btu.
D) 150 Btu.

Question 27

The Carnot efficiency of an engine that operates between the temperatures of 20°C and 50°C is

A) 0.093.
B) 0.90.
C) 0.40.
D) 0.60.

Question 28

The efficiency of a particular Carnot cycle is 100%. The difference in the operating temperatures (in Kelvin) of the reservoir

A) is zero.
B) is equal to the temperature of the hot reservoir.
C) is equal to the temperature of the cold reservoir.
D) cannot be determined from the information given.

Question 29

The entropy of a closed system will

A) always increase.
B) always decrease.
C) increase or remain the same.
D) decrease or remain the same.
E) always remain the same.

Question 30

When a vapor condenses, the entropy of the gas

A) increases.
B) decreases.
C) remains the same.
D) equals zero.

Question 31

A heat engine works between two heat reservoirs with temperatures of 20°C and 100°C. In one cycle the engine produces 35 kJ of work while expelling 85 kJ of heat. The change in entropy is

A) 30 J/K.
B) 100 J/K.
C) 200 J/K.
D) 300 J/K.

Question 32

The change in entropy when 55 g of water (the latent heat of vaporization of water is 22.6 * 10⁵ J/kg) at 100°C is turned into steam at 100°C is

A) 55 J/K.
B) 111 J/K.
C) 333 J/K.
D) 444 J/K.

Question 33

The change in entropy when 55 g of ice at 0°C melts (the heat of fusion is 3.34 * 10⁵ J/kg) to water at 0°C is

A) 0 J/K.
B) 67 J/K.
C) -67 J/K.
D) infinite.

Question 34

An ideal gas is compressed at a constant temperature of 27°C, during which 900 J of work is done on the gas. The change in entropy of the gas is

A) 33 J/K.
B) -33 J/K.
C) 3 J/K.
D) -3 J/K.

Question 35

1.0 mole of an ideal gas is in a container with a volume V1 at a pressure p1 and temperature T1. The gas is slowly compressed isothermally until the final volume is (1/4)V1. The change in entropy is

A) 0 J\K
B) -11 J\K
C) -47 J\K
D) 47 J\K

Question 36

A container of 1.5 kg of water with a specific heat of 4186 J/(kg·°C) is heated from 25°C to 95°C. The change in the entropy of the water is

A) 1300 J/K.
B) 21 J/K.
C) 17 J/K.
D) 4.0 J/K.

Question 37

200 J of work is expended in the adiabatic expansion of a gas. The change in the internal energy of the gas is

A) 0 J
B) 200 J.
C) -200 J
D) Hold on! Not enough information is given to solve the problem.

Question 38

200 J of work is expended in the adiabatic expansion of a gas. The amount of heat that enters the system is

A) 0 J
B) 200 J.
C) -200 J
D) Hold on! Not enough information is given to solve the problem.

Question 39

Two Carnot cycles have the same efficiency. The first operates between T_h = 200°C and T_c = 100°C and the second operates with a hot reservoir of T_h = 400°C. The lower reservoir's temperature is

A) 200°C.
B) 258°C.
C) 315°C.
D) 531°C.

Question 40

A Carnot air conditioner with CP = 8 uses 10 kW of power. The heat expelled to the outdoors is

A) 10 kW.
B) 30 kW.
C) 80 kW.
D) 90 kW.

Question 41

A heat pump with a coefficient of performance of 10 used 50 kW of power. The heat delivered to the house is

A) 5 kW.
B) 50 kW.
C) 60 kW.
D) 500 kW.

Question 42

The coefficient of performance, CP, for a heat pump is defined as

A) Q₁/W.
B) W/Q₁.
C) Q₂/W.
D) W/Q₂.

Question 43

The coefficient of performance, CP, for an air conditioner or refrigerator is defined as

A) Q₁/W.
B) W/Q₁.
C) Q₂/W.
D) W/Q₂.

Question 44

The temperature of 7.6 kg of water is raised from 35°C to 55°C. Given that the specific heat of water is 4186 J/(kg·°C), the change in the entropy is

A) 14,000 J/K.
B) -14,000 J/K.
C) 2000 J/K.
D) -2000 J/K.

Question 45

An ideal diatomic gas undergoes a two-step process. The process begins at a pressure p_i and volume V_i. At the end of the two-step process p_f = 1.5p_i and V_f = 3.0V_i. The first step is an isothermal expansion to a volume V', followed by an adiabatic compression to the final volume. The intermediate volume V', in terms of the initial volume is

A) 1130V_i.
B) 13V_i.
C) 3.0V_i.
D) 130V_i.

Question 46

The efficiency of a Carnot cycle is 0.20 when operating with a hot reservoir of 93°C. If the temperature of the cold reservoir is maintained, the temperature of the hot reservoir necessary to double the efficiency is

A) 47°C.
B) 186°C.
C) 215°C.
D) 488°C.

Question 47

An ideal gas is heated in a closed container. The net work done on the system

A) is zero.
B) is positive.
C) is negative.
D) depends on the gas in the container.

Question 48

During an isobaric (constant pressure) expansion, the volume of an ideal gas increases from 0.15 m³ to 0.35 m³. The pressure during the expansion is 150 kPa. The work done by the system is

A) -30 kJ.
B) 30 kJ.
C) 750 kJ.
D) -750 kJ.

Question 49

During an adiabatic expansion

A) Q > 0 and W = 0.
B) Q < 0 and W < 0.
C) Q = 0 and W > 0.
D) Q = 0 and W < 0.

Question 50

The metric unit associated with the efficiency of a heat engine is

A) joule.
B) kelvin.
C) joule/kelvin.
D) none of the above.