Question 1

The maximum theoretical thermodynamic efficiency of a heat engine operating between hot and cold reservoirs is a function of which of the following?

Accepted Answer

A)  hot reservoir temperature only 
B)  cold reservoir temperature only 
C)  both hot and cold reservoir temperatures 
D)  None of the above choices are valid.

Question 2

A 2-mol ideal gas system undergoes an adiabatic process where it expands and does 16 J of work on its environment.What is its change in internal energy?
​

Accepted Answer

A)  −16 J 
B)  −8 J 
C)  zero 
D)  +16 J 
E)  ​+8 J

Question 3

A heat engine receives 7,100 J of heat from its combustion process and loses 3,100 J through the exhaust and friction.What is its efficiency?
​

Accepted Answer

A)  56% 
B)  32% 
C)  18% 
D)  44% 
E)  ​75%

Question 4

An 870-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ)is discharged to the atmosphere per second?
​

Accepted Answer

A)  3,770 MJ 
B)  2,030 MJ 
C)  870 MJ 
D)  2,900 MJ 
E)  ​4,060 MJ

Question 5

A Carnot engine runs between a hot reservoir at Th and a cold reservoir at Tc.If one of the temperatures is either increased or decreased by 3.5 K,which of the following changes would increase the efficiency by the greatest amount?

Accepted Answer

A)  increasing Th 
B)  increasing Tc 
C)  decreasing Tc 
D)  cannot be determined from information given

Question 6

During an isobaric process which one of the following does not change?

Accepted Answer

A)  volume 
B)  temperature 
C)  internal energy 
D)  pressure

Question 7

An electrical generating plant operates at a boiler temperature of 229°C and exhausts the unused heat into a nearby river at 18°C.If the generating plant has a power output of 870 megawatts (MW)and if the actual efficiency is 3/4 the theoretical efficiency,how much heat per second must be delivered to the boiler? (0°C = 273 K)
​

Accepted Answer

A)  8,279 MW 
B)  4,140 MW 
C)  2,070 MW 
D)  2,760 MW 
E)  1,600 MW

Question 8

On a PV diagram,2 curves are plotted,both starting at the same point (P1,V1)and both ending at the same increased volume (V2).One curve is for an isothermal process;the other is for an adiabatic process.Except for the common starting point,which curve is the upper one?

Accepted Answer

A)  The isothermal process curve will always be the upper one. 
B)  The adiabatic process curve will always be the upper one. 
C)  Since they start at the same point and end at the same volume,they will coincide. 
D)  The isothermal one will start out higher,but the adiabatic one will eventually cross it.

Question 9

Area on a P-V diagram has units associated with:

Accepted Answer

A)  energy. 
B)  momentum. 
C)  temperature. 
D)  change in temperature.

Question 10

A 5-mol ideal gas system undergoes an adiabatic free expansion (a rapid expansion into a vacuum),going from an initial volume of 30 L to a final volume of 50 L.How much work is done on the system during this adiabatic free expansion?
​

Accepted Answer

A)  −150 J 
B)  −30 J 
C)  zero 
D)  +150 J 
E)  ​+30 J

Question 11

What is the change in entropy (ΔS)when one mole of silver (102 g)is completely melted at 962°C? (The heat of fusion of silver is 8.82 × 104 J/kg. )
​

Accepted Answer

A)  9.35 J/K 
B)  7.28 J/K 
C)  3.64 J/K 
D)  14.57 J/K 
E)  ​5.28 J/K

Question 12

In an isobaric process 5 × 104 J of work is done on a quantity of gas while its volume changes from 2.8 m3 to 1.8 m3.What is the pressure during this process?
​

Accepted Answer

A)  4.4 × 104 Pa 
B)  3.8 × 104 Pa 
C)  5.0 × 104 Pa 
D)  5.6 × 104 Pa 
E)  ​6.2 × 104 Pa

Question 13

A refrigerator has a coefficient of performance of 4.When removing 2.3 × 104 J from inside the refrigerator,how much energy is sent into the environment?
​

Accepted Answer

A)  0.6 × 104 J 
B)  2.9 × 104 J 
C)  9.2 × 104 J 
D)  11.5 × 104 J 
E)  ​3.6 × 104 J

Question 14

An electrical power plant manages to send 87% of the heat produced in the burning of fossil fuel into the water-to-steam conversion.Of the heat carried by the steam,40% is converted to the mechanical energy of the spinning turbine.Which of the following choices best describes the overall efficiency of the heat-to-work conversion in the plant (as a percentage)?
​

Accepted Answer

A)  greater than 87% 
B)  64% 
C)  less than 40% 
D)  40% 
E)  ​87%

Question 15

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 980 J of heat energy is transferred from the Sun to the Earth?
​

Accepted Answer

A)  3.38 J/K 
B)  3.21 J/K 
C)  0.17 J/K 
D)  3.55 J/K 
E)  5.38 J/K

Question 16

The volume of an ideal gas changes from 0.3 to 0.52 m3 although its pressure remains constant at 58,000 Pa.What work is done on the system by its environment?
​

Accepted Answer

A)  -12,760 J 
B)  12,760 J 
C)  -17,400 J 
D)  17,400 J 
E)  ​-30,160 J

Question 17

A 2.05-kg block of ice is at STP (0°C,1 atm)while it melts completely to water.What is its change in entropy? (For ice,Lf = 3.34 × 105 J/kg)
​

Accepted Answer

A)  zero 
B)  1,254 J/K 
C)  627 J/K 
D)  2,508 J/K 
E)  ​5,016 J/K

Question 18

Which of the following choices is an appropriate unit for measuring entropy changes?

Accepted Answer

A)  J⋅K 
B)  N⋅K 
C)  J/s 
D)  J/K

Question 19

1.2 kilogram of water at 1.00 atm at the boiling point of 100°C is heated until all the water vaporizes.What is its change in entropy? (For water,Lv = 2.26 × 106 J/kg)
​

Accepted Answer

A)  14,542 J/K 
B)  7,271 J/K 
C)  3,635 J/K 
D)  2,424 J/K 
E)  9,934 J/K

Question 20

Entropy is a measure of the ____ of a system.

Accepted Answer

A)  disorder 
B)  temperature 
C)  heat 
D)  internal energy

Exam 12: The Laws of Thermodynamics Work in Thermodynamic Processes

The maximum theoretical thermodynamic efficiency of a heat engine operating between hot and cold reservoirs is a function of which of the following?

A 2-mol ideal gas system undergoes an adiabatic process where it expands and does 16 J of work on its environment.What is its change in internal energy?

A heat engine receives 7,100 J of heat from its combustion process and loses 3,100 J through the exhaust and friction.What is its efficiency?

An 870-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ) is discharged to the atmosphere per second?

A Carnot engine runs between a hot reservoir at T_h and a cold reservoir at T_c.If one of the temperatures is either increased or decreased by 3.5 K,which of the following changes would increase the efficiency by the greatest amount?

During an isobaric process which one of the following does not change?

On a PV diagram,2 curves are plotted,both starting at the same point (P₁,V₁) and both ending at the same increased volume (V₂) .One curve is for an isothermal process;the other is for an adiabatic process.Except for the common starting point,which curve is the upper one?

Area on a P-V diagram has units associated with:

A 5-mol ideal gas system undergoes an adiabatic free expansion (a rapid expansion into a vacuum) ,going from an initial volume of 30 L to a final volume of 50 L.How much work is done on the system during this adiabatic free expansion?

What is the change in entropy (ΔS) when one mole of silver (102 g) is completely melted at 962°C? (The heat of fusion of silver is 8.82 × 10⁴ J/kg. )

In an isobaric process 5 × 10⁴ J of work is done on a quantity of gas while its volume changes from 2.8 m³ to 1.8 m³.What is the pressure during this process?

A refrigerator has a coefficient of performance of 4.When removing 2.3 × 10⁴ J from inside the refrigerator,how much energy is sent into the environment?

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 980 J of heat energy is transferred from the Sun to the Earth?

The volume of an ideal gas changes from 0.3 to 0.52 m³ although its pressure remains constant at 58,000 Pa.What work is done on the system by its environment?

A 2.05-kg block of ice is at STP (0°C,1 atm) while it melts completely to water.What is its change in entropy? (For ice,L_f = 3.34 × 10⁵ J/kg)

Which of the following choices is an appropriate unit for measuring entropy changes?

1.2 kilogram of water at 1.00 atm at the boiling point of 100°C is heated until all the water vaporizes.What is its change in entropy? (For water,L_v = 2.26 × 10⁶ J/kg)

Entropy is a measure of the ____ of a system.

Exam 12: The Laws of Thermodynamics Work in Thermodynamic Processes

The maximum theoretical thermodynamic efficiency of a heat engine operating between hot and cold reservoirs is a function of which of the following?

A 2-mol ideal gas system undergoes an adiabatic process where it expands and does 16 J of work on its environment.What is its change in internal energy? ​

A heat engine receives 7,100 J of heat from its combustion process and loses 3,100 J through the exhaust and friction.What is its efficiency? ​

An 870-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ) is discharged to the atmosphere per second? ​

A Carnot engine runs between a hot reservoir at Th and a cold reservoir at Tc.If one of the temperatures is either increased or decreased by 3.5 K,which of the following changes would increase the efficiency by the greatest amount?

During an isobaric process which one of the following does not change?

On a PV diagram,2 curves are plotted,both starting at the same point (P1,V1) and both ending at the same increased volume (V2) .One curve is for an isothermal process;the other is for an adiabatic process.Except for the common starting point,which curve is the upper one?

Area on a P-V diagram has units associated with:

A 5-mol ideal gas system undergoes an adiabatic free expansion (a rapid expansion into a vacuum) ,going from an initial volume of 30 L to a final volume of 50 L.How much work is done on the system during this adiabatic free expansion? ​

What is the change in entropy (ΔS) when one mole of silver (102 g) is completely melted at 962°C? (The heat of fusion of silver is 8.82 × 104 J/kg. ) ​

In an isobaric process 5 × 104 J of work is done on a quantity of gas while its volume changes from 2.8 m3 to 1.8 m3.What is the pressure during this process? ​

A refrigerator has a coefficient of performance of 4.When removing 2.3 × 104 J from inside the refrigerator,how much energy is sent into the environment? ​

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 980 J of heat energy is transferred from the Sun to the Earth? ​

The volume of an ideal gas changes from 0.3 to 0.52 m3 although its pressure remains constant at 58,000 Pa.What work is done on the system by its environment? ​

A 2.05-kg block of ice is at STP (0°C,1 atm) while it melts completely to water.What is its change in entropy? (For ice,Lf = 3.34 × 105 J/kg) ​

Which of the following choices is an appropriate unit for measuring entropy changes?

1.2 kilogram of water at 1.00 atm at the boiling point of 100°C is heated until all the water vaporizes.What is its change in entropy? (For water,Lv = 2.26 × 106 J/kg) ​

Entropy is a measure of the ____ of a system.

A 2-mol ideal gas system undergoes an adiabatic process where it expands and does 16 J of work on its environment.What is its change in internal energy?

A heat engine receives 7,100 J of heat from its combustion process and loses 3,100 J through the exhaust and friction.What is its efficiency?

An 870-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ) is discharged to the atmosphere per second?

A Carnot engine runs between a hot reservoir at T_h and a cold reservoir at T_c.If one of the temperatures is either increased or decreased by 3.5 K,which of the following changes would increase the efficiency by the greatest amount?

On a PV diagram,2 curves are plotted,both starting at the same point (P₁,V₁) and both ending at the same increased volume (V₂) .One curve is for an isothermal process;the other is for an adiabatic process.Except for the common starting point,which curve is the upper one?

A 5-mol ideal gas system undergoes an adiabatic free expansion (a rapid expansion into a vacuum) ,going from an initial volume of 30 L to a final volume of 50 L.How much work is done on the system during this adiabatic free expansion?

What is the change in entropy (ΔS) when one mole of silver (102 g) is completely melted at 962°C? (The heat of fusion of silver is 8.82 × 10⁴ J/kg. )

In an isobaric process 5 × 10⁴ J of work is done on a quantity of gas while its volume changes from 2.8 m³ to 1.8 m³.What is the pressure during this process?

A refrigerator has a coefficient of performance of 4.When removing 2.3 × 10⁴ J from inside the refrigerator,how much energy is sent into the environment?

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 980 J of heat energy is transferred from the Sun to the Earth?

The volume of an ideal gas changes from 0.3 to 0.52 m³ although its pressure remains constant at 58,000 Pa.What work is done on the system by its environment?

A 2.05-kg block of ice is at STP (0°C,1 atm) while it melts completely to water.What is its change in entropy? (For ice,L_f = 3.34 × 10⁵ J/kg)

1.2 kilogram of water at 1.00 atm at the boiling point of 100°C is heated until all the water vaporizes.What is its change in entropy? (For water,L_v = 2.26 × 10⁶ J/kg)