Question 1

A violation of the second law of thermodynamics would occur if

Accepted Answer

A) a ball lying on the ground started to bounce. 
B) transfer of energy by heat moved energy from an object at low temperature to an object at a higher temperature. 
C) a motion picture was run backwards through the projector. 
D) any of the above occurred. 
E) (a)or (b)occurred,but not (c). 
A) a ball lying on the ground started to bounce. 
B) transfer of energy by heat moved energy from an object at low temperature to an object at a higher temperature. 
C) a motion picture was run backwards through the projector. 
D) any of the above occurred. 
E) (a)or (b)occurred,but not (c).

Question 2

The change in entropy when 1 kg of ice melts at 0°C is (in J/K).(Lice = 333 J/g. )

Accepted Answer

A) 335. 
B) 603. 
C) 1 220. 
D) 1 310. 
E) 2 160. 
A) 335. 
B) 603. 
C) 1 220. 
D) 1 310. 
E) 2 160.

Question 3

An ideal gas is allowed to undergo a free expansion.If its initial volume is V1 and its final volume is V2,the change in entropy is

Accepted Answer

A) nR ln (V2/V1) 
B) nRT ln (V2/V1) 
C) nk ln (V2/V1) 
D) 0 
E) nR V2/V1 
A) nR ln (V2/V1) 
B) nRT ln (V2/V1) 
C) nk ln (V2/V1) 
D) 0 
E) nR V2/V1

Question 4

An automobile engine operates with an overall efficiency of 12%.How much energy is delivered as waste heat (in gallons of gasoline)for each 10 gallons of fuel burned?

Accepted Answer

A) 1.2 
B) 8.8 
C) 6.5 
D) 4.7 
E) 7.5 
A) 1.2 
B) 8.8 
C) 6.5 
D) 4.7 
E) 7.5

Question 5

A gasoline engine absorbs 2 500 J of heat and performs 1 000 J of mechanical work in each cycle.The efficiency of the engine is

Accepted Answer

A) 80% 
B) 40% 
C) 60% 
D) 20% 
E) 50% 
A) 80% 
B) 40% 
C) 60% 
D) 20% 
E) 50%

Question 6

A vessel containing 10 kg of water is left out where it evaporates.If the temperature remains constant at 20°C,what is the change in entropy (in kcal/K)? (The latent heat of vaporization at 20°C is 585 cal/g. )

Accepted Answer

A) 30 
B) 10 
C) 20 
D) 40 
E) 290 
A) 30 
B) 10 
C) 20 
D) 40 
E) 290

Question 7

Which of the following is an almost reversible process?

Accepted Answer

A) The explosion of hydrogen and oxygen to form water. 
B) Heat transfer through thick insulation. 
C) The adiabatic free expansion of a gas. 
D) A slow isothermal compression of a gas. 
E) A slow leakage of gas into an empty chamber through a small hole in a membrane. 
A) The explosion of hydrogen and oxygen to form water. 
B) Heat transfer through thick insulation. 
C) The adiabatic free expansion of a gas. 
D) A slow isothermal compression of a gas. 
E) A slow leakage of gas into an empty chamber through a small hole in a membrane.

Question 8

An 800-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) 1 200 
B) 1 900 
C) 800 
D) 560 
E) 240 
A) 1 200 
B) 1 900 
C) 800 
D) 560 
E) 240

Question 9

Exactly 500 grams of ice are melted at a temperature of 32°F.(Lice = 333 J/g. )The change in entropy (in J/K)is

Accepted Answer

A) 321 
B) 146 
C) 512 
D) 610 
E) 5 230 
A) 321 
B) 146 
C) 512 
D) 610 
E) 5 230

Question 10

In an engine operating in the Otto cycle,the final volume of the fuel-air mixture is one sixth the initial volume.Assume γ = 1.4.The maximum theoretical efficiency of this cycle,in per cent,is

Accepted Answer

A) 17. 
B) 49. 
C) 51. 
D) 56. 
E) 83. 
A) 17. 
B) 49. 
C) 51. 
D) 56. 
E) 83.

Question 11

Suppose there are 3 molecules in a container.If each molecule has a 1-in-2 chance of being in the left half of the container,what is the probability that there are exactly 2 molecules in the left half of the container?

Accepted Answer

A) 1/2 
B) 1/3 
C) 1/8 
D) 3/8 
E) 3/5 
A) 1/2 
B) 1/3 
C) 1/8 
D) 3/8 
E) 3/5

Question 12

If n moles of an ideal gas are compressed isothermally from an initial volume V1 to a final volume V2,the change in entropy is

Accepted Answer

A) nR ln (V2/V1) 
B) nRT ln (V2/V1) 
C) nkB ln (V2/V1) 
D)    
E) n Cv/T 
A) nR ln (V2/V1) 
B) nRT ln (V2/V1) 
C) nkB ln (V2/V1) 
D)    
E) n Cv/T

Question 13

One end of a copper rod is in thermal contact with a hot reservoir at T = 500 K and the other end is in thermal contact with a cooler reservoir at T = 300 K.Find the entropy change of each reservoir,and the total entropy change,when 8 000 J of heat energy are conducted from one end of the rod to the other with no change in the temperature distribution in the rod.

Accepted Answer

−16.0 J/K,

Question 14

All real engines are less efficient than the Carnot engine because

Accepted Answer

A) they do not operate through the Otto cycle. 
B) they do not operate through a reversible cycle. 
C) the working substance does not maintain a constant volume through the cycle. 
D) the working substance does not maintain a constant pressure through the cycle. 
E) the working substance does not maintain a constant temperature through the cycle. 
A) they do not operate through the Otto cycle. 
B) they do not operate through a reversible cycle. 
C) the working substance does not maintain a constant volume through the cycle. 
D) the working substance does not maintain a constant pressure through the cycle. 
E) the working substance does not maintain a constant temperature through the cycle.

Question 15

A heat pump has a coefficient of performance of 4.If the heat pump absorbs 20 cal of heat from the cold outdoors in each cycle,the heat expelled (in cal)to the warm indoors is

Accepted Answer

A) 34 
B) 27 
C) 36 
D) 40 
E) 80 
A) 34 
B) 27 
C) 36 
D) 40 
E) 80

Exam 22: Heat Engines, entropy, and the Second Law of Thermodynamics

A violation of the second law of thermodynamics would occur if

The change in entropy when 1 kg of ice melts at 0°C is (in J/K).(Lice = 333 J/g. )

An ideal gas is allowed to undergo a free expansion.If its initial volume is V1 and its final volume is V2,the change in entropy is

An automobile engine operates with an overall efficiency of 12%.How much energy is delivered as waste heat (in gallons of gasoline)for each 10 gallons of fuel burned?

A gasoline engine absorbs 2 500 J of heat and performs 1 000 J of mechanical work in each cycle.The efficiency of the engine is

A vessel containing 10 kg of water is left out where it evaporates.If the temperature remains constant at 20°C,what is the change in entropy (in kcal/K)? (The latent heat of vaporization at 20°C is 585 cal/g. )

Which of the following is an almost reversible process?

An 800-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?

Exactly 500 grams of ice are melted at a temperature of 32°F.(Lice = 333 J/g. )The change in entropy (in J/K)is

In an engine operating in the Otto cycle,the final volume of the fuel-air mixture is one sixth the initial volume.Assume γ = 1.4.The maximum theoretical efficiency of this cycle,in per cent,is

Suppose there are 3 molecules in a container.If each molecule has a 1-in-2 chance of being in the left half of the container,what is the probability that there are exactly 2 molecules in the left half of the container?

If n moles of an ideal gas are compressed isothermally from an initial volume V1 to a final volume V2,the change in entropy is

All real engines are less efficient than the Carnot engine because

A heat pump has a coefficient of performance of 4.If the heat pump absorbs 20 cal of heat from the cold outdoors in each cycle,the heat expelled (in cal)to the warm indoors is

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The change in entropy when 1 kg of ice melts at 0°C is (in J/K).(L_ice = 333 J/g. )

An ideal gas is allowed to undergo a free expansion.If its initial volume is V₁ and its final volume is V₂,the change in entropy is

Exactly 500 grams of ice are melted at a temperature of 32°F.(L_ice = 333 J/g. )The change in entropy (in J/K)is

If n moles of an ideal gas are compressed isothermally from an initial volume V₁ to a final volume V₂,the change in entropy is