Question 1

For a pair of dice,how many microstates are there that result in the macrostate of rolling a 7?

Accepted Answer

A) 1 
B) 5 
C) 6 
D) 7 
E) 36 
A) 1 
B) 5 
C) 6 
D) 7 
E) 36 C

Question 2

A 4.00-liter container is divided into two equal parts,one part containing 0.010 0 mole of neon,and the other part containing 0.010 0 mole of helium.The divider is removed and the gases mix.What is the change in entropy (in J/K)of this system?

Accepted Answer

A) 0.057 6 
B) 0.115 
C) 0.173 
D) 0.086 4 
E) 0.144 
A) 0.057 6 
B) 0.115 
C) 0.173 
D) 0.086 4 
E) 0.144 B

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 A

Question 4

Since Lice = 333 J/g,the change in entropy (in cal/K)when 1.00 kg of ice melts is

Accepted Answer

A) 144 
B) 291 
C) 312 
D) 516 
E) 80 
A) 144 
B) 291 
C) 312 
D) 516 
E) 80

Question 5

A vessel containing 10 kg of water is left out where it evaporates.If the temperature remains constant at 20 $\degree$C,what is the change in entropy (in kcal/K)? (The latent heat of vaporization at 20 $\degree$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 6

An adiabatic free expansion of a gas in a thermally isolated container is not reversible because

Accepted Answer

A) work must be done on the gas to return it to its original volume. 
B) heat must be exchanged with the surroundings to return the gas to its original temperature. 
C) its internal energy has a greater value after the expanded gas is returned to its original volume and temperature. 
D) of all of the above. 
E) of (a)and (b)above only. 
A) work must be done on the gas to return it to its original volume. 
B) heat must be exchanged with the surroundings to return the gas to its original temperature. 
C) its internal energy has a greater value after the expanded gas is returned to its original volume and temperature. 
D) of all of the above. 
E) of (a)and (b)above only.

Question 7

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

Question 8

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 9

One kilogram of chilled water (0 $\degree$C)is placed in a freezer which is kept at 0 $\degree$F (-18 $\degree$C).Approximately how much electric energy (in kilocalories)is needed just to freeze the water if the room temperature is maintained at 75 $\degree$F (24 $\degree$C)? (Lice = 333 J/g;cice = 209 J/g. $\degree$C. )

Accepted Answer

A) 11 
B) 15 
C) 16 
D) 13 
E) 33 
A) 11 
B) 15 
C) 16 
D) 13 
E) 33

Question 10

Determine the change in entropy (in J/K)when 5.00 moles of an ideal gas at 0 $\degree$C are compressed isothermally from an initial volume of 100 cm3 to a final volume of 20 cm3.

Accepted Answer

A) -191 
B) -52 
C) -71 
D) -67 
E) -208 
A) -191 
B) -52 
C) -71 
D) -67 
E) -208

Question 11

One kilogram of chilled water at 32$\degree$F (0$\degree$C)is placed in a freezer which is kept at 0$\degree$F (-18$\degree$C).Approximately how much electric energy (in kilocalories)is needed to operate the compressor to cool this water to 0$\degree$F if the room temperature is maintained at 75$\degree$F (24$\degree$C)? (Lice = 3.33 *105 J/kg;cice = 2.09 * 103 J/kg.$\degree$C)

Accepted Answer

A) 13 
B) 1.5 
C) 15 
D) 16 
E) 33 
A) 13 
B) 1.5 
C) 15 
D) 16 
E) 33

Question 12

A Carnot cycle,operating as a heat engine,consists,in the order given,of

Accepted Answer

A) an isothermal expansion,an isothermal compression,an adiabatic expansion and an adiabatic compression. 
B) an adiabatic expansion,an adiabatic compression,an isothermal expansion and an isothermal compression. 
C) an isothermal expansion,an adiabatic compression,an isothermal compression and an adiabatic expansion. 
D) an adiabatic compression,an isothermal compression,an isothermal expansion and an adiabatic expansion. 
E) an isothermal expansion,an adiabatic expansion,an isothermal compression and an adiabatic compression. 
A) an isothermal expansion,an isothermal compression,an adiabatic expansion and an adiabatic compression. 
B) an adiabatic expansion,an adiabatic compression,an isothermal expansion and an isothermal compression. 
C) an isothermal expansion,an adiabatic compression,an isothermal compression and an adiabatic expansion. 
D) an adiabatic compression,an isothermal compression,an isothermal expansion and an adiabatic expansion. 
E) an isothermal expansion,an adiabatic expansion,an isothermal compression and an adiabatic compression.

Question 13

A refrigerator has a coefficient of performance of 4.If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle,the heat expelled (in cal)into the heat reservoir is

Accepted Answer

A) 40.5 
B) 37.5 
C) 36.5 
D) 34.5 
E) 22.5 
A) 40.5 
B) 37.5 
C) 36.5 
D) 34.5 
E) 22.5

Question 14

A steam engine is operating at its theoretical maximum efficiency of 60%.If the waste heat has a temperature of 100 $\degree$F (38 $\degree$C),what is the temperature of the boiler?

Accepted Answer

A) 350 $\degree$C 
B) 94 $\degree$C 
C) 225 $\degree$C 
D) 504 $\degree$C 
E) 775 $\degree$C 
A) 350 $\degree$C 
B) 94 $\degree$C 
C) 225 $\degree$C 
D) 504 $\degree$C 
E) 775 $\degree$C

Question 15

The change in entropy of 1.00 kg of water that is heated from 50 $\degree$C to 100 $\degree$C is (in cal/K)

Accepted Answer

A) 516 
B) 312 
C) 144 
D) 946 
E) 391 
A) 516 
B) 312 
C) 144 
D) 946 
E) 391

Question 16

Every second at Niagara Falls,some 5 000 m3 of water falls a distance of 50 m.What is the increase in entropy per second due to the falling water? (Assume a 20$\degree$C environment).

Accepted Answer

The answer of Every second at Niagara Falls,some 5 000...

Question 17

A vessel containing 5.0 kg of water at 10 $\degree$C is put into a refrigerator.The 1/7 HP motor (1 HP = 746 W)runs for 5.0 minutes to cool the liquid to the refrigerator's low temperature,0 $\degree$C.What is the COP of the refrigerator?

Accepted Answer

A) 5.7 
B) 4.6 
C) 6.5 
D) 7.2 
E) 3.6 
A) 5.7 
B) 4.6 
C) 6.5 
D) 7.2 
E) 3.6

Question 18

A heat engine absorbs 2 500 J of heat from a hot reservoir and expels 1 000 J to a cold reservoir.When it is run in reverse,with the same reservoirs,the engine pumps 2 500 J of heat to the hot reservoir,requiring 1 500 J of work to do so.Find the ratio of the work done by the heat engine to the work done by the pump.Is the heat engine reversible?

Accepted Answer

A) 1.0 (no) 
B) 1.0 (yes) 
C) 1.5 (yes) 
D) 1.5 (no) 
E) 2.5 (no) 
A) 1.0 (no) 
B) 1.0 (yes) 
C) 1.5 (yes) 
D) 1.5 (no) 
E) 2.5 (no)

Question 19

A gasoline engine absorbs 2 500 J of heat at 250 $\degree$C and expels 2 000 J at a temperature of 50 $\degree$C.The magnitude of the change in entropy (in J/K)for the system is

Accepted Answer

A) 6.2 
B) 4.7 
C) 1.4 
D) 10.9 
E) 3.2 
A) 6.2 
B) 4.7 
C) 1.4 
D) 10.9 
E) 3.2

Question 20

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 refrigerator heated the air in the room in which the refrigerator is located. 
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 refrigerator heated the air in the room in which the refrigerator is located. 
D) any of the above occurred. 
E) (a)or (b)occurred,but not (c).

Exam 18: Heat Engines,entropy,and the Second Law of Thermodynamics

For a pair of dice,how many microstates are there that result in the macrostate of rolling a 7?

A 4.00-liter container is divided into two equal parts,one part containing 0.010 0 mole of neon,and the other part containing 0.010 0 mole of helium.The divider is removed and the gases mix.What is the change in entropy (in J/K)of this system?

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

Since Lice = 333 J/g,the change in entropy (in cal/K)when 1.00 kg of ice melts is

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

An adiabatic free expansion of a gas in a thermally isolated container is not reversible 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

All real engines are less efficient than the Carnot engine because

Determine the change in entropy (in J/K)when 5.00 moles of an ideal gas at 0 °\degree° C are compressed isothermally from an initial volume of 100 cm3 to a final volume of 20 cm3.

A Carnot cycle,operating as a heat engine,consists,in the order given,of

A refrigerator has a coefficient of performance of 4.If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle,the heat expelled (in cal)into the heat reservoir is

A steam engine is operating at its theoretical maximum efficiency of 60%.If the waste heat has a temperature of 100 °\degree° F (38 °\degree° C),what is the temperature of the boiler?

The change in entropy of 1.00 kg of water that is heated from 50 °\degree° C to 100 °\degree° C is (in cal/K)

Every second at Niagara Falls,some 5 000 m3 of water falls a distance of 50 m.What is the increase in entropy per second due to the falling water? (Assume a 20 °\degree° C environment).

A vessel containing 5.0 kg of water at 10 °\degree° C is put into a refrigerator.The 1/7 HP motor (1 HP = 746 W)runs for 5.0 minutes to cool the liquid to the refrigerator's low temperature,0 °\degree° C.What is the COP of the refrigerator?

A gasoline engine absorbs 2 500 J of heat at 250 °\degree° C and expels 2 000 J at a temperature of 50 °\degree° C.The magnitude of the change in entropy (in J/K)for the system is

A violation of the second law of thermodynamics would occur if

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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

Since L_ice = 333 J/g,the change in entropy (in cal/K)when 1.00 kg of ice melts is

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

Determine the change in entropy (in J/K)when 5.00 moles of an ideal gas at 0 $\degree$ C are compressed isothermally from an initial volume of 100 cm³ to a final volume of 20 cm³.

A steam engine is operating at its theoretical maximum efficiency of 60%.If the waste heat has a temperature of 100 $\degree$ F (38 $\degree$ C),what is the temperature of the boiler?

The change in entropy of 1.00 kg of water that is heated from 50 $\degree$ C to 100 $\degree$ C is (in cal/K)

Every second at Niagara Falls,some 5 000 m³ of water falls a distance of 50 m.What is the increase in entropy per second due to the falling water? (Assume a 20 $\degree$ C environment).

A vessel containing 5.0 kg of water at 10 $\degree$ C is put into a refrigerator.The 1/7 HP motor (1 HP = 746 W)runs for 5.0 minutes to cool the liquid to the refrigerator's low temperature,0 $\degree$ C.What is the COP of the refrigerator?

A gasoline engine absorbs 2 500 J of heat at 250 $\degree$ C and expels 2 000 J at a temperature of 50 $\degree$ C.The magnitude of the change in entropy (in J/K)for the system is