Question 1

A Carnot engine operates between 200°C and 20°C.Its maximum possible efficiency is:

Accepted Answer

A) 90% 
B) 100% 
C) 38% 
D) 72% 
E) 24% 
A) 90% 
B) 100% 
C) 38% 
D) 72% 
E) 24%

Question 2

The temperature of n moles of a gas is increased from Ti to Tf at constant pressure.If the molar specific heat at constant pressure is Cp and is independent of temperature, then change in the entropy of the gas is:

Accepted Answer

A) nCp ln(Tf/Ti) 
B) nCp ln(Ti/Tf) 
C) nCp ln(Tf - Ti) 
D) nCp ln(1 - Ti/Tf) 
E) nCp (Tf - Ti) 
A) nCp ln(Tf/Ti) 
B) nCp ln(Ti/Tf) 
C) nCp ln(Tf - Ti) 
D) nCp ln(1 - Ti/Tf) 
E) nCp (Tf - Ti)

Question 3

A Carnot heat engine and an irreversible heat engine both operate between the same high temperature and low temperature reservoirs.They absorb the same heat from the high temperature reservoir as heat.The irreversible engine:

Accepted Answer

A) does more work 
B) rejects more energy to the low temperature reservoir as heat 
C) has the greater efficiency 
D) has the same efficiency as the reversible engine 
E) cannot absorb the same energy from the high temperature reservoir as heat without violating the second law of thermodynamics 
A) does more work 
B) rejects more energy to the low temperature reservoir as heat 
C) has the greater efficiency 
D) has the same efficiency as the reversible engine 
E) cannot absorb the same energy from the high temperature reservoir as heat without violating the second law of thermodynamics

Question 4

Is it possible to transfer energy from a low-temperature reservoir to a high-temperature reservoir?

Accepted Answer

A) No, this violates the conservation of energy. 
B) No, this violates the second law of thermodynamics. 
C) Yes, this is what a heat engine does, and it can happen without the engine doing work. 
D) Yes, this is what a refrigerator does, and it can happen without the refrigerator doing work. 
E) Yes, this is what a refrigerator does, and the refrigerator must do work to make this happen. 
A) No, this violates the conservation of energy. 
B) No, this violates the second law of thermodynamics. 
C) Yes, this is what a heat engine does, and it can happen without the engine doing work. 
D) Yes, this is what a refrigerator does, and it can happen without the refrigerator doing work. 
E) Yes, this is what a refrigerator does, and the refrigerator must do work to make this happen.

Question 5

A heat engine absorbs energy of magnitude   from a high temperature reservoir, does work of magnitude  , and transfers energy of   as heat to a low temperature reservoir.Its efficiency is:

Accepted Answer

A)   
B)   
C)   
D)   
E)   
A)   
B)   
C)   
D)   
E)

Question 6

For a system of molecules,

Accepted Answer

A) each configuration is equally probable. 
B) microstates with more configurations are more probable than other microstates. 
C) configurations with more microstates are more probable than other configurations. 
D) microstates with more configurations are less probable than other microstates. 
E) configurations with more microstates are less probable than other configurations. 
A) each configuration is equally probable. 
B) microstates with more configurations are more probable than other microstates. 
C) configurations with more microstates are more probable than other configurations. 
D) microstates with more configurations are less probable than other microstates. 
E) configurations with more microstates are less probable than other configurations.

Question 7

Consider all possible isothermal contractions of an ideal gas.The entropy of the gas:

Accepted Answer

A) does not change for any of them 
B) does not decrease for any of them 
C) does not increase for any of them 
D) increases for all of them 
E) decreases for all of them 
A) does not change for any of them 
B) does not decrease for any of them 
C) does not increase for any of them 
D) increases for all of them 
E) decreases for all of them

Question 8

A heat engine operates between a high temperature reservoir at TH and a low temperature reservoir at TL.Its efficiency is given by 1 - TL/TH:

Accepted Answer

A) only if the working substance is an ideal gas 
B) only if the engine is reversible 
C) only if the engine is quasi-static 
D) only if the engine operates on a Stirling cycle 
E) no matter what characteristics the engine has 
A) only if the working substance is an ideal gas 
B) only if the engine is reversible 
C) only if the engine is quasi-static 
D) only if the engine operates on a Stirling cycle 
E) no matter what characteristics the engine has

Question 9

Twenty-five identical molecules are in a box.Microstates are designated by identifying the molecules in the left and right halves of the box.The Boltzmann constant is 1.38 *10-23 J/K.The entropy associated with the configuration for which 15 molecules are in the left half and 10 molecules are in the right half is:

Accepted Answer

A) 2.07 * 10-22 J/K 
B) 7.31 *10-22 J/K 
C) 4.44 * 10-23 J/K 
D) 6.91 *10-23 J/K 
E) 2.22 * 10-23 J/K 
A) 2.07 * 10-22 J/K 
B) 7.31 *10-22 J/K 
C) 4.44 * 10-23 J/K 
D) 6.91 *10-23 J/K 
E) 2.22 * 10-23 J/K

Question 10

Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water

Accepted Answer

A) 1, 2, 3, 4 
B) 3, 4, 1, 2 
C) 1 and 2 tie, then 3 and 4 tie 
D) 3 and 4 tie, then 1 and 2 tie 
E) 4, 3, 2, 1 
A) 1, 2, 3, 4 
B) 3, 4, 1, 2 
C) 1 and 2 tie, then 3 and 4 tie 
D) 3 and 4 tie, then 1 and 2 tie 
E) 4, 3, 2, 1

Question 11

Consider the following processes:   Which are never found to occur?

Accepted Answer

A) Only I 
B) Only II 
C) Only III 
D) Only II and III 
E) I, II and III 
A) Only I 
B) Only II 
C) Only III 
D) Only II and III 
E) I, II and III

Question 12

According to the second law of thermodynamics:

Accepted Answer

A) heat energy cannot be completely converted to work 
B) work cannot be completely converted to heat energy 
C) for all cyclic processes we have dQ/T < 0 
D) the reason all heat engine efficiencies are less than 100% is friction, which is unavoidable 
E) all of the above are true 
A) heat energy cannot be completely converted to work 
B) work cannot be completely converted to heat energy 
C) for all cyclic processes we have dQ/T < 0 
D) the reason all heat engine efficiencies are less than 100% is friction, which is unavoidable 
E) all of the above are true

Question 13

Let k be the Boltzmann constant.If the configuration of molecules in a gas changes from one with a multiplicity of M1 to one with a multiplicity of M2, then entropy changes by:

Accepted Answer

A) "$\Delta$S = 0" 
B) "$\Delta$S = k(M2 - M1)" 
C) "$\Delta$S = kM2/M1" 
D) "$\Delta$S = k ln(M2M1)" 
E) "$\Delta$S = k ln(M2/M1)" 
A) "$\Delta$S = 0" 
B) "$\Delta$S = k(M2 - M1)" 
C) "$\Delta$S = kM2/M1" 
D) "$\Delta$S = k ln(M2M1)" 
E) "$\Delta$S = k ln(M2/M1)"

Question 14

For a system of molecules,

Accepted Answer

A) each configuration consists of a set of equivalent microstates. 
B) each microstate consists of a set of equivalent configurations. 
C) the number of configurations in a microstate is the multiplicity of the microstate. 
D) the multiplicity of the configuration is the product of the number of molecules in each microstate. 
E) each configuration is equally probable. 
A) each configuration consists of a set of equivalent microstates. 
B) each microstate consists of a set of equivalent configurations. 
C) the number of configurations in a microstate is the multiplicity of the microstate. 
D) the multiplicity of the configuration is the product of the number of molecules in each microstate. 
E) each configuration is equally probable.

Question 15

In a reversible process the system:

Accepted Answer

A) is always close to equilibrium states 
B) is close to equilibrium states only at the beginning and end 
C) might never be close to any equilibrium state 
D) is close to equilibrium states throughout, except at the beginning and end 
E) is none of the above 
A) is always close to equilibrium states 
B) is close to equilibrium states only at the beginning and end 
C) might never be close to any equilibrium state 
D) is close to equilibrium states throughout, except at the beginning and end 
E) is none of the above

Question 16

Twenty-five identical molecules are in a box.Microstates are designated by identifying the molecules in the left and right halves of the box.The multiplicity of the configuration with 15 molecules in the right half and 10 molecules in the left half is:

Accepted Answer

A) 1.03 * 1023 
B) 3.27 * 106 
C) 150 
D) 25 
E) 5 
A) 1.03 * 1023 
B) 3.27 * 106 
C) 150 
D) 25 
E) 5

Question 17

A Carnot cycle:

Accepted Answer

A) is bounded by two isotherms and two adiabats on a p-V graph 
B) consists of two isothermal and two constant volume processes 
C) is any four sided process on a p-V graph 
D) only exists for an ideal gas 
E) has an efficiency equal to the enclosed area on a p-V diagram 
A) is bounded by two isotherms and two adiabats on a p-V graph 
B) consists of two isothermal and two constant volume processes 
C) is any four sided process on a p-V graph 
D) only exists for an ideal gas 
E) has an efficiency equal to the enclosed area on a p-V diagram

Question 18

An ideal gas, consisting of n moles, undergoes an irreversible process in which the temperature has the same value at the beginning and end.If the volume changes from Vi to Vf, the change in entropy is given by:

Accepted Answer

A) n R(Vf - Vi) 
B) n R ln(Vf - Vi) 
C) n R ln(Vi/Vf) 
D) n R ln(Vf/Vi) 
E) none of the above (entropy can't be calculated for an irreversible process) 
A) n R(Vf - Vi) 
B) n R ln(Vf - Vi) 
C) n R ln(Vi/Vf) 
D) n R ln(Vf/Vi) 
E) none of the above (entropy can't be calculated for an irreversible process)

Question 19

A reversible refrigerator operates between a low temperature reservoir at TL and a high temperature reservoir at TH.Its coefficient of performance is given by:

Accepted Answer

A) (TH - TL)/ TL 
B) TL /(TH - TL) 
C) (TH - TL)/TH 
D) TH/(TH - TL) 
E) TH(TH + TL) 
A) (TH - TL)/ TL 
B) TL /(TH - TL) 
C) (TH - TL)/TH 
D) TH/(TH - TL) 
E) TH(TH + TL)

Question 20

Let k be the Boltzmann constant.If the configuration of the molecules in a gas changes so that the multiplicity is reduced to one-third its previous value, the entropy of the gas changes by:

Accepted Answer

A) "$\Delta$S = 0" 
B) "$\Delta$S = 3k ln 2" 
C) "$\Delta$S = -3k ln 2" 
D) "$\Delta$S = k ln(1/3)" 
E) "$\Delta$S = -3 ln 3" 
A) "$\Delta$S = 0" 
B) "$\Delta$S = 3k ln 2" 
C) "$\Delta$S = -3k ln 2" 
D) "$\Delta$S = k ln(1/3)" 
E) "$\Delta$S = -3 ln 3"

Exam 20: Entropy and the Second Law of Thermodynamics

A Carnot engine operates between 200°C and 20°C.Its maximum possible efficiency is:

The temperature of n moles of a gas is increased from Ti to Tf at constant pressure.If the molar specific heat at constant pressure is Cp and is independent of temperature, then change in the entropy of the gas is:

A Carnot heat engine and an irreversible heat engine both operate between the same high temperature and low temperature reservoirs.They absorb the same heat from the high temperature reservoir as heat.The irreversible engine:

Is it possible to transfer energy from a low-temperature reservoir to a high-temperature reservoir?

A heat engine absorbs energy of magnitude from a high temperature reservoir, does work of magnitude , and transfers energy of magnitude as heat to a low temperature reservoir.Its efficiency is:

For a system of molecules,

Consider all possible isothermal contractions of an ideal gas.The entropy of the gas:

A heat engine operates between a high temperature reservoir at TH and a low temperature reservoir at TL.Its efficiency is given by 1 - TL/TH:

Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water

Consider the following processes: Which are never found to occur?

According to the second law of thermodynamics:

Let k be the Boltzmann constant.If the configuration of molecules in a gas changes from one with a multiplicity of M1 to one with a multiplicity of M2, then entropy changes by:

For a system of molecules,

In a reversible process the system:

Twenty-five identical molecules are in a box.Microstates are designated by identifying the molecules in the left and right halves of the box.The multiplicity of the configuration with 15 molecules in the right half and 10 molecules in the left half is:

A Carnot cycle:

An ideal gas, consisting of n moles, undergoes an irreversible process in which the temperature has the same value at the beginning and end.If the volume changes from Vi to Vf, the change in entropy is given by:

A reversible refrigerator operates between a low temperature reservoir at TL and a high temperature reservoir at TH.Its coefficient of performance is given by:

Let k be the Boltzmann constant.If the configuration of the molecules in a gas changes so that the multiplicity is reduced to one-third its previous value, the entropy of the gas changes by:

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The temperature of n moles of a gas is increased from T_i to T_f at constant pressure.If the molar specific heat at constant pressure is C_p and is independent of temperature, then change in the entropy of the gas is:

A heat engine operates between a high temperature reservoir at T_H and a low temperature reservoir at T_L.Its efficiency is given by 1 - T_L/T_H:

Let k be the Boltzmann constant.If the configuration of molecules in a gas changes from one with a multiplicity of M₁ to one with a multiplicity of M₂, then entropy changes by:

An ideal gas, consisting of n moles, undergoes an irreversible process in which the temperature has the same value at the beginning and end.If the volume changes from V_i to V_f, the change in entropy is given by:

A reversible refrigerator operates between a low temperature reservoir at T_L and a high temperature reservoir at T_H.Its coefficient of performance is given by: