Deck 20: Entropy and the Second Law of Thermodynamics

Full screen (f)
exit full mode
Question
An ideal gas expands into a vacuum in a rigid vessel. As a result there is:

A) a change in entropy
B) an increase of pressure
C) a change in temperature
D) a decrease of internal energy
E) a change in phase
Use Space or
up arrow
down arrow
to flip the card.
Question
An ideal gas is to taken reversibly from state i, at temperature T1, to another states labeled I, II, III, IV and V on the p-V diargram below. All are at the same temperature T2. Rank the five processes according to the change in entropy of the gas, least to greatest. <strong>An ideal gas is to taken reversibly from state i, at temperature T<sub>1</sub>, to another states labeled I, II, III, IV and V on the p-V diargram below. All are at the same temperature T<sub>2.</sub> Rank the five processes according to the change in entropy of the gas, least to greatest.  </strong> A) I, II, III, IV, V B) V, IV, III, II, I C) I, then II, III, Iv, and V tied D) I, II, III, and IV, tied, then V E) I and V tied, then II, III, IV <div style=padding-top: 35px>

A) I, II, III, IV, V
B) V, IV, III, II, I
C) I, then II, III, Iv, and V tied
D) I, II, III, and IV, tied, then V
E) I and V tied, then II, III, IV
Question
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) 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
A hot object and a cold object are placed in thermal contact and the combination is isolated. They transfer energy until they reach a common temperature. The change Δ\Delta Sh in the entropy of the hot object, the change Δ\Delta Sc in the entropy of the cold object, and the change Δ\Delta Stotal in the entropy of the combination are:

A) Δ\Delta Sh > 0, Δ\Delta Sc > 0, Δ\Delta Stotal > 0
B) Δ\Delta Sh < 0, Δ\Delta Sc > 0, Δ\Delta Stotal > 0
C) Δ\Delta Sh < 0, Δ\Delta Sc > 0, Δ\Delta Stotal < 0
D) Δ\Delta Sh > 0, Δ\Delta Sc < 0, Δ\Delta Stotal > 0
E) Δ\Delta Sh > 0, Δ\Delta Sc < 0, Δ\Delta Stotal < 0
Question
Which of the following processes leads to a change in entropy of zero for the system undergoing the process?

A) Non-cyclic isobaric (constant pressure)
B) Non-cyclic isochoric (constant volume)
C) Non-cyclic isothermal (constant temperature)
D) Any closed cycle
E) None of these
Question
Possible units of entropy are:

A) J
B) J/K
C) J-1
D) liter.atm
E) cal/mol
Question
Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water <strong>Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water  </strong> A) 1, 2, 3, 4 B) 5,4,3,2 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 <div style=padding-top: 35px>

A) 1, 2, 3, 4
B) 5,4,3,2
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
Consider the following processes: The temperature of two identical gases are increased from the same initial temperature to the same final temperature. Reversible processes are used. For gas A the process is carried out at constant volume while for gas B it is carried out at constant pressure. The change in entropy:

A) is the same for A and B
B) is greater for A
C) is greater for B
D) is greater for A only if the initial temperature is low
E) is greater for A only if the initial temperature is high
Question
In a reversible process the system:

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
For all adiabatic processes:

A) the entropy does not change
B) the entropy increases
C) the entropy decreases
D) the entropy does not increase
E) the entropy does not decrease
Question
The difference in entropy Δ\Delta S = SB - SA for two states A and B of a system can computed as the integral \int dQ/T provided:

A) A and B are on the same adiabat
B) A and B have the same temperature
C) a reversible path is used for the integral
D) the change in internal energy is first computed
E) the energy absorbed as heat by the system is first computed
Question
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) 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
One mole of an ideal gas expands reversibly and isothermally at temperature T until its volume is doubled. The change of entropy of this gas for this process is:

A) R ln 2
B) (ln 2)/T
C) zero
D) RT ln 2
E) 2R
Question
The change in entropy is zero for:

A) reversible adiabatic processes
B) reversible isothermal processes
C) reversible processes during which no work is done
D) reversible isobaric processes
E) all adiabatic processes
Question
Which of the following is NOT a state variable?

A) Work
B) Internal energy
C) Entropy
D) Temperature
E) Pressure
Question
A slow (quasi-static) process is NOT reversible if:

A) the temperature changes
B) energy is absorbed or emitted as heat
C) work is done on the system
D) friction is present
E) the pressure changes
Question
For all reversible processes involving a system and its environment:

A) the entropy of the system does not change
B) the entropy of the system increases
C) the total entropy of the system and its environment does not change
D) the total entropy of the system and its environment increases
E) none of the above
Question
Let SI denote the change in entropy of a sample for an irreversible process from state A to state B. Let SR denote the change in entropy of the same sample for a reversible process from state A to state B. Then:

A) SI > SR
B) SI = SR
C) SI < SR
D) SI = 0
E) SR = 0
Question
Consider all possible isothermal contractions of an ideal gas. The change in entropy of the gas:

A) is zero for all 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
An ideal gas, consisting of n moles, undergoes a reversible isothermal process during which the volume changes from Vi to Vf. The change in entropy of the thermal reservoir in contact with the gas is given by:

A) nR(Vf - Vi)
B) nR ln(Vf - Vi)
C) nR ln(Vi/Vf)
D) nR ln(Vf/Vi)
E) none of the above (entropy can't be calculated for an irreversible process)
Question
According to the second law of thermodynamics:

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
A refrigerator absorbs energy of magnitude \mid QC \mid as heat from a low temperature reservoir and rejects energy of magnitude \mid QH \mid as heat to a high temperature reservoir. Work W is done on the working substance. The coefficient of performance is given by:

A) \mid QC \mid /W
B) \mid QH \mid /W
C) ( \mid QC \mid + \mid QH \mid )/W
D) W/ \mid QC \mid
E) W/ \mid QH \mid
Question
According to the second law of thermodynamics:

A) all heat engines have the same efficiency
B) all reversible heat engines have the same efficiency
C) the efficiency of any heat engine is independent of its working substance
D) the efficiency of a Carnot engine depends only on the temperatures of the two reservoirs
E) all Carnot engines theoretically have 100% efficiency
Question
A Carnot heat engine operates between a hot reservoir at absolute temperature TH and a cold reservoir at absolute temperature TC. Its efficiency is:

A) TH/TC
B) TC/TH
C) 1 - TH/TC
D) 1 - TC/TH
E) 100%
Question
The temperature TC of the cold reservoirs and the temperatures TH of the hot reservoirs for four Carnot heat engines are <strong>The temperature T<sub>C</sub> of the cold reservoirs and the temperatures T<sub>H</sub> of the hot reservoirs for four Carnot heat engines are   Rank these engines according to their efficiencies, least to greatest</strong> A) 1, 2, 3, 4 B) 1 and 2 tie, then 3 and 4 tie C) 2, 1, 3, 4 D) 1, 2, 4, 3 E) 2, 1, 4, 3 <div style=padding-top: 35px> Rank these engines according to their efficiencies, least to greatest

A) 1, 2, 3, 4
B) 1 and 2 tie, then 3 and 4 tie
C) 2, 1, 3, 4
D) 1, 2, 4, 3
E) 2, 1, 4, 3
Question
A Carnot cycle heat engine operates between 400 K and 500 K. Its efficiency is:

A) 20%
B) 25%
C) 44%
D) 79%
E) 100%
Question
A Carnot cycle:

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
For one complete cycle of a reversible heat engine, which of the following quantities is NOT zero?

A) the change in the entropy of the working gas
B) the change in the pressure of the working gas
C) the change in the internal energy of the working gas
D) the work done by the working gas
E) the change in the temperature of the working gas
Question
Consider the following processes: <strong>Consider the following processes:   Which are never found to occur?</strong> A) Only I B) Only II C) Only III D) Only II and III E) I, II and III <div style=padding-top: 35px> Which are never found to occur?

A) Only I
B) Only II
C) Only III
D) Only II and III
E) I, II and III
Question
In a thermally insulated kitchen, an ordinary refrigerator is turned on and its door is left open. The temperature of the room:

A) remains constant according to the first law of thermodynamics
B) increases according to the first law of thermodynamics
C) decreases according to the first law of thermodynamics
D) remains constant according to the second law of thermodynamics
E) increases according to the second law of thermodynamics
Question
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:

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
The maximum theoretical efficiency of a Carnot engine operating between reservoirs at the steam point and at room temperature is about:

A) 10%
B) 20%
C) 50%
D) 80%
E) 99%
Question
A perfectly reversible heat pump with a coefficient of performance of 14 supplies energy to a building as heat to maintain its temperature at 27 °\degree C. If the pump motor does work at the rate of 1 kW, at what rate does the pump supply energy to the building?

A) 15 kW
B) 3.85 kW
C) 1.35 kW
D) 1.07 kW
E) 1.02 kW
Question
A reversible refrigerator operates between a low temperature reservoir at TC and a high temperature reservoir at TH. Its coefficient of performance is given by:

A) (TH - TC)/TC
B) TC/(TH - TC)
C) (TH - TC)/TH
D) TH/(TH - TC)
E) TH(TH + TC)
Question
For all irreversible processes involving a system and its environment:

A) the entropy of the system does not change
B) the entropy of the system increases
C) the total entropy of the system and its environment does not change
D) the total entropy of the system and its environment increases
E) none of the above
Question
An inventor suggests that a house might be heated by using a refrigerator to draw energy as heat from the ground and reject energy as heat into the house. He claims that the energy supplied to the house can exceed the work required to run the refrigerator. This:

A) is impossible by first law
B) is impossible by second law
C) would only work if the ground and the house were at the same temperature
D) is impossible since heat flows from the (hot) house to the (cold) ground
E) is possible
Question
A Carnot heat engine runs between a cold reservoir at temperature TC and a hot reservoir at temperature TH. You want to increase its efficiency. Of the following, which change results in the greatest increase in efficiency? The value of Δ\Delta T is the same for all changes.

A) Raise the temperature of the hot reservoir by Δ\Delta T
B) Raise the temperature of the cold reservoir by Δ\Delta T
C) Lower the temperature of the hot reservoir by Δ\Delta T
D) Lower the temperature of the cold reservoir by Δ\Delta T
E) Lower the temperature of the hot reservoir by (1/2) Δ\Delta T and raise the temperature of the cold reservoir by (1/2) Δ\Delta T
Question
A heat engine that in each cycle does positive work and loses energy as heat, with no heat energy input, would violate:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) Newton's second law
Question
A Carnot engine operates between 200 °\degree C and 20 °\degree C. Its maximum possible efficiency is:

A) 90%
B) 100%
C) 38%
D) 72%
E) 24%
Question
A heat engine:

A) converts heat input to an equivalent amount of work
B) converts work to an equivalent amount of heat
C) takes heat in, does work, and loses energy heat
D) uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir
E) uses positive work done on the system to transfer heat from a high temperature reservoir to a low temperature reservoir
Question
A cyclical process that transfers energy as heat from a high temperature reservoir to a low temperature reservoir with no other change would violate:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Question
Let k be the Boltzmann constant. If the thermodynamic state of gas at temperature T changes isothermally and reversibly to a state with three timesthe number of microstates as initially, the energy input to gas as heat is:

A) Q = 0
B) Q = 3kT
C) Q = -3kT
D) kTln3
E) -kTln3
Question
The thermodynmaic state of gas changes configuration from one with 3.8 * 1018 multiplicity to one with 7.9 * 1019 microstates. The Boltzmann constant is 1.38 *10-23 J/K. The change in entropy is:

A) Δ\Delta S = 0
B) Δ\Delta S = 1.04 *10-23 J/K
C) F Δ\Delta S = -1.04 *10-23 J/K
D) Δ\Delta S = 4.19 *10-23 J/K
E) Δ\Delta S = -4.19 *10-23 J/K
Question
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:

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

A) Δ\Delta S = 0
B) Δ\Delta S = 3k ln 2
C) Δ\Delta S = -3k ln 2
D) Δ\Delta S = k ln 3
E) Δ\Delta S = -3 ln 3
Question
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:

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
A heat engine operates between 200 K and 100 K. In each cycle it takes 100 J from the hot reservoir, loses 25 J to the cold reservoir, and does 75 J of work. This heat engine violates:

A) both the first and second laws of thermodynamics
B) the first law but not the second law of thermodynamics
C) the second law but not the first law of thermodynamics
D) neither the first law nor the second law of thermodynamics
E) cannot answer without knowing the mechanical equivalent of heat
Question
A certain heat engine draws 500 cal/s from a water bath at 27 °\degree C and transfers 400 cal/s to a reservoir at a lower temperature. The efficiency of this engine is:

A) 80%
B) 75%
C) 55%
D) 25%
E) 20%
Question
A heat engine absorbs energy of magnitude \mid QH \mid from a high temperature reservoir, does work of magnitude \mid W \mid , and transferes energy of magnitude \mid QL \mid as heat to a low temperature reservoir. Its efficiency is:

A) \mid QH \mid / \mid W \mid
B) \mid QL \mid / \mid W \mid
C) \mid QH \mid / \mid QL \mid
D) \mid W \mid / \mid QH \mid
E) \mid W \mid / \mid QL \mid
Question
An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150 °\degree C and a low temperature reservoir of 30 °\degree C. This engine:

A) must violate the zeroth law of thermodynamics
B) must violate the first law of thermodynamics
C) must violate the second law of thermodynamics
D) must violate the third law of thermodynamics
E) does not necessarily violate any of the laws of thermodynamics
Question
On a warm day a pool of water transfers energy to the air as heat and freezes. This is a direct violation of:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Question
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:

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
A Carnot refrigerater runs between a cold reservoir at temperature TC and a hot reservoir at temperature TH. You want to increase its coefficient of performance. Of the following, which change results in the greatest increase in the coefficient? The value of Δ\Delta T is the same for all changes.

A) Raise the temperature of the hot reservoir by Δ\Delta T
B) Raise the temperature of the cold reservoir by Δ\Delta T
C) Lower the temperature of the hot reservoir by Δ\Delta T
D) Lower the temperature of the cold reservoir by Δ\Delta T
E) Lower the temperature of the hot reservoir by (1/2) Δ\Delta T and raise the temperature of the cold reservoir by (1/2) Δ\Delta T
Question
A heat engine in each cycle absorbs energy from a reservoir as heat and does an equivalent amount of work, with no other changes. This engine violates:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Question
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) 1.03 * 1023
B) 3.27 * 106
C) 150
D) 25
E) 5
Question
A heat engine in each cycle absorbs energy of magnitude \mid QH \mid as heat from a high temperature reservoir, does work of magnitude \mid W \mid , and then absorbs energy of magnitude \mid QL \mid as heat from a low temperature reservoir. If \mid W \mid = \mid QH \mid + \mid QL \mid this engine violates:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Unlock Deck
Sign up to unlock the cards in this deck!
Unlock Deck
Unlock Deck
1/56
auto play flashcards
Play
simple tutorial
Full screen (f)
exit full mode
Deck 20: Entropy and the Second Law of Thermodynamics
1
An ideal gas expands into a vacuum in a rigid vessel. As a result there is:

A) a change in entropy
B) an increase of pressure
C) a change in temperature
D) a decrease of internal energy
E) a change in phase
a change in entropy
2
An ideal gas is to taken reversibly from state i, at temperature T1, to another states labeled I, II, III, IV and V on the p-V diargram below. All are at the same temperature T2. Rank the five processes according to the change in entropy of the gas, least to greatest. <strong>An ideal gas is to taken reversibly from state i, at temperature T<sub>1</sub>, to another states labeled I, II, III, IV and V on the p-V diargram below. All are at the same temperature T<sub>2.</sub> Rank the five processes according to the change in entropy of the gas, least to greatest.  </strong> A) I, II, III, IV, V B) V, IV, III, II, I C) I, then II, III, Iv, and V tied D) I, II, III, and IV, tied, then V E) I and V tied, then II, III, IV

A) I, II, III, IV, V
B) V, IV, III, II, I
C) I, then II, III, Iv, and V tied
D) I, II, III, and IV, tied, then V
E) I and V tied, then II, III, IV
I, II, III, IV, V
3
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) nCp ln(Tf/Ti)
B) nCp ln(Ti/Tf)
C) nCp ln(Tf - Ti)
D) nCp ln(1 - Ti/Tf)
E) nCp (Tf - Ti)
nCp ln(Tf/Ti)
4
A hot object and a cold object are placed in thermal contact and the combination is isolated. They transfer energy until they reach a common temperature. The change Δ\Delta Sh in the entropy of the hot object, the change Δ\Delta Sc in the entropy of the cold object, and the change Δ\Delta Stotal in the entropy of the combination are:

A) Δ\Delta Sh > 0, Δ\Delta Sc > 0, Δ\Delta Stotal > 0
B) Δ\Delta Sh < 0, Δ\Delta Sc > 0, Δ\Delta Stotal > 0
C) Δ\Delta Sh < 0, Δ\Delta Sc > 0, Δ\Delta Stotal < 0
D) Δ\Delta Sh > 0, Δ\Delta Sc < 0, Δ\Delta Stotal > 0
E) Δ\Delta Sh > 0, Δ\Delta Sc < 0, Δ\Delta Stotal < 0
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
5
Which of the following processes leads to a change in entropy of zero for the system undergoing the process?

A) Non-cyclic isobaric (constant pressure)
B) Non-cyclic isochoric (constant volume)
C) Non-cyclic isothermal (constant temperature)
D) Any closed cycle
E) None of these
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
6
Possible units of entropy are:

A) J
B) J/K
C) J-1
D) liter.atm
E) cal/mol
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
7
Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water <strong>Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water  </strong> A) 1, 2, 3, 4 B) 5,4,3,2 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) 5,4,3,2
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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
8
Consider the following processes: The temperature of two identical gases are increased from the same initial temperature to the same final temperature. Reversible processes are used. For gas A the process is carried out at constant volume while for gas B it is carried out at constant pressure. The change in entropy:

A) is the same for A and B
B) is greater for A
C) is greater for B
D) is greater for A only if the initial temperature is low
E) is greater for A only if the initial temperature is high
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
9
In a reversible process the system:

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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
10
For all adiabatic processes:

A) the entropy does not change
B) the entropy increases
C) the entropy decreases
D) the entropy does not increase
E) the entropy does not decrease
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
11
The difference in entropy Δ\Delta S = SB - SA for two states A and B of a system can computed as the integral \int dQ/T provided:

A) A and B are on the same adiabat
B) A and B have the same temperature
C) a reversible path is used for the integral
D) the change in internal energy is first computed
E) the energy absorbed as heat by the system is first computed
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
12
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) 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)
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
13
One mole of an ideal gas expands reversibly and isothermally at temperature T until its volume is doubled. The change of entropy of this gas for this process is:

A) R ln 2
B) (ln 2)/T
C) zero
D) RT ln 2
E) 2R
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
14
The change in entropy is zero for:

A) reversible adiabatic processes
B) reversible isothermal processes
C) reversible processes during which no work is done
D) reversible isobaric processes
E) all adiabatic processes
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
15
Which of the following is NOT a state variable?

A) Work
B) Internal energy
C) Entropy
D) Temperature
E) Pressure
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
16
A slow (quasi-static) process is NOT reversible if:

A) the temperature changes
B) energy is absorbed or emitted as heat
C) work is done on the system
D) friction is present
E) the pressure changes
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
17
For all reversible processes involving a system and its environment:

A) the entropy of the system does not change
B) the entropy of the system increases
C) the total entropy of the system and its environment does not change
D) the total entropy of the system and its environment increases
E) none of the above
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
18
Let SI denote the change in entropy of a sample for an irreversible process from state A to state B. Let SR denote the change in entropy of the same sample for a reversible process from state A to state B. Then:

A) SI > SR
B) SI = SR
C) SI < SR
D) SI = 0
E) SR = 0
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
19
Consider all possible isothermal contractions of an ideal gas. The change in entropy of the gas:

A) is zero for all 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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
20
An ideal gas, consisting of n moles, undergoes a reversible isothermal process during which the volume changes from Vi to Vf. The change in entropy of the thermal reservoir in contact with the gas is given by:

A) nR(Vf - Vi)
B) nR ln(Vf - Vi)
C) nR ln(Vi/Vf)
D) nR ln(Vf/Vi)
E) none of the above (entropy can't be calculated for an irreversible process)
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
21
According to the second law of thermodynamics:

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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
22
A refrigerator absorbs energy of magnitude \mid QC \mid as heat from a low temperature reservoir and rejects energy of magnitude \mid QH \mid as heat to a high temperature reservoir. Work W is done on the working substance. The coefficient of performance is given by:

A) \mid QC \mid /W
B) \mid QH \mid /W
C) ( \mid QC \mid + \mid QH \mid )/W
D) W/ \mid QC \mid
E) W/ \mid QH \mid
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
23
According to the second law of thermodynamics:

A) all heat engines have the same efficiency
B) all reversible heat engines have the same efficiency
C) the efficiency of any heat engine is independent of its working substance
D) the efficiency of a Carnot engine depends only on the temperatures of the two reservoirs
E) all Carnot engines theoretically have 100% efficiency
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
24
A Carnot heat engine operates between a hot reservoir at absolute temperature TH and a cold reservoir at absolute temperature TC. Its efficiency is:

A) TH/TC
B) TC/TH
C) 1 - TH/TC
D) 1 - TC/TH
E) 100%
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
25
The temperature TC of the cold reservoirs and the temperatures TH of the hot reservoirs for four Carnot heat engines are <strong>The temperature T<sub>C</sub> of the cold reservoirs and the temperatures T<sub>H</sub> of the hot reservoirs for four Carnot heat engines are   Rank these engines according to their efficiencies, least to greatest</strong> A) 1, 2, 3, 4 B) 1 and 2 tie, then 3 and 4 tie C) 2, 1, 3, 4 D) 1, 2, 4, 3 E) 2, 1, 4, 3 Rank these engines according to their efficiencies, least to greatest

A) 1, 2, 3, 4
B) 1 and 2 tie, then 3 and 4 tie
C) 2, 1, 3, 4
D) 1, 2, 4, 3
E) 2, 1, 4, 3
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
26
A Carnot cycle heat engine operates between 400 K and 500 K. Its efficiency is:

A) 20%
B) 25%
C) 44%
D) 79%
E) 100%
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
27
A Carnot cycle:

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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
28
For one complete cycle of a reversible heat engine, which of the following quantities is NOT zero?

A) the change in the entropy of the working gas
B) the change in the pressure of the working gas
C) the change in the internal energy of the working gas
D) the work done by the working gas
E) the change in the temperature of the working gas
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
29
Consider the following processes: <strong>Consider the following processes:   Which are never found to occur?</strong> A) Only I B) Only II C) Only III D) Only II and III E) I, II and III Which are never found to occur?

A) Only I
B) Only II
C) Only III
D) Only II and III
E) I, II and III
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
30
In a thermally insulated kitchen, an ordinary refrigerator is turned on and its door is left open. The temperature of the room:

A) remains constant according to the first law of thermodynamics
B) increases according to the first law of thermodynamics
C) decreases according to the first law of thermodynamics
D) remains constant according to the second law of thermodynamics
E) increases according to the second law of thermodynamics
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
31
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:

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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
32
The maximum theoretical efficiency of a Carnot engine operating between reservoirs at the steam point and at room temperature is about:

A) 10%
B) 20%
C) 50%
D) 80%
E) 99%
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
33
A perfectly reversible heat pump with a coefficient of performance of 14 supplies energy to a building as heat to maintain its temperature at 27 °\degree C. If the pump motor does work at the rate of 1 kW, at what rate does the pump supply energy to the building?

A) 15 kW
B) 3.85 kW
C) 1.35 kW
D) 1.07 kW
E) 1.02 kW
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
34
A reversible refrigerator operates between a low temperature reservoir at TC and a high temperature reservoir at TH. Its coefficient of performance is given by:

A) (TH - TC)/TC
B) TC/(TH - TC)
C) (TH - TC)/TH
D) TH/(TH - TC)
E) TH(TH + TC)
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
35
For all irreversible processes involving a system and its environment:

A) the entropy of the system does not change
B) the entropy of the system increases
C) the total entropy of the system and its environment does not change
D) the total entropy of the system and its environment increases
E) none of the above
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
36
An inventor suggests that a house might be heated by using a refrigerator to draw energy as heat from the ground and reject energy as heat into the house. He claims that the energy supplied to the house can exceed the work required to run the refrigerator. This:

A) is impossible by first law
B) is impossible by second law
C) would only work if the ground and the house were at the same temperature
D) is impossible since heat flows from the (hot) house to the (cold) ground
E) is possible
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
37
A Carnot heat engine runs between a cold reservoir at temperature TC and a hot reservoir at temperature TH. You want to increase its efficiency. Of the following, which change results in the greatest increase in efficiency? The value of Δ\Delta T is the same for all changes.

A) Raise the temperature of the hot reservoir by Δ\Delta T
B) Raise the temperature of the cold reservoir by Δ\Delta T
C) Lower the temperature of the hot reservoir by Δ\Delta T
D) Lower the temperature of the cold reservoir by Δ\Delta T
E) Lower the temperature of the hot reservoir by (1/2) Δ\Delta T and raise the temperature of the cold reservoir by (1/2) Δ\Delta T
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
38
A heat engine that in each cycle does positive work and loses energy as heat, with no heat energy input, would violate:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) Newton's second law
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
39
A Carnot engine operates between 200 °\degree C and 20 °\degree C. Its maximum possible efficiency is:

A) 90%
B) 100%
C) 38%
D) 72%
E) 24%
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
40
A heat engine:

A) converts heat input to an equivalent amount of work
B) converts work to an equivalent amount of heat
C) takes heat in, does work, and loses energy heat
D) uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir
E) uses positive work done on the system to transfer heat from a high temperature reservoir to a low temperature reservoir
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
41
A cyclical process that transfers energy as heat from a high temperature reservoir to a low temperature reservoir with no other change would violate:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
42
Let k be the Boltzmann constant. If the thermodynamic state of gas at temperature T changes isothermally and reversibly to a state with three timesthe number of microstates as initially, the energy input to gas as heat is:

A) Q = 0
B) Q = 3kT
C) Q = -3kT
D) kTln3
E) -kTln3
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
43
The thermodynmaic state of gas changes configuration from one with 3.8 * 1018 multiplicity to one with 7.9 * 1019 microstates. The Boltzmann constant is 1.38 *10-23 J/K. The change in entropy is:

A) Δ\Delta S = 0
B) Δ\Delta S = 1.04 *10-23 J/K
C) F Δ\Delta S = -1.04 *10-23 J/K
D) Δ\Delta S = 4.19 *10-23 J/K
E) Δ\Delta S = -4.19 *10-23 J/K
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
44
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:

A) Δ\Delta S = 0
B) Δ\Delta S = k(M2 - M1)
C) Δ\Delta S = kM2/M1
D) Δ\Delta S = k ln(M2M1)
E) Δ\Delta S = k ln(M2/M1)
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
45
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:

A) Δ\Delta S = 0
B) Δ\Delta S = 3k ln 2
C) Δ\Delta S = -3k ln 2
D) Δ\Delta S = k ln 3
E) Δ\Delta S = -3 ln 3
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
46
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:

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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
47
A heat engine operates between 200 K and 100 K. In each cycle it takes 100 J from the hot reservoir, loses 25 J to the cold reservoir, and does 75 J of work. This heat engine violates:

A) both the first and second laws of thermodynamics
B) the first law but not the second law of thermodynamics
C) the second law but not the first law of thermodynamics
D) neither the first law nor the second law of thermodynamics
E) cannot answer without knowing the mechanical equivalent of heat
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
48
A certain heat engine draws 500 cal/s from a water bath at 27 °\degree C and transfers 400 cal/s to a reservoir at a lower temperature. The efficiency of this engine is:

A) 80%
B) 75%
C) 55%
D) 25%
E) 20%
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
49
A heat engine absorbs energy of magnitude \mid QH \mid from a high temperature reservoir, does work of magnitude \mid W \mid , and transferes energy of magnitude \mid QL \mid as heat to a low temperature reservoir. Its efficiency is:

A) \mid QH \mid / \mid W \mid
B) \mid QL \mid / \mid W \mid
C) \mid QH \mid / \mid QL \mid
D) \mid W \mid / \mid QH \mid
E) \mid W \mid / \mid QL \mid
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
50
An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150 °\degree C and a low temperature reservoir of 30 °\degree C. This engine:

A) must violate the zeroth law of thermodynamics
B) must violate the first law of thermodynamics
C) must violate the second law of thermodynamics
D) must violate the third law of thermodynamics
E) does not necessarily violate any of the laws of thermodynamics
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
51
On a warm day a pool of water transfers energy to the air as heat and freezes. This is a direct violation of:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
52
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:

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
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
53
A Carnot refrigerater runs between a cold reservoir at temperature TC and a hot reservoir at temperature TH. You want to increase its coefficient of performance. Of the following, which change results in the greatest increase in the coefficient? The value of Δ\Delta T is the same for all changes.

A) Raise the temperature of the hot reservoir by Δ\Delta T
B) Raise the temperature of the cold reservoir by Δ\Delta T
C) Lower the temperature of the hot reservoir by Δ\Delta T
D) Lower the temperature of the cold reservoir by Δ\Delta T
E) Lower the temperature of the hot reservoir by (1/2) Δ\Delta T and raise the temperature of the cold reservoir by (1/2) Δ\Delta T
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
54
A heat engine in each cycle absorbs energy from a reservoir as heat and does an equivalent amount of work, with no other changes. This engine violates:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
55
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) 1.03 * 1023
B) 3.27 * 106
C) 150
D) 25
E) 5
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
56
A heat engine in each cycle absorbs energy of magnitude \mid QH \mid as heat from a high temperature reservoir, does work of magnitude \mid W \mid , and then absorbs energy of magnitude \mid QL \mid as heat from a low temperature reservoir. If \mid W \mid = \mid QH \mid + \mid QL \mid this engine violates:

A) the zeroth law of thermodynamics
B) the first law of thermodynamics
C) the second law of thermodynamics
D) the third law of thermodynamics
E) none of the above
Unlock Deck
Unlock for access to all 56 flashcards in this deck.
Unlock Deck
k this deck
locked card icon
Unlock Deck
Unlock for access to all 56 flashcards in this deck.