Question 1

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\DeltaΔ Sh in the entropy of the hot object, the change  Δ\DeltaΔ Sc in the entropy of the cold object, and the change  Δ\DeltaΔ Stotal in the entropy of the combination are:

Accepted Answer

A)   Δ\DeltaΔ Sh > 0,  Δ\DeltaΔ Sc > 0,  Δ\DeltaΔ Stotal > 0
B)    Δ\DeltaΔ Sh Δ\DeltaΔ Sc > 0,  Δ\DeltaΔ Stotal > 0
C)   Δ\DeltaΔ Sh Δ\DeltaΔ Sc > 0,  Δ\DeltaΔ Stotal 
D)   Δ\DeltaΔ Sh > 0,  Δ\DeltaΔ Sc Δ\DeltaΔ Stotal > 0
E)    Δ\DeltaΔ Sh > 0,  Δ\DeltaΔ Sc Δ\DeltaΔ Stotal

Question 2

For all adiabatic processes:

Accepted Answer

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 3

A Carnot cycle heat engine operates between 400 K and 500 K. Its efficiency is:

Accepted Answer

A)   20%
B)   25%
C)   44%
D)   79%
E)   100%

Question 4

An ideal gas expands into a vacuum in a rigid vessel. As a result there is:

Accepted Answer

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

Question 5

The change in entropy is zero for:

Accepted Answer

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 A

Question 6

Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water
1)  goes from 20  °\degree°  to 30  °\degree° C
2)  goes from 30  °\degree°  to 40  °\degree° C.
3)  goes from 40  °\degree° to 45  °\degree° C
4)  foes from 80  °\degree°  to 85  °\degree° C

Accepted Answer

A)   1, 2, 3, 4
B)   4, 3, 2, 1
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.  E

Question 7

Consider the following processes:
I. Energy flows as heat from a hot object to a colder object
II.Work is done on a system and an equivalent amount of energy is
Rejected as heat by the system
III. Energy is absorbed as heat by a system and an equivalent amount
Of work is done by the system
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

Question 8

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

Accepted Answer

A)   10%
B)   20%
C)   50%
D)   80%
E)   99%

Question 9

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:

Accepted Answer

A)   R ln 2
B)   (ln 2) /T
C)   zero
D)   RT ln 2
E)   2R

Question 10

A slow (quasi-static)  process is NOT reversible if:

Accepted Answer

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

Exam 5: Entropy and the Second Law of Thermodynamics

Correct Answer
verified

For all adiabatic processes:

Correct Answer
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A Carnot cycle heat engine operates between 400 K and 500 K. Its efficiency is:

Correct Answer
verified

An ideal gas expands into a vacuum in a rigid vessel. As a result there is:

Correct Answer
verified
A

The change in entropy is zero for:

Correct Answer
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A

Rank from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water 1) goes from 20 $\degree$ to 30 $\degree$ C 2) goes from 30 $\degree$ to 40 $\degree$ C. 3) goes from 40 $\degree$ to 45 $\degree$ C 4) foes from 80 $\degree$ to 85 $\degree$ C

Correct Answer
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E

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

Correct Answer
verified

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:

Correct Answer
verified

A slow (quasi-static) process is NOT reversible if:

Correct Answer
verified

Exam 5: Entropy and the Second Law of Thermodynamics

Correct AnswerverifiedShow Answer

For all adiabatic processes:

Correct AnswerverifiedShow Answer

A Carnot cycle heat engine operates between 400 K and 500 K. Its efficiency is:

Correct AnswerverifiedShow Answer

An ideal gas expands into a vacuum in a rigid vessel. As a result there is:

Correct AnswerverifiedA

The change in entropy is zero for:

Correct AnswerverifiedA

Correct AnswerverifiedE

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

A slow (quasi-static) process is NOT reversible if:

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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A

Correct Answer
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A

Correct Answer
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E

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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