Q. According to the third law of thermodynamics, what happens as the temperature approaches absolute zero?
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A.
Entropy approaches zero
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B.
Entropy approaches infinity
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C.
Internal energy approaches zero
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D.
All molecular motion stops
Solution
The third law states that as the temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.
Correct Answer:
A
— Entropy approaches zero
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Q. If the entropy of a system increases, what can be inferred about the system?
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A.
It is losing energy
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B.
It is becoming more ordered
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C.
It is becoming more disordered
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D.
It is in thermal equilibrium
Solution
An increase in entropy indicates that the system is becoming more disordered.
Correct Answer:
C
— It is becoming more disordered
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Q. In a heat engine, if the input heat is 800 J and the output work is 300 J, what is the efficiency?
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A.
0.375
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B.
0.5
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C.
0.25
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D.
0.625
Solution
Efficiency = Work output / Heat input = 300 J / 800 J = 0.375 or 37.5%.
Correct Answer:
A
— 0.375
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Q. In a heat engine, what is the work done equal to?
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A.
Heat input minus heat output
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B.
Heat output minus heat input
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C.
Total heat energy
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D.
Change in internal energy
Solution
The work done by a heat engine is equal to the heat input minus the heat output.
Correct Answer:
A
— Heat input minus heat output
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Q. In an isothermal process, what remains constant?
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A.
Pressure
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B.
Volume
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C.
Temperature
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D.
Internal energy
Solution
In an isothermal process, the temperature of the system remains constant.
Correct Answer:
C
— Temperature
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Q. What does the second law of thermodynamics state about entropy?
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A.
Entropy can decrease in an isolated system
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B.
Entropy remains constant in reversible processes
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C.
Entropy of an isolated system always increases
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D.
Entropy is a measure of energy
Solution
The second law of thermodynamics states that the entropy of an isolated system always increases over time.
Correct Answer:
C
— Entropy of an isolated system always increases
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Q. What is the relationship between heat transfer and temperature difference in a conductor?
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A.
Directly proportional
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B.
Inversely proportional
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C.
Independent
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D.
Exponential
Solution
Heat transfer through conduction is directly proportional to the temperature difference between the ends of the conductor.
Correct Answer:
A
— Directly proportional
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Q. What is the relationship between temperature and kinetic energy in gases?
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A.
Directly proportional
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B.
Inversely proportional
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C.
No relationship
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D.
Exponential relationship
Solution
The average kinetic energy of gas molecules is directly proportional to the temperature of the gas.
Correct Answer:
A
— Directly proportional
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Q. What is the work done by a gas that expands isothermally from volume V1 to V2 at temperature T?
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A.
nRT ln(V2/V1)
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B.
nRT (V2 - V1)
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C.
P(V2 - V1)
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D.
0
Solution
For isothermal expansion, the work done is given by W = nRT ln(V2/V1).
Correct Answer:
A
— nRT ln(V2/V1)
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Q. Which of the following is a consequence of the third law of thermodynamics?
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A.
Absolute zero cannot be reached
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B.
Entropy can be negative
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C.
Heat engines are 100% efficient
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D.
Energy can be created
Solution
The third law of thermodynamics implies that absolute zero cannot be reached, as the entropy of a perfect crystal approaches zero.
Correct Answer:
A
— Absolute zero cannot be reached
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