Thermodynamics Questions and Answers – First and Second Laws Combined

This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “First and Second Laws Combined”.

1. The equation TdS=dU+pdV is obtained from which law?
a) first law
b) second law
c) both of the mentioned
d) none of the mentioned
View Answer

Answer: c
Explanation: By first law, dQ=dU+pdV and from second law, dQ=TdS.

2. Which of the following equation is true?
a) TdS=dH+Vdp
b) TdS=dH-Vdp
c) TdS=-dH-Vdp
d) TdS=-dH+Vdp
View Answer

Answer: b
Explanation: It comes from TdS=dU+pdV and H=U+pV.

3. The equation dQ=dE+dW holds good for
a) any process, reversible or irreversible
b) only reversible process
c) only irreversible process
d) none of the mentioned
View Answer

Answer: a
Explanation: This equation holds good for any process and for any system.
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4. The equation dQ=dU+pdW holds good for any process undergone by a closed stationary system.
a) true
b) false
View Answer

Answer: a
Explanation: When a closed stationary system undergoes a process, this equation holds true.

5. The equation dQ=dU+pdV holds good for
a) open system
b) closed system
c) both of the mentioned
d) none of the mentioned
View Answer

Answer: b
Explanation: This equation is true only for a reversible(quasi-static) process.
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6. The equation TdS=dU+pdV holds good for
a) reversible process
b) reversible process
c) both of the mentioned
d) none of the mentioned
View Answer

Answer: c
Explanation: This equation holds good for any process undergone by a closed system since it is a relation among properties which are independent of the path.

7. The equation dQ=TdS is true only for a reversible process.
a) true
b) false
View Answer

Answer: a
Explanation: This comes from the second law.
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8. The equation TdS=dH-Vdp
a) relates only the properties of a system
b) there is no path function term in the equation
c) the equation holds good for any process
d) all of the mentioned
View Answer

Answer: d
Explanation: Since there is no path function in the equation hence the equation holds good for any process.

9. The entropy change of a system between two identifiable equilibrium state is ___ when the intervening process is reversible or change of state is irreversible.
a) different
b) same
c) depends on the process
d) none of the mentioned
View Answer

Answer: b
Explanation: To determine the change in entropy, a known reversible path is made to connect the two end states and integration is performed on this path.
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10. It is better to state that “the change of state is irreversible, rather than say it is an irreversible process”.
a) true
b) false
View Answer

Answer: a
Explanation: This is because no irreversible path or process can be plotted on thermodynamic coordinates.

Sanfoundry Global Education & Learning Series – Thermodynamics.
To practice all areas of Thermodynamics, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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