Thermodynamics Questions and Answers – Ideal Gas-2

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Ideal Gas-2”.

1. The value of cp and cv depend on
a) temperature of the gas
b) ɣ and R
c) pressure of the gas
d) all of the mentioned
View Answer

Answer: b
Explanation: The value of cp and cv depends on the number of atoms in a molecule and the molecular weight of the gas.
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2. Which of the following statement is true?
a) value of ɣ for monoatomic gases is 5/3
b) value of ɣ for diatomic gases is 7/5
c) for polyatomic gases, the value of ɣ is approximately taken as 4/3
d) all of the mentioned
View Answer

Answer: d
Explanation: These values of ɣ can be shown by the classical kinetic theory of gases.

3. The maximum and minimum values of ɣ is
a) 1.33, 1
b) 2.00, 1
c) 1.67, 1
d) 1.25, 1
View Answer

Answer: c
Explanation: ɣ=1 when cp=cv and ɣ=1.67=5/3 for monoatomic gases.
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4. Which of the following equation can be used to compute the entropy change between any two states of an ideal gas?
a) s2-s1 = cv*ln(T2/T1) + R*ln(v2/v1)
b) s2-s1 = cp*ln(T2/T1) – R*ln(p2/p1)
c) s2-s1 = cp*ln(v2/v1) + cv*ln(p2/p1)
d) all of the mentioned
View Answer

Answer: d
Explanation: Any of the given three equations can be used.

5. For a reversible adiabatic change, ds=0.
a) true
b) false
View Answer

Answer: a
Explanation: For a reversible adiabatic process, change in entropy is zero.
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6. For a reversible adiabatic process,
a) p*(v^ɣ) = constant
b) T*(v^(ɣ-1)) = constant
c) T*(p^(1-ɣ)/ɣ) = constant
d) all of the mentioned
View Answer

Answer: d
Explanation: All these relations come from the pv=RT and p*(v^ɣ) = constant.

7. Which of the following is true for a polytropic process?
a) p(v^n) is used to describe the process
b) it is not adiabatic
c) it can be reversible
d) all of the mentioned
View Answer

Answer: d
Explanation: These are the properties of an adiabatic process.
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8. In the equation p(v^n), n is calculated by
a) (logp1 + logp2) / (logv2 + logv1)
b) (logp1 – logp2) / (logv2 – logv1)
c) (logp1 – logp2) / (logv2 + logv1)
d) none of the mentioned
View Answer

Answer: b
Explanation: It comes from the p1*(v1^n) = p2*(v2^n).

9. For entropy change in a polytropic process, which of the following statement is true?
a) when n=ɣ, the entropy change becomes zero
b) if p2>p1, for n<=ɣ, the entropy of the gas decreases
c) for n>ɣ, the entropy of the gas increases
d) all of the mentioned
View Answer

Answer: d
Explanation: This comes from the relation s2-s1 = [(n-ɣ)/{n(ɣ-1)}]*R*ln(p2/p1).
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10. Polytropic specific heat is given by cn=cv(ɣ-n)/(1-n) .
a) true
b) false
View Answer

Answer: a
Explanation: The polytropic specific heat is used in the relation Qr=cn*ΔT.

11. Which of the following is true?
a) for n>ɣ, there will be positive heat transfer and gain in entropy
b) for n<ɣ, there will be negative heat transfer and decrease in entropy
c) both of the mentioned
d) none of the mentioned
View Answer

Answer: c
Explanation: This comes from the relation Qr=cn*ΔT and cn=cv(ɣ-n)/(1-n).

Sanfoundry Global Education & Learning Series – Thermodynamics.
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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter