Thermodynamics Questions and Answers – Enthalpy

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Enthalpy”.

1. The enthalpy of a substance(denoted by h), is defined as
a) h=u-pv
b) h=u+pv
c) h=-u+pv
d) h=-u-pv
View Answer

Answer: b
Explanation: This is a basic definition for enthalpy.
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2. In a constant volume process, internal energy change is equal to
a) heat transferred
b) work done
c) zero
d) none of the mentioned
View Answer

Answer: a
Explanation: In a constant volume process, there is no work other than the pdV work.

3. For an ideal gas, enthalpy becomes
a) h=u-RT
b) h=-u-RT
c) h=u+RT
d) h=-u+RT
View Answer

Answer: c
Explanation: For an ideal gas, pv=RT.
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4. Enthalpy is an intensive property of a system.
a) true
b) false
View Answer

Answer: a
Explanation: Enthalpy is an intensive property measured mostly in kJ/kg.

5. Heat transferred at constant pressure _____ the enthalpy of a system.
a) decreases
b) increases
c) first decreases then increases
d) first increases then decreases
View Answer

Answer: b
Explanation: At constant pressure, (dQ)=dh where h=u+pv is the specific enthalpy of the system.
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6. The enthalpy of an ideal gas depends only on the temperature.
a) true
b) false
View Answer

Answer: a
Explanation: This is because the internal energy of an ideal gas depends only on the temperature.

7. Total enthalpy of a system H is given by
a) H=h/m
b) H=m/h
c) H=mh
d) none of the mentioned
View Answer

Answer: c
Explanation: Total enthalpy equals (mass*enthalpy) of substance.
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8. The enthalpy and internal energy are the function of temperature for
a) all gases
b) steam
c) water
d) ideal gas
View Answer

Answer: d
Explanation: The enthalpy of an ideal gas depends only on the temperature because the internal energy of an ideal gas depends only on the temperature.

9. Change in enthalpy of a system is due to heat supplied at
a) constant volume
b) constant pressure
c) both at constant volume and pressure
d) none of the mentioned
View Answer

Answer: b
Explanation: Change in enthalpy occurs when heat is given to a system at constant pressure.
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10. At constant pressure
a) pdv=d(pv)
b) dQ=du+d(pv)
c) dQ=d(u+pv)
d) all of the mentioned
View Answer

Answer: d
Explanation: For a constant pressure process, dQ=du+pdv.

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

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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 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