Enthalpy MCQ – Objective Questions with Answers
Mechanical Engineering › Thermodynamics | Free practice MCQs with detailed explanations
Last Updated: June 2026
📌 About this MCQ Set
Enthalpy (H = U + pV) is a thermodynamic property that combines internal energy with the product of pressure and volume. It is especially useful for flow processes and constant-pressure heat transfer.
These MCQs cover the definition, units, and applications of enthalpy.
8 questions • every answer comes with a worked explanation. Click Show Answer to check yourself.
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Enthalpy MCQs
Q1. Enthalpy is defined as:
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Answer: B. H = U + pV
By definition H = U + pV, where U is internal energy, p pressure and V volume.
Q2. Enthalpy is a:
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Answer: B. Point (state) function
Since U, p and V are all properties, H = U + pV is also a property (point function).
Q3. At constant pressure, the heat transferred equals the change in:
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Answer: B. Enthalpy
At constant pressure Q_p = ΔH, which is why enthalpy is convenient for constant-pressure processes.
Q4. The SI unit of specific enthalpy is:
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Answer: B. kJ/kg
Specific enthalpy is energy per unit mass: kJ/kg.
Q5. For an ideal gas, enthalpy is a function of:
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Answer: B. Temperature only
For an ideal gas, both U and H depend only on temperature.
Q6. In the steady flow energy equation, enthalpy combines internal energy with:
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Answer: B. Flow work (pV)
Enthalpy naturally accounts for flow work (pV), which is why it appears in the SFEE.
Q7. The change in enthalpy of a substance during a phase change at constant pressure equals the:
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Answer: B. Latent heat
At constant pressure the latent heat of phase change equals the enthalpy change.
Q8. If a process is at constant pressure and 50 kJ of heat is added, the enthalpy change is:
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Answer: C. 50 kJ
At constant pressure Q_p = ΔH = 50 kJ.
Frequently Asked Questions
What is enthalpy in simple terms?
Enthalpy is the total heat content of a system: internal energy plus the energy associated with its pressure and volume (H = U + pV).
Why is enthalpy useful?
It simplifies analysis of constant-pressure processes and flow systems, because at constant pressure the heat transfer equals the enthalpy change.
Is enthalpy a state function?
Yes. Since internal energy, pressure and volume are all properties, enthalpy is also a state (point) function.