MHT CET · Chemistry · Thermodynamics (C)

Which from the following defines enthalpy of a system?

A Ratio of pressure to volume
B Product of pressure and volume
C Internal energy (U) + PV
D Internal energy (U) - PV

Verified Solution

Answer & Solution

Correct Answer

(C) Internal energy (U) + PV

Step-by-step Solution

Detailed explanation

- (1) Ratio of pressure to volume: This is incorrect. The ratio of pressure to volume is not related to enthalpy.
- (2) Product of pressure and volume: This is also incorrect. The product of \(P\) and \(V\) is part of the enthalpy formula but doesn't define it by itself.
- (3) Internal energy (U) + PV: This is the correct definition of enthalpy. Enthalpy is the sum of internal energy and \(P \times V\).
- (4) Internal energy (U) - PV: This is incorrect. Enthalpy involves adding, not subtracting, PV from internal energy.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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