Question

From the following list, identify the properties which are equal in both vapor and liquid phases at equilibrium:
(A) Temperature
(B) Density
(C) Enthalpy
(D) Chemical potential
Choose the \textbf{correct} answer from the options given below:

• A. A and B
• B. A and C
• C. C and D
• D. A and D

Hint:

At phase equilibrium, temperature and chemical potential are equal across co-existing phases.

Answer 1

The Correct Option is D

Step 1: Recall equilibrium conditions.
For phase equilibrium (liquid–vapor equilibrium), specific intensive properties must be identical across both phases. Equilibrium requires the same temperature and equal chemical potential.

Step 2: Analyze each property.
- (A) Temperature: Identical in both phases at equilibrium.
- (B) Density: Not identical; liquid is denser than vapor.
- (C) Enthalpy: Different for vapor and liquid.
- (D) Chemical potential: Must be identical in both phases at equilibrium.

Step 3: Conclusion.
The correct answer is (4) A and D.