Question

According to Trouton's rule, the entropy of vaporization is primarily related to:

• A. Heat of fusion
• B. Fusion temperature
• C. Boiling temperature
• D. Crystal structure

Hint:

Trouton’s rule connects entropy of vaporization with boiling point of liquids.

Answer 1

The Correct Option is C

Concept: Trouton's rule states that for many liquids at their normal boiling point: \[ \Delta S_{vap} \approx 85 - 88 \, \text{J mol}^{-1}\text{K}^{-1} \] Entropy of vaporization is defined as: \[ \Delta S_{vap} = \frac{\Delta H_{vap}}{T_b} \]

Step 1: Use thermodynamic definition.
From phase equilibrium: \[ \Delta S = \frac{\Delta H}{T} \] So: \[ \Delta S_{vap} = \frac{\Delta H_{vap}}{T_b} \]

Step 2: Apply Trouton's rule.
Since $\Delta S_{vap}$ is approximately constant: \[ \Delta H_{vap} \propto T_b \] Thus boiling point directly influences entropy change.

Step 3: Evaluate options.
(A) Fusion heat → solid-liquid transition, irrelevant (B) Fusion temperature → not vaporization (C) Boiling temperature → correct controlling factor (D) Crystal structure → indirect influence only Final Answer: \[ \boxed{\text{Boiling temperature}} \]