1. What is Trouton's Rule?

Trouton's rule states that the entropy of vaporization is approximately the same for most liquids at their boiling points, typically around 85 J/mol K. This allows for estimation of boiling points when enthalpy of vaporization is known.

2. How Does the Calculator Work?

The calculator uses Trouton's rule:

Where:

• \( \Delta H_{vap} \) — Enthalpy of vaporization (J/mol)
• \( \Delta S_{vap} \) — Entropy of vaporization (J/mol K), typically ~85 J/mol K
• \( T_b \) — Boiling point in Kelvin

Explanation: The rule works because similar types and degrees of molecular ordering are lost during vaporization for most liquids.

3. Importance of Boiling Point Estimation

Details: Boiling point estimation is crucial for chemical process design, purification methods, and understanding intermolecular forces in liquids.

4. Using the Calculator

Tips: Enter enthalpy of vaporization in J/mol. The entropy of vaporization defaults to 85 J/mol K (Trouton's value) but can be adjusted for specific compounds.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is Trouton's rule?
A: It's approximate (±10%). Notable exceptions include water (109 J/mol K) and alcohols due to hydrogen bonding.

Q2: What are typical ΔS_vap values?
A: Most non-polar liquids: 85±5 J/mol K. Polar liquids may deviate due to stronger intermolecular forces.

Q3: When does Trouton's rule fail?
A: For very low boiling liquids (He, H₂), strongly associated liquids (water, alcohols), and very high boiling metals.

Q4: Can this predict ΔH_vap from T_b?
A: Yes, the equation can be rearranged to estimate enthalpy of vaporization if boiling point is known.

Q5: Why is ΔS_vap roughly constant?
A: Because the increase in positional disorder upon vaporization is similar for most liquids.