1. What is the Normal Boiling Point Equation?

The normal boiling point equation \( T_b = \frac{\Delta H_{vap}}{\Delta S_{vap}} \) calculates the temperature at which a liquid boils at 1 atmosphere pressure using thermodynamic relations at equilibrium.

2. How Does the Calculator Work?

The calculator uses the thermodynamic equation:

Where:

• \( T_b \) — Normal boiling point (K)
• \( \Delta H_{vap} \) — Enthalpy of vaporization (J/mol)
• \( \Delta S_{vap} \) — Entropy of vaporization (J/mol·K)

Explanation: At the boiling point, the liquid and vapor phases are in equilibrium, and the Gibbs free energy change is zero, leading to this thermodynamic relationship.

3. Importance of Normal Boiling Point Calculation

Details: Calculating normal boiling point is essential for chemical process design, separation techniques, and understanding substance behavior under standard conditions.

4. Using the Calculator

Tips: Enter enthalpy of vaporization in J/mol and entropy of vaporization in J/mol·K. Both values must be positive and valid.

5. Frequently Asked Questions (FAQ)

Q1: What is the normal boiling point?
A: The temperature at which a liquid's vapor pressure equals the standard atmospheric pressure (1 atm or 101.325 kPa).

Q2: Why use this thermodynamic approach?
A: It provides a fundamental relationship between enthalpy, entropy, and temperature at phase equilibrium.

Q3: What are typical values for ΔH_vap and ΔS_vap?
A: ΔH_vap typically ranges from 20-50 kJ/mol, while ΔS_vap is often around 85-90 J/mol·K for many liquids (Trouton's rule).

Q4: Are there limitations to this equation?
A: This assumes ideal behavior and may not be accurate for associating liquids or substances with significant molecular interactions.

Q5: How does pressure affect boiling point?
A: This equation calculates boiling point at 1 atm. For other pressures, the Clausius-Clapeyron equation should be used.