1. What is the Normal Boiling Point Formula?

The normal boiling point formula calculates the temperature at which a liquid boils at 1 atmosphere pressure using thermodynamic properties. It's based on the relationship between enthalpy and entropy of vaporization.

2. How Does the Calculator Work?

The calculator uses the boiling point formula:

Where:

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

Explanation: The boiling point occurs when the Gibbs free energy change for vaporization equals zero, leading to this simple relationship between enthalpy and entropy.

3. Importance of Boiling Point Calculation

Details: Accurate boiling point prediction is essential in chemical engineering, pharmaceutical development, and industrial process design where phase changes are critical.

4. Using the Calculator

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

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 is entropy of vaporization important?
A: Entropy of vaporization represents the disorder increase during phase change and is relatively constant for many liquids (Trouton's rule: ~85 J/mol·K).

Q3: Can this formula be used for all substances?
A: This formula works well for many liquids but may have limitations for strongly associated liquids or near critical points.

Q4: How accurate is this calculation?
A: Accuracy depends on the precision of input values. For most applications, it provides a good estimate of boiling point.

Q5: 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 organic compounds.