1. What is the Clausius-Clapeyron Equation?

The Clausius-Clapeyron equation describes the relationship between vapor pressure and temperature for a substance. It's particularly useful for determining the enthalpy of vaporization (ΔH) of water or other liquids.

2. How Does the Calculator Work?

The calculator uses the integrated form of the Clausius-Clapeyron equation:

Where:

• \( R \) — Universal gas constant (8.314 J/mol K)
• \( P1, P2 \) — Vapor pressures at two different temperatures (Pa)
• \( T1, T2 \) — Absolute temperatures corresponding to P1 and P2 (K)

Explanation: The equation relates the natural log of the vapor pressure ratio to the inverse temperature difference, scaled by the enthalpy of vaporization.

3. Importance of ΔH Calculation

Details: The enthalpy of vaporization is a crucial thermodynamic property that indicates the energy required to convert a liquid into vapor at constant pressure. It's important for understanding phase transitions, designing distillation systems, and modeling atmospheric processes.

4. Using the Calculator

Tips: Enter pressures in Pascals (Pa) and temperatures in Kelvin (K). For water, typical values might be P1=3169 Pa at T1=298K and P2=12280 Pa at T2=323K.

5. Frequently Asked Questions (FAQ)

Q1: What are typical ΔH values for water?
A: The enthalpy of vaporization for water is about 40.7 kJ/mol at 100°C, but varies with temperature.

Q2: Why must temperatures be in Kelvin?
A: The equation requires absolute temperature because it involves inverse temperature differences that wouldn't be consistent in Celsius.

Q3: How accurate is this method?
A: It provides reasonable estimates when the temperature range is small and the vapor behaves ideally.

Q4: Can this be used for other liquids?
A: Yes, but the temperature range should be small enough that ΔH remains approximately constant.

Q5: What are limitations of this approach?
A: It assumes ΔH is constant over the temperature range and that the vapor behaves as an ideal gas.