Clausius-Clapeyron Calculator

How this Calculator Works

This calculator computes the vapor pressure (P2) at a second temperature (T2) based on the Clausius-Clapeyron equation. Adjust parameters below:

• Vapor Pressure P1: Reference pressure in kPa (Default: 101.3 kPa)
• Temperature T1: Reference temperature in °C (Default: 100 °C)
• Enthalpy of Vaporization (ΔHvap): Energy to vaporize 1 mole of liquid in kJ/mol (Default: 40.7 kJ/mol)
• Temperature T2: Target temperature in °C (Default: 25 °C)

The results are computed instantly and updated in the results panel on the right.

Formula & Methodology

Where:

• P1, P2: Vapor pressures at absolute temperatures T1 and T2 (Kelvin).
• ΔHvap: Enthalpy of vaporization (J/mol, converted from kJ/mol).
• R: Ideal gas constant (8.314 J/mol·K).

Step-by-Step Calculation Example

To calculate the vapor pressure of water at 25°C manually, follow these steps:

1. Identify the input parameters. For example:
   • P1 = 101.3 kPa, T1 = 100°C (373.15 K)
   • ΔHvap = 40.7 kJ/mol = 40700 J/mol
   • T2 = 25°C (298.15 K), R = 8.314 J/mol·K
2. Apply the formula:
   P2 = 101.3 * exp( - (40700 / 8.314) * (1/298.15 - 1/373.15) ) P2 ≈ 101.3 * exp(-3.465) ≈ 3.17 kPa
3. Verify the calculated value which is updated instantly in the results panel on the right.