Vapor Pressure Calculator

Find vapor pressure at a new temperature (Clausius-Clapeyron).

Known vapor pressure P₁ (kPa)

Temperature T₁ (K)

Temperature T₂ (K)

ΔH vaporization (J/mol)

Vapor pressure at T₂ (kPa) 42.536

Formula: P₂ = P₁ · e^(−ΔH/R · (1/T₂ − 1/T₁))

Step-by-step with your numbers:

1. Values used:

2. Known vapor pressure P₁ = 101.3 kPa

3. Temperature T₁ = 373.15 K

4. Temperature T₂ = 350 K

5. ΔH vaporization = 40,700 J/mol

7. Vapor pressure at T₂ = 42.536kPa

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Find a liquid's vapor pressure at another temperature.

The math behind it

Clausius-Clapeyron: P₂ = P₁ × e^(−ΔHvap/R × (1/T₂ − 1/T₁)).

Water at 350 K → ~41.5 kPa.

Lower temperature?

Lower vapor pressure — fewer molecules escape.