Vapor Pressure Calculator (clausius-clapeyron)

This Clausius Clapeyron Equation calculator will help the chemical engineering student and professional to save time and verify their calculation.

What is Clausius Clapeyron equation?

The Clausius–Clapeyron equation describes how the vapor pressure of a substance changes with temperature. It relates the rate of change in pressure to the heat required for phase change (like boiling or condensation), helping estimate vapor pressure at different temperatures using known values.

Vapor Pressure Calculator

Vapor Pressure Calculator

Clausius-Clapeyron Equation Solver

ln(P₁/P₂) = (ΔHᵥₐₚ/R) × (1/T₂ – 1/T₁)
Where R = 8.314 J/(mol·K)
How to use: Enter known values with preferred units to calculate ΔHᵥₐₚ or any unknown parameter. Leave the field you want to calculate empty.
Initial Conditions (P₁, T₁)
Final Conditions (P₂, T₂)
Heat of Vaporization

Equation

    \[ \ln\left(\frac{P_2}{P_1}\right) = -\frac{\Delta H_{vap}}{R} \left( \frac{1}{T_2} - \frac{1}{T_1} \right) \]

Where:

R = Ideal gas constant = 8.314 \, \text{J/mol·K}
P_1 = Initial vapor pressure (in kPa or mmHg)
P_2 = Final vapor pressure at new temperature (same units as P_1)
T_1 = Initial absolute temperature (in Kelvin)
T_2 = Final absolute temperature (in Kelvin)
\Delta H_{vap} = Enthalpy of vaporization (in J/mol)

Applications in Chemical Engineering

The Clausius–Clapeyron equation is commonly used for:

  • Designing distillation and separation processes
  • Estimating boiling points under varying pressures
  • Analysing refrigeration and phase change systems
  • Predicting the vapour behaviour of volatile compounds

We have posted Antoine Equation Calculator for the students and professionals which is free and an online tool. So do check it out.

FAQ (Vapour Pressure Calculator)

1. What is the Clausius–Clapeyron Equation used for?

This equation is helps to calculate how vapor pressure changes with temperature. It’s commonly applied in chemical engineering, particularly in phase change calculations like boiling, condensation, and distillation design.

2. What is the difference between Clausius–Clapeyron and the Antoine Equation?

Both relate vapor pressure to temperature, but the Antoine Equation is empirical and provides more accurate results over specific temperature ranges and Clausius–Clapeyron equation is more theoretical and widely used in teaching and engineering calculations.

3. Is the Clausius–Clapeyron equation accurate at high pressures?

The equation assumes ideal gas behavior, so its accuracy decreases at high pressures or when the substance is far from its boiling point.

4. Why is enthalpy of vaporization important in this equation?

ΔHvap​ represents the energy needed to convert a substance from liquid to vapor. It’s a key variable in determining how vapor pressure changes with temperature.