Clausius-Clapeyron Calculator

The Vapor Pressure Curve

We know that if you heat a liquid up, it evaporates faster (its vapor pressure increases). But this relationship is not a simple straight line; it is a steep, dramatic exponential curve.

The Clausius-Clapeyron Equation allows us to trace this exact curve. If we know the vapor pressure of a liquid at one temperature, we can use this massive equation to perfectly predict what its vapor pressure will be at any other temperature in the universe.

The Heat of Vaporization

The entire equation revolves around $\Delta H_{vap}$ (The Enthalpy of Vaporization). This is the exact amount of thermal energy required to physically tear the molecules of a liquid apart so they can become a gas.

• Water has a very high $\Delta H_{vap}$ because its molecules are locked together tightly by Hydrogen Bonds. It takes massive heat to force it to evaporate.
• Rubbing alcohol has a low $\Delta H_{vap}$, which is why it evaporates rapidly off your skin, absorbing your body heat and feeling cold.

The Two-Point Equation

Note: The temperatures must always be strictly in Kelvin, and the Enthalpy is typically converted from kJ to standard Joules to match the $8.314$ Gas Constant.