Clausius Clapeyron Equation Calculator

The Clausius Clapeyron Equation Calculator is a free online tool that calculates the molar enthalpy of vapourization at various temperatures. The clausius clapeyron equation calculator tool can speed up the process and displays the result in a fraction of a second.

Clausius Clapeyron Equation Calculator: The Clausius Clapeyron Equation is the basis for this online tool. When a liquid is placed in an evacuated vessel, the vapour of that liquid fills the empty space above it. The vapour pressure of the liquid is the pressure of this vapour. This vapour pressure is proportional to the system's temperature. The above equation connects two vapour pressures at two temperatures.

With this calculator, when and how do I utilise the Clausius-Clapeyron equation? What does all of this have to do with vaporisation enthalpy? Continue reading if you have. All of these questions, and more, will be answered!

What is Clausius Clapeyron Equation and its Derivation?

If the vapour pressure and enthalpy of vaporisation at one temperature are known, the Clausius Clapeyron equation is used to calculate the vapour pressure at any other temperature. The vapourization curve for the majority of liquids is known to be the same. However, when the temperature rises, the vapour pressure rises with it.

The Clapeyron equation states:


  • dP/dT be the derivative of pressure with respect to temperature.
  • H be the specific latent heat that absorbed or released the thermal energy  during a phase transition.
  • T be the corresponding temperature.
  • ΔV be the change of the specific volume during a phase transition.

This formula is deduced via the Clausius-Clapeyron equation. It expresses the relationship between a liquid's vapour pressure and temperature. It's accurate for liquid-to-gas (vaporisation) or solid-to-gas (condensation) transitions (sublimation). When the specific volume of a molecule's gas and condensed phases differ significantly, we can obtain the following equation:

ln(P1/P2) = ΔH/R*(1/T2 - 1/T1)


  • T1 be the initial temperature measured in Kelvin (K)
  • T2 be the final temperature (K)
  • P1 be the initial pressure
  • P2 be the final pressure
  • ΔH be the molar enthalpy of vaporization or sublimation (J/mol)
  • R be the gas constant, The value is 8.3145 J/mol*K

For more concepts check out to get quick answers by using this free tool.

How can you use the Clausius Clapeyron Equation Calculator?

The Clausius Clapeyron Equation calculator is used in the following way:

  • Fill in the appropriate input fields with the initial and final temperatures, as well as the vapour pressure.
  • To acquire the result, click the "Calculate" button.
  • Finally, using the Clausius Clapeyron equation, the molar enthalpy of vapourization will be displayed in the output field.

FAQs on Clausius Clapeyron Equation Calculator

1. What is the use of Clapeyron equation? 

The Clapeyron equation helps us determine thermodynamic values for reactions or phases. When combined with volume data, we can use the slope of an experimentally-determined reaction to calculate the heat of vapourization.


2. In the Clausius-Clapeyron equation, what are T1 and T2?

Clausius Clapeyron equation is ln(P2/P1) = (Hvap/R)((1/T1) - (1/T2)


  • P is the vapour pressure at a certain temperature and pressure, such as atmospheric pressure
  • T is the corresponding temperature in the equation.

3. What is the vaporisation heat?

The energy necessary for a phase shift is converting a liquid into a gas - is known as the heat of vaporisation, or Enthalpy of vaporisation. Similarly, the enthalpy of sublimation is the amount of energy required for a straight phase transition from a solid to a gaseous state.

4. When is it appropriate to apply the Clausius-Clapeyron equation?

The phase transition between two phases of matter with the same composition is described by the equation. As a result, the Clausius-Clapeyron equation can be used to calculate vapour pressure as a function of temperature or to calculate the heat of phase change using vapour pressures at two different temperatures.