# Boiling Point

ln(P_1/P_2) = -(\DeltaH)/R * (1/T_1 - 1/T_2)

Boiling point calculator using Clausius-Clapeyron equation.

Enter 'x' in the field to be calculated.
in J/mol
ideal gas constant in J/mol/K

This tool calculates the boiling point of a liquid using the Clausius-Clapeyron formula.

A simple application of this formula consists on calculating the boiling point of water at altitude. Indeed, water has a boiling temperature (T1 = 100°C) under normal conditions (P1 = 101325 Pa at sea level), the boiling temperature can be calculated at a different pressure (P2) at a certain altitude using Clausius-Clapeyron equation (See detailed example below). Here is the general formula:

ln(P_1/P_2) = -(\DeltaH)/R * (1/T_1 - 1/T_2)

P1: Pressure in state 1 in pascal (Pa)
T1: Boiling temperature of substance in state 1 in kelvin (at pressure P1)
P2: Pressure in state 2 in pascal (Pa)
T2: Boiling temperature of substance in state 2 in kelvin (at pressure P2)
ΔH: Enthalpy of vaporization of the substance in J/mol
R: ideal gas constant (\approx 8.314463 J/ (mol.K))

## How to calculate water boiling temperature at altitude ?

To do so, the Clausius-Clapeyron calculator can be combined with the atmospheric pressure calculator.

Application: What is the boiling temperature of water at top of Everest ?
1/ calculation of atmospheric pressure at top of mount Everest :
- Pressure at sea level: 101325 Pa
- Altitude at top of Everest: 8848 m
- Average temperature at top of Everest : -36 °C

We get this calculator : pressure at the top of Everest = 28324 Pa

2/ Calculation of boiling water temperature under calculated pressure
P2 = 28324 Pa
The boiling temperature of the water at sea level is 100 °C therefore,
T1 = 100 °C
P1 = 101325 Pa
ΔH (enthalpy of water vaporization) = 40660 J/mol

We use the above calculator ang get, boiling water temperature at top of mount Everest = 67 °C