How do you calculate the boiling point at different pressures?

Boiling occurs when the vapour pressure of a liquid equals the air pressure of the atmosphere above the liquid. Calculating the boiling point based on pressure can be done using several formulas. One formula for calculating the boiling point of water uses the known boiling point at sea level, 100°C, the atmospheric pressure at sea level and the atmospheric pressure at the time and elevation where the boiling takes place. For variations in Boiling Point as a function of Vapour Pressure use the Clausis-Clapeyron Equation

The Clausis-Clapeyron Equation is derived from VP2=VP1e−ΔHvRT at two different temperatures. The classic form is

ln(VP2/VP1) = ΔHv/R (1/T1−1/T2)

BP1=T1=373K at VP1=760mmHg
Determine BP2=T2 at VP2=700mmHg
R=0.008314 Kj/mole⋅K


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