How is the boiling point relate to vapor pressure?

1 Answer
Jun 11, 2018

Answer:

An old question....and an old problem....

Explanation:

The boiling point of a liquid are those conditions of temperature and pressure, when the VAPOUR pressure of a liquid is equal to the ambient pressure, and bubbles of vapour form directly in the liquid. The #"normal boiling point"# is specified when the AMBIENT pressure, and ALSO the vapour pressure of the BOILING LIQUID is #"ONE ATMOSPHERE"#.

And this underlies the principle of vacuum distillation. A vacuum pump can SUBSTANTIALLY reduce the ambient pressure...and at an accessible temperature, the vapour pressure of the liquid may be #1*mm*Hg# or even lower...and so the liquid comes across...

AS a first approx. we can sometimes use a vapour pressure nomograph to approximate the boiling point of a liquid AT REDUCED pressure...

picstopin.com

I know there is such a nomograph on the front of the #"Chemists Companion"#...and also instructions on how to use it....