Why is the vapour pressure of a boiling liquid the same as the ambient pressure?

1 Answer
Mar 29, 2016

Because that is the definition of a boiling point.


Boiling points are the 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.

At the normal boiling point, the ambient pressure is specified to be #1# #"atmosphere,"# and thus the vapour pressure of the substance is #1# #atm#.