Question

How are vapour pressure and boiling point related?

Answer 1

Relation between Vapour pressure and Boiling point:

• Vapour pressure is the equilibrium pressure that is exerted by the vapours when they are in equilibrium with the solid or liquid phase.
• The boiling point is defined as the temperature at which the vapour pressure of the liquid phase becomes equal to atmospheric pressure.
• Whereas vapour pressure and boiling point are inversely related to each other. When the vapor pressure increases, the boiling point decreases, and vice versa.
• If the intermolecular force of attraction will be lesser in molecules, the liquid will be easily escapable hence, they will have high vapor pressure and accordingly, with respect to the weaker attraction between molecules, a lower temperature will be required to separate them, hence the boiling point will be low.

Therefore, vapour pressure and boiling point are related to each other by their inverse properties i.e when the vapor pressure is lower, it indicates a high boiling point and vice versa.