Raoult's Law Definition

Raoult's Law can be used to calculate vapor pressure.
Raoult's Law can be used to calculate vapor pressure. Steve McAlister, Getty Images
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated March 06, 2017

Raoult's Law Definition: Raoult's Law is a law that relates the the vapor pressure of a solution is dependent on the mole fraction of a solute added to solution.

Raoult's Law is expressed by

Psolution = ΧsolventP0solvent

where
Psolution is the vapor pressure of the solution
Χsolvent is mole fraction of the solvent
P0solvent is the vapor pressure of the pure solvent

If more than one solute is added to the solution, each individual solvent's component is added to the total pressure.