Later, Raoult extended this thinking to liquids. Raoult's Law states the vapor pressure contributed by each component of a mixture of liquids is the vapor pressure of that component multiplied by its mol fraction of the mixture.
This is because the mol fraction of a component governs the proportion of the liquid surface the component occupies, and the "share" of the surface occupied by a component controls its ability to escape and make pressure.
X1 = mols of substance 1 in liquid/ (mols of substance 1 + mols of substance 2)
X2 = mols of substance 2 in liquid/ (mols of substance 1 + mols of substance 2)
P1* = vapor pressure of substance 1 on its own
P2* = vapor pressure of substance 2 on its own
P1 = X1P1* = vapor pressure from substance 1 in the mix
P2 = X2P2 * = vapor pressure from substance 2 in the mix
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