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Chemical Sciences
Physical Chemistry
1887
Intermediate

Raoult's Law

Pi=xiPiP_i = x_i P_i^*

Vapor pressure of a component equals its mole fraction times pure vapor pressure.

By François-Marie Raoult

Chemical Sciences
Raoult's Law
1887 · François-Marie Raoult
Why it matters: Basis of distillation, phase diagrams, and solution thermodynamics.

Discoverers: François-Marie Raoult (1887)

What does it mean?

Vapor pressure of a component equals its mole fraction times pure vapor pressure.

Why should I care?

Basis of distillation, phase diagrams, and solution thermodynamics.

Variables & Units

SymbolNameUnitMeaning
PiP_iPartial pressureVapor pressure of component
xix_iMole fractionLiquid mole fraction
PiP_i*Pure vapor pressureOf pure component

Worked Example

Ideal binary mixture: total P = x_A P_A* + x_B P_B*.

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Raoult's Law

Pi=xiPiP_i = x_i P_i^*

Real-world impact

Distillation

Basis of distillation, phase diagrams, and solution thermodynamics.

Photo: Unsplash — technology

Vapor pressure of a component equals its mole fraction times pure vapor pressure.

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