Raoult's Law Distillation Calculator

Raoult's Law states that a component's vapor pressure in a mixture is proportional to its concentration — the Raoult's Law Distillation Calculator applies this to predict how a liquid mixture behaves at equilibrium. Select a calculation mode (binary volatile or nonvolatile solute), then enter the vapor pressures of pure A and B and the mole fraction of A to get the total vapor pressure, partial pressures for each component, and the vapor mole fractions showing how the vapor phase differs from the liquid. Also try the Heat Exchanger Calculator.

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Results

Total Vapor Pressure

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Partial Pressure A

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Partial Pressure B

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Vapor Mole Fraction A

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Vapor Mole Fraction B

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Frequently Asked Questions

What is Raoult's law used for?

Raoult's law is used to calculate the vapor pressure of ideal solutions and predict vapor-liquid equilibrium behavior. It's essential in distillation design, chemical engineering processes, and understanding how components separate in mixtures. See also our Filtration Rate Calculator.

What does Raoult's law state?

Raoult's law states that the partial vapor pressure of each component in an ideal solution is equal to the vapor pressure of the pure component multiplied by its mole fraction in the liquid phase.

What is the equation of Raoult's law?

The Raoult's law equation is Pi = xi × Pi°, where Pi is the partial pressure of component i, xi is its mole fraction in the liquid, and Pi° is the vapor pressure of pure component i.

How do I calculate mole fraction using Raoult's law?

To calculate mole fraction using Raoult's law, rearrange the equation: xi = Pi / Pi°. You need to know the partial pressure of the component and its pure vapor pressure.

When does Raoult's law apply accurately?

Raoult's law applies most accurately to ideal solutions where molecular interactions between different components are similar to those in pure components. It works best for chemically similar substances and at moderate pressures.

What is the difference between partial pressure and total pressure?

Partial pressure is the pressure exerted by each individual component in a mixture. Total pressure is the sum of all partial pressures according to Dalton's law.

How is vapor composition different from liquid composition?

Vapor composition (y-values) differs from liquid composition (x-values) because components with higher vapor pressures are enriched in the vapor phase. This difference enables separation by distillation.