Raoult's Law Calculator

Raoult's Law states that each component in an ideal liquid mixture contributes to the total vapor pressure in proportion to its concentration — the Raoult's Law Calculator applies this principle to find the total vapor pressure of a solution. Select a calculation mode — a binary ideal solution (two volatile components) or a solution with a nonvolatile solute — then enter the pure vapor pressures and mole fractions of your components. You'll get the total vapor pressure along with each component's partial pressure and its vapor mole fraction above the liquid.

Calculation Mode *

mmHg

Value between 0 and 1

mmHg
mmHg

Value between 0 and 1

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 how adding a solute affects the vapor pressure of a solvent. It's essential in distillation, chemical engineering, and understanding solution behavior.

What does Raoult's law state?

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

What is the equation of Raoult's law?

The equation is P_i = x_i × P°_i, where P_i is the partial pressure of component i, x_i is its mole fraction, and P°_i is the vapor pressure of pure component i.

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

Rearrange the equation to x_i = P_i / P°_i. You need to know the partial pressure of the component and the vapor pressure of the pure component to calculate the mole fraction.

What is the vapor pressure of a solution with a mole fraction of 0.86?

The vapor pressure depends on the pure component's vapor pressure. Use P_solution = x_solvent × P°_solvent. If the pure solvent has a vapor pressure of 100 mmHg, then P_solution = 0.86 × 100 = 86 mmHg.

When does Raoult's law not apply?

Raoult's law only applies to ideal solutions. It fails for solutions with strong intermolecular interactions, electrolytes, or when components have significantly different molecular sizes or polarities.

What is the difference between partial pressure and total pressure?

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

How do you calculate vapor composition using Raoult's law?

Calculate each partial pressure using Raoult's law, then find the vapor mole fraction: y_i = P_i / P_total. The vapor composition differs from liquid composition due to different volatilities.