Raoult's Law Calculator

The Raoult's Law Calculator computes vapor pressure of an ideal solution from the mole fraction of the solvent and the pure solvent vapor pressure. Raoult's law states that the relative lowering of vapor pressure equals the mole fraction of the solute.

$$p_{\text{solution}} = x_{\text{solvent}} \times p^\circ_{\text{solvent}}$$

where $p_{\text{solution}}$ is the vapor pressure of the solution, $x_{\text{solvent}}$ is the mole fraction of the solvent, and $p^\circ_{\text{solvent}}$ is the vapor pressure of the pure solvent.

Example: A solution with solvent mole fraction 0.86 and pure solvent vapor pressure 24.7 mmHg gives $p = 0.86 \times 24.7 = 21.24$ mmHg.

Frequently Asked Questions

What does Raoult's law state?

Raoult's law states that the vapor pressure of a solution equals the mole fraction of the solvent multiplied by the vapor pressure of the pure solvent. It applies to ideal solutions with non-volatile solutes.

How do I find mole fraction from Raoult's law?

Rearrange the formula: $x_{\text{solvent}} = p_{\text{solution}} / p^\circ_{\text{solvent}}$. Divide the solution vapor pressure by the pure solvent vapor pressure.

What is the vapor pressure of a solution with mole fraction 0.25?

If the pure solvent vapor pressure is 12 mmHg, then $p = 0.25 \times 12 = 3$ mmHg. Multiply the mole fraction by the pure solvent vapor pressure.

When does Raoult's law not apply?

Raoult's law fails for non-ideal solutions where strong solute-solvent interactions occur. Electrolyte solutions and concentrated mixtures often require activity coefficients instead of mole fractions.

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Raoult's Law Calculator

Raoult's Law Calculator

Frequently Asked Questions

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