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Raoult's Law

P_A = x_A × P°_A
Quick Reference
Formula / NotationP_A = x_A × P°_A
Also Known AsRaoult's vapor pressure law, ideal solution law, partial pressure law

What is Raoult's Law?

Raoult's Law states that the partial vapor pressure of a component in an ideal solution is equal to the mole fraction of that component multiplied by its pure vapor pressure at the same temperature. It applies to ideal solutions where intermolecular interactions between different molecules are the same as between like molecules. Deviations from Raoult's Law indicate non-ideal behavior.

Formula & Notation

P_A = x_A × P°_A

Other Names / Synonyms: Raoult's vapor pressure law, ideal solution law, partial pressure law

Properties & Characteristics

P_A = x_A × P°_A. Where P_A = partial vapor pressure of A, x_A = mole fraction of A, P°_A = vapor pressure of pure A. For binary solution: P_total = x_A × P°_A + x_B × P°_B. Positive deviation: stronger repulsion between unlike molecules (e.g., acetone + hexane). Negative deviation: stronger attraction (e.g., acetone + chloroform).

Uses & Applications

Distillation column design (vapor-liquid equilibrium). Predicting boiling point elevation (colligative property). Understanding azeotropes. Solvent selection for extractions. Vapor pressure calculations in chemical engineering. Understanding volatile solvent mixtures.

Safety Information

Theoretical law — no direct safety concerns. Practical applications involve volatile solvents with associated fire/toxicity hazards.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Raoult's Law
Formula P_A = x_A × P°_A
Synonyms Raoult's vapor pressure law, ideal solution law, partial pressure law

Frequently Asked Questions

Raoult's Law states that the partial vapor pressure of a component in an ideal solution is equal to the mole fraction of that component multiplied by its pure vapor pressure at the same temperature. It applies to ideal solutions where intermolecular interactions between different molecules are the same as between like molecules. Deviations from Raoult's Law indicate non-ideal behavior.

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