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Vapor Pressure Francois Marie Raoult William Henry.

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Presentation on theme: "Vapor Pressure Francois Marie Raoult William Henry."— Presentation transcript:

1 Vapor Pressure Francois Marie Raoult William Henry

2 Henrys Law The concentration of a dissolved gas in a solution is directly proportional to the pressure of the gas above the solution Applies most accurately for dilute solutions of gases that do not dissociate or react with the solvent Yes CO 2, N 2, O 2 No HCl, HI

3 Raoults Law The presence of a nonvolatile solute lowers the vapor pressure of the solvent. P solution P solution = Observed Vapor pressure of the solution P 0 solvent P 0 solvent = Vapor pressure of the pure solvent solvent solvent = Mole fraction of the solvent

4 Liquid-liquid solutions in which both components are volatile Modified Raoult's Law: P 0 P 0 is the vapor pressure of the pure solvent P A P B P A and P B are the partial pressures

5 Raoults Law – Ideal Solution A solution that obeys Raoults Law is called an ideal solution

6 Negative Deviations from Raoults Law Strong solute-solvent interaction results in a vapor pressure lower than predicted Exothermic mixing = Negative deviation

7 Positive Deviations from Raoults Law Weak solute-solvent interaction results in a vapor pressure higher than predicted Endothermic mixing = Positive deviation


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