Summary: Raoult's Law and Vapor-Liquid Equilibrium
- Raoult's law assumes ideal gases and ideal liquid solution. For similar molecules (e.g., n-hexane and n-octane), Raoult's law may be a good approximation.
- When a vapor mixture is cooled or its pressure is increased, both components condense.
- Bubble pressure is the pressure where the first bubble of vapor forms as the pressure above a liquid decreases at constant temperature.
- Bubble temperature is the temperature where the first bubble of vapor forms as the temperature of a liquid increases at constant pressure.
- Dew pressure is the pressure where the first drop of liquid forms as the pressure of a vapor increases at constant temperature.
- Dew temperature is the temperature where the first drop of liquid forms as the temperature of a vapor decreases at constant pressure.
- Unlike a pure component, at constant pressure a mixture does not evaporate at constant temperature.
Prepared by John L. Falconer and Kimberly R. Bourland
Department of Chemical and Biological Engineering, University of Colorado Boulder
Additional screencasts and interactive simulations for vapor-liquid equilibrium of ideal solutions are available on LearnChemE and YouTube