Interactive Self-Study Module: Raoult's Law and Vapor-Liquid Equilibrium
Department of Chemical and Biological Engineering, University of Colorado Boulder 

This module uses screencasts and interactive simulations to explain the vapor-liquid phase equilibrium of two liquids that form an ideal solution. Both pressure-composition and temperature-composition diagrams are explained. It then provides step-by-step quiz simulations and example problems to allow the user to test themselves. We suggest using the learning resources in the following order:

  1. Attempt to answer the multiple choice ConcepTests before watching the screencasts or working with the simulations.
  2. Watch the screencast that describes the phase diagrams and answer the questions within the screencast.
  3. Use the interactive simulation to further understand the behavior of the phase diagrams.
  4. Use the quiz interactive simulations to test your understanding by carrying out step-by-step preparation of phase diagrams.
  5. Try to solve the example problem before watching the solution in the screencast.
  6. Answer the ConcepTests.

The differences in compositions of liquid and vapor mixtures in equilibrium is the basis for the separation of mixtures by distillation.

          This module is intended for Material and Energy Balances, Thermodynamics, and Separations courses.

Before studying this module, you need to:

After studying this module, you should be able to:
  1. Given a vapor composition and saturation pressure versus temperature data, determine the dew temperature (at constant pressure) or the dew pressure (at constant temperature). 
  2. Given a liquid composition and saturation pressure versus temperature data, determine the bubble temperature (at constant pressure) or the bubble pressure (at constant temperature). 
  3. Use Raoult's law to calculate equilibrium compositions and/or equilibrium pressures for ideal solutions and ideal gases. 
  4. Construct a pressure-composition diagram for an ideal mixture given saturation pressures at a given temperature.
  5. Construct a temperature-composition diagram for an idea mixture given Antoine equations at a given pressure.