Interactive Self-Study Module: Gas-Phase Chemical Equilibrium
Department of Chemical and Biological Engineering, University of Colorado Boulder 

This module uses screencasts and interactive simulations to explain how to calculate chemical equilibrium for reactions involving gases. The effects of pressure, temperature and inerts on chemical equilibrium are discussed. It then provides example problems and step-by-step quiz simulations 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 screencasts and answer the questions within the screencasts.
  3. Use the two interactive simulations to further understand gas-phase chemical equilibrium.
  4. Try to solve the two example problems before watching the solutions in the screencasts.
  5. Answer the ConcepTests.

Determining equilibrium conversion and how it depends on pressure, temperature, and concentrations is important for chemical reactor design. 

This module is intended for a thermodynamics or kinetics course.

Before studying this module, you should:

After studying this module, you should be able to:
  1. Express equilibrium constants in terms of thermodynamic activities.
  2. Explain why the chemical equilibrium constant is dimensionless.
  3. Explain why the equilibrium constant is independent of pressure.
  4. Calculate heat of reaction at 298 K from heats of formation.
  5. Calculate how the equilibrium constant changes with temperature.
  6. Calculate the standard Gibbs free energy change for a reaction at 298 K, and its equilibrium constant, from Gibbs free energies of formation.
  7. Calculate equilibrium conversions.
  8. Explain why pressures must be in bar in equilibrium calculations.
  9. Describe how equilibrium constants change with temperature for endothermic and exothermic reactions.
  10. Calculate equilibrium mole fraction for ideal gases and non-ideal gases.
  11. Predict how pressure changes will shift equilibrium conversion for a gas-phase reaction with a mole change.
  12. Predict how an addition of an inert will affect equilibrium conversion.