Interactive Self-Study Module: Gas-Phase Chemical Equilibrium

Overview:

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. Your retention of material in this module will increase if you write down reasons for your answers to ConcepTests, questions in screencasts, and questions to answer before using interactive simulations, and you try to solve the example problems before watching the screencast solutions. We suggest using the learning resources in the following order:

  1. Attempt to answer the multiple-choice ConcepTest and solve the example problem before watching the screencasts or working with the simulations.
  2. Watch the screencasts and answer the questions within the screencasts.
  3. Review important equations for gas-phase chemical equilibrium.
  4. Use the interactive simulations to further understand gas-phase chemical equilibrium.
  5. Try to solve the example problems before watching the solutions in the screencasts.
  6. Answer the ConcepTests.
  7. Look at the list of key points, but only after you try to list the key points yourself.
Motivation:
  • 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:
  • Express equilibrium constants in terms of thermodynamic activities.
  • Explain why the chemical equilibrium constant is dimensionless.
  • Explain why the equilibrium constant is independent of pressure.
  • Calculate heat of reaction at 298 K from heats of formation.
  • Calculate how the equilibrium constant changes with temperature.
  • Calculate the standard Gibbs free energy change for a reaction at 298 K, and its equilibrium constant, from Gibbs free energies of formation.
  • Calculate equilibrium conversions.
  • Explain why pressures must be in bar in equilibrium calculations.
  • Describe how equilibrium constants change with temperature for endothermic and exothermic reactions.
  • Calculate equilibrium mole fraction for ideal gases and non-ideal gases.
  • Predict how pressure changes will shift equilibrium conversion for a gas-phase reaction with a mole change.
  • Predict how an addition of an inert will affect equilibrium conversion.