Heterogeneous Chemical Equilibrium: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  • Adding more of a reactant or product that is in a single-component phase does not change equilibrium because it does not change the activity of that component..
  • When a single component solid or liquid is involved in a reaction, its activity is one in the equilibrium expression.
  • The activity and fugacity of solids and liquids do not change much with pressure.
  • The activity and fugacity of a component does not depend on the amount of a phase, but on the concentration within the phase.
  • Heterogeneous reactions can exhibit significantly different behavior from gas-phase reactions: all of one component can react if it is present in as a pure phase so that the equilibrium expression cannot be satisfied.
From studying this module, you should now be able to:
  • Calculate equilibrium conversions for systems that contain more than one phase.
  • Predict how pressure changes will affect equilibrium conversion for a heterogeneous reaction.
  • Predict how the addition of a reactant or product to an equilibrium mixture will shift equilibrium for a heterogeneous reaction.


Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder