Fugacities of Mixtures: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  • Fugacity is an intensive variable; it does not depend on the amount of the phase.
  • When phases are in equilbrium, the fugacity of component 1 is the same in each phase, the fugacity of component 2 is the same in each phase, etc..
  • For an ideal gas mixture, the fugacity of each component is equal to its partial pressure.
  • For an ideal liquid, the fugacity of each component is its mole fraction times its saturation pressure.
  • In a mixture, the component with the lowest concentration can have the highest fugacity.
  • When temperature increases for an ideal gas mixture, the fugacities do not change.
  • As the concentration of a component in a mixture increases, its fugacity usually increases.
  • As the pressure of a mixture increases, the fugacity of each component increases, but the increase will be much smaller for a liquid or solid than a gas.
From studying this module, you should now be able to:
  • Calculate fugacities of each component in an ideal gas mixture.
  • Calculate liquid phase fugacities of each component in an ideal solution.
  • Explain criteria that are used to determine phase equilibrium for multicomponent mixtures.
  • Sketch fugacity versus temperature for each component in an ideal binary mixture.

 

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