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  Home > JCE Print > Journal of Chemical Education > Issues > 1999  > November  >
Research: Science and Education
The Gibbs Phase Rule Revisited: Interrelationships between Components and Phases
Joseph S. Alper
Department of Chemistry, University of Massachusetts-Boston, Boston, MA 02125
Cover
November 1999
Vol. 76 No. 11
p. 1567
Abstract
The Gibbs phase rule relates the number of degrees of freedom to the number of components and number of phases in a system at thermodynamic equilibrium. In determining the number of components, one must determine the number of independent reactions and the number of stoichiometric constraints. Textbooks focus on the problem of determining the number of independent reactions. This paper discusses the stoichiometric constraints in multiphase reactive systems. It is shown that two simple, seemingly similar systems can differ in their number of components. The analysis of these systems is then extended to show that (i) the number of components can be affected by the temperature and pressure of the system and (ii) in certain situations, a system containing arbitrary amounts of two different chemical compounds should be regarded as a one-component system.
More Information
*  Citation
 Alper, Joseph S. J. Chem. Educ. 1999 76 1567.
*  Keywords
 Physical Chemistry; Phase Transitions / Diagrams; Equilibrium; Thermodynamics
*  History
 Created:
Last Updated:		 October 12, 1999
June 23, 2005
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