5
Phase Equilibrium
PRINCIPAL FACTS AND IDEAS
- The laws of thermodynamics determine equilibrium between phases.
- The fundamental fact of phase equilibrium is that at equilibrium the
chemical potential of any substance must have the same value in all
phases in which that substance appears.
- The Gibbs phase rule gives the number of independent intensive variables
in a multicomponent multiphase system at equilibrium:
fc−p+ 2
wherefis the number of independent intensive variables,cis the number
of components, andpis the number of phases.
- The Gibbs phase rule allows phase diagrams to be understood.
- The Clausius and Clausius–Clapeyron equations govern the curves in
phase diagrams.
- Thermodynamics allows analysis of the stability of phases in systems.
- Surface effects must be included in a complete thermodynamic treatment,
but are usually negligible.
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