5
Phase Equilibrium
PRINCIPAL FACTS AND IDEAS
1. The laws of thermodynamics determine equilibrium between phases.
2. 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.
3. The Gibbs phase rule gives the number of independent intensive variables
in a multicomponent multiphase system at equilibrium:
f c − p + 2
where f is the number of independent intensive variables, c is the number
of components, and p is the number of phases.
4. The Gibbs phase rule allows phase diagrams to be understood.
5. The Clausius and Clausius–Clapeyron equations govern the curves in
phase diagrams.
6. Thermodynamics allows analysis of the stability of phases in systems.
7. Surface effects must be included in a complete thermodynamic treatment,
but are usually negligible.
199
Phase Equilibrium
PRINCIPAL FACTS AND IDEAS
1. The laws of thermodynamics determine equilibrium between phases.
2. 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.
3. The Gibbs phase rule gives the number of independent intensive variables
in a multicomponent multiphase system at equilibrium:
f c − p + 2
where f is the number of independent intensive variables, c is the number
of components, and p is the number of phases.
4. The Gibbs phase rule allows phase diagrams to be understood.
5. The Clausius and Clausius–Clapeyron equations govern the curves in
phase diagrams.
6. Thermodynamics allows analysis of the stability of phases in systems.
7. Surface effects must be included in a complete thermodynamic treatment,
but are usually negligible.
199