Phase coexistence and Clapeyron slope
Pure phases coexist at common T and p when their molar Gibbs energies are equal.
Key knowledge
Pure phases coexist at common T and p when their molar Gibbs energies are equal. Along a first-order coexistence curve, dp/dT=Δs_m/Δv_m=L_m/(TΔv_m), with phase differences taken in the same direction and L_m=TΔs_m.
Values and equations
g₁=g₂; dp/dT=Δs_m/Δv_m=L_m/(TΔv_m)
- g₁,g₂,L_m
- Molar Gibbs energies and molar latent heat J mol⁻¹
- s_m
- Molar entropy J mol⁻¹ K⁻¹
- v_m
- Molar volume m³ mol⁻¹
- T
- Temperature K
- p
- Pressure Pa
Conditions and scope
- Equilibrium pure substance, nonzero molar volume difference and finite latent heat; no extra work coordinates.
- The differential Clapeyron equation is not the approximate integrated vapour-pressure formula. Critical endpoints and mixtures require separate treatment.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Richard Fitzpatrick / University of Texas at Austin2 sources
Evidence and review
Thermodynamics and Statistical Mechanics (2016): Equilibrium between phases: Equations 9.59–9.63: fixed-amount Gibbs minimum and equal molar Gibbs energies. Thermodynamics and Statistical Mechanics (2016): Clausius–Clapeyron equation: Equations 9.72–9.74: exact coexistence derivative and latent heat; excludes v₂−v₂ typographical error in 9.71.
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Entry details
Permanent link to this entry ↗- Record identity
- physics-phase-coexistence-clapeyron
- Revision
- university-core.1
- Structured reference record
- University core expansion