The thermodynamic description of mixtures
Start with the big picture
Chemical potential is the partial molar Gibbs energy, while partial molar properties describe how extensive mixture properties change as a component is added. At phase equilibrium, each component has equal chemical potential in the phases. The Gibbs–Duhem equation links changes in component chemical potentials at fixed temperature and pressure. Ideal gas and solution models express chemical potential using composition; activity and fugacity extend this description to nonideal systems. The lesson also relates mixing and excess properties to nonideality, and introduces the phase rule, tie-lines, the lever rule, and vapor–liquid equilibrium. Together, these ideas show how thermodynamic descriptions connect composition, measurable properties, and phase coexistence.
What you'll learn
- Define chemical potential and relate it to partial molar Gibbs energy.
- State the chemical-potential condition for component equilibrium between phases.
- Distinguish ideal-mixture descriptions from activity- and fugacity-based treatments.
- Explain how mixing and excess properties characterize mixture behavior.
- Identify how phase-rule and mass-balance concepts describe multiphase systems.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
