The change in Gibbs energy per mole of added component, controlling phase and reaction equilibria.
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The chemical potential, symbolized mu, is the partial molar Gibbs energy of a component, defined as the change in total Gibbs energy when a small amount of that component is added at constant temperature and pressure. Matter spontaneously moves from regions of higher chemical potential to regions of lower chemical potential, so it acts as the driving force for transport and reaction. At equilibrium the chemical potential of each species is the same in all phases in contact, which governs phase equilibria such as ice and water coexisting. Chemical potential also determines how reaction equilibria shift with composition. It is the most general criterion of equilibrium in multicomponent systems.
Key ideas: It is the slope of Gibbs energy with respect to amount, at constant T, P and other amounts. For an ideal gas, mu equals mu degree plus RT ln(P over P degree), and for a solute mu equals mu degree plus RT ln c. Equality across phases defines equilibrium.
Common mistakes and connections: Do not confuse it with electric potential or with potential energy. Substances flow from high to low chemical potential. It is the foundation of osmotic pressure, boiling point elevation, solubility and electrode potentials.
Chemical potential rises logarithmically with concentration, mu = mu standard + RT ln a (298 K). Matter flows from high to low chemical potential. The interactive lesson shows this as a live animation or chart.
At 0 degrees Celsius and 1 bar, liquid water and ice have equal chemical potentials, so the two phases coexist in equilibrium.
The change in Gibbs energy per mole of added component, controlling phase and reaction equilibria.
Chemical Potential is a advanced topic in Thermodynamics & Energetics. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Thermodynamics & Energetics first: Statistical Thermodynamics, Partition Function, Boltzmann Distribution.
The next topics in Thermodynamics & Energetics are Fugacity and Activity and Gibbs Phase Rule.
Yes. The interactive lesson includes a self-check question on Chemical Potential, and the Thermodynamics & Energetics quiz draws on every topic in this area.
Chemical Potential is topic 65 of 91 in Thermodynamics & Energetics.