Nernst equation

The Nernst equation relates an electrode’s equilibrium potential to its standard potential, temperature, and the activities of reacting chemical species.

Electrochemical potential: The potential energy of a charged species in a chemical and electrical environment. The equation expresses equilibrium through the electrochemical potentials of reacting species.
Chemical equilibrium: A state in which forward and reverse reaction rates are equal and macroscopic composition is constant. The Nernst relation gives the electrode potential at which the redox reaction is in equilibrium.
Potentiometry: An electroanalytical method that determines chemical information by measuring cell voltage with negligible current. Its interpretation often uses the Nernst response between potential and analyte activity.
Butler–Volmer equation: An equation describing how electrode current depends on overpotential for an electrochemical reaction. Unlike the equilibrium Nernst relation, it describes current under nonequilibrium conditions.
Reaction quotient: A ratio of product to reactant activities, each raised to its stoichiometric coefficient. Its logarithm determines how far the potential shifts from the standard value.
Gibbs free energy: A thermodynamic state function that measures the maximum non-expansion work available at constant temperature and pressure. Equating reaction free energy with electrical work yields the equation.
pH electrode: An ion-selective electrode that produces a voltage related to hydrogen-ion activity. Its voltage response follows a Nernst-type dependence on hydrogen-ion activity.
Tafel equation: A logarithmic relation between electrode overpotential and current density in a kinetic regime. It links voltage to reaction rate, whereas Nernst links equilibrium voltage to activities.
Faraday constant: The electric charge carried by one mole of elementary charges. It converts electron transfer per mole into the potential’s electrical scale.
Redox reaction: A chemical reaction involving electron transfer and changes in oxidation states. Its balanced electron stoichiometry sets the equation’s charge factor.

Linked from 50 pages