2.17 : Redox Equilibria: Overview

A reduction-oxidation reaction is commonly called a redox reaction. In a redox reaction, electrons are transferred from one species to another rather than being shared between or among atoms. The reducing agent or reductant is the species that loses electrons and gets oxidized in the process. The species that gains electrons and gets reduced in the process is the oxidizing agent or oxidant. Redox reactions are represented as two separate equations called half-reactions, where one equation represents the species that gains electrons, and the other represents the species that loses electrons.

Generally, the thermodynamics of a reaction is expressed in terms of the change in Gibbs free energy (ΔG), which is a function of concentrations of reactants and products. However, the thermodynamics of a redox reaction is expressed in terms of electrochemical potential (E) and the Nernst equation, as the reaction involves the movement of electrons. The Nernst Equation expresses the relationship between the electrochemical potential and the concentrations of the reactants and products.