ABSTRACT
Electrochemistry comprises reactions that involve charged particles, and the transfer of electrons. For their thermodynamic description, authors have to expand their definition of the chemical potential, and have to include a term that represents the electrochemical work associated with the transport of charges in an electric field. Reactions that involve the transfer of electrons are called redox reactions. A reduction reaction is the uptake of one electrons. The reverse reaction, the release of one or more electrons is called an oxidation. For zinc, the equilibrium is on the side of the ion, meaning the release of two electrons is an exergonic reaction, and thus the dissolution of zinc metal is the spontaneous direction: the zinc from the electrode is oxidized. For copper, on the other hand, the equilibrium is on the side of elemental copper. There are different types of half-cells. Half-cells can also consist of a gas and an ionic solution.
