The Nernst equation is a chemical thermodynamic relationship used in electrochemistry to calculate the reduction potential of a reaction (half-cell or full cell reaction) from the standard electrode potential, absolute temperature, and the reaction quotient. It enables the determination of cell potential under non-standard conditions and relates the measured cell potential to the reaction quotient, allowing the accurate determination of equilibrium constants/Electrochemistry/Nernst_Equation). The equation is derived from the Gibbs free energy under standard conditions and relates the instantaneous potential, E, to the standard potential, E°, and the reaction quotient, Q. The Nernst equation can be expressed as:

$$E = E^o - \dfrac{RT}{nF} \ln Q$$

where E is the cell potential of the cell, E° is the cell potential under standard conditions, R is the ideal gas constant, T is the temperature, n is the number of electrons transferred in the redox reaction, F is Faradays constant, and Q is the reaction quotient. The equation can also be written in the form of log base 10/Electrochemistry/Nernst_Equation). The Nernst equation is useful for determining the increase in cell potential for an increase in the concentration of a reactant and can be used to calculate the electric potential of a cell membrane with respect to one type of ion.