Nernst Equation Definition

Definition: Equation relating the voltage of a chemical cell to its standard cell potential and to the concentrations of the reactants and product.

The Nernst equation is:

E_cell = E⁰_cell - (RT/nF) x log₁₀Q

where
E_cell is the cell potential
E⁰_cell refers to standard cell potential
R is the gas constant
T is the absolute temperature
n is the number of moles of electrons transferred by the cell's reaction
F is Faraday's constant
Q is the reaction quotient, where

Q = [C]^c·[D]^d / [A]^a·[B]^b

where A, B, C, and D are chemical species; and a, b, c, and d are coefficients in the balanced equation:
a A + b B → c C + d D

Example: At 25 °C, the Nernst Equation can be expressed as:

E_cell = E⁰_cell - 0.0591/n x log₁₀Q