The Nernst Equation  >>  >>   The use of standard reduction
potentials to predict the course of a reaction is somewhat
limited, in that they are only valid under standard conditions.
However, they can be used to predict the course of redox
reactions under nonstandard conditions.  This process of
extrapolation of the properties of a reaction under one set of
conditions to those under another set of conditions uses the
Nernst equation.  The Nernst Equation  If we know the Gibbs free
energy of reaction at under one set of conditions, it can be
used to predict the Gibbs free energy of reaction, and from that
the reduction potential, under a new set of conditions.
Derivation of the Nernst equation Consider the reaction: The
Gibbs free reaction energy can be related to the standard Gibbs
free reaction energy: Q is the reaction quotient: The reduction
potentials may be related to the free energies of reaction:
Therefore, the Nernst equation is the result:  The Nernst
equation relates the non-equilibrium properties