For 10 points, identify this equation, named for a German chemist, which allows one to find either the electromotive force or standard electrode potential, provided the reaction quotient is known.
When the Butler-Volmer equation is used to describe the charge transfer reaction rate, this equation is used to describe the open circuit potential, except in the case of intercalation electrodes, for which it does not hold. One variant of this equation calculates membrane potential provided membrane permeability and ion concentration, the Goldman-Hodgkin-Katz equation. The change in Gibbs free energy is directly proportional to this equation, which is used to find a cell's electric potential. For 10 points, identify this equation, named for a German chemist, which allows one to find either the electromotive force or standard electrode potential, provided the reaction quotient is known. 
When the Butler-Volmer equation is used to describe the charge transfer reaction rate, this equation is used to describe the open circuit potential, except in the case of intercalation electrodes, for which it does not hold.
Nernst Equation 