The magnitude of an electrical difference that exists across the membrane can be determined by
Gibbs-Donnan equation
Henderson-Hasselbalch equation
Nernst equation
Fick's law
In electrochemistry, the Nernst equation is an equation that relates the reduction potential of an electrochemical reaction (half-cell or full cell reaction) to the standard electrode potential, temperature, and activities (often approximated by concentrations) of the chemical species undergoing reduction and oxidation Ref: guyton and hall textbook of medical physiology 12 edition page number:58,59,60
General physiology