<prompt> The magnitude of an electrical difference that exists across the membrane can be determined byGibbs-Donnan equationHenderson-Hasselbalch equationNernst equationFicks law  <response>: 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 