Nernst Equation

Nernst Equation

Aug 26, 2022, 16:45 IST

About Nernst Equation

Cells need not operate at standard state conditions. We can use the equation for the free energy change of a reaction to derive a relationship that tells us how the cell potential changes as the concentrations and/or temperature change. The free energy change for a reaction is Delta G = Delta Go + RT ln Q

where  Delta Go is the free energy change for the reaction with reactants and products at standard state activities (1 molar concentrations, 1 atmosphere pressures, pure solids or liquids), G is the free energy change under some other set of conditions, and Q is the reaction quotient for the reaction at the second set of conditions. Because Delta G = − nFECell and Delta Go = − nFEoCell, we can write

−nFECell = −nFEoCell + RT ln Q

Applications of Nernst equation:

• Determination of equilibrium constant for cell reaction:
• Determination of solubility product
• Ionization constant and degree of dissociation of weak acid or weak base:
• Determination of pH of a solution

Find solved example and formula of nernst equation in the following pdf