Applications of EMF Measurements

The standard cell potential helps find out the Gibbs free energy change and then the equilibrium constant of the reaction using thermodynamic relationships.

The temperature coefficient of the standard cell potential, its temperature derivative, allows calculation of the standard entropy change of the cell reaction; combining this with Gibbs energy and its relation to EMF yields the standard reaction enthalpy.

The difference between the cell potential and its standard value reflects the ions’ activity coefficient, which accounts for non-ideal interactions and modifies effective concentrations.

The electrochemical series ranks metals by standard electrode potentials, showing that a metal can reduce ions of metals placed above it; for example, zinc cannot reduce magnesium ions but can reduce hydrogen ions.

The anion transference number, describing anion current and its effect on concentration and potential gradients, can be derived from the EMF ratio of two concentration cells—one with transference and one without—provided the end electrodes are cation-reversible.

But, if the end electrodes are anion-reversible, this EMF ratio yields the cation’s transference number.