Nernst equation - Definition

In electrochemistry, the Nernst equation gives the electrode potential (E), relative to the standard electrode potential, (E⁰), of the electrode couple or, equivalently, of the half cells of a battery

<math>

E = E^0 - \frac{RT}{zF} \ln\frac{a_{\mbox{red}}}{a_{\mbox{ox}}} <math>

<math>

E = E^0 - \frac{0.0591}{n} \log\frac{[\mbox{red}]}{[\mbox{ox}]} <math>

• R is the universal gas constant, equal to 8.314570 J K^-1 mol^-1
• T the temperature in kelvins
• z the charge number or valence of the electrode reaction
• a the chemical activities on the reduced and oxidized side, respectively
• F is the Faraday constant, equal to 96,485 C mol^-1
• n is the number of electrons transferred in the half-reaction.
• [red] is the concentration of oxidizing agent (the reduced species).
• [ox] is the concentration of reducing agent (the oxidized species).

History

The Nernst equation is named after the German physical chemist Walther Nernst who first formulated it.

See also

• Electrodiffusion.