Nernst equation

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. In physiology the Nernst equation is used for finding the electric potential of a cell membrane with respect to one ion.

$E = E^0 - \frac{RT}{nF} \ln\frac{a_{\mbox{red}}}{a_{\mbox{ox}}}$

At room temperature the following is true

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

For a cell membrane potential with respect to one ion

$E = E^0 - \frac{0.0591}{n} \log\frac{[\mbox{ion out of cell}]}{[\mbox{ion inside cell}]}$

History

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