Nernst equation
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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.
- <math>
E = E^0 - \frac{RT}{nF} \ln\frac{a_{\mbox{red}}}{a_{\mbox{ox}}} <math>
At room temperature the following is true
- <math>
E = E^0 - \frac{0.0591}{n} \log\frac{[\mbox{red}]}{[\mbox{ox}]} <math>
For a cell membrane potential with respect to one ion
- <math>
E = E^0 - \frac{0.0591}{n} \log\frac{[\mbox{ion out of cell}]}{[\mbox{ion inside cell}]} <math>
- R is the universal gas constant, equal to 8.314510 J K-1 mol-1
- T the temperature in kelvins
- a the chemical activities on the reduced and oxidized side, respectively
- F is the Faraday constant, equal to 9.6485309*10^4 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
de:Nernst-Gleichung fr:Équation de Nernst nl:Wet van Nernst ja:ネルンストの式 pl:Równanie Nernsta sl:Nernstov potencial