Nernst Equation
Last Updated: 5/7/19 by Tim Paschkewitz
1Nernst Equation
There are many resources that describe the detailed background, derivation, and applications of this equation.
Bard, A. J.; Faulkner, L. A. Electrochemical Methods: Fundamentals and Applications, 2nd ed. Wiley-Interscience: New York, 2000.
Kissinger, P.; Heineman, W. R. Laboratory Techniques in Electroanalytical Chemistry, 2nd ed. Marcel Dekker, Inc: New York, 1996.
Wang, J. Analytical Electrochemistry, 3rd ed. John Wiley & Sons, Inc.: Hoboken, NJ, 2006.
Langhus, D. L. Fundamentals of Electroanalytical Chemistry. J. Chem. Educ., 2002, 79(10), 1207. Here, we present just a snippet to get you started.
Bard, A. J.; Faulkner, L. A. Electrochemical Methods: Fundamentals and Applications, 2nd ed. Wiley-Interscience: New York, 2000.Kissinger, P.; Heineman, W. R. Laboratory Techniques in Electroanalytical Chemistry, 2nd ed. Marcel Dekker, Inc: New York, 1996.
Wang, J. Analytical Electrochemistry, 3rd ed. John Wiley & Sons, Inc.: Hoboken, NJ, 2006.
Langhus, D. L. Fundamentals of Electroanalytical Chemistry. J. Chem. Educ., 2002, 79(10), 1207. Here, we present just a snippet to get you started.
To account for the possibility of non-unity activities in an electrochemical reaction, the Nernst equation (see below) can be used to express the equilibrium electrode potential 
in terms of the actual activities,
in terms of the actual activities,
where 
is the standard potential for the electrochemical couple,
Wikipedia - Standard Electrode Potential
is the Universal Gas Constant (8.314 J/mol K),
Wikipedia - Universal Gas Constant
is absolute temperature,
Wikipedia - Thermodynamic Temperature
is the number of electrons, and 
is Faraday's Constant (96,485 C/mol).
Wikipedia - Faraday Constant
Usually, the activities of molecules or ions dissolved in solution are assumed to be the same as their molar concentrations, so the Nernst Equation is often written as
is the standard potential for the electrochemical couple,
Wikipedia - Standard Electrode Potential
is the Universal Gas Constant (8.314 J/mol K),
Wikipedia - Universal Gas Constant
is absolute temperature,
Wikipedia - Thermodynamic Temperature
is the number of electrons, and is Faraday's Constant (96,485 C/mol).
Wikipedia - Faraday Constant
Usually, the activities of molecules or ions dissolved in solution are assumed to be the same as their molar concentrations, so the Nernst Equation is often written as
where 
is the formal potential for the electrochemical couple, 
and 
are the concentrations of the dissolved molecules or ions in the oxidized and reduced forms, respectively, at the surface of the electrode. Note that any liquid or solid phase materials at the electrode surface (such as the solvent or the electrode itself) have unity activity and thus do not appear in the Nernst equation.
is the formal potential for the electrochemical couple, and are the concentrations of the dissolved molecules or ions in the oxidized and reduced forms, respectively, at the surface of the electrode. Note that any liquid or solid phase materials at the electrode surface (such as the solvent or the electrode itself) have unity activity and thus do not appear in the Nernst equation.2References
- Bard, A. J.; Faulkner, L. A. Electrochemical Methods: Fundamentals and Applications, 2nd ed. Wiley-Interscience: New York, 2000.
- Kissinger, P.; Heineman, W. R. Laboratory Techniques in Electroanalytical Chemistry, 2nd ed. Marcel Dekker, Inc: New York, 1996.
- Wang, J. Analytical Electrochemistry, 3rd ed. John Wiley & Sons, Inc.: Hoboken, NJ, 2006.
- Langhus, D. L. Fundamentals of Electroanalytical Chemistry. J. Chem. Educ., 2002, 79(10), 1207.
