Standard electrode potential (data page)

Data values of standard electrode potential

The data below tabulates standard electrode potentials (E°), in volts relative to the standard hydrogen electrode, at:

• Temperature 298.15 K (25.00 °C; 77.00 °F);
• Effective concentration 1 mol/L for each aqueous or amalgamated (mercury-alloyed) species;
• Unit activity for each solvent and pure solid or liquid species; and
• Absolute partial pressure 101.325 kPa (1.00000 atm; 1.01325 bar) for each gaseous reagent — the convention in most literature data but not the current standard state (100 kPa).

The Nernst equation adjusts for general concentrations, pressures, or temperatures.

Simultaneous half-reactions do not in general add voltages, but instead add Gibbs free energy change: the product of the voltage and the number of electrons transferred, typically the Faraday constant. For example, from Fe²⁺ + 2 e⁻ ⇌ Fe(s) (–0.44 V), the energy to create one neutral atom of Fe(s) from one Fe²⁺ ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84 895 J/(mol  e⁻). That value is also the standard formation energy for an Fe²⁺ ion, since  e⁻ and Fe(s) both have zero formation energy.

Data from different sources may cause table inconsistencies. For example: $${\displaystyle {\begin{alignedat}{4}&{\ce {Cu+ + e-}}&{}\rightleftharpoons {}&{\ce {Cu}}(s)&\quad \quad E_{1}=+0.520{\text{ V}}\\&{\ce {Cu^2+ + 2e-}}&{}\rightleftharpoons {}&{\ce {Cu}}&\quad \quad E_{2}=+0.337{\text{ V}}\\&{\ce {Cu^2+ + e-}}&{}\rightleftharpoons {}&{\ce {Cu+}}&\quad \quad E_{3}=+0.159{\text{ V}}\end{alignedat}}}$$ Additivity of Gibbs energy implies $${\displaystyle E_{3}={\frac {2\cdot E_{2}-1\cdot E_{1}}{1}}=0.154{\text{ V,}}}$$ not the experimental 0.159 V.

Table of standard electrode potentials

Legend: (s) – solid; (l) – liquid; (g) – gas; (aq) – aqueous (default for all charged species); (Hg) – amalgam; bold – water electrolysis equations.

See also

• Galvanic series lists electrode potentials in saltwater
• Standard apparent reduction potentials in biochemistry at pH 7
• Reactivity series#Comparison with standard electrode potentials

Notes

1. Not specified in the indicated reference, but assumed due to the difference between the value −0.454 and that computed by (2×(−0.499) + (−0.508))/3 = −0.502, exactly matching the difference between the values for white (−0.063) and red (−0.111) phosphorus in equilibrium with PH₃.

References

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External links

• Chemistry LibreTexts (2021-04-26). "P1: Standard Reduction Potentials by Element". Chemistry LibreTexts. Retrieved 2021-11-30.
• California State University, Northridge (CSUN). "Standard Reduction Potentials" (PDF). csun.edu. Archived (PDF) from the original on 2017-12-15. Retrieved 2021-11-30.
• Wardman, Peter (1989). "Reduction potentials of one-electron couples involving free radicals in aqueous solution" (PDF). srd.nist.gov. Archived (PDF) from the original on 2022-10-09. Retrieved 2021-11-30.
• http://www.jesuitnola.org/upload/clark/Refs/red_pot.htm Archived 2008-07-20 at the Wayback Machine
• https://web.archive.org/web/20150924015049/http://www.fptl.ru/biblioteka/spravo4niki/handbook-of-Chemistry-and-Physics.pdf
• http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/electpot.html#c1