The data below tabulates standard electrode potentials (E°), in volts relative to the standard hydrogen electrode (SHE), at:
- Temperature ;
- Effective concentration (activity) 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 for each gaseous reagent — the convention in most literature data but not the current standard state (100 kPa).
Variations from these ideal conditions affect measured voltage via the Nernst equation.
Electrode potentials of successive elementary half-reactions cannot be directly added. However, the corresponding Gibbs free energy changes (∆G°) can be added. Those free energy changes satisfy
:,
where electrons are transferred, and the Faraday constant is the conversion factor describing Coulombs transferred per mole electrons. For example, from
:,
the energy to form one neutral atom of Fe(s) from one Fe ion and two electrons is or 84 907 J/(mol ). That value is also the standard formation energy (∆G<sub>f</sub>°) for an Fe ion, since and Fe(s) both have zero formation energy.
Data from different sources may cause table inconsistencies. For example: <math chem display=block>\begin{alignat}{4}
&\ce{Cu+ + e-} &{}\rightleftharpoons{}&\ce{Cu(s)}&\quad\quad E_1=+0.520\text{ V} \\
&\ce{Cu^2+ + 2e-}&{}\rightleftharpoons{}&\ce{Cu(s)} &\quad\quad E_2=+0.337\text{ V} \\
&\ce{Cu^2+ + e-}&{}\rightleftharpoons{}&\ce{Cu+} &\quad\quad E_3=+0.159\text{ V}
\end{alignat}</math> From additivity of Gibbs energies and canceling common factors, one must have <math display=block>2\cdot E_2=1\cdot E_1+1\cdot E_3</math> But that equation does not hold exactly with the cited values.
__TOC__
Table of standard electrode potentials
<!-- This page is very close to the post-include size limit. Please be careful when adding additional data; the editor will likely (but is not guaranteed) to warn you as you cross the limit. If free space becomes necessary, consider removing deducible or otherwise duplicative entries. -->
Legend: (s) – solid; (l) – liquid; (g) – gas; (aq) – aqueous (default for all charged species); (Hg) – amalgam; bold – water electrolysis equations.
{|class="sortable wikitable col2right"
|-
! rowspan="2" | Element
!colspan="3" class="unsortable"| Half-reaction
! rowspan="2" | E°<br />(volt)
! rowspan="2" |Electrons<br />transferred
! class="unsortable noprint" rowspan="2"|Reference
|-
! Oxidant
! class="unsortable" | ⇌
! Reductant
|-
|Sr
| +
|⇌
|Sr(s)
| −4.101
|1
|<!-- Estimated? -->
|-
| Ca
| +
|⇌
| Ca(s)
| −3.8
|1
|class="noprint"|<!-- Estimated? -->
|-
| Pr
| +
|⇌
|
| −3.1
|1
|class="noprint"|Estimated
|-
| Al
| + 3
|⇌
| Al(s) + 6
| −2.069
|3
|class="noprint"|
|-
| C || C(s) + 3(l) + 2 || ⇌ || (l) + 2 || −1.148 || 2 || class=noprint |
|-
| Cr || [Cr(edta)(H<sub>2</sub>O)]<sup>−</sup> + || ⇌ || [Cr(edta)(H<sub>2</sub>O)]<sup>2−</sup> || −0.99 || 1 || class=noprint |
|-
| Bi
| + 3
|⇌
| Bi(s)
| 0.308
|3
|class="noprint"|
|-
| Fe
| +
|⇌
|
| 0.3704
|1
|class="noprint"|
|-
| C
| (CN)<sub>2</sub> + 2 + 2
|⇌
| 2HCN
| 0.373
|2
|class="noprint"|
|-
| V || + 2 + || ⇌ || + (l) || 0.481 || 1 || class=noprint |
|-
| Mo
| (aq) + 2 + 2
|⇌
| (s) + 2
| 0.65
|2
|class="noprint"|
|-
| N || HN<sub>3</sub>(aq) + 11 + 8 || ⇌ || 3NH || 0.69 || 8 || class=noprint |
|-
| Pt
| + 2
|⇌
| Pt(s) + 4
| 0.758
|2
|class="noprint"|
|-
| N || (aq) + + || ⇌ || NO(g) + (l) || 0.996 || 1 || class=noprint |
|-
| Te
| (aq) + 2 + 2
|⇌
| (s) + 4
| 1.02
|2
|class="noprint"|
|-
| N || NO<sub>2</sub>(g) + 2 + 2 || ⇌ || NO(g) + H<sub>2</sub>O(l) || 1.03 || 2 || class=noprint |
|-
| Ag
| AgO(s) + 2 +
|⇌
| +
| 1.77
|1
|class="noprint"|
|-
| N || (g) + 2 + 2 || ⇌ || (g) + (l) || 1.77 || 2 ||
|-
| Xe
| (aq) + 2 + 2
|⇌
| Xe(g) + 2HF(aq)
| 2.32
|2
|class="noprint"|
|}
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
<templatestyles src="Reflist/styles.css" /><div class="reflist">
</references></div>
References
</references>
External links
- http://www.jesuitnola.org/upload/clark/Refs/red_pot.htm
- 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