The data values of
standard electrode potentials (''E''°) are given in the table below, in
volts relative to the
standard hydrogen electrode, and are for the following conditions:
* A temperature of .
* An
effective concentration of 1 mol/L for each aqueous species or a species in a mercury
amalgam
Amalgam most commonly refers to:
* Amalgam (chemistry), mercury alloy
* Amalgam (dentistry), material of silver tooth fillings
** Bonded amalgam, used in dentistry
Amalgam may also refer to:
* Amalgam Comics, a publisher
* Amalgam Digital, an in ...
(an alloy of mercury with another metal).
* A
partial pressure
In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas ...
of 101.325
kPa (absolute) (1
atm, 1.01325
bar
Bar or BAR may refer to:
Food and drink
* Bar (establishment), selling alcoholic beverages
* Candy bar
* Chocolate bar
Science and technology
* Bar (river morphology), a deposit of sediment
* Bar (tropical cyclone), a layer of cloud
* Bar (u ...
) for each gaseous reagent. This pressure is used because most literature data are still given for this value (1 atm) rather than for the current standard of 100 kPa (1 bar) presently considered in the
standard state
In chemistry, the standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions. A superscript circle ° (degree symbol) or a Plimsoll (⦵) character is use ...
.
* An
activity of unity for each pure solid, pure liquid, or for water (solvent). The relation in
electrode potential of metals in saltwater (as
electrolyte
An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...
) is given in the ''
galvanic series''.
* Although many of the half cells are written for multiple-electron transfers, the tabulated potentials are for a single-electron transfer. All of the reactions should be divided by the stoichiometric coefficient for the electron to get the corresponding corrected reaction equation. For example, the equation Fe + 2 Fe(''s'') (–0.44 V) means that it requires 2 × 0.44 eV = 0.88
eV of energy to be absorbed (hence the minus sign) in order to create one neutral atom of Fe(''s'') from one Fe ion and two electrons, or 0.44 eV per electron, which is 0.44 J/C of electrons, which is 0.44 V.
* After dividing by the number of electrons, the standard potential ''E''° is related to the
standard Gibbs free energy of formation
The standard Gibbs free energy of formation (''G''f°) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most s ...
''ΔG
f°'' by:
where ''F'' is the
Faraday constant. For example, in the equation Fe + 2 Fe(''s'') (–0.44 V), the Gibbs energy required to create one neutral atom of Fe(''s'') from one Fe ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84 895 J/mol of electrons, which is just the Gibbs energy of formation of an Fe ion, since the energies of formation of and Fe(''s'') are both zero.
:The
Nernst equation will then give potentials at concentrations, pressures, and temperatures other than standard.
* Note that the table may lack consistency due to data from different sources. For example:
:
:Calculating the potential using
Gibbs free energy ( = 2 – ) gives the potential for as 0.154 V, not the experimental value of 0.159 V.
:
__TOC__
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
*
Standard apparent reduction potentials in biochemistry at pH 7
*
Standard state
In chemistry, the standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions. A superscript circle ° (degree symbol) or a Plimsoll (⦵) character is use ...
Notes
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
{{DEFAULTSORT:Standard Electrode Potentials
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