Elektrokimika-en iturria ikusi

[[Fitxategi:SS-faraday.jpg|thumb|[[Michael Faraday]], elektrokimikaren aitatzat hartzen den ingeles kimikaria]]
'''Elektrokimika''' [[energia elektriko]]a eta [[energia kimiko]]aren arteko konbertsioa ikertzen duen [[kimika]]ren adarra da.

Erreakzio kimikoen bidez elektrizitatea lor daiteke; hori da piletan edo baterietan gertatzen dena. Bestalde, korronte elektriko batek bultza dezake erreakzio kimiko bat; adibidez elektrolisian. Bi kasuetan ematen diren erreakzioek '''erreakzio elektrokimiko''' izena hartzen dute. Erreakzio elektrokimiko hauek ioi positiboek negatiboekin duten elkarrekintzan oinarritzen dira: ioi negatiboak ioi positiboak erakarri egiten ditu, korronte elektrikoa sortuz.

== Historia ==
[[XVIII. mendea|XVIII]]. mende amaieran, [[Argien Garaia|ilustrazio]] garaian, [[Luigi Galvani]] anatomista eta mediku italiarrak definitu zuen lehenengoz elektrokimika kontzeptua modu zientifiko batean igelen hanketatik elektrizitatea pasatzen zela ohartu zenean.

Ondorengo ekarpenak [[Alessandro Volta]] fisikari italiarrak egin zituen lehen bateria sortu zuenean.

[[XIX. mendea|XIX. mende]] erdialdean [[Michael Faraday]]-ek eta [[John Daniell]]-ek elektrokimikaren azterketa egin eta zenbait kontzeptu argitu zituzten. Mende amaieran elektrokimikak zenbait alorretan eragin zuen, hala nola, elektrolitoen eroankortasunean eta baterien modelatze matematikoan.

[[XX. mendea|XX. mende]]<nowiki/>tik aurrera elektrokimikak zenbait aurkikuntza ekarri zituen, besteak beste, elektroiaren karga aurkitu zen, Bronsted eta Lowry azido eta baseen teoria modernoa ezarri zen eta medikuntza zein biologian gai ugari ikertu ahal izan ziren, esaterako, [[elektroforesi]]a.

== Erredox erreakzioak ==
'''Erredox erreakzioak''' espezie kimikoen arteko [[elektroi]]<nowiki/>en transferentzian oinarritzen diren erreakzio kimikoak dira. Espezieetako batek elektroiak galduko ditu, hau da, oxidatu egingo da. Elektroi<nowiki/>en galera horrek bere oxidazio zenbakia positiboagoa izatea eragingo du. Beste espezieak, ordea, irabazi egingo ditu elektroiak: erreduzitu egingo da. Bere oxidazio zenbakia, beraz, negatiboagoa bihurtuko da.

Espezie bat oxidatzen deneko erreakzioari oxidazio deritzogu eta espeziea erreduzitu egin bada erredukzio.

Honakoa erredox erreakzio baten adibidea da:

Cu<sup>2+</sup> + Zn <math>\longrightarrow</math> Zn<sup>2+</sup> + Cu

Erreakzio totala bi erdierreakziotan bana dezakegu:

Cu<sup>2+</sup> + 2e<sup>-</sup> <math>\longrightarrow</math> Cu (erredukzioa)

Zn <math>\longrightarrow</math> Zn<sup>2+</sup> + 2e<sup>-</sup> (oxidazioa)

Kupre katioiak bi elektroi irabazi ditu [[Kobre|kupre]] metalikora pasatzeko eta alderantziz, [[zink]] metalikoak bi elektroi galdu ditu. Zinkaren oxidazioak kuprearen erredukzioa ahalbideratu duenez, zinkak erreduktore moduan jokatu duela esaten dugu. Bestalde, kuprea oxidatzaile gisa aritu da, zink metalikoaren oxidazioa eragin duelako.

== Pila elektrokimikoa ==
'''Pila elektrokimikoa''' erreakzio kimikoetatik abiatuz energia elektrikoa lortzea ahalbidetzen duen gailua da.

=== Daniell pila ===
[[Fitxategi:Daniell.png|thumb|Zelula galbanikoaren diagrama eskematikoa. Elektroiak zinkezko elektrodotik kuprezko elektrodora pasatzen dira.]]
Zink metaliko zati bat jartzen badugu CuSO<sub>4</sub> disoluzio batean bi erreakzio gertatuko dira: batetik, zink metalikoa disolbatu egingo da Zn<sup>2+</sup> katioi moduan, eta bestetik, disoluzioan zeuden Cu<sup>2+</sup> ioiak kupre metalikora erreduzituko dira elektrodoan. Erredox errakzio hau bat batekoa izango da:

Cu<sup>2+</sup> + Zn <math>\longrightarrow</math> Zn<sup>2+</sup> + Cu

Denbora pasa ahala, disoluzioaren urdin kolorea argituz joango da. Honen antzera, kupre metalikozko alanbre bat jartzen badugu AgNO<sub>3</sub> disoluzio batean, zilar metalikoa sortuko da honen gainean eta disoluzioa urdinduz joango da Cu<sup>2+</sup> ioi hidratatuen presentziaren eraginez.

Demagun oraingoan zink eta kupre metalikoa jartzen ditugula konpartimentu ezberdinetan. Konpartimentu batean ZnSO<sub>4</sub> disoluzioa egongo da eta bestean CuSO<sub>4</sub>, irudian ikus daitekeen moduan. Disoluzioak ''gatz zubi'' batez lotzen dira. Gatz zubia disoluzio elektrolitiko geldoa duen hodi bat da, KCl -zkoa adibidez. Hodiaren ertzak agar-agarra bezalako material likatsu batekin estaltzen dira, disoluzioak nahas ez daitezen. Elektrodoak alanbre metaliko batez lotzen badira, elektroiak zinkezko elektrodotik kuprezko elektrodora pasako dira. Izan ere, zinka oxidatu egingo da ezkerreko konpartimentuan eta Zn<sup>2+</sup> ioiak sortuko dira, elektroiekin batera. Elektroi horiek eragiten duten korrontearen bidez, Cu<sup>2+</sup> ioiak kupre metalikora erreduzituko dira kuprezko elektrodoan. Oxidatu den elektrodoari, kasu honetan zinkezkoari, '''anodo''' deitzen diogu. Erreduzitu denari, berriz, '''katodoa'''. Gatz zubiaren helburua zirkuitu elektrikoa osatzea da, elektroien mugimendua ahalbidetzen duelarik.

Deskribatutako pila Daniell zelula bezala ezagutzen da eta ''zelula galbaniko''aren edo ''boltaiko''ren adibide esanguratsuena da.

Zelula galbanikoen funtzionamendua erredox erreakzioetan oinarritzen da. Zink eta kuprezko kasuan, erredox erreakzioak bi erdierreakzio gisa adieraz daitezke:

Anodoa: Zn(s) <math>\longrightarrow</math> Zn<sup>2+</sup>(aq) + 2e<sup>-</sup>

Katodoa: Cu<sup>2+</sup>(aq) + 2e<sup>-</sup> <math>\longrightarrow</math> Cu(s)

Danielen pilaren diagrama honako hau da:

Zn(s) | ZnSO<sub>4</sub>(1.00M) || CuSO<sub>4</sub>(1.00M) | Cu(s)

=== Pila motak ===
Pilak transferentziazkoak eta transferentziarik gabekoak izan daitezke.

Transferentziazko piletan pareta porotsu edo gatz-zubia dago bi disoluzioen artean.

Transferentziarik gabeko piletan, aldiz, elektrolito amankomuna dute eta pilaerdien artean ez dago banaketarik.

Transferentziazko pilen artean, aipagarria da kontzentraziozko pila.

==== Kontzentraziozko pilak ====
Mota honetako pila baten elektrodoak metal berdinarekin osatutakoak dira eta bi disoluzioetan dauden katioiak berdinak izango dira. Bien arteko diferentzia disoluzioen kontzentrazioa da.

Esaterako, ZnSO<sub>4</sub> -ren kontzentraziozko pila aztertuko dugu.

Zn(s) | ZnSO<sub>4</sub>(0.10M) || ZnSO<sub>4</sub>(1.0M) | Zn(s)

Katodoan zink metalikoa sortuko da, disoluzioko katioiak kontsumituz. Anodoan, ordea, zink metalikoa oxidatzen denez katioiak areagotzen dira. Bi disoluzio horiek kontzentrazioak berdintzeko joera izango dutenez, katodoan izan beharko dugu katioien kontzentrazio handiena eta anodoan txikiena. Horrela, erredox erreakzioak aurrera doazen heinean katodoko kontzentrazioa txikitu eta anodokoa handituko da, bi kontzentrazioak berdindu arte. Egoera horretara heltzean, pilak ez du lanik egingo.

Honakoak dira erdierreakzioak:

Anodoa: Zn(s) <math>\longrightarrow</math> Zn<sup>2+</sup>(0.10M) + 2e<sup>-</sup>

Katodoa: Zn<sup>2+</sup>(1.0M) + 2e<sup>-</sup> <math>\longrightarrow</math> Zn(s)

Osoa: Zn<sup>2+</sup>(1.0M) <math>\longrightarrow</math> Zn<sup>2+</sup>(0.10M)

==== Difusiozko pilak ====

Difusiozko pilak gai kimikoaren zabalkuntzak katioien eta anioien arteko elkarrekintza ahalbidetzen duenean gertatzen da, anodoaren eta katodoaren arteko orekara heldu arte. Gai kimokoaren kontzentrazioa faktore garrantzitsua da erreakzioan, zabalkuntza eragingo den ala ez. Oraindik asko aplikatzen ez diren pilak dira, eta esperimentazio fasean daude ibilgailu elektrikoetan, baino etorkizun handia dute difusio prozesuak gai kimikoaren pisua arindu egiten duelako.

== Erredukzio-potentzialak ==
Pila baten potentziala, E<sub>pila</sub>, bi pilaerdien artean sortzen den potentzial diferentzia da. Potentzial diferentzia hori baldintza estandarretan neurtu denean, potentzial diferentzia estandar deritzogu: E<sup>0</sup>. Elektrodo bakoitzaren erredukzio potentziala izango bagenu, katodoaren E<sup>0</sup> eta anodoaren E<sup>0</sup>, alegia, bien arteko diferentzia kalkulatuz pila osoaren potentzial estandarra kalkulatuko genuke. Baina pilaerdi isolatu bakoitzaren potentziala ez denez neurgarria, beti beharko ditugu bi elektrodo eta beraien arteko potentzial diferentzia kalkulatuko dugu.
[[Fitxategi:Standard hydrogen electrode 2009-02-06.svg|thumb|296x296px|Hidrogenozko elektrodo estandarra.]]
Arazoa saihesteko, hidrogenoaren elektrodoa erreferentziazko elektrodotzat hartu da eta bere potentzial estandarra 0 izatea erabaki da hitzarmenez. Horrela, edozein pilaerdiren eta hidrogenozko pilaerdiaren artean sortzen den potentzial diferentzia izango da jakin nahi dugun elektrodo isolatu horren erredukzio potentziala.

H<sup>+</sup>(aq) + e<sup>-</sup> <math>\longrightarrow</math><math>\frac{1}{2}</math>H<sub>2</sub> (g) E<sup>0</sup>=0V

Hidrogenozko elektrodoan platinozko xafla bat sartzen da disoluzio azido batean eta elektrodoaren gainazalean hidrogeno gaseosoaren korronte bat pasarazten da (1bar). Platinoaren gainazalak gasa adsorbatuko du.

Elektrodo baten potentziala jakiteko, beraz, hidrogenozko elektrodoaz baliatuko gara. Gure muntaia neurtu nahi dugun elektrodoaren eta hidrogenoaren arteko pila bat izango da. Pila horretan sortzen den potentzial diferentzia elektrodo ezezagunaren potentzialaren modulua izango da. Hidrogenozko elektrodoak anodo gisa funtzionatzen badu, beste elektrodoan eman da erredukzioa; beraz, hidrogenoa baino erredukzio-ahalmen handiagoa du eta ondorioz, bere erredukzio-potentziala positiboa izango da. Hidrogenoaren elektrodoa katodo gisa aritu bada, ordea, neurtu nahi dugun elektrodoaren potentzialaren balioa negatiboa izango da.

Honako taula honetan zenbait elektrodoren erredukzio potentzial estandarrak (E<sup>0</sup>) ageri dira:
{| class="wikitable sortable" cellpadding="10"
! colspan="3" class="unsortable" |[[erreakzioerdi]]
! rowspan="2" |''E°'' (V)
! rowspan="2" class="unsortable noprint" |Ref.
|-
!Oxidant
! class="unsortable" |{{eqm}}
!Reductant
|-
|- style="display:none"
|&
| class="noprint" | -9
|- style="display:none"
|Zz
| class="noprint" |9
|- class="Unicode"
|[[Estrontzio|Sr]]<sup>+</sup> + {{e-}}
|{{eqm}}
|[[Estrontzio|Sr]]
|−4.101
| class="noprint" |<ref name="CRC" />
|-
|Ca<sup>+</sup> + {{e-}}
|{{eqm}}
|[[Kaltzio|Ca]]
|−3.8
| class="noprint" |<ref name="CRC" />
|-
|[[Praseodimio|Pr]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Pr<sup>2+</sup>
|−3.1
| class="noprint" |<ref name="CRC">{{RubberBible87th}}</ref>
|-
|{{hs|N}}3{{hsp}}[[Nitrogeno|N{{sub2}}]](''g'') + 2{{H+}} +  2{{e-}}
|{{eqm}}
|2[[Hydrogen azide|HN<sub>3</sub>]](''aq'')
|−3.09
| class="noprint" |<ref name="Gre" /><ref name="van92" />
|-
|[[Litio|Li]]{{+}} + {{e-}}
|{{eqm}}
|[[Litio|Li]](''s'')
|−3.0401
| class="noprint" |<ref name="van92" /><ref name="atkinshriver" />
|-
|[[Nitrogen gas|N{{sub2}}]](''g'') + 4{{H2O}} +  2{{e-}}
|{{eqm}}
|2{{hsp}}[[Hidroxilamina|NH{{sub2}}OH]](''aq'') + 2{{OH-}}
|−3.04
| class="noprint" |<ref name="Gre" />
|-
|[[Zesio|Cs]]{{+}} + {{e-}}
|{{eqm}}
|[[Zesio|Cs]](''s'')
|−3.026
| class="noprint" |<ref name="van92" />
|-
|[[Kaltzio hidroxido|Ca(OH)<sub>2</sub>]] + 2{{e-}}
|{{eqm}}
|[[Kaltzio|Ca]] + 2 OH<sup>−</sup>
|−3.02
| class="noprint" |<ref name="CRC" />
|-
|[[Erbio|Er]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Er<sup>2+</sup>
|−3.0
| class="noprint" |<ref name="CRC" />
|-
|[[Bario hidroxido|Ba(OH)<sub>2</sub>]] + 2{{e-}}
|{{eqm}}
|[[Bario|Ba]] + 2 OH<sup>−</sup>
|−2.99
| class="noprint" |<ref name="CRC" />
|-
|[[Rubidio|Rb]]{{+}} + {{e-}}
|{{eqm}}
|[[Rubidio|Rb]](''s'')
|−2.98
| class="noprint" |<ref name="van92" />
|-
|[[Potasio|K]]{{+}} + {{e-}}
|{{eqm}}
|[[Potasio|K]](''s'')
|−2.931
| class="noprint" |<ref name="van92" />
|-
|[[Bario|Ba]]{{2+}} + 2{{e-}}
|{{eqm}}
|[[Bario|Ba]](''s'')
|−2.912
| class="noprint" |<ref name="van92" />
|-
|[[Lantano|La]](OH)<sub>3</sub>(''s'') + 3{{e-}}
|{{eqm}}
|[[Lantano|La]](''s'') + 3{{OH-}}
|−2.90
| class="noprint" |<ref name="van92" />
|-
|[[Frantzio|Fr]]<sup>+</sup> + {{e-}}
|{{eqm}}
|[[Frantzio|Fr]]
|−2.9
| class="noprint" |<ref name="CRC" />
|-
|[[Estrontzio|Sr]]{{2+}} + 2{{e-}}
|{{eqm}}
|[[Estrontzio|Sr]](''s'')
|−2.899
| class="noprint" |<ref name="van92" />
|-
|Sr(OH)<sub>2</sub> + 2{{e-}}
|{{eqm}}
|Sr + 2 OH<sup>−</sup>
|−2.88
| class="noprint" |<ref name="CRC" />
|-
|[[Kaltzio|Ca]]{{2+}} + 2{{e-}}
|{{eqm}}
|[[Kaltzio|Ca]](''s'')
|−2.868
| class="noprint" |<ref name="van92" /><ref name="atkinshriver" />
|-
|[[Litio|Li]]{{+}} + C''6''(''s'') + {{e-}}
|{{eqm}}
|[[Litio|LiC6]](''s'')
|−2.84
| class="noprint" |<ref name="van92" />
|-
|[[Europio|Eu]]{{2+}} + 2{{e-}}
|{{eqm}}
|Eu(''s'')
|−2.812
| class="noprint" |<ref name="van92" />
|-
|[[Radio|Ra]]{{2+}} + 2{{e-}}
|{{eqm}}
|Ra(''s'')
|−2.8
| class="noprint" |<ref name="van92" />
|-
|[[Holmio|Ho]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Ho<sup>2+</sup>
|−2.8
| class="noprint" |<ref name="CRC" />
|-
|[[Berkelio|Bk]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Bk<sup>2+</sup>
|−2.8
| class="noprint" |<ref name="CRC" />
|-
|[[Iterbio|Yb]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Yb
|−2.76
| class="noprint" |<ref name="CRC" />
|-
|[[Sodio|Na]]{{+}} + {{e-}}
|{{eqm}}
|Na(''s'')
|−2.71
| class="noprint" |<ref name="van92" /><ref name="Atk" />
|-
|[[Magnesio|Mg]]<sup>+</sup> + {{e-}}
|{{eqm}}
|Mg
|−2.70
| class="noprint" |<ref name="CRC" />
|-
|[[Neodimio|Nd]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Nd<sup>2+</sup>
|−2.7
| class="noprint" |<ref name="CRC" />
|-
|[[Magnesio|Mg]](OH)<sub>2</sub> + 2{{e-}}
|{{eqm}}
|Mg + 2 OH<sup>−</sup>
|−2.690
| class="noprint" |<ref name="CRC" />
|-
|[[Samario|Sm]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Sm
|−2.68
| class="noprint" |<ref name="CRC" />
|-
|[[Berilio|Be]]<sub>2</sub>O<sub>3</sub><sup>2−</sup> + 3 H<sub>2</sub>O + 4{{e-}}
|{{eqm}}
|2 Be + 6 OH<sup>−</sup>
|−2.63
| class="noprint" |<ref name="CRC" />
|-
|[[Prometio|Pm]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Pm<sup>2+</sup>
|−2.6
| class="noprint" |<ref name="CRC" />
|-
|[[Disprosio|Dy]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Dy<sup>2+</sup>
|−2.6
| class="noprint" |<ref name="CRC" />
|-
|[[Nobelio|No]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|No
|−2.50
| class="noprint" |<ref name="CRC" />
|-
|[[Hafnio|Hf]]O(OH)<sub>2</sub> + H<sub>2</sub>O + 4{{e-}}
|{{eqm}}
|Hf + 4 OH<sup>−</sup>
|−2.50
| class="noprint" |<ref name="CRC" />
|-
|[[Torio|Th]](OH)<sub>4</sub> + 4{{e-}}
|{{eqm}}
|Th + 4 OH<sup>−</sup>
|−2.48
| class="noprint" |<ref name="CRC" />
|-
|[[Mendelevio|Md]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Md
|−2.40
| class="noprint" |<ref name="CRC" />
|-
|[[Tulio|Tm]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Tm
|−2.4
| class="noprint" |<ref name="CRC" />
|-
|[[Lantano|La]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|La(''s'')
|−2.379
| class="noprint" |<ref name="van92" />
|-
|[[Itrio|Y]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Y(''s'')
|−2.372
| class="noprint" |<ref name="van92" />
|-
|[[Magnesio|Mg]]{{2+}} + 2{{e-}}
|{{eqm}}
|Mg(''s'')
|−2.372
| class="noprint" |<ref name="van92" />
|-
|[[Zirkonio|Zr]]O(OH){{sub2}}(''s'') + {{H2O}} + 4{{e-}}
|{{eqm}}
|Zr(''s'') + 4{{OH-}}
|−2.36
| class="noprint" |<ref name="van92" />
|-
|[[Praseodimio|Pr]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Pr
|−2.353
| class="noprint" |<ref name="CRC" />
|-
|[[Zerio (elementua)|Ce]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Ce
|−2.336
| class="noprint" |<ref name="CRC" />
|-
|[[Erbio|Er]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Er
|−2.331
| class="noprint" |<ref name="CRC" />
|-
|[[Holmio|Ho]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Ho
|−2.33
| class="noprint" |<ref name="CRC" />
|-
|H<sub>2</sub>[[Aluminio|Al]]O<sub>3</sub><sup>−</sup> + H<sub>2</sub>O + 3{{e-}}
|{{eqm}}
|Al + 4 OH<sup>−</sup>
|−2.33
| class="noprint" |<ref name="CRC" />
|-
|[[Neodimio|Nd]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Nd
|−2.323
| class="noprint" |<ref name="CRC" />
|-
|[[Tulio|Tm]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Tm
|−2.319
| class="noprint" |<ref name="CRC" />
|-
|Al(OH)<sub>3</sub>(''s'') + 3{{e-}}
|{{eqm}}
|Al(''s'') + 3{{OH-}}
|−2.31
| class="noprint" |
|-
|[[Samario|Sm]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Sm
|−2.304
| class="noprint" |<ref name="CRC" />
|-
|[[Fermio|Fm]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Fm
|−2.30
| class="noprint" |<ref name="CRC" />
|-
|[[Amerizio|Am]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Am<sup>2+</sup>
|−2.3
| class="noprint" |<ref name="CRC" />
|-
|[[Disprosio|Dy]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Dy
|−2.295
| class="noprint" |<ref name="CRC" />
|-
|[[Lutezio|Lu]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Lu
|−2.28
| class="noprint" |<ref name="CRC" />
|-
|[[Terbio|Tb]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Tb
|−2.28
| class="noprint" |<ref name="CRC" />
|-
|[[Gadolinio|Gd]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Gd
|−2.279
| class="noprint" |<ref name="CRC" />
|-
|[[Hidrogeno|H{{sub2}}]] + 2{{e-}}
|{{eqm}}
|2{{hsp}}H<sup>−</sup>
|−2.23
| class="noprint" |<ref name="CRC" />
|-
|[[Einsteinio|Es]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Es
|−2.23
| class="noprint" |<ref name="CRC" />
|-
|[[Prometio|Pm]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Pm
|−2.2
| class="noprint" |<ref name="CRC" />
|-
|[[Tulio|Tm]]<sup>3+</sup> + {{e-}}
|{{eqm}}
|Tm<sup>2+</sup>
|−2.2
| class="noprint" |<ref name="CRC" />
|-
|[[Disprosio|Dy]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Dy
|−2.2
| class="noprint" |<ref name="CRC" />
|-
|[[Aktinio|Ac]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Ac
|−2.20
| class="noprint" |<ref name="CRC" />
|-
|[[Iterbio|Yb]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Yb
|−2.19
| class="noprint" |<ref name="CRC" />
|-
|[[Kalifornio|Cf]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Cf
|−2.12
| class="noprint" |<ref name="CRC" />
|-
|[[Neodimio|Nd]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Nd
|−2.1
| class="noprint" |<ref name="CRC" />
|-
|[[Holmio|Ho]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Ho
|−2.1
| class="noprint" |<ref name="CRC" />
|-
|[[Eskandio|Sc]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Sc(''s'')
|−2.077
| class="noprint" |<ref>David R. Lide, ed., CRC Handbook of Chemistry and Physics, Internet Version 2005, <https://web.archive.org/web/20170724011402/http://www.hbcpnetbase.com/>, CRC Press, Boca Raton, FL, 2005.</ref>
|-
|[[Hexafluoroaluminate|AlF<sub>6</sub><sup>3−</sup>]] + 3{{e-}}
|{{eqm}}
|[[Aluminium|Al]] + 6 F<sup>−</sup>
|−2.069
| class="noprint" |<ref name="CRC" />
|-
|[[Amerizio|Am]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Am
|−2.048
| class="noprint" |<ref name="CRC" />
|-
|[[Kurio|Cm]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Cm
|−2.04
| class="noprint" |<ref name="CRC" />
|-
|[[Plutonio|Pu]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Pu
|−2.031
| class="noprint" |<ref name="CRC" />
|-
|[[Praseodimio|Pr]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Pr
|−2.0
| class="noprint" |<ref name="CRC" />
|-
|[[Erbio|Er]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Er
|−2.0
| class="noprint" |<ref name="CRC" />
|-
|[[Europio|Eu]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Eu
|−1.991
| class="noprint" |<ref name="CRC" />
|-
|[[Lawrentzio|Lr]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Lr
|−1.96
| class="noprint" |<ref name="CRC" />
|-
|[[Kalifornio|Cf]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Cf
|−1.94
| class="noprint" |<ref name="CRC" />
|-
|[[Einsteinio|Es]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Es
|−1.91
| class="noprint" |<ref name="CRC" />
|-
|[[Protaktinio|Pa]]<sup>4+</sup> + {{e-}}
|{{eqm}}
|Pa<sup>3+</sup>
|−1.9
| class="noprint" |<ref name="CRC" />
|-
|[[Amerizio|Am]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|Am
|−1.9
| class="noprint" |<ref name="CRC" />
|-
|[[Torio|Th]]<sup>4+</sup> + 4{{e-}}
|{{eqm}}
|Th
|−1.899
| class="noprint" |<ref name="CRC" />
|-
|[[Fermio|Fm]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Fm
|−1.89
| class="noprint" |<ref name="CRC" />
|-
|[[Neptunio|Np]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Np
|−1.856
| class="noprint" |<ref name="CRC" />
|-
|[[Berilio|Be]]{{2+}} + 2{{e-}}
|{{eqm}}
|Be
|−1.847
| class="noprint" |<ref name="CRC" />
|-
|H<sub>2</sub>PO<sub>2</sub><sup>−</sup> + {{e-}}
|{{eqm}}
|P + 2 OH<sup>−</sup>
|−1.82
| class="noprint" |<ref name="CRC" />
|-
|[[Uranio|U]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|U
|−1.798
| class="noprint" |<ref name="CRC" />
|-
|[[Estrontzio|Sr]]<sup>2+</sup> + 2{{e-}}
|{{eqm}}
|[[Amalgam (chemistry)|Sr/Hg]]
|−1.793
| class="noprint" |<ref name="CRC" />
|-
|H<sub>2</sub>BO<sub>3</sub><sup>−</sup> + H<sub>2</sub>O + 3{{e-}}
|{{eqm}}
|B + 4 OH<sup>−</sup>
|−1.79
| class="noprint" |<ref name="CRC" />
|-
|[[Thorium dioxide|ThO<sub>2</sub>]] + 4H<sup>+</sup> + 4{{e-}}
|{{eqm}}
|Th + 2 H<sub>2</sub>O
|−1.789
| class="noprint" |<ref name="CRC" />
|-
|[[Hafnio|Hf]]O<sup>2+</sup> + 2 H<sup>+</sup> + 4{{e-}}
|{{eqm}}
|Hf + H<sub>2</sub>O
|−1.724
| class="noprint" |<ref name="CRC" />
|-
|HPO<sub>3</sub><sup>2−</sup> + 2 H<sub>2</sub>O + 3{{e-}}
|{{eqm}}
|P + 5 OH<sup>−</sup>
|−1.71
| class="noprint" |<ref name="CRC" />
|-
|[[Silizio|Si]]O<sub>3</sub><sup>2−</sup> + H<sub>2</sub>O + 4{{e-}}
|{{eqm}}
|Si + 6 OH<sup>−</sup>
|−1.697
| class="noprint" |<ref name="CRC" />
|-
|[[Aluminio|Al]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Al(''s'')
|−1.662
| class="noprint" |<ref name="CRC" />
|-
|[[Titanio|Ti]]{{2+}} + 2{{e-}}
|{{eqm}}
|Ti(''s'')
|−1.63
| class="noprint" |<ref name="Atk" />
|-
|[[Zirconio dioxido|ZrO{{sub2}}]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|Zr(''s'') + 2{{H2O}}
|−1.553
| class="noprint" |<ref name="van" />
|-
|[[Zirkonio|Zr<sup>4+</sup>]] + 4{{e-}}
|{{eqm}}
|Zr(''s'')
|−1.45
| class="noprint" |<ref name="van" />
|-
|Ti<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Ti(''s'')
|−1.37
| class="noprint" |<ref name="si" />
|-
|[[Titanio(II) oxido|TiO]](''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|Ti(''s'') + {{H2O}}
|−1.31
| class="noprint" |
|-
|[[Titanium(III) oxide|Ti{{sub2}}O<sub>3</sub>]](''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|2{{hsp}}TiO(''s'') + {{H2O}}
|−1.23
| class="noprint" |
|-
|Zn(OH)<sub>4</sub><sup>2−</sup> + 2{{e-}}
|{{eqm}}
|Zn(''s'') + 4{{OH-}}
|−1.199
| class="noprint" |<ref name="van" />
|-
|[[Manganeso|Mn]]{{2+}} + 2{{e-}}
|{{eqm}}
|Mn(''s'')
|−1.185
| class="noprint" |<ref name="van" />
|-
|[[Burdina|Fe]](CN)<sub>6</sub><sup>4−</sup> + 6{{H+}} + 2 {{e-}}
|{{eqm}}
|Fe(''s'') + 6HCN(''aq'')
|−1.16
| class="noprint" |<ref name="webelements_fe">[http://www.webelements.com/iron/compounds.html WebElements Periodic Table of the Elements | Iron | compounds information]</ref>
|-
|[[Telurio|Te]](''s'') + 2{{e-}}
|{{eqm}}
|Te<sup>2−</sup>
|−1.143
| class="noprint" |<ref name="Bar" />
|-
|[[Banadio|V]]{{2+}} + 2{{e-}}
|{{eqm}}
|V(''s'')
|−1.13
| class="noprint" |<ref name="Bar" />
|-
|[[Niobio|Nb]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Nb(''s'')
|−1.099
| class="noprint" |
|-
|[[Eztainu|Sn]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|SnH<sub>4</sub>(''g'')
|−1.07
| class="noprint" |
|-
|[[Silicon dioxide|SiO]]{{sub2}}(''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|Si(''s'') + 2{{H2O}}
|−0.91
| class="noprint" |
|-
|[[Boric acid|B(OH)]]<sub>3</sub>(''aq'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|B(''s'') + 3{{H2O}}
|−0.89
| class="noprint" |
|-
|Fe(OH){{sub2}}(''s'') + 2{{e-}}
|{{eqm}}
|Fe(''s'') + 2{{OH-}}
|−0.89
| class="noprint" |<ref name="webelements_fe" />
|-
|Fe{{sub2}}O<sub>3</sub>(''s'') + 3{{H2O}} + 2{{e-}}
|{{eqm}}
|2Fe(OH){{sub2}}(''s'') + 2{{OH-}}
|−0.86
| class="noprint" |<ref name="webelements_fe" />
|-
|TiO{{2+}} + 2{{H+}} + 4{{e-}}
|{{eqm}}
|Ti(''s'') + {{H2O}}
|−0.86
| class="noprint" |
|-
|'''{{hs|H}}2[[Water|H<sub>2</sub>O]] + 2{{e-}} '''
|{{eqm}}
|H{{sub2}}(''g'') + 2{{OH-}}
|−0.8277
| class="noprint" |<ref name="van" />
|-
|[[Bismuth|Bi]](''s'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|[[Bismuthine|BiH<sub>3</sub>]]
|−0.8
| class="noprint" |<ref name="van" />
|-
|[[Zink|Zn]]{{2+}} + 2{{e-}}
|{{eqm}}
|Zn(''Hg'')
|−0.7628
| class="noprint" |<ref name="van" />
|-
|[[Zink|Zn]]{{2+}} + 2{{e-}}
|{{eqm}}
|Zn(''s'')
|−0.7618
| class="noprint" |<ref name="van" />
|-
|[[Tantalum pentoxide|Ta{{sub2}}O<sub>5</sub>]](''s'') + 10{{H+}} + 10{{e-}}
|{{eqm}}
|2{{hsp}}[[Tantalum|Ta]](''s'') + 5{{H2O}}
|−0.75
| class="noprint" |
|-
|[[Kromo|Cr]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Cr(''s'')
|−0.74
| class="noprint" |
|-
|[[Silver sulfide|Ag<sub>2</sub>S]](''s'') + 2{{e-}}
|{{eqm}}
|2Ag(''s'') + [[Sulphur|S]]<sup>2−</sup>(''aq'')
|−0.69
| class="noprint" |
|-
|{{hs|Au}}[<span>Au(CN)[[Txantiloi:Sub2]]</span>]<sup>−</sup> + {{e-}}
|{{eqm}}
|[[Gold|Au]](''s'') + 2{{hsp}}CN<sup>−</sup>
|−0.60
| class="noprint" |
|-
|Ta<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Ta(''s'')
|−0.6
| class="noprint" |
|-
|PbO(''s'') + {{H2O}} + 2{{e-}}
|{{eqm}}
|Pb(''s'') + 2{{OH-}}
|−0.58
| class="noprint" |
|-
|{{hs|Ti}}2{{hsp}}TiO{{sub2}}(''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|Ti{{sub2}}O<sub>3</sub>(''s'') + {{H2O}}
|−0.56
| class="noprint" |
|-
|[[Galio|Ga]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Ga(''s'')
|−0.53
| class="noprint" |
|-
|U<sup>4+</sup> + {{e-}}
|{{eqm}}
|U<sup>3+</sup>
|−0.52
| class="noprint" |<ref name="Bar2" />
|-
|{{hs|P }}[[Hypophosphorous acid|H<sub>3</sub>PO{{sub2}}]](''aq'') + {{H+}} + {{e-}}
|{{eqm}}
|P(''white'')<ref group="note" name="rwP" /> + 2{{H2O}}
|−0.508
| class="noprint" |<ref name="van" />
|-
|{{hs|P }}H<sub>3</sub>PO<sub>3</sub>(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|H<sub>3</sub>PO{{sub2}}(''aq'') + {{H2O}}
|−0.499
| class="noprint" |<ref name="van" />
|-
|{{hs|P }}[[Phosphorous acid|H<sub>3</sub>PO<sub>3</sub>]](''aq'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|P(''red'')<ref group="note" name="rwP" /> + 3{{H2O}}
|−0.454
| class="noprint" |<ref name="van" />
|-
|[[Burdina|Fe]]{{2+}} + 2{{e-}}
|{{eqm}}
|Fe(''s'')
|−0.44
| class="noprint" |<ref name="Atk" />
|-
|{{hs|C}}2{{hsp}}[[Carbon dioxide|CO{{sub2}}]](''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|[[Oxalic acid|HOOCCOOH]](''aq'')
|−0.43
| class="noprint" |
|-
|Cr<sup>3+</sup> + {{e-}}
|{{eqm}}
|Cr{{2+}}
|−0.42
| class="noprint" |
|-
|[[Kadmio|Cd]]{{2+}} + 2{{e-}}
|{{eqm}}
|Cd(''s'')
|−0.40
| class="noprint" |<ref name="Atk" />
|-
|[[Germanium dioxide|GeO{{sub2}}]](''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|GeO(''s'') + {{H2O}}
|−0.37
| class="noprint" |
|-
|[[Kobre(I) oxido|Cu{{sub2}}O]](''s'') + {{H2O}} + 2{{e-}}
|{{eqm}}
|2{{hsp}}Cu(''s'') + 2{{OH-}}
|−0.360
| class="noprint" |<ref name="van" />
|-
|[[Lead(II) sulfate|PbSO<sub>4</sub>]](''s'') + 2{{e-}}
|{{eqm}}
|[[Lead|Pb]](''s'') + SO<sub>4</sub><sup>2−</sup>
|−0.3588
| class="noprint" |<ref name="van" />
|-
|PbSO<sub>4</sub>(''s'') + 2{{e-}}
|{{eqm}}
|Pb(''Hg'') + SO<sub>4</sub><sup>2−</sup>
|−0.3505
| class="noprint" |<ref name="van" />
|-
|[[Europio|Eu<sup>3+</sup>]] + {{e-}}
|{{eqm}}
|Eu{{2+}}
|−0.35
| class="noprint" |<ref name="Bar2" />
|-
|[[Indio|In]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|In(''s'')
|−0.34
| class="noprint" |<ref name="Bar" />
|-
|[[Talio|Tl]]{{+}} + {{e-}}
|{{eqm}}
|Tl(''s'')
|−0.34
| class="noprint" |<ref name="Bar" />
|-
|[[Germanio|Ge]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|GeH<sub>4</sub>(''g'')
|−0.29
| class="noprint" |
|-
|[[Kobalto|Co]]{{2+}} + 2{{e-}}
|{{eqm}}
|Co(''s'')
|−0.28
| class="noprint" |<ref name="van" />
|-
|{{hs|P }}[[Phosphoric acid|H<sub>3</sub>PO<sub>4</sub>]](''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|H<sub>3</sub>PO<sub>3</sub>(''aq'') + {{H2O}}
|−0.276
| class="noprint" |<ref name="van" />
|-
|V<sup>3+</sup> + {{e-}}
|{{eqm}}
|V{{2+}}
|−0.26
| class="noprint" |<ref name="Atk" />
|-
|[[Nikel|Ni]]{{2+}} + 2{{e-}}
|{{eqm}}
|Ni(''s'')
|−0.25
| class="noprint" |
|-
|[[Arseniko|As]](''s'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|[[Arsine|AsH<sub>3</sub>]](''g'')
|−0.23
| class="noprint" |<ref name="Bar" />
|-
|[[Silver iodide|AgI]](''s'') + {{e-}}
|{{eqm}}
|Ag(''s'') + I<sup>−</sup>
|−0.15224
| class="noprint" |<ref name="van" />
|-
|[[Molybdenum dioxide|MoO]]{{sub2}}(''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|Mo(''s'') + 2{{H2O}}
|−0.15
| class="noprint" |
|-
|[[Silizio|Si]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|SiH<sub>4</sub>(''g'')
|−0.14
| class="noprint" |
|-
|Sn{{2+}} + 2{{e-}}
|{{eqm}}
|Sn(''s'')
|−0.13
| class="noprint" |
|-
|[[Oxigeno|O]]{{sub2}}(''g'') + {{H+}} + {{e-}}
|{{eqm}}
|HO{{sub2}}•(''aq'')
|−0.13
| class="noprint" |
|-
|[[Berun|Pb]]{{2+}} + 2{{e-}}
|{{eqm}}
|Pb(''s'')
|−0.126
| class="noprint" |<ref name="Atk" />
|-
|[[Tungsten(IV) oxide|WO{{sub2}}]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|[[Tungsten|W]](''s'') + 2{{H2O}}
|−0.12
| class="noprint" |
|-
|[[Fosforo|P]](''red'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|[[Phosphine|PH<sub>3</sub>]](''g'')
|−0.111
| class="noprint" |<ref name="van" />
|-
|{{hs|C}} CO{{sub2}}(''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|[[Formic acid|HCOOH]](''aq'')
|−0.11
| class="noprint" |
|-
|[[Selenio|Se]](''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|H{{sub2}}Se(''g'')
|−0.11
| class="noprint" |
|-
|{{hs|C}} CO{{sub2}}(''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|CO(''g'') + {{H2O}}
|−0.11
| class="noprint" |
|-
|[[Tin(II) oxide|SnO]](''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|Sn(''s'') + {{H2O}}
|−0.10
| class="noprint" |
|-
|[[Tin dioxide|SnO{{sub2}}]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|SnO(''s'') + 2{{H2O}}
|−0.09
| class="noprint" |
|-
|[[Tungsten(VI) oxide|WO<sub>3</sub>]](''aq'') + 6{{H+}} + 6{{e-}}
|{{eqm}}
|W(''s'') + 3{{H2O}}
|−0.09
| class="noprint" |<ref name="Bar" />
|-
|[[Phosphorus|P]](''white'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|[[Phosphine|PH<sub>3</sub>]](''g'')
|−0.063
| class="noprint" |<ref name="van" />
|-
|Fe<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Fe(''s'')
|−0.04
| class="noprint" |<ref name="webelements_fe" />
|-
|{{hs|C}} [[Formic acid|HCOOH]](''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|[[Formaldehyde|HCHO]](''aq'') + {{H2O}}
|−0.03
| class="noprint" |
|- style="background-color:#d0d0FF; font-weight: bold"
|{{hs|H}} 2{{H+}} + 2{{e-}}
|{{eqm}}
|H{{sub2}}(''g'')
|0.0000
| class="noprint" |= 0
|-
|[[Silver bromide|AgBr]](''s'') + {{e-}}
|{{eqm}}
|Ag(''s'') + Br<sup>−</sup>
| +0.07133
| class="noprint" |<ref name="van" />
|-
|[[Tetrathionate|S<sub>4</sub>O<sub>6</sub><sup>2−</sup>]] + 2{{e-}}
|{{eqm}}
|2{{hsp}}[[Thiosulfate|S{{sub2}}O<sub>3</sub><sup>2−</sup>]]
| +0.08
| class="noprint" |
|-
|[[Magnetite|Fe<sub>3</sub>O<sub>4</sub>]](''s'') + 8{{H+}} + 8{{e-}}
|{{eqm}}
|3{{hsp}}Fe(''s'') + 4{{H2O}}
| +0.085
| class="noprint" |<ref name="Pou" />
|-
|[[Nitrogen|N{{sub2}}]](''g'') + 2{{H2O}} + 6{{H+}} + 6{{e-}}
|{{eqm}}
|2{{hsp}}[[Ammonium hydroxide|NH<sub>4</sub>OH]](''aq'')
| +0.092
| class="noprint" |
|-
|[[Mercury(II) oxide|HgO]](''s'') + {{H2O}} + 2{{e-}}
|{{eqm}}
|Hg(''l'') + 2{{OH-}}
| +0.0977
| class="noprint" |
|-
|Cu(NH<sub>3</sub>)<sub>4</sub>{{2+}} + {{e-}}
|{{eqm}}
|Cu(NH<sub>3</sub>){{sub2}}{{+}} + 2{{hsp}}NH<sub>3</sub>
| +0.10
| class="noprint" |<ref name="Bar" />
|-
|[[Ruthenium|Ru(NH<sub>3</sub>)<sub>6</sub><sup>3+</sup>]] + {{e-}}
|{{eqm}}
|Ru(NH<sub>3</sub>)<sub>6</sub>{{2+}}
| +0.10
| class="noprint" |<ref name="Bar2" />
|-
|[[Hydrazine|N{{sub2}}H<sub>4</sub>]](''aq'') + 4{{H2O}} + 2{{e-}}
|{{eqm}}
|2{{hsp}}NH<sub>4</sub>{{+}} + 4{{OH-}}
| +0.11
| class="noprint" |<ref name="Gre" />
|-
|{{hs|Mo}} [[Molybdic acid|H{{sub2}}MoO<sub>4</sub>]](''aq'') + 6{{H+}} + 6{{e-}}
|{{eqm}}
|Mo(''s'') + 4{{H2O}}
| +0.11
| class="noprint" |
|-
|Ge<sup>4+</sup> + 4{{e-}}
|{{eqm}}
|Ge(''s'')
| +0.12
| class="noprint" |
|-
|[[Carbon|C]](''s'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|[[Methane|CH<sub>4</sub>]](''g'')
| +0.13
| class="noprint" |<ref name="Bar" />
|-
|{{hs|C}} [[Formaldehyde|HCHO]](''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|[[Methanol|CH<sub>3</sub>OH]](''aq'')
| +0.13
| class="noprint" |
|-
|[[Sulfur|S]](''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|H{{sub2}}S(''g'')
| +0.14
| class="noprint" |
|-
|Sn<sup>4+</sup> + 2{{e-}}
|{{eqm}}
|Sn{{2+}}
| +0.15
| class="noprint" |
|-
|[[Copper|Cu]]{{2+}} + {{e-}}
|{{eqm}}
|Cu{{+}}
| +0.159
| class="noprint" |<ref name="Bar" />
|-
|{{hs|S}} HSO<sub>4</sub><sup>−</sup> + 3{{H+}} + 2{{e-}}
|{{eqm}}
|SO{{sub2}}(''aq'') + 2{{H2O}}
| +0.16
| class="noprint" |
|-
|[[Uranyl|UO{{sub2}}{{2+}}]] + {{e-}}
|{{eqm}}
|UO{{sub2}}{{+}}
| +0.163
| class="noprint" |<ref name="Bar2" />
|-
|{{hs|S}} SO<sub>4</sub><sup>2−</sup> + 4{{H+}} + 2{{e-}}
|{{eqm}}
|SO{{sub2}}(''aq'') + 2{{H2O}}
| +0.17
| class="noprint" |
|-
|TiO{{2+}} + 2{{H+}} + {{e-}}
|{{eqm}}
|Ti<sup>3+</sup> + {{H2O}}
| +0.19
| class="noprint" |
|-
|SbO{{+}} + 2{{H+}} + 3{{e-}}
|{{eqm}}
|Sb(''s'') + {{H2O}}
| +0.20
| class="noprint" |
|-
|[[Silver chloride|AgCl]](''s'') + {{e-}}
|{{eqm}}
|Ag(''s'') + Cl<sup>−</sup>
| +0.22233
| class="noprint" |<ref name="van" />
|-
|{{hs|As}} H<sub>3</sub>AsO<sub>3</sub>(''aq'') + 3{{H+}} + 3{{e-}}
|{{eqm}}
|As(''s'') + 3{{H2O}}
| +0.24
| class="noprint" |
|-
|GeO(''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|Ge(''s'') + {{H2O}}
| +0.26
| class="noprint" |
|-
|UO{{sub2}}{{+}} + 4{{H+}} + {{e-}}
|{{eqm}}
|U<sup>4+</sup> + 2{{H2O}}
| +0.273
| class="noprint" |<ref name="Bar2" />
|-
|[[Rhenium|Re]]<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Re(''s'')
| +0.300
| class="noprint" |
|-
|Bi<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Bi(''s'')
| +0.308
| class="noprint" |<ref name="van" />
|-
|Cu{{2+}} + 2{{e-}}
|{{eqm}}
|Cu(''s'')
| +0.337
| class="noprint" |<ref name="Bar" />
|-
|VO{{2+}} + 2{{H+}} + {{e-}}
|{{eqm}}
|V<sup>3+</sup> + {{H2O}}
| +0.34
| class="noprint" |
|-
|{{hs|Fe}} [Fe(CN)<sub>6</sub>]<sup>3−</sup> + {{e-}}
|{{eqm}}
|[Fe(CN)<sub>6</sub>]<sup>4−</sup>
| +0.36
| class="noprint" |
|-
|[[Ferrocene|Fc]]{{+}} + {{e-}}
|{{eqm}}
|Fc(''s'')
| +0.4
| class="noprint" |<ref>{{erreferentzia|last=Connelly|first=Neil G.|author2=Geiger, William E.|title=Chemical Redox Agents for Organometallic Chemistry|journal=Chemical Reviews|date=1 January 1996|volume=96|issue=2|pages=877–910|doi=10.1021/cr940053x|pmid=11848774}}</ref>
|-
|O{{sub2}}(''g'') + 2{{H2O}} + 4{{e-}}
|{{eqm}}
|4{{OH-}}(''aq'')
| +0.401
| class="noprint" |<ref name="Atk" />
|-
|{{hs|Mo}} H{{sub2}}MoO<sub>4</sub> + 6{{H+}} + 3{{e-}}
|{{eqm}}
|Mo<sup>3+</sup> + 2{{H2O}}
| +0.43
| class="noprint" |
|-
|{{hs|C}} CH<sub>3</sub>OH(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|CH<sub>4</sub>(''g'') + {{H2O}}
| +0.50
| class="noprint" |
|-
|{{hs|S}} SO{{sub2}}(''aq'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|S(''s'') + 2{{H2O}}
| +0.50
| class="noprint" |
|-
|Cu{{+}} + {{e-}}
|{{eqm}}
|Cu(''s'')
| +0.520
| class="noprint" |<ref name="Bar" />
|-
|{{hs|C}} [[Carbon monoxide|CO]](''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|C(''s'') + {{H2O}}
| +0.52
| class="noprint" |
|-
|I<sub>3</sub><sup>−</sup> + 2{{e-}}
|{{eqm}}
|3{{hsp}}I<sup>−</sup>
| +0.53
| class="noprint" |<ref name="Atk" />
|-
|[[Iodine|I]]{{sub2}}(''s'') + 2{{e-}}
|{{eqm}}
|2{{hsp}}I<sup>−</sup>
| +0.54
| class="noprint" |<ref name="Atk" />
|-
|{{hs|Au}} [AuI<sub>4</sub>]<sup>−</sup> + 3{{e-}}
|{{eqm}}
|Au(''s'') + 4{{hsp}}I<sup>−</sup>
| +0.56
| class="noprint" |
|-
|{{hs|As}} H<sub>3</sub>AsO<sub>4</sub>(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|H<sub>3</sub>AsO<sub>3</sub>(''aq'') + {{H2O}}
| +0.56
| class="noprint" |
|-
|{{hs|Au}} [<span>AuI[[Txantiloi:Sub2]]</span>]<sup>−</sup> + {{e-}}
|{{eqm}}
|Au(''s'') + 2{{hsp}}I<sup>−</sup>
| +0.58
| class="noprint" |
|-
|MnO<sub>4</sub><sup>−</sup> + 2{{H2O}} + 3{{e-}}
|{{eqm}}
|MnO{{sub2}}(''s'') + 4{{OH-}}
|1.692
| class="noprint" |
|-
|S{{sub2}}O<sub>3</sub><sup>2{{hsp}}−</sup> + 6{{H+}} + 4{{e-}}
|{{eqm}}
|2{{hsp}}S(''s'') + 3{{H2O}}
| +0.60
| class="noprint" |
|-
|{{hs|Mo}} H{{sub2}}MoO<sub>4</sub>(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|MoO{{sub2}}(''s'') + 2{{H2O}}
| +0.65
| class="noprint" |
|-
|2[[Hematite|Fe<sub>2</sub>O<sub>3</sub>]](s) + 2{{H+}} + 2{{e-}}
|{{eqm}}
|2 [[Magnetite|Fe<sub>3</sub>O<sub>4</sub>]](s)  + {{H2O}}
| +0.66
| class="noprint" |<ref name="Pang2007" />{{rp|p.100}}
|-
|{{hs|C}} [[Fitxategi:1,4-Benzochinon.svg|link=P-Benzoquinone|70x70px]] + 2{{H+}} + 2{{e-}}
|{{eqm}}
|[[Fitxategi:Hydrochinon2.svg|link=Hydroquinone|110x110px]]
| +0.6992
| class="noprint" |<ref name="van" />
|-
|O{{sub2}}(''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|[[Hydrogen Peroxide|H{{sub2}}O{{sub2}}]](''aq'')
| +0.70
| class="noprint" |
|-
|Tl<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Tl(''s'')
| +0.72
| class="noprint" |
|-
|PtCl<sub>6</sub><sup>2−</sup> + 2{{e-}}
|{{eqm}}
|PtCl<sub>4</sub><sup>2−</sup> + 2{{hsp}}Cl<sup>−</sup>
| +0.726
| class="noprint" |<ref name="Bar2" />
|-
|{{hs|Se}} H{{sub2}}SeO<sub>3</sub>(''aq'') + 4{{H+}} + 4{{e-}}
|{{eqm}}
|Se(''s'') + 3{{H2O}}
| +0.74
| class="noprint" |
|-
|PtCl<sub>4</sub><sup>2−</sup> + 2{{e-}}
|{{eqm}}
|Pt(''s'') + 4{{hsp}}Cl<sup>−</sup>
| +0.758
| class="noprint" |<ref name="Bar2" />
|-
|Fe<sup>3+</sup> + {{e-}}
|{{eqm}}
|Fe{{2+}}
| +0.77
| class="noprint" |
|-
|[[Silver|Ag]]{{+}} + {{e-}}
|{{eqm}}
|Ag(''s'')
| +0.7996
| class="noprint" |<ref name="van" />
|-
|[[Mercury (element)|Hg]]{{sub2}}{{2+}} + 2{{e-}}
|{{eqm}}
|2{{hsp}}Hg(''l'')
| +0.80
| class="noprint" |
|-
|{{hs|N}} [[Nitrate|NO<sub>3</sub><sup>−</sup>]](''aq'') + 2{{H+}} + {{e-}}
|{{eqm}}
|[[Nitrogen dioxide|NO{{sub2}}]](''g'') + {{H2O}}
| +0.80
| class="noprint" |
|-
|{{hs|Fe}} 2[[Ferrate|FeO<sub>4</sub><sup>2−</sup>]] + 5{{H2O}} + 6{{e-}}
|{{eqm}}
|Fe{{sub2}}O<sub>3</sub>(''s'') + 10 {{OH-}}
| +0.81
| class="noprint" |<ref name="webelements_fe" />
|-
|{{hs|Au}} [AuBr<sub>4</sub>]<sup>−</sup> + 3{{e-}}
|{{eqm}}
|Au(''s'') + 4{{hsp}}Br<sup>−</sup>
| +0.85
| class="noprint" |
|-
|Hg{{2+}} + 2{{e-}}
|{{eqm}}
|Hg(''l'')
| +0.85
| class="noprint" |
|-
|{{hs|Ir}} [IrCl<sub>6</sub>]<sup>2−</sup> + {{e-}}
|{{eqm}}
|[IrCl<sub>6</sub>]<sup>3−</sup>
| +0.87
| class="noprint" |<ref name="atkinshriver" />
|-
|MnO<sub>4</sub><sup>−</sup> + {{H+}} + {{e-}}
|{{eqm}}
|HMnO<sub>4</sub><sup>−</sup>
| +0.90
| class="noprint" |
|-
|{{hs|Hg}}2{{hsp}}Hg{{2+}} + 2{{e-}}
|{{eqm}}
|Hg{{sub2}}{{2+}}
| +0.91
| class="noprint" |<ref name="Bar" />
|-
|[[Palladium|Pd{{2+}}]] + 2{{e-}}
|{{eqm}}
|Pd(''s'')
| +0.915
| class="noprint" |<ref name="Bar2" />
|-
|{{hs|Au}} [AuCl<sub>4</sub>]<sup>−</sup> + 3{{e-}}
|{{eqm}}
|Au(''s'') + 4{{hsp}}Cl<sup>−</sup>
| +0.93
| class="noprint" |
|-
|[[Hematite|Fe<sub>2</sub>O<sub>3</sub>]](s) + 6{{H+}} + 2{{e-}}
|{{eqm}}
|2[[Ferrous|Fe<sup>2+</sup>]] + 3{{H2O}}
| +0.94
| class="noprint" |<ref name="Pang2007" />{{rp|p.100}}
|-
|MnO{{sub2}}(''s'') + 4{{H+}} + {{e-}}
|{{eqm}}
|Mn<sup>3+</sup> + 2{{H2O}}
| +0.95
| class="noprint" |
|-
|[[Nitrate|NO<sub>3</sub><sup>−</sup>]](''aq'') + 4{{H+}} + 3{{e-}}
|{{Eqm}}
|[[Nitrogen oxide|NO]](''g'') + 2{{H2O}}(''l)''
|<nowiki>+0.958</nowiki>
| class="noprint" |
|-
|{{hs|Au}}[<span>AuBr[[Txantiloi:Sub2]]</span>]<sup>−</sup> + {{e-}}
|{{eqm}}
|Au(''s'') + 2{{hsp}}Br<sup>−</sup>
| +0.96
| class="noprint" |
|-
|{{hs|Xe}}[HXeO<sub>6</sub>]<sup>3−</sup> + 2{{H2O}} + 2{{e-}} +
|{{eqm}}
|[HXeO<sub>4</sub>]<sup>−</sup> + 4{{hsp}}{{OH-}}
| +0.99
| class="noprint" |<ref name="webelements_xe">[http://www.webelements.com/xenon/compounds.html WebElements Periodic Table of the Elements | Xenon | compounds information]</ref>
|-
|[VO<sub>2</sub>]<sup>+</sup>(''aq'') + 2{{H+}} + {{e-}}
|{{eqm}}
|[[Vanadyl ion|[VO]<sup>2+</sup>]](''aq'') + {{H2O}}
| +1.0
| class="noprint" |<ref name="Cotton">{{Cotton&Wilkinson6th}}</ref>
|-
|{{hs|Te}}[[Telluric acid|H<sub>6</sub>TeO<sub>6</sub>]](''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|TeO{{sub2}}(''s'') + 4{{H2O}}
| +1.02
| class="noprint" |<ref name="Cotton">{{Cotton&Wilkinson6th}}</ref>
|-
|Br{{sub2}}(''l'') + 2{{e-}}
|{{eqm}}
|2{{hsp}}Br<sup>−</sup>
| +1.066
| class="noprint" |<ref name="van" />
|-
|Br{{sub2}}(''aq'') + 2{{e-}}
|{{eqm}}
|2{{hsp}}Br<sup>−</sup>
| +1.0873
| class="noprint" |<ref name="van" />
|-
|[[Magnetite|Fe<sub>3</sub>O<sub>4</sub>]](s) + 8{{H+}} + 2{{e-}}
|{{eqm}}
|3[[Ferrous|Fe<sup>2+</sup>]] + 4{{H2O}}
| +1.09
| class="noprint" |<ref name="Pang2007" />{{rp|p.100}}
|-
|{{hs|I}} IO<sub>3</sub><sup>−</sup> + 5{{H+}} + 4{{e-}}
|{{eqm}}
|HIO(''aq'') + 2{{H2O}}
| +1.13
| class="noprint" |
|-
|{{hs|Au}} [<span>AuCl[[Txantiloi:Sub2]]</span>]<sup>−</sup> + {{e-}}
|{{eqm}}
|Au(''s'') + 2{{hsp}}Cl<sup>−</sup>
| +1.15
| class="noprint" |
|-
|{{hs|Se}} HSeO<sub>4</sub><sup>−</sup> + 3{{H+}} + 2{{e-}}
|{{eqm}}
|H{{sub2}}SeO<sub>3</sub>(''aq'') + {{H2O}}
| +1.15
| class="noprint" |
|-
|Ag{{sub2}}O(''s'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|2{{hsp}}Ag(''s'') + {{H2O}}
| +1.17
| class="noprint" |
|-
|ClO<sub>3</sub><sup>−</sup> + 2{{H+}} + {{e-}}
|{{eqm}}
|ClO{{sub2}}(''g'') + {{H2O}}
| +1.18
| class="noprint" |
|-
|{{hs|Xe}}[HXeO<sub>6</sub>]<sup>3−</sup> + 5{{H2O}} + 8 {{e-}}
|{{eqm}}
|Xe(''g'') + 11{{OH-}}
| +1.18
| class="noprint" |<ref name="webelements_xe" />
|-
|[[Platinum|Pt{{2+}}]] + 2{{e-}}
|{{eqm}}
|Pt(''s'')
| +1.188
| class="noprint" |<ref name="Bar2" />
|-
|ClO{{sub2}}(''g'') + {{H+}} + {{e-}}
|{{eqm}}
|HClO{{sub2}}(''aq'')
| +1.19
| class="noprint" |
|-
|{{hs|I}} 2{{hsp}}IO<sub>3</sub><sup>−</sup> + 12{{H+}} + 10{{e-}}
|{{eqm}}
|I{{sub2}}(''s'') + 6{{H2O}}
| +1.20
| class="noprint" |
|-
|ClO<sub>4</sub><sup>−</sup> + 2{{H+}} + 2{{e-}}
|{{eqm}}
|ClO<sub>3</sub><sup>−</sup> + {{H2O}}
| +1.20
| class="noprint" |
|-
|'''O{{sub2}}(''g'') + 4{{H+}} + 4{{e-}} '''
|{{eqm}}
|2{{H2O}}
| +1.229
| class="noprint" |<ref name="Atk" />
|-
|MnO{{sub2}}(''s'') + 4{{H+}} + 2{{e-}}
|{{eqm}}
|Mn{{2+}} + 2{{H2O}}
| +1.23
| class="noprint" |
|-
|{{hs|Xe}}[HXeO<sub>4</sub>]<sup>−</sup> + 3{{H2O}} + 6 {{e-}}
|{{eqm}}
|Xe(''g'') + 7{{OH-}}
| +1.24
| class="noprint" |<ref name="webelements_xe" />
|-
|Tl<sup>3+</sup> + 2{{e-}}
|{{eqm}}
|Tl{{+}}
| +1.25
| class="noprint" |
|-
|Cr{{sub2}}O<sub>7</sub><sup>2−</sup> + 14{{H+}} + 6{{e-}}
|{{eqm}}
|2{{hsp}}Cr<sup>3+</sup> + 7{{H2O}}
| +1.33
| class="noprint" |
|-
|Cl{{sub2}}(''g'') + 2{{e-}}
|{{eqm}}
|2{{hsp}}Cl<sup>−</sup>
| +1.36
| class="noprint" |<ref name="Atk" />
|-
|CoO{{sub2}}(''s'') + 4{{H+}} + {{e-}}
|{{eqm}}
|Co<sup>3+</sup> + 2{{H2O}}
| +1.42
| class="noprint" |
|-
|{{hs|N}} 2{{hsp}}[[Hydroxylamine|NH<sub>3</sub>OH<sup>+</sup>]] + {{H+}} + 2{{e-}}
|{{eqm}}
|[[Hydrazine|N{{sub2}}H<sub>5</sub>{{+}}]] + 2{{H2O}}
| +1.42
| class="noprint" |<ref name="Gre" />
|-
|{{hs|I}} 2{{hsp}}HIO(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|I{{sub2}}(''s'') + 2{{H2O}}
| +1.44
| class="noprint" |
|-
|BrO<sub>3</sub><sup>−</sup> + 5{{H+}} + 4{{e-}}
|{{eqm}}
|HBrO(''aq'') + 2{{H2O}}
| +1.45
| class="noprint" |
|-
|{{hs|PbO}} [[Lead dioxide|β-PbO{{sub2}}]](''s'') + 4{{H+}} + 2{{e-}}
|{{eqm}}
|Pb{{2+}} + 2{{H2O}}
| +1.460
| class="noprint" |<ref name="Bar" />
|-
|{{hs|PbO}} α-PbO{{sub2}}(''s'') + 4{{H+}} + 2{{e-}}
|{{eqm}}
|Pb{{2+}} + 2{{H2O}}
| +1.468
| class="noprint" |<ref name="Bar" />
|-
|{{hs|Br}} 2{{hsp}}BrO<sub>3</sub><sup>−</sup> + 12{{H+}} + 10{{e-}}
|{{eqm}}
|Br{{sub2}}(''l'') + 6{{H2O}}
| +1.48
| class="noprint" |
|-
|{{hs|Cl}} 2ClO<sub>3</sub><sup>−</sup> + 12{{H+}} + 10{{e-}}
|{{eqm}}
|Cl{{sub2}}(''g'') + 6{{H2O}}
| +1.49
| class="noprint" |
|-
|{{hs|Cl}} HClO(''aq'') + {{H+}} + 2{{e-}}
|{{eqm}}
|Cl<sup>−</sup>(''aq'') + {{H2O}}
| +1.49
| class="noprint" |<ref name="CRC" />
|-
|MnO<sub>4</sub><sup>−</sup> + 8{{H+}} + 5{{e-}}
|{{eqm}}
|Mn{{2+}} + 4{{H2O}}
| +1.51
| class="noprint" |
|-
|{{hs|O}} HO{{sub2}}<sup>•</sup> + {{H+}} + {{e-}}
|{{eqm}}
|{{H2O}}{{sub2}}(''aq'')
| +1.51
| class="noprint" |
|-
|Au<sup>3+</sup> + 3{{e-}}
|{{eqm}}
|Au(''s'')
| +1.52
| class="noprint" |
|-
|NiO{{sub2}}(''s'') + 4{{H+}} + 2{{e-}}
|{{eqm}}
|Ni{{2+}} + 2{{OH-}}
| +1.59
| class="noprint" |
|-
|Ce<sup>4+</sup> + {{e-}}
|{{eqm}}
|Ce<sup>3+</sup>
| +1.61
| class="noprint" |
|-
|{{hs|Cl}} 2{{hsp}}HClO(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|Cl{{sub2}}(''g'') + 2{{H2O}}
| +1.63
| class="noprint" |
|-
|Ag{{sub2}}O<sub>3</sub>(''s'') + 6{{H+}} + 4{{e-}}
|{{eqm}}
|2{{hsp}}Ag{{+}} + 3{{H2O}}
| +1.67
| class="noprint" |
|-
|{{hs|Cl}} HClO{{sub2}}(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|HClO(''aq'') + {{H2O}}
| +1.67
| class="noprint" |
|-
|Pb<sup>4+</sup> + 2{{e-}}
|{{eqm}}
|Pb{{2+}}
| +1.69
| class="noprint" |<ref name="Bar" />
|-
|[[Permanganate|MnO<sub>4</sub><sup>−</sup>]] + 4{{H+}} + 3{{e-}}
|{{eqm}}
|[[Manganese(IV) oxide|MnO{{sub2}}]](''s'') + 2{{H2O}}
| +1.70
| class="noprint" |
|-
|AgO(''s'') + 2{{H+}} + {{e-}}
|{{eqm}}
|Ag{{+}} + {{H2O}}
| +1.77
| class="noprint" |
|-
|{{hs|O}} [[Hydrogen peroxide|H<sub>2</sub>O<sub>2</sub>]](''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|2{{H2O}}
| +1.78
| class="noprint" |
|-
|Co<sup>3+</sup> + {{e-}}
|{{eqm}}
|Co{{2+}}
| +1.82
| class="noprint" |
|-
|Au{{+}} + {{e-}}
|{{eqm}}
|Au(''s'')
| +1.83
| class="noprint" |<ref name="Bar" />
|-
|BrO<sub>4</sub><sup>−</sup> + 2{{H+}} + 2{{e-}}
|{{eqm}}
|BrO<sub>3</sub><sup>−</sup> + {{H2O}}
| +1.85
| class="noprint" |
|-
|Ag{{2+}} + {{e-}}
|{{eqm}}
|Ag{{+}}
| +1.98
| class="noprint" |<ref name="Bar" />
|-
|[[Peroxodisulfate|S{{sub2}}O<sub>8</sub><sup>2−</sup>]] + 2{{e-}}
|{{eqm}}
|2{{hsp}}[[Sulfate|SO<sub>4</sub><sup>2−</sup>]]
| +2.010
| class="noprint" |<ref name="van" />
|-
|[[Ozono|O<sub>3</sub>]](''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|O{{sub2}}(''g'') + {{H2O}}
| +2.075
| class="noprint" |<ref name="Bar2" />
|-
|{{hs|Mn}} HMnO<sub>4</sub><sup>−</sup> + 3{{H+}} + 2{{e-}}
|{{eqm}}
|MnO{{sub2}}(''s'') + 2{{H2O}}
| +2.09
| class="noprint" |
|-
|XeO<sub>3</sub>(''aq'') + 6{{H+}} + 6 {{e-}}
|{{eqm}}
|Xe(''g'') + 3{{H2O}}
| +2.12
| class="noprint" |<ref name="webelements_xe" />
|-
|{{hs|Xe}}H<sub>4</sub>XeO<sub>6</sub>(''aq'') + 8{{H+}} + 8 {{e-}}
|{{eqm}}
|Xe(''g'') + 6 {{H2O}}
| +2.18
| class="noprint" |<ref name="webelements_xe" />
|-
|[[Ferrate|FeO<sub>4</sub><sup>2−</sup>]] + 3{{e-}} + 8{{H+}}
|{{eqm}}
|Fe<sup>3+</sup> + 4{{H2O}}
| +2.20
| class="noprint" |<ref name="wou">[http://www.wou.edu/las/physci/ch412/redox.htm Redox Reactions, Western Oregon University website]</ref>
|-
|XeF{{sub2}}(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|Xe(''g'') + 2HF(''aq'')
| +2.32
| class="noprint" |<ref name="webelements_xe" />
|-
|{{hs|Xe}}H<sub>4</sub>XeO<sub>6</sub>(''aq'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|XeO<sub>3</sub>(''aq'') + 3{{H2O}}
| +2.42
| class="noprint" |<ref name="webelements_xe" />
|-
|[[Fluorine|F]]{{sub2}}(''g'') + 2{{e-}}
|{{eqm}}
|2{{hsp}}F<sup>−</sup>
| +2.87
| class="noprint" |<ref name="atkinshriver">{{erreferentzia|last=Atkins|first=Peter|title=Inorganic Chemistry (5th Edition)|year=2010|publisher=W. H. Freeman and Company|location=New York|isbn=978-1-42-921820-7|pages=153}}</ref><ref name="Atk" /><ref name="Bar" />
|-
|F{{sub2}}(''g'') + 2{{H+}} + 2{{e-}}
|{{eqm}}
|2{{hsp}}HF(''aq'')
| +3.05
| class="noprint" |<ref name="Bar" />
|-
|[[Krypton difluoride|KrF{{sub2}}]](''aq'') + 2{{e-}}
|{{eqm}}
|{{hsp}}Kr(''g'') + 2{{hsp}}F<sup>−</sup>(''aq'')
| +3.27
| class="noprint" |<ref>https://web.archive.org/web/20131107223339/http://acta.chem-soc.si/60/60-3-455.pdf</ref>
|}

== Zelula elektrokimikoen termodinamika ==
Pila baten potentzial diferentzia erreakzioaren energia askearen aldaketarekin zuzenki lotuta dago, ekuazio honek adierazten duen moduan:

<math>\Delta G^0= - nFE^0</math>

'''n''': trukatu den elektroi kopurua.

'''ΔG<sup>0</sup>''': energia askearen aldaketa baldintza estandarretan.

'''F''': Faraday konstantea (96485 C/mol)

'''E<sup>0</sup>''': pilaren potentzial estandarra

Erreakzio bat presio eta tenperatura konstantepean ematen denean, energia askearen aldaketaren zeinuak adieraziko digu prozesua berezkoa izango den edo ez. Aldaketa horren balioa negatiboa baldin bada erreakzioa berezkoa izango da. F eta n-ren balioak positiboak direla kontutan hartzen badugu, E<sup>0</sup> balioak positiboa izan beharko du ΔG<sup>0</sup> negatiboa izan dadin.

Zelula elektrokimiko bati dagokion energia elektrokimikoa Δ<sub>r</sub>G duen zelula batekin erlazionatu ahal izateko, zelulak itzulkorra izan behar du. Kanpotik potentzial bat gehituko bagenu zelularen potentzial berekoa baina zeinuz kontrakoa, ez litzateke erreakziorik gertatuko. Aldiz, kanpoko potentzialaren balioa infinitesimalki handitu edota txikituko bagenu zelularen berezko edo alderantzizko erreakzioa gertatuko litzateke. Baldintza hauek betetzen dituen edozein zelula ''itzulkorra'' dela esaten da.

== Nernst-en ekuazioa ==
'''Nernst-en ekuazioa''' baldintza estandarretatik (1 M, 1 atm, 25&nbsp;°C) kanpo dagoen pila baten potentziala kalkulatzeko erabiltzen da. [[Walter Nernst|Walther Hermann Nernst]] kimikari alemaniarrak formulatu zuen 1889. urtean.

<math>E=E_0-\frac{RT}{nF}lnK_a</math>

'''E'''= zehaztutako baldintzetan pilaren potentziala.

'''E<sub>0</sub>'''= Baldintza estandarretan pilaren potentziala.

'''R'''= Gasen konstantea.

'''T'''= tenperatura Kelvinetan.

'''n'''= transferitutako elektroi kantitatea.

'''F'''= Faraday konstantea (96485 C/mol)

'''K<sub>a</sub>'''= Oreka konstante termodinamikoa.

== Oharrak ==
{{erreferentzia zerrenda|group=Note}}

== Erreferentziak ==
{{erreferentzia zerrenda|2}}

== Bibliografia ==
''FISICOQUÍMICA para las ciencias químicas y biológicas''. Raymond Chang, 2008. ISBN-13: 978-970-10-6652-2 ISBN-10: 970-10-6652-9

''Termodinámica química''. Juan A. Rodríguez Renuncio, Juan J. Ruiz Sánchez, José S. Urieta Navarro. 1999. ISBN: 84-7738-581-5

== Kanpo estekak ==
{{autoritate kontrola}}

[[Kategoria:Elektrokimika]]