Appendix: Standard Reduction Potentials by Value

Standard Cathode (Reduction) Half-Reaction Standard Reduction Potential E° (volts)

Li+(aq) + e ⇌ Li(s)

–3.040

Ba2+ + 2e⇌ Ba(s)

–2.92

Rb+ + e ⇌ Rb (s)

-2.98

K+(aq) + e ⇌ K(s)

-2.93

Cs+(aq) + e ⇌ Cs(s)

-2.92

Ba2+(aq) + 2e- ⇌ Ba(s)

-2.91

Sr2+(aq) + 2e- ⇌ Sr(s)

-2.89

Ca2+(aq) + 2e- ⇌ Ca(s)

–2.84

Na+(aq) + e ⇌ Na(s)

–2.713

Mg(OH)2(s) + 2e⇌ Mg(s) + 2OH

–2.687

La3+ + 3e⇌ La(s)

–2.38

Mg2+(aq) + 2e ⇌ Mn(s)

-2.356

Ce3+ + 3e⇌ Ce(s)

–2.336

Al(OH)4 + 3e⇌ Al(s) + 4OH

–2.310

AlF63− + 3e⇌ Al(s) + 6F

–2.07

Be2+ + 2e⇌ Be(s)

–1.99

B(OH)4 + 3e⇌ B(s) + 4OH

–1.811

U3+ + 3e⇌ U(s)

–1.66

Al3+(aq) + 3e ⇌ Al(s)

–1.676

SiF62− + 4e⇌ Si(s) + 6F

–1.37

Zn(CN)42− + 2e⇌ Zn(s) + 4CN

–1.34

Zn(OH)42− + 2e⇌ Zn(s) + 4OH

–1.285

Mn2+ + 2e⇌ Mn(s)

–1.17

V2+ + 2e⇌ V(s)

–1.13

2SO32− + 2H2O(l) + 2e− ⇌ S2O42− + 4OH

–1.13

Zn(NH3)42+ + 2e− ⇌ Zn(s) + 4NH3

–1.04

O2 (aq) + e ⇌ O2(aq)

-1.0

Cd(CN)42− + 2e⇌ Cd(s) + 4CN

–0.943

MoO42− + 4H2O(l) + 6e⇌Mo(s) + 8OH

–0.913

SiO2(s) + 4H+ + 4e⇌ Si(s) + 2H2O(l)

–0.909

SO42− + H2O(l) + 2e ⇌ SO32−+ 2OH

–0.936

Cr2+ + 2e− ⇌ Cr(s)

–0.90

B(OH)3 + 3H+ + 3e− ⇌ B(s) + 3H2O(l)

–0.890

2H2O(l) + 2e ⇌ H2(g) + 2OH(aq)

-0.828

Zn2+(aq) + 2e ⇌ Zn(s)

–0.7618

Co(OH)2(s) + 2e⇌ Co(s) + 2OH

–0.746

Cr3+(aq) + 3e ⇌ Cr(s)

–0.424

Ni(OH)2 + 2e⇌ Ni(s) + 2OH

–0.72

Ag2S(s) + 2e⇌ 2Ag(s) + S2−

–0.71

Se(s) + 2e⇌ Se2−

–0.67 in 1 M NaOH

Cd(NH3)42+ + 2e⇌ Cd(s) + 4NH3

–0.622

2SO32− + 3H2O(l) + 4e− ⇌S2O32− + 6OH

–0.576 in 1 M NaOH

U4+ + e− ⇌ U3+

–0.52

SiO2(s) + 8H+ + 8e− ⇌ SiH4(g) + 2H2O(l)

–0.516

Sb + 3H+ + 3e− ⇌ SbH3(g)

–0.510

H3PO3+ 2H+ + 2e− ⇌ H3PO2 + H2O(l)

-0.50

Ni(NH3)62+ + 2e− ⇌ Ni(s) + 6NH3

–0.49

2CO2(g) + 2H+ +2e⇌ H2C2O4

–0.481

Cr3+ + e⇌ Cr2+

–0.424

Fe2+(aq) + 2e ⇌ Fe(s)

-0.44

S(s) + 2e⇌ S2−

–0.407

Cd2+(aq) + 2e ⇌ Cd(s)

–0.4030

Ag(NH3)2+ + e⇌ Ag(s) + 2NH3

–0.373

Ti3+ + e⇌ Ti2+

–0.37

PbSO4(s) + 2e⇌ Pb(s) + SO42−

–0.356

Co2+(aq) + 2e ⇌ Co(s)

–0.277

2SO42− + 4H+ + 2e− ⇌ S2O62− + 2H2O(l)

–0.25

N2(g) + 5H+ + 4e⇌ N2H5+

–0.23

H3PO4 + 2H+ + 2e⇌ H3PO3 + H2O(l)

-0.28

Ni2+(aq) + 2e ⇌ Ni(s)

–0.257

V3+ + e− ⇌ V2+

–0.255

As + 3H+ + 3e− ⇌ AsH3(g)

–0.225

CO2(g) + 2H+ + 2e− ⇌ HCO2H

–0.20

Mo3+ + 3e− ⇌ Mo(s)

–0.2

Sn2+ + 2e− ⇌ Sn(s)

–0.19 in 1 M HCl

Ti2+ + 2e⇌ Ti(s)

–0.163

MoO2(s) + 4H+ + 4e⇌ Mo(s) + 2H2O(l)

–0.152

AgI(s) + e− ⇌ Ag(s) + I

–0.152

Sn2+(aq) + 2e ⇌ Sn(s)

-0.14

Pb2+(aq) + 2e ⇌ Pb(s)

-0.126

CrO42− + 4H2O(l) + 3e− ⇌2Cr(OH)4 + 4OH

–0.13 in 1 M NaOH

WO2(s) + 4H+ + 4e⇌ W(s) + 2H2O(l)

–0.119

Se(s) + 2H+ + 2e⇌ H2Se(g)

–0.115

CO2(g) + 2H+ + 2e⇌ CO(g) + H2O(l)

–0.106

WO3(s) + 6H+ + 6e⇌ W(s) + 3H2O(l)

–0.090

Hg2I2(s) + 2e⇌ 2Hg(l) + 2I

–0.0405

Fe3+(aq) + 3e ⇌ Fe(s)

-0.037

2H+(aq) + 2e ⇌ H2(g)

0.00

P(s,white) + 3H+ + 3e⇌ PH3(g)

0.06

AgBr(s) + e⇌ Ag(s) + Br

0.071

S4O62− + 2e⇌2S2O32−

0.080

Co(NH3)63+ +e⇌Co(NH3)62+

0.1

Ru(NH3)63+ + e⇌ Ru(s) + Ru(NH3)62+

0.10

S(s) + 2H+ + 2e⇌ H2S

0.144

Sn4+(aq) + 2e ⇌ Sn2+(aq)

0.154

Cu2+(aq) + e ⇌ Cu+(aq)

0.159

UO22+ + e− ⇌UO2+

0.16

Co(OH)3(s) + e⇌ Co(OH)2(s) + OH

0.17

ClO4(aq) + H2O(l) + 2e- ⇌ ClO3(aq) + 2OH(aq)

0.17

SO42− + 4H+ + 2e− ⇌ H2SO32−+ H2O(l)

0.172

BiCl4 + 3e⇌ Bi(s) + 4Cl

0.199

SbO+ 2H+ + 3e⇌ Sb(s) + H2O(l)

0.212

AgCl(s) + e ⇌ Ag(s) + Cl(aq)

0.2223

HCHO + 2H+ + 2e⇌ CH3OH

0.2323

HAsO2 + 3H+ + 3e⇌ As(s) + 2H2O(l)

0.240

Ru3+ + e⇌ Ru2+

0.249

IO3+ 3H2O(l) + 6e⇌ I + 6OH

0.257

Hg2Cl2(s) + 2e⇌ 2Hg(l) + 2Cl

0.2682

UO2+ + 4H+ + e− ⇌U4+ + 2H2O(l)

0.27

Bi3+ + 3e⇌ Bi(s)

0.317

UO22+ + 4H+ + 2e− ⇌ U4+ + 2H2O(l)

0.327

VO2+ + 2H+ +e⇌V3+ + H2O(l)

0.337

Cu2+(aq) + 2e ⇌ Cu(s)

0.3419

ClO3(aq) + H2O(l) + 2e ⇌ ClO2(aq) + 2OH(aq)

0.35

Fe(CN)63− + e− ⇌ Fe(CN)64−

0.356

O2(g) + 2H2O(l) + 4e⇌ 4OH

0.401

ClO + H2O(l) + e− ⇌ ½Cl2(g) + 2OH

0.421 in 1 M NaOH

 Ag2C2O4(s) + 2e⇌ 2Ag(s) + C2O42−

0.47

Cu+(aq) + e ⇌ Cu(s)

0.52

I2(s) + 2e ⇌ 2I(aq)

0.5355

I3 + 2e⇌ 3I

0.536

Ga3+ + 3e⇌ Ga(s)

-0.56

Cu2+ + Cl + e⇌ CuCl(s)

0.559

S2O62− + 4H+ + 2e⇌ 2H2SO3

0.569

H3AsO4 + 2H+ + 2e⇌ HAsO2 + 2H2O(l)

0.560

ClO2(aq) + H2O(l) + 2e ⇌ ClO(aq) + 2OH(aq)

0.59

MnO4 + 2H2O(l) + 3e⇌ MnO2(s) + 4OH

0.60

Sb2O5(s) + 6H+ + 4e⇌ 2SbO+ + 3H2O(l)

0.605

PtCl62− + 2e⇌ PtCl42- + 2Cl

0.68

RuO2(s) + 4H+ + 4e⇌ Ru(s) + 2H2O(l)

0.68

O2(g) + 2H+ + 2e⇌ H2O2

0.695

PtCl42− + 2e⇌ Pt(s) + 4Cl

0.73

H2SeO3 + 4H+ + 4e⇌ Se(s) + 3H2O(l)

0.74

Tl3+ + 3e⇌ Tl(s)

0.742

Fe3+(aq) + e ⇌ Fe2+(aq)

0.771

Hg22+(aq) + 2e ⇌ 2Hg(l)

0.7960

Ag+(aq) + e- ⇌ Ag(s)

0.7996

Hg2+(aq) + 2e ⇌ Hg(l)

0.8535

Cu2+ + I +e⇌ CuI(s)

0.86

Ru(CN)63− +e⇌ Ru(s) + Ru(CN)64−

0.86

ClO + H2O(l) + 2e⇌ Cl + 2OH

0.890 in 1 M NaOH

2Hg2+(aq) + 2e ⇌ Hg22+(aq)

0.911

HgO(s) + 2H+ + 2e⇌ Hg(l) + H2O(l)

0.926

NO3 + 3H+ + 2e⇌ HNO2 + H2O(l)

0.94

MnO2(s) + 4H+ + e ⇌ Mn3+ (aq) + H2O(I)

0.95

NO3(aq) + 4H+(aq) + 3e ⇌ NO(g) + 2H2O(l)

0.96

HIO + H+ + 2e⇌ I + H2O(l)

0.985

HNO2 + H+ +e⇌ NO(g) + H2O(l)

0.996

VO22+ + 2H+  +e⇌ VO2+ + H2O(l)

1.000

AuCl4 + 3e⇌ Au(s) + 4Cl

1.002

NO2 (g) + H+ (aq) + e ⇌ HNO2 (aq)

1.07

Br2(l) + 2e ⇌ 2Br(aq)

1.087

Fe(phen)63+ +e− ⇌ Fe(phen)62+

1.147

SeO43− + 4H+ + e⇌ H2SeO3 + H2O(l)

1.151

ClO3 + 2H+ + e⇌ ClO2(g) + H2O

1.175

ClO3 + 3H+ + 2e− ⇌ HClO2 + H2O

1.181

IO3 + 6H+ + 5e⇌ ½I2(s) + 3H2O(l)

1.195

Pt2+ + 2e⇌ Pt(s)

1.2

ClO4 + 2H+ + 2e− ⇌ ClO3 + H2O

1.201

O2(g) + 4H+(aq) + 4e ⇌ 2H2O(l)

1.229

MnO2(s) + 4H+ + 2e⇌ Mn2+ + 2H2O(l)

1.23

Tl3+ + 2e− ⇌ Tl+

0.77 in 1 M HCl

2HNO2 + 4H+ + 4e⇌ N2O(g) + 3H2O(l)

1.297

HOBr + H+ + 2e⇌ Br + H2O(l)

1.341

Cr2O72-(aq) + 14H+(aq) + 6e ⇌ 2Cr3+(aq) + 7H2O(l)

1.36

Cr2O72− + 14H+ + 6e− ⇌ 2Cr3+ + 7H2O(l)

1.36

Cl2(g) + 2e ⇌ 2Cl(aq)

1.396

Au3+ + 2e⇌ Au+

1.36

Hg2Br2(s) + 2e⇌ 2Hg(l) + 2Br

1.392

Ce4+(aq) + e ⇌ Ce3+(aq)

1.44

PbO2(s) + 4H+ +2e ⇌ Pb2+(aq) + 2H2O(l)

1.46

BrO3 + 6H+ + 6e⇌ Br + 3H2O

1.478

Mn3+ + e⇌ Mn2+

1.5

MnO4(aq) + 8H+(aq) + 5e ⇌ Mn2+(aq) + 4H2O(l)

1.51

BrO3 + 6H+ + 5e⇌ ½Br2(l) + 3H2O

1.5

Au3+ + 3e⇌ Au(s)

1.52

2NO(g) + 2H+ + 2e⇌ N2O(g) + H2O(l)

1.59

HOBr + H+ + e⇌ ½Br + H2O(l)

1.604

HClO2 + 2H+ + 2e⇌ HOCl + H2O

1.64

PbO2(s) + 4SO42− + 4H+ + 2e⇌ PbSO4(s) + 2H2O(l)

1.690

MnO4 + 4H+ +3e⇌ MnO2(s) + 2H2O(l)

1.70

Ce4+ + e⇌ Ce3+

1.72

N2O(g) + 2H+ + 2e⇌ N2(g) + H2O(l)

1.77

H2O2(aq) + 2H+(aq) + 2e ⇌ 2H2O(l)

1.763

Au+ + e⇌ Au(s)

1.83

Co3+(aq) + e ⇌ Co2+(aq)

1.92

S2O82− + 2e⇌2SO42−

1.96

O3(g) + 2H+(aq) + 2e ⇌ O2(g) + H2O(l)

2.07

BaO(s) + 2H+ + 2e⇌ Ba(s) + H2O(l)

2.365

F2(g) + 2e ⇌ 2F(aq)

2.87

F2(g) + 2H+ + 2e⇌ 2HF

3.053

From UC Davis Chem Wiki (creative commons licence): UC Davis GeoWiki by University of California, Davis. CC-BY-NC-SA-3.0

Original source materials: Bard, A. J.; Parsons, B.; Jordon, J., eds. Standard Potentials in Aqueous Solutions, Dekker: New York, 1985; Milazzo, G.; Caroli, S.; Sharma, V. K. Tables of Standard Electrode Potentials, Wiley: London, 1978; Swift, E. H.; Butler, E. A. Quantitative Measurements and Chemical Equilibria, Freeman: New York, 1972.

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