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P2: Standard Reduction Potentials by Value

Table of Contents

The following table provides Eo for selected reduction reactions. Values are from the following sources: 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.

The table is ordered such that the stronger (more reactive) reductants are at the top and the stronger oxidants are at the bottom.

Standard Cathode (Reduction) Half-Reaction Standard Reduction Potential E° (volts)
Li+(aq) + e- \(\rightleftharpoons\) Li(s) –3.040
Ba2+ + 2e\(\rightleftharpoons\) Ba(s) –2.92
Rb+ + e- \(\rightleftharpoons\) Rb (s) -2.98
K+(aq) + e- \(\rightleftharpoons\) K(s) -2.93
Cs+(aq) + e- \(\rightleftharpoons\) Cs(s) -2.92
Ba2+(aq) + 2e- \(\rightleftharpoons\) Ba(s) -2.91
Sr2+(aq) + 2e- \(\rightleftharpoons\) Sr(s) -2.89
Ca2+(aq) + 2e- \(\rightleftharpoons\) Ca(s) –2.84
Na+(aq) + e- \(\rightleftharpoons\) Na(s) –2.713

Mg(OH)2(s) + 2e\(\rightleftharpoons\) Mg(s) + 2OH

–2.687
La3+ + 3e\(\rightleftharpoons\) La(s) –2.38
Mg2+(aq) + 2e- \(\rightleftharpoons\) Mn(s) -2.356
Ce3+ + 3e\(\rightleftharpoons\) Ce(s) –2.336

Al(OH)4 + 3e\(\rightleftharpoons\) Al(s) + 4OH

–2.310

AlF63− + 3e\(\rightleftharpoons\) Al(s) + 6F

–2.07
Be2+ + 2e\(\rightleftharpoons\) Be(s) –1.99

B(OH)4 + 3e\(\rightleftharpoons\) B(s) + 4OH

–1.811
U3+ + 3e\(\rightleftharpoons\) U(s) –1.66
Al3+(aq) + 3e- \(\rightleftharpoons\) Al(s) –1.676

SiF62− + 4e\(\rightleftharpoons\) Si(s) + 6F

–1.37

Zn(CN)42− + 2e\(\rightleftharpoons\) Zn(s) + 4CN

–1.34

Zn(OH)42− + 2e\(\rightleftharpoons\) Zn(s) + 4OH

–1.285
Mn2+ + 2e\(\rightleftharpoons\) Mn(s) –1.17

V2+ + 2e\(\rightleftharpoons\) V(s)

–1.13

2SO32− + 2H2O(l) + 2e \(\rightleftharpoons\) S2O42− + 4OH

–1.13

Zn(NH3)42+ + 2e \(\rightleftharpoons\) Zn(s) + 4NH3

–1.04
O2 (aq) + e- \(\rightleftharpoons\) O2-(aq) -1.0

Cd(CN)42− + 2e\(\rightleftharpoons\) Cd(s) + 4CN

–0.943

MoO42− + 4H2O(l) + 6e\(\rightleftharpoons\)Mo(s) + 8OH

–0.913

SiO2(s) + 4H+ + 4e\(\rightleftharpoons\) Si(s) + 2H2O(l)

–0.909

SO42− + H2O(l) + 2e \(\rightleftharpoons\) SO32−+ 2OH

–0.936
Cr2+ + 2e \(\rightleftharpoons\) Cr(s) –0.90

B(OH)3 + 3H+ + 3e \(\rightleftharpoons\) B(s) + 3H2O(l)

–0.890
2H2O(l) + 2e- \(\rightleftharpoons\) H2(g) + 2OH-(aq) -0.828
Zn2+(aq) + 2e- \(\rightleftharpoons\) Zn(s) –0.7618

Co(OH)2(s) + 2e\(\rightleftharpoons\) Co(s) + 2OH

–0.746
Cr3+(aq) + 3e- \(\rightleftharpoons\) Cr(s) –0.424

Ni(OH)2 + 2e\(\rightleftharpoons\) Ni(s) + 2OH

–0.72

Ag2S(s) + 2e\(\rightleftharpoons\) 2Ag(s) + S2−

–0.71

Se(s) + 2e\(\rightleftharpoons\) Se2−

–0.67 in 1 M NaOH

Cd(NH3)42+ + 2e\(\rightleftharpoons\) Cd(s) + 4NH3

–0.622

2SO32− + 3H2O(l) + 4e \(\rightleftharpoons\)S2O32− + 6OH

–0.576 in 1 M NaOH

U4+ + e \(\rightleftharpoons\) U3+

–0.52

SiO2(s) + 8H+ + 8e \(\rightleftharpoons\) SiH4(g) + 2H2O(l)

–0.516
Sb + 3H+ + 3e \(\rightleftharpoons\) SbH3(g) –0.510

H3PO3+ 2H+ + 2e \(\rightleftharpoons\) H3PO2 + H2O(l)

-0.50

Ni(NH3)62+ + 2e \(\rightleftharpoons\) Ni(s) + 6NH3

–0.49

2CO2(g) + 2H+ +2e\(\rightleftharpoons\) H2C2O4

–0.481
Cr3+ + e\(\rightleftharpoons\) Cr2+ –0.424
Fe2+(aq) + 2e- \(\rightleftharpoons\) Fe(s) -0.44

S(s) + 2e\(\rightleftharpoons\) S2−

–0.407
Cd2+(aq) + 2e- \(\rightleftharpoons\) Cd(s) –0.4030

Ag(NH3)2+ + e\(\rightleftharpoons\) Ag(s) + 2NH3

–0.373

Ti3+ + e\(\rightleftharpoons\) Ti2+

–0.37

PbSO4(s) + 2e\(\rightleftharpoons\) Pb(s) + SO42−

–0.356
Co2+(aq) + 2e- \(\rightleftharpoons\) Co(s) –0.277

2SO42− + 4H+ + 2e \(\rightleftharpoons\) S2O62− + 2H2O(l)

–0.25

N2(g) + 5H+ + 4e\(\rightleftharpoons\) N2H5+

–0.23

H3PO4 + 2H+ + 2e\(\rightleftharpoons\) H3PO3 + H2O(l)

-0.28
Ni2+(aq) + 2e- \(\rightleftharpoons\) Ni(s) –0.257

V3+ + e \(\rightleftharpoons\) V2+

–0.255
As + 3H+ + 3e \(\rightleftharpoons\) AsH3(g) –0.225

CO2(g) + 2H+ + 2e \(\rightleftharpoons\) HCO2H

–0.20
Mo3+ + 3e \(\rightleftharpoons\) Mo(s) –0.2
Sn2+ + 2e \(\rightleftharpoons\) Sn(s) –0.19 in 1 M HCl

Ti2+ + 2e\(\rightleftharpoons\) Ti(s)

–0.163

MoO2(s) + 4H+ + 4e\(\rightleftharpoons\) Mo(s) + 2H2O(l)

–0.152
AgI(s) + e \(\rightleftharpoons\) Ag(s) + I –0.152
Sn2+(aq) + 2e- \(\rightleftharpoons\) Sn(s) -0.14
Pb2+(aq) + 2e- \(\rightleftharpoons\) Pb(s) -0.126

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

–0.13 in 1 M NaOH

WO2(s) + 4H+ + 4e\(\rightleftharpoons\) W(s) + 2H2O(l)

–0.119

Se(s) + 2H+ + 2e\(\rightleftharpoons\) H2Se(g)

–0.115

CO2(g) + 2H+ + 2e\(\rightleftharpoons\) CO(g) + H2O(l)

–0.106

WO3(s) + 6H+ + 6e\(\rightleftharpoons\) W(s) + 3H2O(l)

–0.090

Hg2I2(s) + 2e\(\rightleftharpoons\) 2Hg(l) + 2I

–0.0405
Fe3+(aq) + 3e- \(\rightleftharpoons\) Fe(s) -0.037
2H+(aq) + 2e- \(\rightleftharpoons\) H2(g) 0.00

P(s,white) + 3H+ + 3e\(\rightleftharpoons\) PH3(g)

0.06
AgBr(s) + e\(\rightleftharpoons\) Ag(s) + Br 0.071

S4O62− + 2e\(\rightleftharpoons\)2S2O32−

0.080

Co(NH3)63+ +e\(\rightleftharpoons\)Co(NH3)62+

0.1

Ru(NH3)63+ + e\(\rightleftharpoons\) Ru(s) + Ru(NH3)62+

0.10

S(s) + 2H+ + 2e\(\rightleftharpoons\) H2S

0.144
Sn4+(aq) + 2e- \(\rightleftharpoons\) Sn2+(aq) 0.154
Cu2+(aq) + e- \(\rightleftharpoons\) Cu+(aq) 0.159

UO22+ + e \(\rightleftharpoons\)UO2+

0.16

Co(OH)3(s) + e\(\rightleftharpoons\) Co(OH)2(s) + OH

0.17
ClO4-(aq) + H2O(l) + 2e- \(\rightleftharpoons\) ClO3-(aq) + 2OH-(aq) 0.17

SO42− + 4H+ + 2e \(\rightleftharpoons\) H2SO32−+ H2O(l)

0.172

BiCl4 + 3e\(\rightleftharpoons\) Bi(s) + 4Cl

0.199

SbO+ + 2H+ + 3e\(\rightleftharpoons\) Sb(s) + H2O(l)

0.212
AgCl(s) + e- \(\rightleftharpoons\) Ag(s) + Cl-(aq) 0.2223
HCHO + 2H+ + 2e\(\rightleftharpoons\) CH3OH 0.2323

HAsO2 + 3H+ + 3e\(\rightleftharpoons\) As(s) + 2H2O(l)

0.240
Ru3+ + e\(\rightleftharpoons\) Ru2+ 0.249

IO3+ 3H2O(l) + 6e\(\rightleftharpoons\) I + 6OH

0.257

Hg2Cl2(s) + 2e\(\rightleftharpoons\) 2Hg(l) + 2Cl

0.2682

UO2+ + 4H+ + e \(\rightleftharpoons\)U4+ + 2H2O(l)

0.27
Bi3+ + 3e\(\rightleftharpoons\) Bi(s) 0.317

UO22+ + 4H+ + 2e \(\rightleftharpoons\) U4+ + 2H2O(l)

0.327

VO2+ + 2H+ +e\(\rightleftharpoons\)V3+ + H2O(l)

0.337
Cu2+(aq) + 2e- \(\rightleftharpoons\) Cu(s) 0.3419
ClO3-(aq) + H2O(l) + 2e- \(\rightleftharpoons\) ClO2-(aq) + 2OH-(aq) 0.35

Fe(CN)63− + e \(\rightleftharpoons\) Fe(CN)64−

0.356

O2(g) + 2H2O(l) + 4e\(\rightleftharpoons\) 4OH

0.401

ClO + H2O(l) + e \(\rightleftharpoons\) ½Cl2(g) + 2OH

0.421 in 1 M NaOH

 Ag2C2O4(s) + 2e\(\rightleftharpoons\) 2Ag(s) + C2O42−

0.47
Cu+(aq) + e- \(\rightleftharpoons\) Cu(s) 0.52
I2(s) + 2e- \(\rightleftharpoons\) 2I-(aq) 0.5355

I3 + 2e\(\rightleftharpoons\) 3I

0.536

Ga3+ + 3e\(\rightleftharpoons\) Ga(s)

-0.56
Cu2+ + Cl + e\(\rightleftharpoons\) CuCl(s) 0.559

S2O62− + 4H+ + 2e\(\rightleftharpoons\) 2H2SO3

0.569

H3AsO4 + 2H+ + 2e\(\rightleftharpoons\) HAsO2 + 2H2O(l)

0.560
ClO2-(aq) + H2O(l) + 2e- \(\rightleftharpoons\) ClO-(aq) + 2OH-(aq) 0.59
MnO4 + 2H2O(l) + 3e\(\rightleftharpoons\) MnO2(s) + 4OH 0.60

Sb2O5(s) + 6H+ + 4e\(\rightleftharpoons\) 2SbO+ + 3H2O(l)

0.605
PtCl62− + 2e\(\rightleftharpoons\) PtCl42- + 2Cl 0.68

RuO2(s) + 4H+ + 4e\(\rightleftharpoons\) Ru(s) + 2H2O(l)

0.68

O2(g) + 2H+ + 2e\(\rightleftharpoons\) H2O2

0.695
PtCl42− + 2e\(\rightleftharpoons\) Pt(s) + 4Cl 0.73

H2SeO3 + 4H+ + 4e\(\rightleftharpoons\) Se(s) + 3H2O(l)

0.74
Tl3+ + 3e\(\rightleftharpoons\) Tl(s) 0.742
Fe3+(aq) + e- \(\rightleftharpoons\) Fe2+(aq) 0.771
Hg22+(aq) + 2e- \(\rightleftharpoons\) 2Hg(l) 0.7960
Ag+(aq) + e- \(\rightleftharpoons\) Ag(s) 0.7996
Hg2+(aq) + 2e- \(\rightleftharpoons\) Hg(l) 0.8535
Cu2+ + I +e\(\rightleftharpoons\) CuI(s) 0.86

Ru(CN)63− +e\(\rightleftharpoons\) Ru(s) + Ru(CN)64−

0.86

ClO + H2O(l) + 2e\(\rightleftharpoons\) Cl + 2OH

0.890 in 1 M NaOH
2Hg2+(aq) + 2e- \(\rightleftharpoons\) Hg22+(aq) 0.911

HgO(s) + 2H+ + 2e\(\rightleftharpoons\) Hg(l) + H2O(l)

0.926

NO3 + 3H+ + 2e\(\rightleftharpoons\) HNO2 + H2O(l)

0.94
MnO2(s) + 4H+ + e- \(\rightleftharpoons\) Mn3+ (aq) + H2O(I) 0.95
NO3-(aq) + 4H+(aq) + 3e- \(\rightleftharpoons\) NO(g) + 2H2O(l) 0.96

HIO + H+ + 2e\(\rightleftharpoons\) I + H2O(l)

0.985

HNO2 + H+ +e\(\rightleftharpoons\) NO(g) + H2O(l)

0.996

VO22+ + 2H+  +e\(\rightleftharpoons\) VO2+ + H2O(l)

1.000

AuCl4 + 3e\(\rightleftharpoons\) Au(s) + 4Cl

1.002
NO2 (g) + H+ (aq) + e- \(\rightleftharpoons\) HNO2 (aq)
 
1.07
Br2(l) + 2e- \(\rightleftharpoons\) 2Br-(aq) 1.087

Fe(phen)63+ +e \(\rightleftharpoons\) Fe(phen)62+

1.147

SeO43− + 4H+ + e\(\rightleftharpoons\) H2SeO3 + H2O(l)

1.151

ClO3 + 2H+ + e\(\rightleftharpoons\) ClO2(g) + H2O

1.175

ClO3 + 3H+ + 2e \(\rightleftharpoons\) HClO2 + H2O

1.181

IO3 + 6H+ + 5e\(\rightleftharpoons\) ½I2(s) + 3H2O(l)

1.195
Pt2+ + 2e\(\rightleftharpoons\) Pt(s) 1.2

ClO4 + 2H+ + 2e \(\rightleftharpoons\) ClO3 + H2O

1.201
O2(g) + 4H+(aq) + 4e- \(\rightleftharpoons\) 2H2O(l) 1.229

MnO2(s) + 4H+ + 2e\(\rightleftharpoons\) Mn2+ + 2H2O(l)

1.23

Tl3+ + 2e \(\rightleftharpoons\) Tl+

0.77 in 1 M HCl

2HNO2 + 4H+ + 4e\(\rightleftharpoons\) N2O(g) + 3H2O(l)

1.297

HOBr + H+ + 2e\(\rightleftharpoons\) Br + H2O(l)

1.341
Cr2O72-(aq) + 14H+(aq) + 6e- \(\rightleftharpoons\) 2Cr3+(aq) + 7H2O(l) 1.36

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

1.36
Cl2(g) + 2e- \(\rightleftharpoons\) 2Cl-(aq) 1.396

Au3+ + 2e\(\rightleftharpoons\) Au+

1.36

Hg2Br2(s) + 2e\(\rightleftharpoons\) 2Hg(l) + 2Br

1.392
Ce4+(aq) + e- \(\rightleftharpoons\) Ce3+(aq) 1.44
PbO2(s) + 4H+ +2e- \(\rightleftharpoons\) Pb2+(aq) + 2H2O(l) 1.46

BrO3 + 6H+ + 6e\(\rightleftharpoons\) Br + 3H2O

1.478

Mn3+ + e\(\rightleftharpoons\) Mn2+

1.5
MnO4-(aq) + 8H+(aq) + 5e- \(\rightleftharpoons\) Mn2+(aq) + 4H2O(l) 1.51

BrO3 + 6H+ + 5e\(\rightleftharpoons\) ½Br2(l) + 3H2O

1.5
Au3+ + 3e\(\rightleftharpoons\) Au(s) 1.52

2NO(g) + 2H+ + 2e\(\rightleftharpoons\) N2O(g) + H2O(l)

1.59

HOBr + H+ + e\(\rightleftharpoons\) ½Br + H2O(l)

1.604

HClO2 + 2H+ + 2e\(\rightleftharpoons\) HOCl + H2O

1.64

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

1.690

MnO4 + 4H+ +3e\(\rightleftharpoons\) MnO2(s) + 2H2O(l)

1.70
Ce4+ + e\(\rightleftharpoons\) Ce3+ 1.72

N2O(g) + 2H+ + 2e\(\rightleftharpoons\) N2(g) + H2O(l)

1.77
H2O2(aq) + 2H+(aq) + 2e- \(\rightleftharpoons\) 2H2O(l) 1.763
Au+ + e\(\rightleftharpoons\) Au(s) 1.83
Co3+(aq) + e- \(\rightleftharpoons\) Co2+(aq) 1.92

S2O82− + 2e\(\rightleftharpoons\)2SO42−

1.96
O3(g) + 2H+(aq) + 2e- \(\rightleftharpoons\) O2(g) + H2O(l) 2.07

BaO(s) + 2H+ + 2e\(\rightleftharpoons\) Ba(s) + H2O(l)

2.365
F2(g) + 2e- \(\rightleftharpoons\) 2F-(aq) 2.87

F2(g) + 2H+ + 2e\(\rightleftharpoons\) 2HF

3.053
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