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Chapter 29 Appendix E: Standard Reduction Potentials at 25°C

Half-Reaction	E° (V)
Ac³⁺ + 3e⁻→ Ac	−2.20
Ag⁺ + e⁻→ Ag	0.7996
AgBr + e⁻→ Ag + Br⁻	0.07133
AgCl + e⁻→ Ag + Cl⁻	0.22233
Ag₂CrO₄ + 2e⁻→ 2Ag + CrO₄²⁻	0.4470
AgI + e⁻→ Ag + I⁻	−0.15224
Ag₂S + 2e⁻→ 2Ag + S²⁻	−0.691
Ag₂S + 2H⁺ + 2e⁻→ 2Ag + H₂S	−0.0366
AgSCN + e⁻→ Ag + SCN⁻	0.08951
Al³⁺ + 3e⁻→ Al	−1.662
Al(OH)₄⁻ + 3e⁻→ Al + 4OH⁻	−2.328
Am³⁺ + 3e⁻→ Am	−2.048
As + 3H⁺ + 3e⁻→ AsH₃	−0.608
H₃AsO₄ + 2H⁺ + 2e⁻→ HAsO₂ + 2H₂O	0.560
Au⁺ + e⁻→ Au	1.692
Au³⁺ + 3e⁻→ Au	1.498
H₃BO₃ + 3H⁺ + 3e⁻→ B + 3H₂O	−0.8698
Ba²⁺ + 2e⁻→ Ba	−2.912
Be²⁺ + 2e⁻→ Be	−1.847
Bi³⁺ + 3e⁻→ Bi	0.308
BiO⁺ + 2H⁺ + 3e⁻→ Bi + H₂O	0.320
Br₂(aq) + 2e⁻→ 2Br⁻	1.0873
Br₂(l) + 2e⁻→ 2Br⁻	1.066
BrO₃⁻ + 6H⁺ + 5e⁻→ $\frac{1}{2}$ Br₂ + 3H₂O	1.482
BrO₃⁻ + 6H⁺ + 6e⁻→ Br⁻ + 3H₂O	1.423
CO₂ + 2H⁺ + 2e⁻→ HCO₂H	−0.199
Ca²⁺ + 2e⁻→ Ca	−2.868
Ca(OH)₂ + 2e⁻→ Ca + 2OH⁻	−3.02
Cd²⁺ + 2e⁻→ Cd	−0.4030
CdSO₄ + 2e⁻→ Cd + SO₄²⁻	−0.246
Cd(OH)₄²⁻ + 2e⁻→ Cd + 4OH⁻	−0.658
Ce³⁺ + 3e⁻→ Ce	−2.336
Ce⁴⁻ + e⁻→ Ce³⁺	1.72
Cl₂(g) + 2e⁻→ 2Cl⁻	1.35827
HClO + H⁺ + e⁻→ $\frac{1}{2}$ Cl₂ + H₂O	1.611
HClO + H⁺ + 2e⁻→ Cl⁻ + H₂O	1.482
ClO⁻ + H₂O + 2e⁻→ Cl⁻ + 2OH⁻	0.81
ClO₃⁻ + 6H⁺ + 5e⁻→ $\frac{1}{2}$ Cl₂ + 3H₂O	1.47
ClO₃⁻ + 6H⁺ + 6e⁻→ Cl⁻ + 3H₂O	1.451
ClO₄⁻ + 8H⁺ + 7e⁻→ $\frac{1}{2}$ Cl₂ + 4H₂O	1.39
ClO₄⁻ + 8H⁺ + 8e⁻→ Cl⁻ + 4H₂O	1.389
Co²⁺ + 2e⁻→ Co	−0.28
Co³⁺ + e⁻→ Co²⁺	1.92
Cr²⁺ + 2e⁻→ Cr	−0.913
Cr³⁺ + e⁻→ Cr²⁺	−0.407
Cr³⁺ + 3e⁻→ Cr	−0.744
Cr₂O₇²⁻ + 14H⁺ + 6e⁻→ 2Cr³⁺ + 7H₂O	1.232
CrO₄²⁻ + 4H₂O + 3e⁻→ Cr(OH)₃ + 5OH⁻	−0.13
Cs⁺ + e⁻→ Cs	−3.026
Cu⁺ + e⁻→ Cu	0.521
Cu²⁺ + e⁻→ Cu⁺	0.153
Cu²⁺ + 2e⁻→ Cu	0.3419
CuI₂⁻ + e⁻→ Cu + 2I⁻	0.00
Cu₂O + H₂O + 2e⁻→ 2Cu + 2OH⁻	−0.360
Dy³⁺ + 3e⁻→ Dy	−2.295
Er³⁺ + 3e⁻→ Er	−2.331
Es³⁺ + 3e⁻→ Es	−1.91
Eu²⁺ + 2e⁻→ Eu	−2.812
Eu³⁺ + 3e⁻→ Eu	−1.991
F₂ + 2e⁻→ 2F⁻	2.866
Fe²⁺ + 2e⁻→ Fe	−0.447
Fe³⁺ + 3e⁻→ Fe	−0.037
Fe³⁺ + e⁻→ Fe²⁺	0.771
[Fe(CN)₆]³⁻ + e⁻→ [Fe(CN)₆]⁴⁻	0.358
Fe(OH)₃ + e⁻→ Fe(OH)₂ + OH⁻	−0.56
Fm³⁺ + 3e⁻→ Fm	−1.89
Fm²⁺ + 2e⁻→ Fm	−2.30
Ga³⁺ + 3e⁻→ Ga	−0.549
Gd³⁺ + 3e⁻→ Gd	−2.279
Ge²⁺ + 2e⁻→ Ge	0.24
Ge⁴⁺ + 4e⁻→ Ge	0.124
2H⁺ + 2e⁻→ H₂	0.00000
H₂ + 2e⁻→ 2H⁻	−2.23
2H₂O + 2e⁻→ H₂ + 2OH⁻	−0.8277
H₂O₂ + 2H⁺ + 2e⁻→ 2H₂O	1.776
Hf⁴⁺ + 4e⁻→ Hf	−1.55
Hg²⁺ + 2e⁻→ Hg	0.851
2Hg²⁺ + 2e⁻→ Hg₂²⁺	0.920
Hg₂Cl₂ + 2e⁻→ 2Hg + 2Cl⁻	0.26808
Ho²⁺ + 2e⁻→ Ho	−2.1
Ho³⁺ + 3e⁻→ Ho	−2.33
I₂ + 2e⁻→ 2I⁻	0.5355
I₃⁻ + 2e⁻→ 3I⁻	0.536
2IO₃⁻ + 12H⁺ + 10e⁻→ I₂ + 6H₂O	1.195
IO₃⁻ + 6H⁺ + 6e⁻→ I⁻ + 3H₂O	1.085
In⁺ + e⁻→ In	−0.14
In³⁺ + 2e⁻→ In⁺	−0.443
In³⁺ + 3e⁻→ In	−0.3382
Ir³⁺ + 3e⁻→ Ir	1.156
K⁺ + e⁻→ K	−2.931
La³⁺ + 3e⁻→ La	−2.379
Li⁺ + e⁻→ Li	−3.0401
Lr³⁺ + 3e⁻→ Lr	−1.96
Lu³⁺ + 3e⁻→ Lu	−2.28
Md³⁺ + 3e⁻→ Md	−1.65
Md²⁺ + 2e⁻→ Md	−2.40
Mg²⁺ + 2e⁻→ Mg	−2.372
Mn²⁺ + 2e⁻→ Mn	−1.185
MnO₂ + 4H⁺ + 2e⁻→ Mn²⁺ + 2H₂O	1.224
MnO₄⁻ + 8H⁺ + 5e⁻→ Mn²⁺ + 4H₂O	1.507
MnO₄⁻ + 2H₂O + 3e⁻→ MnO₂ + 4OH⁻	0.595
Mo³⁺ + 3e⁻→ Mo	−0.200
N₂ + 2H₂O + 6H⁺ + 6e⁻→ 2NH₄OH	0.092
HNO₂ + H⁺ + e⁻→ NO + H₂O	0.983
NO₃⁻ + 4H⁺ + 3e⁻→ NO + 2H₂O	0.957
Na⁺ + e⁻→ Na	−2.71
Nb³⁺ + 3e⁻→ Nb	−1.099
Nd³⁺ + 3e⁻→ Nd	−2.323
Ni²⁺ + 2e⁻→ Ni	−0.257
No³⁺ + 3e⁻→ No	−1.20
No²⁺ + 2e⁻→ No	−2.50
Np³⁺ + 3e⁻→ Np	−1.856
O₂ + 2H⁺ + 2e⁻→ H₂O₂	0.695
O₂ + 4H⁺ + 4e⁻→ 2H₂O	1.229
O₂ + 2H₂O + 2e⁻→ H₂O₂ + 2OH⁻	−0.146
O₃ + 2H⁺ + 2e⁻→ O₂ + H₂O	2.076
OsO₄ + 8H⁺ + 8e⁻→ Os + 4H₂O	0.838
P + 3H₂O + 3e⁻→ PH₃(g) + 3OH⁻	−0.87
PO₄³⁻ + 2H₂O + 2e⁻→ HPO₃²⁻ + 3OH⁻	−1.05
Pa³⁺ + 3e⁻→ Pa	−1.34
Pa⁴⁺ + 4e⁻→ Pa	−1.49
Pb²⁺ + 2e⁻→ Pb	−0.1262
PbO + H₂O + 2e⁻→ Pb + 2OH⁻	−0.580
PbO₂ + SO₄²⁻ + 4H⁺ + 2e⁻→ PbSO₄ + 2H₂O	1.6913
PbSO₄ + 2e⁻→ Pb + SO₄²⁻	−0.3588
Pd²⁺ + 2e⁻→ Pd	0.951
Pm³⁺ + 3e⁻→ Pm	−2.30
Po⁴⁺ + 4e⁻→ Po	0.76
Pr³⁺ + 3e⁻→ Pr	−2.353
Pt²⁺ + 2e⁻→ Pt	1.18
[PtCl₄]²⁻ + 2e⁻→ Pt + 4Cl⁻	0.755
Pu³⁺ + 3e⁻→ Pu	−2.031
Ra²⁺ + 2e⁻→ Ra	−2.8
Rb⁺ + e⁻→ Rb	−2.98
Re³⁺ + 3e⁻→ Re	0.300
Rh³⁺ + 3e⁻→ Rh	0.758
Ru³⁺ + e⁻→ Ru²⁺	0.2487
S + 2e⁻→ S²⁻	−0.47627
S + 2H⁺ + 2e⁻→ H₂S(aq)	0.142
2S + 2e⁻→ S₂²⁻	−0.42836
H₂SO₃ + 4H⁺ + 4e⁻→ S + 3H₂O	0.449
SO₄²⁻ + H₂O + 2e⁻→ SO₃²⁻ + 2OH⁻	−0.93
Sb + 3H⁺ + 3e⁻→ SbH₃	−0.510
Sc³⁺ + 3e⁻→ Sc	−2.077
Se + 2e⁻→ Se²⁻	−0.924
Se + 2H⁺ + 2e⁻→ H₂Se	−0.082
SiF₆²⁻ + 4e⁻→ Si + 6F⁻	−1.24
Sm³⁺ + 3e⁻→ Sm	−2.304
Sn²⁺ + 2e⁻→ Sn	−0.1375
Sn⁴⁺ + 2e⁻→ Sn²⁺	0.151
Sr²⁺ + 2e⁻→ Sr	−2.899
Ta³⁺ + 3e⁻→ Ta	−0.6
TcO₄⁻ + 4H⁺ + 3e⁻→ TcO₂ + 2H₂O	0.782
TcO₄⁻ + 8H⁺ + 7e⁻→ Tc + 4H₂O	0.472
Tb³⁺ + 3e⁻→ Tb	−2.28
Te + 2e⁻→ Te²⁻	−1.143
Te⁴⁺ + 4e⁻→ Te	0.568
Th⁴⁺ + 4e⁻→ Th	−1.899
Ti²⁺ + 2e⁻→ Ti	−1.630
Tl⁺ + e⁻→ Tl	−0.336
Tl³⁺ + 2e⁻→ Tl⁺	1.252
Tl³⁺ + 3e⁻→ Tl	0.741
Tm³⁺ + 3e⁻→ Tm	−2.319
U³⁺ + 3e⁻→ U	−1.798
VO₂⁺ + 2H⁺ + e⁻→ VO²⁺ + H₂O	0.991
V₂O₅ + 6H⁺ + 2e⁻→ 2VO²⁺ + 3H₂O	0.957
W₂O₅ + 2H⁺ + 2e⁻→ 2WO₂ + H₂O	−0.031
XeO₃ + 6H⁺ + 6e⁻→ Xe + 3H₂O	2.10
Y³⁺ + 3e⁻→Y	−2.372
Yb³⁺ + 3e⁻→Yb	−2.19
Zn²⁺ + 2e⁻→ Zn	−0.7618
Zn(OH)₄²⁻ + 2e⁻→ Zn + 4OH⁻	−1.199
Zn(OH)₂ + 2e⁻→ Zn + 2OH⁻	−1.249
ZrO₂ + 4H⁺ + 4e⁻→ Zr + 2H₂O	−1.553
Zr⁴⁺ + 4e⁻→ Zr	−1.45

Source of data: CRC Handbook of Chemistry and Physics, 84th Edition (2004).