Antimony
Sb2O5(s)
6H
4e 8 2SbO
3H2O
0.581
Arsenic
H3AsO4
2H
2e 8 H3AsO3
H2O
0.559 0.577 in 1 M HCl, HClO4
Barium
Ba2
2e 8 Ba(s)
2.906
Bismuth
BiO
2H
3e 8 Bi(s)
H2O
0.320
BiCl4
3e 8 Bi(s)
4Cl
0.16
Bromine
Br2(l )
2e 8 2Br
Br2(aq)
1.065 1.05 in 4 M HCl
2e 8 2Br
1.087‡
BrO3
6H
5e 8 12
Br2(l )
3H2O
1.52
BrO3
6H
6e 8 Br
3H2O
1.44
Cadmium
Cd2
2e 8 Cd(s)
0.403
Calcium
Ca2
2e 8 Ca(s)
2.866
Carbon
C6H4O2 (quinone)
2CO2(g)
2H
2H
2e 8 C6H4(OH)2
2e 8 H2C2O4
0.699 0.696 in 1 M HCl, HClO4, H2SO4
0.49
Cerium
Ce4
e 8 Ce3
1.70 in 1 M HClO4;
1 M H2SO4
Chlorine
Standard and
Formal Electrode Potentials
Cl2(g)
2e 8 2Cl
HClO
H
Cl2(g)
H2O
Half-Reaction E0, V* Formal Potential, V†
Aluminum
ClO3
Al3
Cl2(g)
3e 8 Al(s)
1.662
6H
e 8 12
1.63
5e 8 12
3H2O
1.47
1.359
1.61 in 1 M HNO3; 1.44 in
Chromium
H5IO6
Cr3
e 8 Cr2
0.408
Cr3
3e 8 Cr(s)
14H
0.744
6e 8 2Cr3
7H2O
1.33
Fe2
2e 8 Fe(s)
Fe3
e 8 Fe2
2e 8 Co(s)
Co3
e 8 Co2
0.277
0.771 0.700 in 1 M HCl; 0.732 in 1 M HClO4; 0.68 in 1 M H2SO4
1.808
2e 8 Cu(s)
Cu2
e 8 Cu
0.153
Cu
e 8 Cu(s)
0.521
I
CuI(s)
0.337
e 8 CuI(s)
e 8 Cu(s)
I
Pb2
2
0.185
Lithium
F2(g)
Mg2
2e 8 2HF(aq)
3.06
Hydrogen
0.005 in 1 M HCl, HClO4
Iodine
2e 8 2I
0.5355
2e 8 2I
2e 8 Pb(s)
2H2O
1.455
SO4
e 8 Li(s)
3.045
2e 8 Mg(s)
2.363
0.615‡
Mn2
2e 8 Mn(s)
Mn3
e 8 Mn2 1.51 in 7.5 M H2SO4
MnO2(s)
4H
0.536
2e 8 Mn2
5e 8 Mn2
2H2O
1.23
4H2O
1.51
MnO4
4H
e 8 12
1.180
MnO4
ICl2
3e 8 MnO2(s)
2H2O
1.695
MnO4
2Cl
1.056
IO3
e 8 MnO4
2
5e 8 12
3H2O
Hg2
2
5e 8 12
3H2O
IO3
2
Hg2
6H
3H2O
1.24
2e 8 2Hg(l)
2Hg2
1.178‡
2Cl
0.564
Mercury
1.196
IO3
I2(aq)
2e 8 Pb2
0.29 in 1 M H2SO4
0.350
8H
2e 8 3I
6H
0.14 in 1 M HClO4;
Magnesium
I3
6H
0.126
Manganese
2e 8 H2(g) 0.000
I2(aq)
4H
PbSO4(s)
0.86
Li
2H
2e 8 Ps(s)
PbO2(s)
Half-Reaction E0, V* Formal Potential, V†
Fluorine
2H
0.36 0.71 in 1 M HCl; 0.72 in 1 M HClO4, H2SO4
4
Lead
Cu2
Cu2
e 8 Fe(CN)6
3
Copper
I2(s)
0.440
Fe(CN)6
Co2
I2(s)
1.601
Iron
Cobalt
I2(s)
2e 8 IO3
3H2O
Cr2O7
2
H
4e 8 ICl2
0.788 0.274 in 1 M HCl; 0.776 in 1 M HClO4; 0.674 in 1 M H2SO4
2e 8 Hg2
0.920 0.907 in 1 M HClO4
2e 8 Hg(l )
Hg2Cl2(s)
0.854
2e 8 2Hg(l )
2Cl
0.268 0.244 in sat’d KCl; 0.282 in 1 M KCl; 0.334 in 0.1 M KCl
Hg2SO4(s)
2e 8 2Hg(l )
SO4
Ag(CN)2
0.615
2
e 8 Ag(s)
Nickel
Ag2CrO4(s)
Ni2
2e 8 Ni(s)
0.250
2
Nitrogen
N2( g )
4e 8 N2H5
3
H
e 8 NO(g)
2e 8 2Ag(s)
CrO4
e 8 Ag(s)
I
0.151
Ag(S2O3)2
0.23
HNO2
0.31
0.446
AgI(s)
5H
2CN
H2O
1.00
2
NO3
e 8 Ag(s)
2S2O3
0.017
Sodium
3H
2e 8 HNO2
H2O
0.94 0.92 in 1 M HNO3
Oxygen
H 2 O2
Na
e 8 Na(s)
Sulfur
2H
2e 8 2H2O
1.776
S(s)
HO2
2H
H2SO3
H 2O
2e 8 3OH
0.88
4H
4e 8 2H2O
1.229
O2(g)
2H
2e 8 H2O2
0.682
O3(g)
2H
2e 8 O2( g )
2
2.07
2
2
0.987
0.141
3H2O
0.450
4H
2e 8 H2SO3
H2O
0.172
2e 8 2S2O3
0.08
S2O8
Half-Reaction E0, V* Formal Potential, V†
Platinum
2
2
PtCl4
2
4e 8 S(s)
S4O6
H 2O
Palladium
2e 8 Pd(s)
2e 8 H2S(g)
4H
SO4
O2(g)
Pd2
2.714
2e 8 2SO4
2.01
Thallium
2e 8 Pt(s)
4Cl
0.755
PtCl6
Tl
e 8 Tl(s)
Tl3
2e 8 Tl
0.336
0.551 in 1 M HCl;
1.25 0.77 in 1 M HCl
2
2e 8 PtCl4
Tin
2
2Cl
Sn2
2e 8 Sn(s)
0.136
Sn4
2e 8 Sn2
0.154 0.14 in 1 M HCl
0.68
Potassium
K
e 8 K(s)
2.925
Ti3
4H
4e 8 Se(s)
3H2
0.740
SeO4
2
0.16 in 1 M HClO4
Titanium
Selenium
H2SeO3
e 8 Ti2
TiO2
2H
0.369
e 8 Ti3
H 2O
0.099 0.04 in 1 M H2SO4
Uranium
4H
2e 8 H2SeO3
H2
1.15
Silver
Ag
UO2
2
e 8 Ag(s)
0.33 in 1 M HClO4, H2SO4
0.799 0.228 in 1 M HCl; 0.792 in 1 M HClO4; 0.77 in 1 M H2SO4
AgBr(s)
e 8 Ag(s)
Br
0.073
AgCl(s)
e 8 Ag(s)
Cl
0.222 0.228 in 1 M KCl
4H
2e 8 U4
Vanadium
V3
e 8 V2
0.255
2H2O
0.334
VO2
2H
e 8 V3
H2O
0.337
V(OH)4
2H
e 8 VO2
3H2O
1.00 1.02 in 1 M HCl, HClO4
Zinc
Zn2
2e 8 Zn(s)
0.763
*G. Milazzo, S. Caroli, and V. K. Sharma, Tables of Standard Electrode Potentials, London: Wiley, 1978.
†E.
H. Swift and E. A. Butler, Quantitative Measurements and Chemical Equilibria, New York: Freeman,
1972.
‡These
potentials are hypothetical because they correspond to solutions that are 1.00 M in Br2 or I2.
The solubilities of these two compounds at
25°C are 0.18 M and 0.0020 M, respectively. In saturated solutions containing an excess of Br2(l ) or
I2(s), the standard potentials for the
half-reaction Br2(l )
2e 8 2Br or I2(s)
2e 8 2I should be used. In contrast, at Br2 and I2
concentrations less than saturation, these
hypothetical electrode potentials should be used.