The values of standard electrode potentials are given in the table below in volts relative to the standard hydrogen electrode and are for the following conditions:
- A temperature of 298.15 K (25 °C);
- An effective concentration of 1 mol/L for each aqueous species or a species in a mercury amalgam;
- A partial pressure of 101.325 kPa (absolute) (1 atm, 1.01325 bar) for each gaseous reagent. This pressure is used because most literature data are still given for this value rather than for the current standard of 100 kPa.
- An activity of unity for each pure solid, pure liquid, or for water (solvent).
Legend: (s) – solid; (l) – liquid; (g) – gas; (aq) – aqueous (default for all charged species); (Hg) – amalgam.
Half-reaction | E° (V) | Ref. |
---|---|---|
Sr+ + e− Sr | -3.80 −3.80 | |
Ca+ + e− Ca | -3.80 −3.80 | |
Pr3+ + e− Pr2+ | -3.1 −3.1 | |
N3⁄2 N2(g) + H+ + e− HN3(aq) | -3.09 −3.09 | |
Li+ + e− Li(s) | -3.0401 −3.0401 | |
N2(g) + 4 H2O + 2 e− 2 NH2OH(aq) + 2 OH− | -3.04 −3.04 | |
Cs+ + e− Cs(s) | -3.026 −3.026 | |
Ca(OH)2 + 2 e− Ca + 2 OH- | -3.02 −3.02 | |
Er3+ + e− Er2+ | -3.0 −3.0 | |
Ba(OH)2 + 2 e− Ba + 2 OH- | -2.99 −2.99 | |
Rb+ + e− Rb(s) | -2.98 −2.98 | |
K+ + e− K(s) | -2.931 −2.931 | |
Ba2+ + 2 e− Ba(s) | -2.912 −2.912 | |
La(OH)3(s) + 3 e− La(s) + 3 OH− | -2.90 −2.90 | |
Fr+ + e− Fr | -2.9 −2.9 | |
Sr2+ + 2 e− Sr(s) | -2.899 −2.899 | |
Sr(OH)2 + 2 e− Sr + 2 OH- | -2.88 −2.88 | |
Ca2+ + 2 e− Ca(s) | -2.868 −2.868 | |
Eu2+ + 2 e− Eu(s) | -2.812 −2.812 | |
Ra2+ + 2 e− Ra(s) | -2.8 −2.8 | |
Ho3+ + e− Ho2+ | -2.8 −2.8 | |
Bk3+ + e− Bk2+ | -2.8 −2.8 | |
Yb2+ + 2 e− Yb | -2.76 −2.76 | |
Na+ + e− Na(s) | -2.71 −2.71 | |
Mg+ + e− Mg | -2.70 −2.70 | |
Nd3+ + e− Nd2+ | -2.7 −2.7 | |
Mg(OH)2 + 2 e− Mg + 2 OH- | -2.690 −2.690 | |
Sm2+ + 2 e− Sm | -2.68 −2.68 | |
Be2O32- + 3 H2O + 4 e− 2 Be + 6 OH- | -2.63 −2.63 | |
Pm3+ + e− Pm2+ | -2.6 −2.6 | |
Dy3+ + e− Dy2+ | -2.6 −2.6 | |
No2+ + 2 e− No | -2.50 −2.50 | |
HfO(OH)2 + H2O + 4 e− Hf + 4 OH- | -2.50 −2.50 | |
Th(OH)4 + 4 e− Th + 4 OH- | -2.48 −2.48 | |
Md2+ + 2 e− Md | -2.40 −2.40 | |
Tm2+ + 2 e− Tm | -2.4 −2.4 | |
La3+ + 3 e− La(s) | -2.379 −2.379 | |
Y3+ + 3 e− Y(s) | -2.372 −2.372 | |
Mg2+ + 2 e− Mg(s) | -2.372 −2.372 | |
ZrO(OH)2(s) + H2O + 4 e− Zr(s) + 4 OH− | -2.36 −2.36 | |
Pr3+ + 3 e− Pr | -2.353 −2.353 | |
Ce3+ + 3 e− Ce | -2.336 −2.336 | |
Er3+ + 3 e− Er | -2.331 −2.331 | |
Ho3+ + 3 e− Ho | -2.33 −2.33 | |
H2AlO3- + H2O + 3 e− Al + 4 OH- | -2.33 −2.33 | |
Nd3+ + 3 e− Nd | -2.323 −2.323 | |
Tm3+ + 3 e− Tm | -2.319 −2.319 | |
Al(OH)3(s) + 3 e− Al(s) + 3 OH− | -2.31 −2.31 | |
Sm3+ + 3 e− Sm | -2.304 −2.304 | |
Pr3+ + 3 e− Pr | -2.30 −2.30 | |
Fm2+ + 2 e− Fm | -2.30 −2.30 | |
Am3+ + e− Am2+ | -2.3 −2.3 | |
Dy3+ + 3 e− Dy | -2.295 −2.295 | |
Lu3+ + 3 e− Lu | -2.28 −2.28 | |
Tb3+ + 3 e− Tb | -2.28 −2.28 | |
Gd3+ + 3 e− Gd | -2.279 −2.279 | |
H2 + 2 e− 2 H- | -2.23 −2.23 | |
Es2+ + 2 e− Es | -2.23 −2.23 | |
Pm2+ + 2 e− Pm | -2.2 −2.2 | |
Tm3+ + e− Tm2+ | -2.2 −2.2 | |
Dy2+ + 2 e− Dy | -2.2 −2.2 | |
Ac3+ + 3 e− Ac | -2.20 −2.20 | |
Yb3+ + 3 e− Yb | -2.19 −2.19 | |
Cf2+ + 2 e− Cf | -2.12 −2.12 | |
Nd2+ + 2 e− Nd | -2.1 −2.1 | |
Ho2+ + 2 e− Ho | -2.1 −2.1 | |
Sc3+ + 3 e− Sc(s) | -2.077 −2.077 | |
AlF63- + 3 e− Al + 6 F- | -2.069 −2.069 | |
Am3+ + 3 e− Am | -2.048 −2.048 | |
Cm3+ + 3 e− Cm | -2.04 −2.04 | |
Pu3+ + 3 e− Pu | -2.031 −2.031 | |
Pr2+ + 2 e− Pr | -2.0 −2.0 | |
Er2+ + 2 e− Er | -2.0 −2.0 | |
Eu3+ + 3 e− Eu | -1.991 −1.991 | |
Lr3+ + 3 e− Lr | -1.96 −1.96 | |
Cf3+ + 3 e− Cf | -1.94 −1.94 | |
Es3+ + 3 e− Es | -1.91 −1.91 | |
Pa4+ + e− Pa3+ | -1.9 −1.9 | |
Am2+ + 2 e− Am | -1.9 −1.9 | |
Th4+ + 4 e− Th | -1.899 −1.899 | |
Fm3+ + 3 e− Fm | -1.89 −1.89 | |
Np3+ + 3 e− Np | -1.856 −1.856 | |
Be2+ + 2 e− Be | -1.847 −1.847 | |
H2PO2- + e− P + 2 OH- | -1.82 −1.82 | |
U3+ + 3 e− U | -1.798 −1.798 | |
Sr2+ + 2 e− Sr/Hg | -1.793 −1.793 | |
H2BO3- + H2O + 3 e− B + 4 OH- | -1.79 −1.79 | |
ThO2 + 4H+ + 4 e− Th + 2 H2O | -1.789 −1.789 | |
HfO2+ + 2 H+ + 4 e− Hf + H2O | -1.724 −1.724 | |
HPO32- + 2 H2O + 3 e− P + 5 OH- | -1.71 −1.71 | |
SiO32- + H2O + 4 e− Si + 6 OH- | -1.697 −1.697 | |
Al3+ + 3 e− Al(s) | -1.662 −1.662 | |
Ti2+ + 2 e− Ti(s) | -1.63 −1.63 | |
ZrO2(s) + 4 H+ + 4 e− Zr(s) + 2 H2O | -1.553 −1.553 | |
Zr4+ + 4 e− Zr(s) | -1.45 −1.45 | |
Ti3+ + 3 e− Ti(s) | -1.37 −1.37 | |
TiO(s) + 2 H+ + 2 e− Ti(s) + H2O | -1.31 −1.31 | |
Ti2O3(s) + 2 H+ + 2 e− 2 TiO(s) + H2O | -1.23 −1.23 | |
Zn(OH)42− + 2 e− Zn(s) + 4 OH− | -1.199 −1.199 | |
Mn2+ + 2 e− Mn(s) | -1.185 −1.185 | |
Fe(CN)64− + 6 H+ + 2 e− Fe(s) + 6HCN(aq) | -1.16 −1.16 | |
Te(s) + 2 e− Te2− | -1.143 −1.143 | |
V2+ + 2 e− V(s) | -1.13 −1.13 | |
Nb3+ + 3 e− Nb(s) | -1.099 −1.099 | |
Sn(s) + 4 H+ + 4 e− SnH4(g) | -1.07 −1.07 | |
SiO2(s) + 4 H+ + 4 e− Si(s) + 2 H2O | -0.91 −0.91 | |
B(OH)3(aq) + 3 H+ + 3 e− B(s) + 3 H2O | -0.89 −0.89 | |
Fe(OH)2(s) + 2 e− Fe(s) + 2 OH− | -0.89 −0.89 | |
Fe2O3(s) + 3 H2O + 2 e− 2Fe(OH)2(s) + 2 OH− | -0.86 −0.86 | |
TiO2+ + 2 H+ + 4 e− Ti(s) + H2O | -0.86 −0.86 | |
H2 H2O + 2 e− H2(g) + 2 OH− | -0.8277 −0.8277 | |
Bi(s) + 3 H+ + 3 e− BiH3 | -0.8 −0.8 | |
Zn2+ + 2 e− Zn(Hg) | -0.7628 −0.7628 | |
Zn2+ + 2 e− Zn(s) | -0.7618 −0.7618 | |
Ta2O5(s) + 10 H+ + 10 e− 2 Ta(s) + 5 H2O | -0.75 −0.75 | |
Cr3+ + 3 e− Cr(s) | -0.74 −0.74 | |
Au− + e− Au(s) + 2 CN− | -0.60 −0.60 | |
Ta3+ + 3 e− Ta(s) | -0.6 −0.6 | |
PbO(s) + H2O + 2 e− Pb(s) + 2 OH− | -0.58 −0.58 | |
Ti2 TiO2(s) + 2 H+ + 2 e− Ti2O3(s) + H2O | -0.56 −0.56 | |
Ga3+ + 3 e− Ga(s) | -0.53 −0.53 | |
U4+ + e− U3+ | -0.52 −0.52 | |
P H3PO2(aq) + H+ + e− P(white) + 2 H2O | -0.508 −0.508 | |
P H3PO3(aq) + 2 H+ + 2 e− H3PO2(aq) + H2O | -0.499 −0.499 | |
P H3PO3(aq) + 3 H+ + 3 e− P(red) + 3 H2O | -0.454 −0.454 | |
Fe2+ + 2 e− Fe(s) | -0.44 −0.44 | |
C2 CO2(g) + 2 H+ + 2 e− HOOCCOOH(aq) | -0.43 −0.43 | |
Cr3+ + e− Cr2+ | -0.42 −0.42 | |
Cd2+ + 2 e− Cd(s) | -0.40 −0.40 | |
GeO2(s) + 2 H+ + 2 e− GeO(s) + H2O | -0.37 −0.37 | |
Cu2O(s) + H2O + 2 e− 2 Cu(s) + 2 OH− | -0.360 −0.360 | |
PbSO4(s) + 2 e− Pb(s) + SO42− | -0.3588 −0.3588 | |
PbSO4(s) + 2 e− Pb(Hg) + SO42− | -0.3505 −0.3505 | |
Eu3+ + e− Eu2+ | -0.35 −0.35 | |
In3+ + 3 e− In(s) | -0.34 −0.34 | |
Tl+ + e− Tl(s) | -0.34 −0.34 | |
Ge(s) + 4 H+ + 4 e− GeH4(g) | -0.29 −0.29 | |
Co2+ + 2 e− Co(s) | -0.28 −0.28 | |
P H3PO4(aq) + 2 H+ + 2 e− H3PO3(aq) + H2O | -0.276 −0.276 | |
V3+ + e− V2+ | -0.26 −0.26 | |
Ni2+ + 2 e− Ni(s) | -0.25 −0.25 | |
As(s) + 3 H+ + 3 e− AsH3(g) | -0.23 −0.23 | |
AgI(s) + e− Ag(s) + I− | -0.15224 −0.15224 | |
MoO2(s) + 4 H+ + 4 e− Mo(s) + 2 H2O | -0.15 −0.15 | |
Si(s) + 4 H+ + 4 e− SiH4(g) | -0.14 −0.14 | |
Sn2+ + 2 e− Sn(s) | -0.13 −0.13 | |
O2(g) + H+ + e− HO2•(aq) | -0.13 −0.13 | |
Pb2+ + 2 e− Pb(s) | -0.13 −0.13 | |
WO2(s) + 4 H+ + 4 e− W(s) + 2 H2O | -0.12 −0.12 | |
P(red) + 3 H+ + 3 e− PH3(g) | -0.111 −0.111 | |
C CO2(g) + 2 H+ + 2 e− HCOOH(aq) | -0.11 −0.11 | |
Se(s) + 2 H+ + 2 e− H2Se(g) | -0.11 −0.11 | |
C CO2(g) + 2 H+ + 2 e− CO(g) + H2O | -0.11 −0.11 | |
SnO(s) + 2 H+ + 2 e− Sn(s) + H2O | -0.10 −0.10 | |
SnO2(s) + 2 H+ + 2 e− SnO(s) + H2O | -0.09 −0.09 | |
WO3(aq) + 6 H+ + 6 e− W(s) + 3 H2O | -0.09 −0.09 | |
P(white) + 3 H+ + 3 e− PH3(g) | -0.063 −0.063 | |
Fe3+ + 3 e− Fe(s) | -0.04 −0.04 | |
C HCOOH(aq) + 2 H+ + 2 e− HCHO(aq) + H2O | -0.03 −0.03 | |
H 2 H+ + 2 e− H2(g) | 0.0000 | ≡ 0 |
AgBr(s) + e− Ag(s) + Br− | +0.07133 | |
S4O62− + 2 e− 2 S2O32− | +0.08 | |
Fe3O4(s) + 8 H+ + 8 e− 3 Fe(s) + 4 H2O | +0.085 | |
N2(g) + 2 H2O + 6 H+ + 6 e− 2 NH4OH(aq) | +0.092 | |
HgO(s) + H2O + 2 e− Hg(l) + 2 OH− | +0.0977 | |
Cu(NH3)42+ + e− Cu(NH3)2+ + 2 NH3 | +0.10 | |
Ru(NH3)63+ + e− Ru(NH3)62+ | +0.10 | |
N2H4(aq) + 4 H2O + 2 e− 2 NH4+ + 4 OH− | +0.11 | |
Mo H2MoO4(aq) + 6 H+ + 6 e− Mo(s) + 4 H2O | +0.11 | |
Ge4+ + 4 e− Ge(s) | +0.12 | |
C(s) + 4 H+ + 4 e− CH4(g) | +0.13 | |
C HCHO(aq) + 2 H+ + 2 e− CH3OH(aq) | +0.13 | |
S(s) + 2 H+ + 2 e− H2S(g) | +0.14 | |
Sn4+ + 2 e− Sn2+ | +0.15 | |
Cu2+ + e− Cu+ | +0.159 | |
S HSO4− + 3 H+ + 2 e− SO2(aq) + 2 H2O | +0.16 | |
UO22+ + e− UO2+ | +0.163 | |
S SO42− + 4 H+ + 2 e− SO2(aq) + 2 H2O | +0.17 | |
TiO2+ + 2 H+ + e− Ti3+ + H2O | +0.19 | |
SbO+ + 2 H+ + 3 e− Sb(s) + H2O | +0.20 | |
AgCl(s) + e− Ag(s) + Cl− | +0.22233 | |
As H3AsO3(aq) + 3 H+ + 3 e− As(s) + 3 H2O | +0.24 | |
GeO(s) + 2 H+ + 2 e− Ge(s) + H2O | +0.26 | |
UO2+ + 4 H+ + e− U4+ + 2 H2O | +0.273 | |
Re3+ + 3 e− Re(s) | +0.300 | |
Bi3+ + 3 e− Bi(s) | +0.308 | |
VO2+ + 2 H+ + e− V3+ + H2O | +0.34 | |
Cu2+ + 2 e− Cu(s) | +0.340 | |
Fe 3− + e− 4− | +0.36 | |
O2(g) + 2 H2O + 4 e− 4 OH−(aq) | +0.40 | |
Mo H2MoO4 + 6 H+ + 3 e− Mo3+ + 2 H2O | +0.43 | |
C CH3OH(aq) + 2 H+ + 2 e− CH4(g) + H2O | +0.50 | |
S SO2(aq) + 4 H+ + 4 e− S(s) + 2 H2O | +0.50 | |
Cu+ + e− Cu(s) | +0.520 | |
C CO(g) + 2 H+ + 2 e− C(s) + H2O | +0.52 | |
I3− + 2 e− 3 I− | +0.53 | |
I2(s) + 2 e− 2 I− | +0.54 | |
Au − + 3 e− Au(s) + 4 I− | +0.56 | |
As H3AsO4(aq) + 2 H+ + 2 e− H3AsO3(aq) + H2O | +0.56 | |
Au − + e− Au(s) + 2 I− | +0.58 | |
MnO4− + 2 H2O + 3 e− MnO2(s) + 4 OH− | +0.59 | |
S2O32 − + 6 H+ + 4 e− 2 S(s) + 3 H2O | +0.60 | |
Fc+ + e− Fc(s) | +0.641 | |
Mo H2MoO4(aq) + 2 H+ + 2 e− MoO2(s) + 2 H2O | +0.65 | |
C + 2 H+ + 2 e− | +0.6992 | |
O2(g) + 2 H+ + 2 e− H2O2(aq) | +0.70 | |
Tl3+ + 3 e− Tl(s) | +0.72 | |
PtCl62− + 2 e− PtCl42− + 2 Cl− | +0.726 | |
Se H2SeO3(aq) + 4 H+ + 4 e− Se(s) + 3 H2O | +0.74 | |
PtCl42− + 2 e− Pt(s) + 4 Cl− | +0.758 | |
Fe3+ + e− Fe2+ | +0.77 | |
Ag+ + e− Ag(s) | +0.7996 | |
Hg22+ + 2 e− 2 Hg(l) | +0.80 | |
N NO3−(aq) + 2 H+ + e− NO2(g) + H2O | +0.80 | |
Fe 2FeO42− + 5 H2O + 6 e− Fe2O3(s) + 10 OH− | +0.81 | |
Au − + 3 e− Au(s) + 4 Br− | +0.85 | |
Hg2+ + 2 e− Hg(l) | +0.85 | |
Ir 2- + e− 3- | +0.87 | |
MnO4− + H+ + e− HMnO4− | +0.90 | |
Hg2 Hg2+ + 2 e− Hg22+ | +0.91 | |
Pd2+ + 2 e− Pd(s) | +0.915 | |
Au − + 3 e− Au(s) + 4 Cl− | +0.93 | |
MnO2(s) + 4 H+ + e− Mn3+ + 2 H2O | +0.95 | |
Au− + e− Au(s) + 2 Br− | +0.96 | |
Xe3− + 2 H2O + 2 e− + − + 4 OH− | +0.99 | |
TeH6TeO6(aq) + 2 H+ + 2 e− TeO2(s) + 4 H2O | +1.02 | |
Br2(l) + 2 e− 2 Br− | +1.066 | |
Br2(aq) + 2 e− 2 Br− | +1.0873 | |
I IO3− + 5 H+ + 4 e− HIO(aq) + 2 H2O | +1.13 | |
Au − + e− Au(s) + 2 Cl− | +1.15 | |
Se HSeO4− + 3 H+ + 2 e− H2SeO3(aq) + H2O | +1.15 | |
Ag2O(s) + 2 H+ + 2 e− 2 Ag(s) + H2O | +1.17 | |
ClO3− + 2 H+ + e− ClO2(g) + H2O | +1.18 | |
Xe3− + 5 H2O + 8 e− Xe(g) + 11 OH− | +1.18 | |
Pt2+ + 2 e− Pt(s) | +1.188 | |
ClO2(g) + H+ + e− HClO2(aq) | +1.19 | |
I 2 IO3− + 12 H+ + 10 e− I2(s) + 6 H2O | +1.20 | |
ClO4− + 2 H+ + 2 e− ClO3− + H2O | +1.20 | |
O2(g) + 4 H+ + 4 e− 2 H2O | +1.229 | |
MnO2(s) + 4 H+ + 2 e− Mn2+ + 2 H2O | +1.23 | |
Xe− + 3 H2O + 6 e− Xe(g) + 7 OH− | +1.24 | |
Tl3+ + 2 e− Tl+ | +1.25 | |
Cr2O72− + 14 H+ + 6 e− 2 Cr3+ + 7 H2O | +1.33 | |
Cl2(g) + 2 e− 2 Cl− | +1.36 | |
CoO2(s) + 4 H+ + e− Co3+ + 2 H2O | +1.42 | |
N 2 NH3O H+ + H+ + 2 e− N2H5+ + 2 H2O | +1.42 | |
I 2 HIO(aq) + 2 H+ + 2 e− I2(s) + 2 H2O | +1.44 | |
Ce4+ + e− Ce3+ | +1.44 | |
BrO3− + 5 H+ + 4 e− HBrO(aq) + 2 H2O | +1.45 | |
PbO β-PbO2(s) + 4 H+ + 2 e− Pb2+ + 2 H2O | +1.460 | |
PbO α-PbO2(s) + 4 H+ + 2 e− Pb2+ + 2 H2O | +1.468 | |
Br 2 BrO3− + 12 H+ + 10 e− Br2(l) + 6 H2O | +1.48 | |
Cl 2ClO3− + 12 H+ + 10 e− Cl2(g) + 6 H2O | +1.49 | |
MnO4− + 8 H+ + 5 e− Mn2+ + 4 H2O | +1.51 | |
O HO2• + H+ + e− H2O2(aq) | +1.51 | |
Au3+ + 3 e− Au(s) | +1.52 | |
NiO2(s) + 4 H+ + 2 e− Ni2+ + 2 OH− | +1.59 | |
Cl 2 HClO(aq) + 2 H+ + 2 e− Cl2(g) + 2 H2O | +1.63 | |
Ag2O3(s) + 6 H+ + 4 e− 2 Ag+ + 3 H2O | +1.67 | |
Cl HClO2(aq) + 2 H+ + 2 e− HClO(aq) + H2O | +1.67 | |
Pb4+ + 2 e− Pb2+ | +1.69 | |
MnO4− + 4 H+ + 3 e− MnO2(s) + 2 H2O | +1.70 | |
AgO(s) + 2 H+ + e− Ag+ + H2O | +1.77 | |
O H2O2(aq) + 2 H+ + 2 e− 2 H2O | +1.78 | |
Co3+ + e− Co2+ | +1.82 | |
Au+ + e− Au(s) | +1.83 | |
BrO4− + 2 H+ + 2 e− BrO3− + H2O | +1.85 | |
Ag2+ + e− Ag+ | +1.98 | |
S2O82− + 2 e− 2 SO42− | +2.010 | |
O3(g) + 2 H+ + 2 e− O2(g) + H2O | +2.075 | |
Mn HMnO4− + 3 H+ + 2 e− MnO2(s) + 2 H2O | +2.09 | |
XeO3(aq) + 6 H+ + 6 e− Xe(g) + 3 H2O | +2.12 | |
XeH4XeO6(aq) + 8 H+ + 8 e− Xe(g) + 6 H2O | +2.18 | |
FeO42− + 3 e− + 8 H+ Fe3+ + 4 H2O | +2.20 | |
XeF2(aq) + 2 H+ + 2 e− Xe(g) + 2HF(aq) | +2.32 | |
XeH4XeO6(aq) + 2 H+ + 2 e− XeO3(aq) + H2O | +2.42 | |
F2(g) + 2 e− 2 F− | +2.87 | |
F2(g) + 2 H+ + 2 e− 2 HF(aq) | +3.05 |
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