P1: Standard Reduction Potentials by Element
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The following table provides Eo and Eo´ values 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.
Solids, gases, and liquids are identified; all other species are aqueous. Reduction reactions in acidic solution are written using H+ in place of H3O+. You may rewrite a reaction by replacing H+ with H3O+ and adding to the opposite side of the reaction one molecule of H2O per H+; thus
\(\ce{H3AsO4 + 2H^{+} + 2e^{–} <=> HAsO2 + 2H2O} \nonumber\)
becomes
\(\ce{H3AsO4 + 2H3O^{+} + 2e^{–} <=> HAsO2 + 4H2O} \nonumber\)
Conditions for formal potentials (Eo´) are listed next to the potential.
Aluminum |
E° (V) |
Al3+ + 3e− \(\rightleftharpoons\) Al(s) |
–1.676 |
Al(OH)4− + 3e− \(\rightleftharpoons\) Al(s) + 4OH− |
–2.310 |
AlF63− + 3e− \(\rightleftharpoons\) Al(s) + 6F− |
–2.07 |
Antimony |
E° (V) |
Sb + 3H+ + 3e− \(\rightleftharpoons\) SbH3(g) |
–0.510 |
Sb2O5(s) + 6H+ + 4e− \(\rightleftharpoons\) 2SbO+ + 3H2O(l) |
0.605 |
SbO+ + 2H+ + 3e− \(\rightleftharpoons\) Sb(s) + H2O(l) |
0.212 |
Arsenic |
E° (V) |
As + 3H+ + 3e− \(\rightleftharpoons\) AsH3(g) |
–0.225 |
H3AsO4 + 2H+ + 2e− \(\rightleftharpoons\) HAsO2 + 2H2O(l) |
0.560 |
HAsO2 + 3H+ + 3e− \(\rightleftharpoons\) As(s) + 2H2O(l) |
0.240 |
Barium |
E° (V) |
Ba2+ + 2e− \(\rightleftharpoons\) Ba(s) |
–2.91 |
BaO(s) + 2H+ + 2e−\(\rightleftharpoons\) Ba(s) + H2O(l) |
2.365 |
Beryllium |
E° (V) |
Be2+ + 2e− \(\rightleftharpoons\) Be(s) |
–1.99 |
Bismuth |
E° (V) |
Bi3+ + 3e− \(\rightleftharpoons\) Bi(s) |
0.317 |
BiCl4− + 3e− \(\rightleftharpoons\) Bi(s) + 4Cl− |
0.199 |
Boron |
E° (V) |
B(OH)3 + 3H+ + 3e− \(\rightleftharpoons\) B(s) + 3H2O(l) |
–0.890 |
B(OH)4− + 3e− \(\rightleftharpoons\) B(s) + 4OH− |
–1.811 |
Bromine |
E° (V) |
Br2 + 2e− \(\rightleftharpoons\) 2Br− |
1.087 |
HOBr + H+ + 2e− \(\rightleftharpoons\) Br− + H2O(l) |
1.341 |
HOBr + H+ + e− \(\rightleftharpoons\) ½Br− + H2O(l) |
1.604 |
BrO− + H2O(l) +2e− \(\rightleftharpoons\) Br− + 2OH− |
0.76 in 1 M NaOH |
BrO3− + 6H+ + 5e− \(\rightleftharpoons\) ½Br2(l) + 3H2O |
1.5 |
BrO3− + 6H+ + 6e− \(\rightleftharpoons\)Br− + 3H2O |
1.478 |
Cadmium |
E° (V) |
Cd2+ + 2e− \(\rightleftharpoons\) Cd(s) |
–0.4030 |
Cd(CN)42− + 2e− \(\rightleftharpoons\) Cd(s) + 4CN− |
–0.943 |
Cd(NH3)42+ + 2e− \(\rightleftharpoons\) Cd(s) + 4NH3 |
–0.622 |
Calcium |
E° (V) |
Ca2+ + 2e− \(\rightleftharpoons\) Ca(s) |
–2.84 |
Carbon |
E° (V) |
CO2(g) + 2H+ + 2e− \(\rightleftharpoons\) CO(g) + H2O(l) |
–0.106 |
CO2(g) + 2H+ + 2e− \(\rightleftharpoons\) HCO2H |
–0.20 |
2CO2(g) + 2H+ +2e− \(\rightleftharpoons\) H2C2O4 |
–0.481 |
HCHO + 2H+ + 2e− \(\rightleftharpoons\) CH3OH |
0.2323 |
Cerium |
E° (V) |
Ce3+ + 3e− \(\rightleftharpoons\) Ce(s) |
–2.336 |
Ce4+ + e− \(\rightleftharpoons\) Ce3+ |
1.61 |
Cesium |
E° (V) |
\(Cs^+(aq) + e^- \rightleftharpoons Cs (s) \) |
-2.92 |
Chlorine |
E° (V) |
Cl2(g) + 2e− \(\rightleftharpoons\) 2Cl− |
1.396 |
ClO− + H2O(l) + e− \(\rightleftharpoons\)½Cl2(g) + 2OH− |
0.421 in 1 M NaOH |
ClO− + H2O(l) + 2e− \(\rightleftharpoons\) Cl− + 2OH− |
0.890 in 1 M NaOH |
HClO2 + 2H+ + 2e− \(\rightleftharpoons\) HOCl + H2O |
1.64 |
ClO3− + 2H+ + e− \(\rightleftharpoons\) ClO2(g) + H2O |
1.175 |
ClO3− + 3H+ + 2e−\(\rightleftharpoons\)HClO2 + H2O |
1.181 |
ClO4− + 2H+ + 2e−\(\rightleftharpoons\) ClO3− + H2O |
1.201 |
ClO4-(aq) + H2O(l) + 2e- \(\rightleftharpoons\) ClO3-(aq) + 2OH-(aq) |
0.17 |
ClO3-(aq) + H2O(l) + 2e- \(\rightleftharpoons\) ClO2-(aq) + 2OH-(aq) |
0.35 |
ClO2-(aq) + H2O(l) + 2e- \(\rightleftharpoons\) ClO-(aq) + 2OH-(aq) |
0.59 |
Chromium |
E° (V) |
Cr3+ + e− \(\rightleftharpoons\) Cr2+ |
–0.424 |
Cr2+ + 2e− \(\rightleftharpoons\) Cr(s) |
–0.90 |
Cr2O72− + 14H+ + 6e−\(\rightleftharpoons\) 2Cr3+ + 7H2O(l) |
1.36 |
CrO42− + 4H2O(l) + 3e−\(\rightleftharpoons\)2Cr(OH)4− + 4OH− |
–0.13 in 1 M NaOH |
Cobalt |
E° (V) |
Co2+ + 2e− \(\rightleftharpoons\) Co(s) |
–0.277 |
Co3+ + e− \(\rightleftharpoons\) Co2+ |
1.92 |
Co(NH3)63+ +e− \(\rightleftharpoons\) Co(NH3)62+ |
0.1 |
Co(OH)3(s) + e− \(\rightleftharpoons\) Co(OH)2(s) + OH− |
0.17 |
Co(OH)2(s) + 2e− \(\rightleftharpoons\) Co(s) + 2OH− |
–0.746 |
Copper |
E° (V) |
Cu+ + e− \(\rightleftharpoons\) Cu(s) |
0.520 |
Cu2+ + e− \(\rightleftharpoons\) Cu+ |
0.159 |
Cu2+ + 2e− \(\rightleftharpoons\) Cu(s) |
0.3419 |
Cu2+ + I− +e− \(\rightleftharpoons\) CuI(s) |
0.86 |
Cu2+ + Cl− + e− \(\rightleftharpoons\) CuCl(s) |
0.559 |
Fluorine |
E° (V) |
F2(g) + 2H+ + 2e− \(\rightleftharpoons\) 2HF |
3.053 |
F2(g) + 2e− \(\rightleftharpoons\) 2F− |
2.87 |
Gallium |
E° (V) |
\(Ga^{3+} + 3e^− \rightleftharpoons Ga(s)\) |
-0.56 |
Gold |
E° (V) |
Au+ + e− \(\rightleftharpoons\) Au(s) |
1.83 |
Au3+ + 2e− \(\rightleftharpoons\) Au+ |
1.36 |
Au3+ + 3e− \(\rightleftharpoons\) Au(s) |
1.52 |
AuCl4− + 3e− \(\rightleftharpoons\) Au(s) + 4Cl− |
1.002 |
Hydrogen |
E° (V) |
\(2H^+ + 2e^− \rightleftharpoons H_2(g) \) |
0.00000 |
H2O + e− \(\rightleftharpoons\) ½H2(g) + OH− |
–0.828 |
Iodine |
E° (V) |
\(I_2(s) + 2e^− \rightleftharpoons 2I^−\) |
0.5355 |
I3− + 2e− \(\rightleftharpoons\) 3I− |
0.536 |
HIO + H+ + 2e− \(\rightleftharpoons\) I− + H2O(l) |
0.985 |
IO3− + 6H+ + 5e− \(\rightleftharpoons\) ½I2(s) + 3H2O(l) |
1.195 |
IO3−+ 3H2O(l) + 6e− \(\rightleftharpoons\) I− + 6OH− |
0.257 |
Iron |
E° (V) |
Fe2+ + 2e− \(\rightleftharpoons\) Fe(s) |
–0.44 |
Fe3+ + 3e− \(\rightleftharpoons\) Fe(s) |
–0.037 |
Fe3+ + e− \(\rightleftharpoons\) Fe2+ |
0.771 |
Fe(CN)63− + e−\(\rightleftharpoons\) Fe(CN)64− |
0.356 |
Fe(phen)63+ +e−\(\rightleftharpoons\)Fe(phen)62+ |
1.147 |
Lanthanum |
E° (V) |
La3+ + 3e− \(\rightleftharpoons\) La(s) |
–2.38 |
Lead |
E° (V) |
Pb2+ + 2e− \(\rightleftharpoons\) Pb(s) |
–0.126 |
PbO2(s) + 4H+ +2e- \(\rightleftharpoons\) Pb2+(aq) + 2H2O(l) |
1.46 |
PbO2(s) + SO42− + 4H+ + 2e− \(\rightleftharpoons\) PbSO4(s) + 2H2O(l) |
1.690 |
PbSO4(s) + 2e− \(\rightleftharpoons\) Pb(s) + SO42− |
–0.356 |
Lithium |
E° (V) |
Li+ + e− \(\rightleftharpoons\) Li(s) |
–3.040 |
Magnesium |
E° (V) |
Mg2+ + 2e− \(\rightleftharpoons\) Mg(s) |
–2.356 |
Mg(OH)2(s) + 2e− \(\rightleftharpoons\) Mg(s) + 2OH− |
–2.687 |
Manganese |
E° (V) |
Mn2+ + 2e− \(\rightleftharpoons\) Mn(s) |
–1.17 |
Mn3+ + e− \(\rightleftharpoons\) Mn2+ |
1.5 |
MnO2(s) + 4H+ + 2e− \(\rightleftharpoons\) Mn2+ + 2H2O(l) |
1.23 |
MnO2(s) + 4H+ + e- \(\rightleftharpoons\) Mn3+ (aq) + 2H2O(I) |
0.95 |
MnO4− + 4H+ +3e− \(\rightleftharpoons\) MnO2(s) + 2H2O(l) |
1.70 |
MnO4−+ 8H+ + 5e− \(\rightleftharpoons\) Mn2+ + 4H2O(l) |
1.51 |
MnO4− + 2H2O(l) + 3e− \(\rightleftharpoons\) MnO2(s) + 4OH− |
0.60 |
Mercury |
E° (V) |
Hg2+ + 2e− \(\rightleftharpoons\) Hg(l) |
0.8535 |
2Hg2+ + 2e− \(\rightleftharpoons\) Hg22+ |
0.911 |
Hg22+ + 2e− \(\rightleftharpoons\) 2Hg(l) |
0.7960 |
Hg2Cl2(s) + 2e− \(\rightleftharpoons\) 2Hg(l) + 2Cl− |
0.2682 |
HgO(s) + 2H+ + 2e− \(\rightleftharpoons\) Hg(l) + H2O(l) |
0.926 |
Hg2Br2(s) + 2e− \(\rightleftharpoons\) 2Hg(l) + 2Br− |
1.392 |
Hg2I2(s) + 2e− \(\rightleftharpoons\) 2Hg(l) + 2I− |
–0.0405 |
Molybdenum |
E° (V) |
Mo3+ + 3e− \(\rightleftharpoons\) Mo(s) |
–0.2 |
MoO2(s) + 4H+ + 4e− \(\rightleftharpoons\) Mo(s) + 2H2O(l) |
–0.152 |
MoO42− + 4H2O(l) + 6e− \(\rightleftharpoons\)Mo(s) + 8OH− |
–0.913 |
Nickel |
E° (V) |
Ni2+ + 2e− \(\rightleftharpoons\) Ni(s) |
–0.257 |
Ni(OH)2 + 2e− \(\rightleftharpoons\) Ni(s) + 2OH− |
–0.72 |
Ni(NH3)62+ + 2e− \(\rightleftharpoons\) Ni(s) + 6NH3 |
–0.49 |
Nitrogen |
E° (V) |
\(N_2(g) + 5H^+ + 4e^− \rightleftharpoons N_2H_5^+\) |
–0.23 |
N2O(g) + 2H+ + 2e− \(\rightleftharpoons\) N2(g) + H2O(l) |
1.77 |
2NO(g) + 2H+ + 2e− \(\rightleftharpoons\) N2O(g) + H2O(l) |
1.59 |
HNO2 + H+ +e− \(\rightleftharpoons\) NO(g) + H2O(l) |
0.996 |
2HNO2 + 4H+ + 4e− \(\rightleftharpoons\) N2O(g) + 3H2O(l) |
1.297 |
NO3− + 3H+ + 2e− \(\rightleftharpoons\) HNO2 + H2O(l) |
0.94 |
\(\ce{ NO2(g) + H+ (aq) + e- \rightleftharpoons HNO2(aq) } \) |
1.07 |
NO3-(aq) + 4H+(aq) + 3e- \(\rightleftharpoons\) NO(g) + 2H2O(l) |
0.96 |
Oxygen |
E° (V) |
\( O_2(g) + 2H^+ + 2e^− \rightleftharpoons H_2O_2\) |
0.695 |
O2(g) + 4H+ + 4e− \(\rightleftharpoons\) 2H2O(l) |
1.229 |
H2O2 + 2H+ + 2e− \(\rightleftharpoons\) 2H2O(l) |
1.763 |
O2(g) + 2H2O(l) + 4e− \(\rightleftharpoons\) 4OH− |
0.401 |
O3(g) + 2H+ + 2e− \(\rightleftharpoons\) O2(g) + H2O(l) |
2.07 |
O2 (g) + e- \(\rightleftharpoons\) O2-(aq) |
-0.33 |
O2 (aq) + e- \(\rightleftharpoons\) O2-(aq) |
-0.16 |
Phosphorous |
E° (V) |
\(P(s,white) + 3H^+ + 3e^− \rightleftharpoons PH_3(g)\) |
0.06 |
H3PO3+ 2H+ + 2e− \(\rightleftharpoons\) H3PO2 + H2O(l) |
-0.50 |
H3PO4 + 2H+ + 2e− \(\rightleftharpoons\) H3PO3 + H2O(l) |
-0.28 |
Platinum |
E° (V) |
Pt2+ + 2e− \(\rightleftharpoons\) Pt(s) |
1.2 |
PtCl42− + 2e− \(\rightleftharpoons\) Pt(s) + 4Cl− |
0.73 |
PtCl62− + 2e− \(\rightleftharpoons\) PtCl42- + 2Cl− |
0.68 |
Potassium |
E° (V) |
K+ + e− \(\rightleftharpoons\) K(s) |
-2.93 |
Rubidium |
E° (V) |
Rb+ + e- \(\rightleftharpoons\) Rb (s) |
-2.98 |
Ruthenium |
E° (V) |
Ru3+ + e− \(\rightleftharpoons\) Ru2+ |
0.249 |
RuO2(s) + 4H+ + 4e− \(\rightleftharpoons\) Ru(s) + 2H2O(l) |
0.68 |
Ru(NH3)63+ + e− \(\rightleftharpoons\) Ru(s) + Ru(NH3)62+ |
0.10 |
Ru(CN)63− +e− \(\rightleftharpoons\) Ru(s) + Ru(CN)64− |
0.86 |
Selenium |
E° (V) |
\(Se(s) + 2e^−\rightleftharpoons Se^{2−}\) |
–0.67 in 1 M NaOH |
Se(s) + 2H+ + 2e− \(\rightleftharpoons\) H2Se(g) |
–0.115 |
H2SeO3 + 4H+ + 4e− \(\rightleftharpoons\) Se(s) + 3H2O(l) |
0.74 |
SeO43− + 4H+ + e− \(\rightleftharpoons\) H2SeO3 + H2O(l) |
1.151 |
Silicon |
E° (V) |
\(SiF_6^{2−} + 4e^− \rightleftharpoons Si(s) + 6F^−\) |
–1.37 |
SiO2(s) + 4H+ + 4e− \(\rightleftharpoons\) Si(s) + 2H2O(l) |
–0.909 |
SiO2(s) + 8H+ + 8e− \(\rightleftharpoons\) SiH4(g) + 2H2O(l) |
–0.516 |
Silver |
E° (V) |
Ag+ + e− \(\rightleftharpoons\) Ag(s) |
0.7996 |
AgBr(s) + e− \(\rightleftharpoons\) Ag(s) + Br− |
0.071 |
Ag2C2O4(s) + 2e− \(\rightleftharpoons\) 2Ag(s) + C2O42− |
0.47 |
AgCl(s) + e− \(\rightleftharpoons\) Ag(s) + Cl− |
0.2223 |
AgI(s) + e− \(\rightleftharpoons\) Ag(s) + I− |
–0.152 |
Ag2S(s) + 2e− \(\rightleftharpoons\) 2Ag(s) + S2− |
–0.71 |
Ag(NH3)2+ + e− \(\rightleftharpoons\) Ag(s) + 2NH3 |
–0.373 |
Sodium |
E° (V) |
\(Na^+ + e^− \rightleftharpoons Na(s)\) |
–2.713 |
Strontium |
E° (V) |
\(Sr^{2+} + 2e^− \rightleftharpoons Sr(s)\) |
–2.89 |
Sulfur |
E° (V) |
\(S(s) + 2e^− \rightleftharpoons S^{2−}\) |
–0.407 |
S(s) + 2H+ + 2e− \(\rightleftharpoons\) H2S |
0.144 |
S2O62− + 4H+ + 2e− \(\rightleftharpoons\) 2H2SO3 |
0.569 |
S2O82− + 2e− \(\rightleftharpoons\)2SO42− |
1.96 |
S4O62− + 2e− \(\rightleftharpoons\)2S2O32− |
0.080 |
2SO32− + 2H2O(l) + 2e−\(\rightleftharpoons\) S2O42− + 4OH− |
–1.13 |
2SO32− + 3H2O(l) + 4e−\(\rightleftharpoons\)S2O32− + 6OH− |
|
2SO42− + 4H+ + 2e−\(\rightleftharpoons\) S2O62− + 2H2O(l) |
–0.25 |
SO42− + H2O(l) + 2e−\(\rightleftharpoons\) SO32−+ 2OH− |
–0.936 |
SO42− + 4H+ + 2e−\(\rightleftharpoons\) H2SO32−+ H2O(l) |
0.172 |
Thallium |
E° (V) |
\(Tl^{3+} + 2e^− \rightleftharpoons Tl^+\) |
0.77 in 1 M HCl |
Tl3+ + 3e− \(\rightleftharpoons\) Tl(s) |
0.742 |
Tin |
E° (V) |
Sn2+ + 2e−\(\rightleftharpoons\) Sn(s) |
-0.14 |
Sn4+ + 2e− \(\rightleftharpoons\) Sn2+ |
0.154 |
Titanium |
E° (V) |
\(Ti^{2+} + 2e^− \rightleftharpoons Ti(s)\) |
–0.163 |
Ti3+ + e− \(\rightleftharpoons\) Ti2+ |
–0.37 |
Tungsten |
E° (V) |
\(WO_2(s) + 4H^+ + 4e^− \rightleftharpoons W(s) + 2H_2O(l)\) |
–0.119 |
WO3(s) + 6H+ + 6e− \(\rightleftharpoons\) W(s) + 3H2O(l) |
–0.090 |
Uranium |
E° (V) |
U3+ + 3e− \(\rightleftharpoons\) U(s) |
–1.66 |
U4+ + e− \(\rightleftharpoons\) U3+ |
–0.52 |
UO2+ + 4H+ + e−\(\rightleftharpoons\)U4+ + 2H2O(l) |
0.27 |
UO22+ + e−\(\rightleftharpoons\)UO2+ |
0.16 |
UO22+ + 4H+ + 2e−\(\rightleftharpoons\) U4+ + 2H2O(l) |
0.327 |
Vanadium |
E° (V) |
\(V^{2+} + 2e^− \rightleftharpoons V(s)\) |
–1.13 |
V3+ + e− \(\rightleftharpoons\) V2+ |
–0.255 |
VO2+ + 2H+ +e− \(\rightleftharpoons\)V3+ + H2O(l) |
0.337 |
VO22+ + 2H+ +e− \(\rightleftharpoons\) VO2+ + H2O(l) |
1.000 |
Zinc |
E° (V) |
Zn2+(aq) + 2e− \(\rightleftharpoons\) Zn(s) |
–0.7618 |
Zn(OH)42− + 2e− \(\rightleftharpoons\) Zn(s) + 4OH− |
–1.285 |
Zn(NH3)42+ + 2e− \(\rightleftharpoons\) Zn(s) + 4NH3 |
–1.04 |
Zn(CN)42− + 2e− \(\rightleftharpoons\) Zn(s) + 4CN |
–1.34 |
ZnO2 + 4H+ + 4e− \(\rightleftharpoons\) Zn(s) + 2H2O |
-1.473 |