The following table provides E o 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 Rb+ + e- \(\rightleftharpoons\) Rb (s) -2.98 K+(aq) + e- \(\rightleftharpoons\) K(s) -2.93 Ba2+ + 2e−\(\rightleftharpoons\) Ba(s) -2.92 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- \(\rightleftharpoons\) Mg(s) -2.356 Ce3+ + 3e−\(\rightleftharpoons\) Ce(s) -2.336 Al(OH)4− + 3e−\(\rightleftharpoons\) Al(s) + 4OH− -2.310 BaO(s) + 2H+ + 2e– \(\rightleftharpoons\) Ba(s) + H2O(l) -2.166 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 Al3+(aq) + 3e- \(\rightleftharpoons\) Al(s) -1.676 U3+ + 3e−\(\rightleftharpoons\) U(s) -1.66 ZnO2 + 4H+ + 4e− \(\rightleftharpoons\) Zn(s) + 2H2O -1.473 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 CdS(s) + 2e− \(\rightleftharpoons\) Cd(s) + S2− -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 SO42− + H2O(l) + 2e− \(\rightleftharpoons\) SO32−+ 2OH− -0.936 SiO2(s) + 4H+ + 4e−\(\rightleftharpoons\) Si(s) + 2H2O(l) -0.909 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) -0.74 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 Ga3+ + 3e−\(\rightleftharpoons\) Ga(s) -0.56 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 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) -0.136 CrO42− + 4H2O(l) + 3e− \(\rightleftharpoons\)2Cr(OH)4− + 4OH− -0.13 in 1 M NaOH Pb2+(aq) + 2e- \(\rightleftharpoons\) Pb(s) -0.126 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− \(\rightleftharpoons\) H2SO3 (aq) + 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 Cu2+ + Cl− + e−\(\rightleftharpoons\) CuCl(s) 0.559 H3AsO4 + 2H+ + 2e−\(\rightleftharpoons\) HAsO2 + 2H2O(l) 0.560 S2O62− + 4H+ + 2e−\(\rightleftharpoons\) 2H2SO3 0.569 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 Tl3+ + 2e− \(\rightleftharpoons\) Tl+ 0.77 in 1 M HCl 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) + 2H2O(l) 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 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 Au3+ + 2e−\(\rightleftharpoons\) Au+ 1.36 Hg2Br2(s) + 2e−\(\rightleftharpoons\) 2Hg(l) + 2Br− 1.392 Cl2(g) + 2e- \(\rightleftharpoons\) 2Cl-(aq) 1.396 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 BrO3− + 6H+ + 5e−\(\rightleftharpoons\) ½Br2(l) + 3H2O 1.5 MnO4-(aq) + 8H+(aq) + 5e- \(\rightleftharpoons\) Mn2+(aq) + 4H2O(l) 1.51 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) + SO42− + 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 F2(g) + 2e- \(\rightleftharpoons\) 2F-(aq) 2.87 F2(g) + 2H+ + 2e−\(\rightleftharpoons\) 2HF 3.053