Skip to main content
Chemistry LibreTexts

P1: Standard Reduction Potentials by Element

  • Page ID
    6649
  • [ "article:topic" ]

    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

    H3AsO4 + 2H+ + 2e \(\rightleftharpoons\) HAsO2 + 2H2O

    becomes

    H3AsO4 + 2H3O+ + 2e \(\rightleftharpoons\) HAsO2 + 4H2O

    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  
    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  
    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  
    Ba2+ + 2e \(\rightleftharpoons\) Ba(s) –2.91

    BaO(s) + 2H+ + 2e\(\rightleftharpoons\) Ba(s) + H2O(l)

    2.365
    Beryllium  
    Be2+ + 2e \(\rightleftharpoons\) Be(s) –1.99
    Bismuth  
    Bi3+ + 3e \(\rightleftharpoons\) Bi(s) 0.317

    BiCl4 + 3e \(\rightleftharpoons\) Bi(s) + 4Cl

    0.199
    Boron  
    B(OH)3 + 3H+ + 3e \(\rightleftharpoons\) B(s) + 3H2O(l) –0.890

    B(OH)4 + 3e \(\rightleftharpoons\) B(s) + 4OH

    –1.811
    Bromine  
    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  
    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  
    Ca2+ + 2e \(\rightleftharpoons\) Ca(s) –2.84
    Carbon  
    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  
    Ce3+ + 3e \(\rightleftharpoons\) Ce(s) –2.336
    Ce4+ + e \(\rightleftharpoons\) Ce3+ 1.44
    Cesium  
    \[Cs^+(aq) + e^- \rightleftharpoons Cs (s) \] -2.92
    Chlorine  
    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  
    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  
    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  
    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  

    F2(g) + 2H+ + 2e \(\rightleftharpoons\) 2HF

    3.053

    F2(g) + 2e \(\rightleftharpoons\) 2F

    2.87
    Gallium  

    \[Ga^{3+} + 3e^− \rightleftharpoons Ga(s)\]

    -0.56
    Gold  
    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  

    \[2H^+ + 2e^− \rightleftharpoons H_2(g) \]

    0.00000

    H2O + e \(\rightleftharpoons\) ½H2(g) + OH

    –0.828
    Iodine  

    \[I_2(s) + 2e^− \rightleftharpoons 2I^−\]

    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  
    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  
    La3+ + 3e \(\rightleftharpoons\) La(s) –2.38
    Lead  
    Pb2+ + 2e \(\rightleftharpoons\) Pb(s) –0.126
    PbO2(s) + 4H+ +2e- \(\rightleftharpoons\) Pb2+(aq) + 2H2O(l) 1.46

    PbO2(s) + 4SO42− + 4H+ + 2e \(\rightleftharpoons\) PbSO4(s) + 2H2O(l)

    1.690

    PbSO4(s) + 2e \(\rightleftharpoons\) Pb(s) + SO42−

    –0.356
    Lithium  
    Li+ + e \(\rightleftharpoons\) Li(s) –3.040
    Magnesium  
    Mg2+ + 2e \(\rightleftharpoons\) Mg(s) –2.356

    Mg(OH)2(s) + 2e \(\rightleftharpoons\) Mg(s) + 2OH

    –2.687
    Manganese  
    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) + H2O(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  
    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  
    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  
    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  
    \[N_2(g) + 5H^+ + 4e^− \rightleftharpoons N_2H_5^+\] –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  
    \[ O_2(g) + 2H^+ + 2e^− \rightleftharpoons H_2O_2\] 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  
    \[P(s,white) + 3H^+ + 3e^− \rightleftharpoons PH_3(g)\] 0.06

    H3PO3+ 2H+ + 2e \(\rightleftharpoons\) H3PO2 + H2O(l)

    -0.50

    H3PO4 + 2H+ + 2e \(\rightleftharpoons\) H3PO3 + H2O(l)

    -0.28

    Platinum  
    Pt2+ + 2e \(\rightleftharpoons\) Pt(s) 1.2
    PtCl42− + 2e \(\rightleftharpoons\) Pt(s) + 4Cl 0.73
    PtCl62− + 2e \(\rightleftharpoons\) PtCl42- + 2Cl 0.68
    Potassium  
    K+ + e \(\rightleftharpoons\) K(s) -2.93
    Rubidium  
    Rb+ + e- \(\rightleftharpoons\) Rb (s) -2.98
    Ruthenium  
    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  
    \[Se(s) + 2e^−\rightleftharpoons Se^{2−}\] –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  
    \[SiF_6^{2−} + 4e^− \rightleftharpoons Si(s) + 6F^−\] –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  
    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  
    \[Na^+ + e^− \rightleftharpoons Na(s)\] –2.713
    Strontium  
    \[Sr^{2+} + 2e^− \rightleftharpoons Sr(s)\] –2.89
    Sulfur  
    \[S(s) + 2e^− \rightleftharpoons S^{2−}\] –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  
    \[Tl^{3+} + 2e^− \rightleftharpoons Tl^+\] 0.77 in 1 M HCl
    Tl3+ + 3e \(\rightleftharpoons\) Tl(s) 0.742
    Tin  
    Sn2+ + 2e\(\rightleftharpoons\) Sn(s) -0.14

    Sn4+ + 2e \(\rightleftharpoons\) Sn2+

    0.154
    Titanium  
    \[Ti^{2+} + 2e^− \rightleftharpoons Ti(s)\] –0.163

    Ti3+ + e \(\rightleftharpoons\) Ti2+

    –0.37
    Tungsten  
    \[WO_2(s) + 4H^+ + 4e^− \rightleftharpoons W(s) + 2H_2O(l)\] –0.119

    WO3(s) + 6H+ + 6e \(\rightleftharpoons\) W(s) + 3H2O(l)

    –0.090
    Uranium  
    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  
    \[V^{2+} + 2e^− \rightleftharpoons V(s)\] –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  

    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