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16.15: Polarographic Half-Wave Potentials

  • Page ID
    220812
  • The following table provides E1/2 values for selected reduction reactions. Values are from Dean, J. A. Analytical Chemistry Handbook, McGraw-Hill: New York, 1995.

    Element \(E_{1/2}\) (volts vs. SCE) Matrix
    \(\ce{Al^{3+}}(aq) + \ce{3 e-} \ce{<=>} \ce{Al}(s)\) –0.5 0.2 M acetate (pH 4.5–4.7)
    \(\ce{Cd^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Cd}(s)\) –0.6

    0.1 M KCl

    0.050 M H2SO4

    1 M HNO3

    \(\ce{Cr^{3+}}(aq) + \ce{3 e-} \ce{<=>} \ce{Cr}(s)\)

    –0.35 \((+3 \ce{->} +2)\)

    –1.70 \((+2 \ce{->} 0)\)

    1 M NH4Cl plus 1 M NH3

    1 M NH4+/NH3 buffer (pH 8–9)

    \(\ce{Co^{3+}}(aq)+ \ce{3 e-} \ce{<=>} \ce{Co}(s)\)

    –0.5 \((+3 \ce{->} +2)\)

    –1.3 \((+2 \ce{->} 0)\)

    1 M NH4Cl plus 1 M NH3
    \(\ce{Co^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Co}(s)\) –1.03

    1 M KSCN

    \(\ce{Cu^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Cu}(s)\)

    0.04

     

     

    –0.22

    0.1 M KSCN

    0.1 M NH4ClO4

    1 M Na2SO4

    0.5 M potassium citrate (pH 7.5)

    \(\ce{Fe^{3+}}(aq) + \ce{3 e-} \ce{<=>} \ce{Fe}(s)\)

    –0.17 \((+3 \ce{->} +2)\)

    –1.52 \((+2 \ce{->} 0)\)

    0.5 M sodium tartrate (pH 5.8)
    \(\ce{Fe^{3+}}(aq) + \ce{e-} \ce{<=>} \ce{Fe^{2+}}(aq)\) –0.27 0.2 M Na2C2O4 (pH < 7.9)
    \(\ce{Pb^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Pb}(s)\)

    –0.405

    –0.435

    1 M HNO3

    1 M KCl

    \(\ce{Mn^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Mn}(s)\) –1.65 1 M NH4Cl plus 1 M NH3
    \(\ce{Ni^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Ni}(s)\)

    –0.70

    –1.09

    1 M KSCN

    1 M NH4Cl plus 1 M NH3

    \(\ce{Zn^{2+}}(aq) + \ce{2 e-} \ce{<=>} \ce{Zn}(s)\)

    –0.995

    –1.33

    0.1 M KCl

    1 M NH4Cl plus 1 M NH3

     

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