3.5.3 Redox Equilibria - Electrochemical series

Specification

Students should:
  • know that standard electrode potentials can be listed as an electrochemical series
  • be able to use E values to predict the direction of simple redox reactions and to calculate the e.m.f of a cell

Standard electrode potentials

These are often shown as a list of reductions with the most negative at the top:

Cathode (Reduction) Half-Reaction
Standard Potential
E° (volts)
Li+(aq) + e- Li(s) -3.04
K+(aq) + e- K(s) -2.92
Ca2+(aq) + 2e- Ca(s) -2.76
Na+(aq) + e- Na(s) -2.71
Mg2+(aq) + 2e- Mg(s) -2.38
Al3+(aq) + 3e- Al(s) -1.66
2H2O(l) + 2e- H2(g) + 2OH-(aq) -0.83
Zn2+(aq) + 2e- Zn(s) -0.76
Cr3+(aq) + 3e- Cr(s) -0.74
Fe2+(aq) + 2e- Fe(s) -0.41
Cd2+(aq) + 2e- Cd(s) -0.40
Ni2+(aq) + 2e- Ni(s) -0.23
Sn2+(aq) + 2e- Sn(s) -0.14
Pb2+(aq) + 2e- Pb(s) -0.13
Fe3+(aq) + 3e- Fe(s) -0.04
2H+(aq) + 2e- H2(g)  0.00
S4O62-(aq) + 2e- 2S2O32-(g)  +0.08
Sn4+(aq) + 2e- Sn2+(aq) +0.15
Cu2+(aq) + e- Cu+(aq) +0.16
ClO4-(aq) + H2O(l) + 2e- ClO3-(aq) + 2OH-(aq) +0.17
SO42-(aq) + 4H+ + 2e H2SO3(aq) + H2O +0.17
AgCl(s) + e- Ag(s) + Cl-(aq) +0.22
Cu2+(aq) + 2e- Cu(s) +0.34
ClO3-(aq) + H2O(l) + 2e- ClO2-(aq) + 2OH-(aq) +0.35
IO-(aq) + H2O(l) + 2e- I-(aq) + 2OH-(aq) +0.49
Cu+(aq) + e- Cu(s) +0.52
I2(s) + 2e- 2I-(aq) +0.54
ClO2-(aq) + H2O(l) + 2e- ClO-(aq) + 2OH-(aq) +0.59
Fe3+(aq) + e- Fe2+(aq) +0.77
Hg22+(aq) + 2e- 2Hg(l) +0.80
Ag+(aq) + e- Ag(s) +0.80
Hg2+(aq) + 2e- Hg(l) +0.85
ClO-(aq) + H2O(l) + 2e- Cl-(aq) + 2OH-(aq) +0.90
2Hg2+(aq) + 2e- Hg22+(aq) +0.90
NO3-(aq) + 4H+(aq) + 3e- NO(g) + 2H2O(l) +0.96
Br2(l) + 2e- 2Br-(aq) +1.07
O2(g) + 4H+(aq) + 4e- 2H2O(l) +1.23
Cr2O72-(aq) + 14H+(aq) + 6e- 2Cr3+(aq) + 7H2O(l) +1.33
Cl2(g) + 2e- 2Cl-(aq) +1.36
Ce4+(aq) + e- Ce3+(aq) +1.44
MnO4-(aq) + 8H+(aq) + 5e- Mn2+(aq) + 4H2O(l) +1.49
H2O2(aq) + 2H+(aq) + 2e- 2H2O(l) +1.78
Co3+(aq) + e- Co2+(aq) +1.82
S2O82-(aq) + 2e- 2SO42-(aq) +2.01
O3(g) + 2H+(aq) + 2e- O2(g) + H2O(l) +2.07
F2(g) + 2e- 2F-(aq) +2.87

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