Standard electrode potentials  

These notes were written for the old IB syllabus (2009). The new IB syllabus for first examinations 2016 can be accessed by clicking the link below.

IB syllabus for first examinations 2016

Topic 20 - Oxidation and reduction


Standard Electrode Potentials in Aqueous Solution at 25C

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
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
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