Practice Problem 6
Use cell potentials to explain why hydrogen peroxide disproportionates to form oxygen and water.
2 H2O2(aq) 2 H2O(l) + O2(g)
Because the oxygen atoms in hydrogen peroxide are in the -1 oxidation state, H2O2 can be either oxidized to O2 or reduced to water.
|H2O2 + 2 H+ +
||Eored = 1.776 V|
+ 2 H+ +
||+Eoox = -(0.682 V)|
|2 H2O2 2 H2O + O2||Eo = Eored + Eoox = 1.094 V|
The overall cell potential for the disproportionation of H2O2 is positive, which means this should be a spontaneous oxidation-reduction reaction.