2 H2O(l) + O2(g)
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)
Answer
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+ +  2 H2O |
Eored = 1.776 V | |
| H2O2 O2
+ 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.
