To balance the equation using the oxidation number method, we need to assign oxidation numbers to each element in the equation.

- Oxygen (O) has an oxidation number of -2, except in peroxides where it is -1.
- Hydrogen (H) has an oxidation number of +1.
- The sum of oxidation numbers in a neutral compound is zero.
- The sum of oxidation numbers in a polyatomic ion is equal to the charge of the ion.

Oxidation numbers for the given compounds:
- H2O2: H = +1, O = -1
- Fe2: Fe = ?
- Fe3: Fe = ?
- H2O: H = +1, O = -2



In this step, we determine the change in oxidation numbers for the elements undergoing oxidation and reduction.

- The oxidation number of hydrogen in H2O2 changes from +1 to 0 (reduction).
- The oxidation number of oxygen in H2O2 changes from -1 to -2 (oxidation).
- The oxidation number of iron in Fe2 changes from 0 to +3 (oxidation).



Now, we balance the equation by equalizing the changes in oxidation numbers.

1. Balance the hydrogen atoms:
- There are 2 hydrogen atoms on the left side (H2O2).
- To balance it on the right side, we need 2 hydrogen atoms. Therefore, the product is H2O.

2. Balance the oxygen atoms:
- There are 2 oxygen atoms on the left side (H2O2).
- To balance it on the right side, we need 2 oxygen atoms. Therefore, the product is H2O.

3. Balance the charge:
- The total charge on the left side is +2 (2H).
- The total charge on the right side is 0.
- To balance the charge, we need to add electrons to the right side.
- The product is Fe3+ + 2e-.

4. Balance the iron atoms:
- There are 2 iron atoms on the left side (Fe2).
- To balance it on the right side, we need 2 iron atoms. Therefore, the product is 2Fe3+ + 4e-.



H2O2 + Fe2 → 2Fe3+ + 2e- + H2O