Question

What are the oxidation numbers in the compound H2O2?

Answer 1

The oxidation number of `"H"` is +1. The oxidation number of `"O"` is -1.

Explanation:

You assign oxidation numbers to the elements in a compound by using the Rules for Oxidation Numbers.

The important rules for this problem are:

1. The oxidation number of `"H"` is +1, but it is -1 in when combined with less electronegative elements.

2. The oxidation number of `"O"` in compounds is usually -2, but it is -1 in peroxides.

3. The sum of the oxidation numbers of all the atoms in a neutral compound is 0.

The oxidation number of `"H"` is +1 (Rule 1).

If you know that `"H"_2"O"_2` is hydrogen peroxide, you can immediately assign oxygen the ON = -1.

If you don't know that `"H"_2"O"_2` is hydrogen peroxide, you can use Rule 3.

The oxidation number of `"H"` is +1. For two `"H"` atoms, the sum is +2.

Since `"H"_2"O"_2` has no charge, the total oxidation number of the two `"O"` atoms must be -2.

The oxidation number of one oxygen atom must be -1.