Practice Oxidation Number in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

A number assigned to an atom in a compound that represents the number of electrons it has gained, lost, or shared unequally.

An imaginary 'electron bookkeeping' system. If an atom 'owns' more electrons than usual, its oxidation number is negative; fewer means positive.

Example 1

easy
Assign oxidation numbers to each element in \text{H}_2\text{SO}_4.

Example 2

medium
Assign oxidation numbers to each atom in \text{KMnO}_4 and determine the oxidation number of manganese.

Example 3

easy
What is the oxidation number of nitrogen in \text{NO}_3^-?

Example 4

hard
In the reaction \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2, determine the oxidation number of iron and carbon on each side. Which element is oxidized and which is reduced?
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