Hydrogen peroxide

Structural formula of hydrogen peroxide. H is hydrogen and O is oxygen. The lines represent the chemical bonds between the atoms.
A picture to show simply how the atoms may fill space. The white is hydrogen and the red is oxygen.

Hydrogen peroxide is a chemical compound. Its molecular formula is H2O2. It is used as a cleaner, and as hair bleach. In a concentration of 3% (meaning there are 3 grams of hydrogen peroxide for 100 grams of a water solution), it can be used to treat wounds. Over time, it will slowly become oxygen gas and water through decomposition.

Chemists often use hydrogen peroxide in chemical reactions. It is a very strong oxidizing agent when used with acid and water. Oxidizing agents take electrons from other compounds.

2 Fe2+ (aq) + H2O2 + 2 H+ (aq) → 2 Fe3+ (aq) + 2 H2O (l)

In the example above, hydrogen peroxide takes an electron from the Fe2+ ions and becomes water. The iron is oxidized (loses electrons) to the Fe3+ ion.

It can also be a reducing agent when used with stronger oxidizers like sodium hypochlorite. When it acts as a reducing agent, oxygen gas is also produced. Reducing agents give electrons to other compounds. This method is often used to make oxygen in laboratories.

NaOCl + H2O2 → O2 + NaCl + H2O

Hydrogen peroxide can be bought in shops when mixed with lots of water, but is very dangerous when the concentration is higher. Because it is an oxidizer, it can cause flammable materials to ignite.