Hydrogen peroxide

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 that 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.

Stuctural formula of hydrogen peroxide. H is hydrogen and O is oxygen. The lines repsent 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.

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

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

Here hydrogen peroxide takes an electron from the Fe²⁺ ions and becomes water. The iron is oxidised (loses electrons) to the Fe³⁺ ion.

It can also be a reducing agent when used with stronger oxidisers 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 oxidiser, it can cause flammable materials to ignite.