Chemical Properties and Chemical Reaction of Hydrogen Peroxide

Hydrogen peroxide exhibits some interesting chemical properties. These properties are expressed in unique and simple chemical reactions and Equations. Here we will be taking a Tour of the Chemistry of the entire Process.

The ability of Hydrogen peroxide to donate oxygen or accept electrons makes it a potent oxidising Agent. It is a strong oxidising Agent that become reduced to water once the oxygen is off.

H₂O₂ (l) → H₂O(l) + [O]

The process by which hydrogen peroxide accept electrons during Oxidation can be expressed ionically,

H₂O₂ (l) + 2H⁺(aq) +2e^- → 2H₂O(l)

Here, the electron is donated by the substance oxidised.

A typical equation of reaction of Hydrogen peroxide oxidation-reduction (Red-ox) reaction can be expressed by oxidation of acidified potassium Iodide (KI) solution.

With Potassium Iodide

Here, the acid is Tetraoxosulphate (VI) acid which reacts with the KI to form Iodic acid (HI). Then, the Iodic acid is oxidised to Iodine by the Hydrogen peroxide which is reduced to water.

2KI(aq) + H₂O₂(aq) + H₂SO₄(aq) → K₂SO₄(aq) + 2H₂O(l) + I₂(aq)

The reaction can be expressed Ionically as,

2I^- (aq) + H₂O₂(aq) + 2H⁺(aq) → 2H₂O(l) + I₂(aq)

It is worthwhile to state that Hydrogen peroxide is not an absolute oxidising agent. Its red-ox behaviour depends on the compound it is reacting with. As such, it can also act as a reducing agent in the presence of strong oxidising agents.

Hydrogen peroxide decomposes slowly to Water and Oxygen gas when exposed directly to air.

2H₂O₂(l) → 2H₂O(l) + O₂(g)

The decomposition of Hydrogen peroxide brings in two important perceptions: whether there is a need to generate water and oxygen from hydrogen peroxide, or to protect the integrity of the hydrogen peroxide. This position was effectively thought out in the commercial production of hydrogen peroxide where Propan-1,2,3-triol and mineral acids are used to retard the decomposition.

Certain methods are used to hasten the decomposition if the intention is to obtain the water and Oxygen products. Direct heating or the addition of Alkalis are usually used to hasten the decomposition. Finely divided metallic Catalysts such as Manganese (IV) Oxide, Platinum and Gold are also used to hasten the decomposition.

Here, hydrogen peroxide is oxidised by stronger oxidising agents like Potassium tetraoxomanganate (VII) KMnO₄ Solution, Silver oxide Ag₂O and Chlorine to gaseous Oxygen O₂ .

Hydrogen peroxide as a reducing agent, can either accept Oxygen,

H₂O₂(l) + [O] → H₂O(l) + O₂(g)

Or donate electrons,

H₂O₂(l) → 2H⁺(aq) + O₂(g) + 2e^-

Now, let's consider oxidation with KMnO₄,

With Tetraoxomanganate (VII)

Hydrogen peroxide discharges the colour of acidified potassium tetraoxomanganate (VII) by reducing the purple manganate (VII) Ion to pink Manganese (II) Ion.

2KMnO₄ (aq) + 3H₂SO₄(aq) + 5H₂O₂(aq) → K₂SO₄(aq) + 2MnSO₄(aq) + 8H₂O(l) + 5O₂(g)

This can also be expressed ionically as,

2MnO₄^- (aq) + 6H⁺(aq) + 5H₂O₂(aq) → 2Mn²⁺(aq) + 8H₂O(l) + 5O₂(g)

With Chlorine and Silver Oxide

In the case of Chlorine, the Hydrogen peroxide acts as a reducing agent that reduces chlorine to Hydrochloric acid while it gets oxidised to Oxygen gas.

Cl₂(g) + H₂O₂ (aq) → 2HCl(aq) + O₂(g)

Silver oxide on the other hand, is reduced to metallic silver while liquid water and Oxygen gas are also produced.

Ag₂O(s) + H₂O₂(aq) → 2Ag(s) + H₂O(l) + O₂(g)