Hydrogen Peroxide (H2O2)

H₂O₂ was discovered by J.L. Thenard in 1818. It is an important compound used in pollution control treatment of domestic and industrial effluents.

Preparation of Hydrogen Peroxide:

From Barium peroxide

By electrolysis of 50% H₂SO₄

Electrolysis of a cold 50% solution of H₂SO₄ at high current density in an electrolytic cell using pe as anode and graphite as cathode.

At Cathode:

At Anode:

peroxodisulphuric acid formed around anode is withdrawn and then distilled with water under reduced pressure.

Physical Properties of Hydrogen Peroxide

Structure of Hydrogen Peroxide

Hydrogen peroxide has a non-planar structure. The molecular dimensions in the gas phase and solid phase are shown in fig.

Storage of Hydrogen Peroxide (H₂O₂)

It is stored in the presence of traces of alcohol, acetanilide or sodium pyrophosphate which slow down the rate of decomposition of hydrogen peroxide.

Chemical Properties of H₂O₂

Acidic nature of H₂O₂:

It is weakly acidic in nature and pure hydrogen peroxide turns blue litmus red.

H₂O_{2 as} Oxidising agent:

It acts as a strong oxidising agent in acidic as well as in basic medium.

H₂O_{2 as} Reducing agent:

• In acidic medium

• In basic medium

Bleaching properties:

Its bleaching action is due to oxidation by atomic oxygen and permanent.

dye + [O] dye is oxidized and bleached

Uses of H₂O₂:

• It is used as a mild disinfectant. It is marketed as perhydrol (an Antiseptic).
• It is used in the manufacture of high quality detergents.
• It is used in the synthesis of hydroquinone tartaric acid and certain food products and pharmaceuticals.
• It is used as bleaching agent for textiles, paper pulp etc.
• It is used for pollution control treatment of domestic and industrial effluents.
• 93% H₂0₂ is used as an oxidant for rocket fuel.