Hydrogen Peroxide

HYDROGEN PEROXIDE

Preparation of hydrogen peroxide

(a) Na₂O₂+ dil. H₂SO₄ H₂O₂+ Na₂SO₄

(b) BaO₂+ H₂SO₄ H₂O₂+ BaSO₄↓

(c) 3BaO₂+ 2H₃PO₄ 3H₂O₂+ Ba₃(PO₄)₂↓

(d) BaO₂+ H₂O + CO₂H₂O₂+ BaCO₃

(ii) By electrolysis of Ammonium hydrogen sulphate (NH₄HSO₄) in presence of excess of H₂SO₄

(a) NH₄HSO₄→ NH₄SO^-₄+ H+

at anode

2NH₄SO^-₄ → (NH₄)₂S₂O₈+ 2e−

Ammonium perdisulphate

at cathode:−

2H+ + 2e− → H₂↑

On heating Ammonium perdisulphate in presence of water hydrolysis occurs and H2O2 is produced.

(NH₄)₂S₂O₈+ 2H₂O H₂O₂+ NH₄HSO₄

(iii) Auto oxidation of 2−ethyl or Butyl Anthraquinone

The aqueous product contains 20% H₂O₂.

Physical Properties of hydrogen peroxide

(1) Pale blue colour, diamagnetic, surupy liquid.

(2) Unstable in presence of sunlight.

(3) Have high dielectric constant and therefore its aqueous solution is very good solvent for ionic compounds.

Structure of hydrogen peroxide

1. The structure of hydrogen peroxide (H₂O₂) consists of two hydrogen atoms and two oxygen atoms bonded together.

2. The molecule has a non-planar shape.

Chemical Properties of hydrogen peroxide

It acts as an oxidising as well as reducing agent in both acidic and alkaline media. Simple reactions are described below.

(i) Oxidising action in acidic medium

(ii) Reducing action in acidic medium

(iii) Oxidising action in basic medium

(iv) Reducing action in basic medium

Storage of hydrogen peroxide

H₂O₂decomposes slowly on exposure to light.

In the presence of metal surfaces or traces of alkali (present in glass containers), the above reaction is catalysed. It is, therefore, stored in wax-lined glass or plastic vessels in dark. Urea can be added as a stabiliser. It is kept away from dust because dust can induce explosive decomposition of the compound.