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Hydrogen Peroxide

Structural Formula of Hydrogen Peroxide

Hydrogen peroxide molecule has molecular formula H2O2 having an interesting gouache structural unit uses widely in industrial solutions and antiseptic in medicine. Due to oxidizing properties of pure hydrogen peroxide, the chemical solution uses as bleaching products and liquid hydrogen peroxide widely uses in textiles, paper, pump, lather, and oil industry in our everyday life. Hydrogen peroxide mainly prepared by the electrolysis of concentrated sulfuric acid by vacuum distillation. In hydrogen peroxide structure, two O-H planes lie perpendicular to each other. But the solid structural formula is slightly modified by intermolecular hydrogen bonding.

Structure, uses, and formula of hydrogen peroxide, H2O2

The valence shell electronic configuration of oxygen shows that pz-orbitals oxygen conation a single electron in each orbital. Therefore, oxygen forms O-O linkages by using the pz-orbitals of the two oxygen atom. The two oxygen atoms form another covalent bonding with the hydrogen atom.

Preparation of Hydrogen Peroxide

H2O2 may be prepared in the laboratory by reacting dilute sulfuric acid with crystalline barium peroxide.

BaO + H2SO4 → BaSO4 + H2O2

Hydrogen Peroxide by Electrolysis

Hydrogen peroxide makes by electrolysis of 50% sulfuric acid followed by careful vacuum distillation. In this process, H2S2O8 acid first formed by anodic oxidation which hydrolyzed to form H2SO5 and then to H2O2.

At anode
H2SO4 → H+ + HSO4
2HSO4 → H2S2O8 + 2e
At cathode
2H+ + 2e → H2
Hydrolysis
H2S2O8 + H2O → H2SO5 + H2SO4
H2SO5 + H2O → H2O2 + H2SO4

Physical Properties

Pure hydrogen peroxide molecule is an extremely plate blue liquid, m.p -0.43°C, and b.p 150°C. The heat of formation of liquid H2O2 = -187 kJ mol-1. Therefore, the properties of hydrogen peroxide are unstable due to thermodynamics decomposition.

H2O2 (l) → H2O (l) + [O]

However, at the ordinary temperature, the decomposition is very slow but rapidly at a high temp. Thus H2O2 kept preferably in polythene containers which stabilize like urea or phosphoric acid.

Chemical Properties

The chemical solution of hydrogen peroxide behaves like a weak dibasic acid but the pH level is lower than water with oxidizing and reducing properties.

H2O2 → H+ + HO2 pKa (200C) = 11.75

Therefore, it behaves as a strong oxidant in both acid and bases solution. The potentials for the redox reactions

H2O2 + 2H+ + 2e → 2H2O (1.77 volt)
HO2 +H2O + 2e → 3OH (087 volt)

Due to high ionization properties, an acid solution of peroxides easily oxidizes iron (II) to iron(III), bromide to bromine, iodide to iodine.

2Fe+2 + H2O2 +2H+ → 2Fe+3 + 2H2O
2I + H2O2 + 2H+ → I2 + 2H2O

In the presence of very strong oxidizing agents such as chlorine or permanganate or dichromate in acid solution, H2O2 oxidizes to form oxygen. In other situations, H2O2 acts as a reducing agent.

Cl2 + H2O2 → 2HCl + O2

Uses of Hydrogen Peroxide Solution

Industrial peroxide is widely uses in medicine and bleaching agent in our everyday life.

  1. About 30% of peroxide used as a bleaching agent for textiles, paper, pump, later, oils, etc.
  2. A large quantity of about 33% uses in the manufacture of borax, epoxides, propylene oxide, and other chemicals.
  3. Hydrogen peroxide uses as a mild antiseptic to prevent the small cut, scapes, and buns on the skin. It may also use as a mouth rinse in medicine to the freshness of mouth.
  4. In environmental science, peroxides use in pollution control for the treatment of sewage cleanup and wastes.