Structural Formula of Hydrogen Peroxide
Hydrogen peroxide has molecular formula H2O2 having an interesting gouache structural molecule and uses widely in industrial solutions and antiseptic in medicine. Due to oxidizing properties of pure hydrogen peroxide (H2O2), 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 H2SO4 by vacuum distillation.
In hydrogen peroxide (H2O2) structure, two O-H planes lie perpendicular to each other. But the solid structural formula is slightly modified by intermolecular hydrogen bonding.
The valence shell electron configuration of oxygen
Thus oxygen form O-O linkages by using the PZ orbitals of the two oxygen atom.
Preparation of Hydrogen Peroxide
H2O2 may be prepared in the laboratory by reacting dilute H2SO4 with crystalline barium peroxide.
BaO + H2SO4 → BaSO4 + H2O2
Hydrogen Peroxide by Electrolysis
Hydrogen peroxide makes by electrolysis of 50% H2SO4 followed by careful vacuum distillation. In this process, H2S2O8 acid first formed by anodic oxidation which hydrolyzed to form H2SO5 and then to H2O2.
H2SO4 → H+ + HSO4–
2HSO4– → H2S2O8 + 2e
2H+ + 2e → H2
H2S2O8 + H2O → H2SO5 + H2SO4
H2SO5 + H2O → H2O2 + H2SO4
Physical Properties of H2O2
Pure hydrogen peroxide molecule is an extremely plate blue liquid, m.p -0.430C and b.p 1500C. The heat of formation of liquid H2O2 = -187 kJ mol-1 but it is thermodynamically unstable due to decomposition.
H2O2 (l) → H2O (l) + [O]
However, at the ordinary temperature, the decomposition is very slow but rapidly at a high temp. Thus it kept preferably in polythene containers which stabilize like urea or phosphoric acid.
Chemical Properties of H2O2
The chemical solution of hydrogen peroxide (H2O2) behaves like a weak dibasic acid but slightly stronger acid 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 base solution. The potentials for the redox reaction
H2O2 + 2H+ + 2e → 2H2O E0 = 1.77 volt
HO2– +H2O + 2e → 3OH– E0 = 087 volt
The high potential shows that in an acid solution of H2O2 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, it oxidizes to form oxygen. In other words, it acts as a reducing agent.
Cl2 + H2O2 → 2HCl + O2
Uses of Hydrogen Peroxide Solution
Industrial uses of Hydrogen peroxide as a medicine or a bleaching agent in our everyday life.
- About 30% of peroxide used as a bleaching agent for textiles, paper, pump, later, oils, etc.
- A large quantity of about 33% uses in the manufacture of borax, epoxides, propylene oxide, and other chemicals.
- Hydrogen peroxide used in 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.
- In environmental science, its use in pollution control for the treatment of sewage cleanup and wastes.