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Hydrogen PerOxide

Hydrogen peroxide (H2O2) can be prepared in the laboratory by treating sodium peroxide or barium peroxide with dilute sulphuric acid at 273 K.
Na2O2 + H2SO4 Na2SO4 + H2O2
BaO2 + H2SO4 BaSO4 + H2O2

On a commercial scale, it is obtained by electrolysis of dilute sulphuric acid subsequent distillation of the product (perdisulphuric acid) under reduced pressure.

It may also be manufactured by catalytically reducing 2-ethyl (or butyl) anthraquinone to corresponding quinol and oxidizing the latter with oxygen. The quinone is regenerated and the hydrogen peroxide formed is extracted with water to obtain its 20% solution.

Physical Properties and Structure
Pure hydrogen peroxide is a very pale blue viscous liquid (density at 298 K, 1.44 g cm-3) which freezes at 272.1 K and boils at 423.2 K (with decomposition) It is more hydrogen bonded than water and the two liquids are freely miscible with each other.

Structurally, hydrogen peroxide is represented by the dihydroxyl formula as shown in the below figure in which two O-H groups do not lie in the same plane. In the crystalline phase of the molecule, the dihedral angle reduces from 111.5o to 90.2 o due to hydrogen bonding, and the O-O-H angle expands from 94.8 o to 101.9 o .

Nonplanar Dihydroxyl Structure of Hydrogen Peroxide in (a) Gaseous Phase and (b) Crystalline Solid Phase

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