Hydrogen and S-Block Element: Compounds of Hydrogen and Hydrogen Peroxide (For CBSE, ICSE, IAS, NET, NRA 2022)

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Compounds of Hydrogen


  • This oxide of hydrogen is essential to all life.
  • It occurs in the form of snow, water in rivers, lakes, sea etc. and as vapour in the atmosphere.
  • Water is covalent compound made up of two hydrogen atoms linked with one oxygen atom through covalent bond.
  • Lewis structure and molecular structure of water are shown below.
Oxide of Hydrogen
  • Water molecule is highly polar because of higher electro-negativity of Oxygen.
  • The remarkable characteristic of water is in solid form, it is less dense than liquid form and leads to an ice cube floats on water.
  • In Solid form, Water molecules are together in an extensive three-dimensional network in which oxygen atom is bonded to four hydrogen atoms, two by hydrogen bonds and two by normal covalent bonds, in a near tetrahedral hydrogen bonded structure (Fig) Which has got an open space. This is responsible for its low density.
Oxide of Hydrogen

Heavy Water

  • Water containing deuterium in place of ordinary hydrogen (protium) is termed as heavy water .
  • Heavy water is separated from water by electrolysis.
  • The equilibrium constant for the dissociation of water containing protium is very high as compared to water containing deuterium .

  • If water is electrolyzed, is liberated much faster than because bonds are broken more rapidly than bonds and the remaining water becomes enriched in heavy water .
  • To obtain one litter of , we have to electrolyze about 30000 litters of ordinary water.

Uses of Heavy Water

  • Heavy water is used as a moderator in nuclear reactors.
  • It is used in the study of mechanism of chemical reactions involving hydrogen.
  • It is used as the starting material for the preparation of a number of deuterium compounds, for example:

Hydrogen Peroxide

Chemical formula for Hydrogen peroxide is .

Method of Preparation of Hydrogen Peroxide

By the action of dilute mineral acids on metallic peroxides (barium peroxide, sodium peroxide)

By the electrolysis of followed by distillation

At cathode:

At anode:

The anodic solution which contains per sulphate ions is distilled sulphuric acid at reduced pressure yielding :

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