Decomposition Reaction

Question 1 What are decomposition reactions?

Question 2 What happens when ferrous sulphate crystals are decomposed?

Question 3 What is electrolysis?

Question 4 What is photochemical decomposition. Give example?

Decomposition Reaction

Those reactions in which a compound split up into two or more simpler substances are called as decomposition reaction. They are carried out by applying heat, light, electricity.

For Example:

       CaCO₃ (s)           →              CaO (s) + CO₂ (g)
Limestone                 Heat            (Quick lime)

When decomposition reaction is carried out by heating it is called thermal decomposition.

2FeSO_4(s)       →   Fe₂O_3(s)   +  SO_2(g)   +   SO_{3(g)
Ferrous Sulphate                Ferric oxide         Sulphur dioxide      Sulphur trioxide}

 

A smell of burning sulphur is obtained due to the formation of sulphur dioxide gas. When the decomposition is carried out by electricity, it is called electrolysis.

2H₂O(l)                    →                   2H₂(g)        + O₂(g)
  Water              electricity decomposition                 Hydrogen                 Oxygen 

 

2 Al₂O₃ (cryolite) → 4 Al (s) + 3 O₂ (g)

 

When decomposition reaction is carried out by light it is called Photochemical decomposition.

 

        2AgBr(s)           →        2Ag(s) +Br₂(g)
Light Yellow          Sunlight             Grey

 

2AgCl(s)    →       2Ag(s) + Cl₂(g)
White                             Grey

 

         2H₂0₂(l)           →          2H₂0(l) + O₂(g)
Light

 

The digestion of food in our body is an example of decomposition reaction.