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Decomposition Reaction - Definition, Classification, Double Decomposition Reaction, Examples and Uses

Decomposition Reaction

A decomposition reaction is a chemical reaction in which one reactant breaks two from two or more products. It is the converse of a combination reaction. For example, in a displacement reaction, the atom is replaced by an atom of another element. The chemical reaction will be shown by a chemical equation. It represents the change from reactants to products. The left-hand side represents the reactant side and the right-hand side represents the product of the reaction. There are many parenthetical notes for each compound like for solid (S), liquid (l), gas(g), aqueous (aq).
The form of chemical reaction be like
A (aq) + B(g) = C(s) + D(aq)

In our day-to-day chemistry lab, the decomposition reaction takes place. The food is broken down to form water, CO2, and heat. Food like protein, fats, and carbohydrates will break down into simple units. The decomposition of hydrogen peroxide into oxygen and hydrogen gas is also done by this process -
H2 O2 —> H2 + O2

Classification of Decomposition Reaction

Decomposition Reaction

Decomposition reactions are of three types -
Thermolysis - Thermolysis is decomposition due to heat.
Electrolysis - Electrolysis is decomposition due to electricity.
Photolysis - Photolysis is decomposition due to light.

1) Thermal Decomposition Reaction
Chemical reaction where one substance breaks into two or more substances during the heat. This heat is required to break the bond which is present between the substances. The reaction is endothermic.
Calcium Carbonate Decomposition Reaction
Limestone or calcium decomposes into calcium oxide or quicklime and CO2 during the heat.
CaCO3 (s) —heat—> CaO(s) + CO2
Potassium Chlorate Decomposition Reaction
Potassium Chlorate decomposes into potassium chloride and O2 during heating. The reaction is used for the preparation of oxygen.
The Decomposition is done In the presence of manganese dioxide as a catalyst.
2KClO3(s) —> 2KClO(s) + 3O2 (g)
Hydrated Oxalic Acid Decomposition Reaction The decomposition of hydrated Oxalic Acid into oxalic Acid and water takes place when heated.
H2C2O4.2H2O —heat—> H2C2O4 + 2H2O

2) Electrolytic Decomposition Reaction
In this reaction, an electric current is passed through the aqueous solution of a compound. E.g., electrolysis of water.
2H2O (l) —> 2H2 (g) + O2 (g)
Sodium Chloride Decomposition Reaction
When electricity is passed through molten sodium chloride, it gets converted into sodium and chlorine.
2NaCl —> 2Na + Cl2

3) Photo Decomposition Reaction
This reaction is done in the presence of sunlight.
Silver Chloride Decomposition Reaction
When a small amount of AgCl is placed into a watch glass, the crystal changes to a grey color. The decomposition of Silver chloride into silver takes place.
2AgCl(s) —> 2Ag(s) + Cl2 (g)
Some examples of Decomposition reactions are -
The Carbonates get decomposed into metal oxide and carbon dioxide after heating.
CaCO3 (s) —> CaO (s) + CO2 (g) Na2CO3(s) —> Na2O (s) +CO2 (g)

Double Decomposition Reaction

The reaction in which one part of a compound changes to form two new compounds. The positive ion is exchanged with another positive ion of the compound this is known as a double replacement reaction.

Uses of Decomposition Reaction

  • It is used for metal extraction.
  • It helps in the formation of cement.
  • It helps to get relief from indigestion.
  • It is used to decompose silver chloride in silver.
  • It is also used for thermite welding.
  • Reactions involving light, heat, and electricity help to break the bonds of a compound.
  • The fizz in a soda bottle is due to a decomposition reaction.
  • It is used in the formation of quicklime.

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