A decomposition reaction can be defined as a chemical reaction in which one reactant breaks down into two or more products.
General representation of the reaction
The general format of a decomposition reaction is provided below.
AB ———> A + B
Where AB is the parent molecule (reactant) and A and B are the product molecules.
H2CO3 → H2O + CO2
Types of decomposition reaction
The three primary types of decomposition reactions are:
Thermal decomposition reaction
A thermal decomposition reaction can be defined as a decomposition reaction which is activated by thermal energy. In simpler words, a thermal decomposition reaction needs energy to be supplied to the reactants in the form of heat. These reactions are generally endothermic since energy is required to break the chemical bonds and separate the constituent elements
An example of a thermal decomposition reaction is provided below.
CaCO3 → CaO + CO2
When heated, calcium carbonate decomposes into calcium oxide and carbon dioxide. This process is employed in the manufacturing of quick lime, which is an important substance in many industries.
Electrolytic decomposition reaction
An electrolytic decomposition reaction is a type of decomposition reaction in which the activation energy for decomposition is provided in the form of electrical energy. An example of an electrolytic decomposition reaction is the electrolysis of water, which can be represented by the given chemical equation:
2H2O→ 2H2 + O2
Photo decomposition/ photolytic decomposition/ photochemical decomposition
A photodecomposition reaction is a type of decomposition reaction in which the reactant is broken down to its constituents by absorbing energy from photons. An example of a photo decomposition reaction is the decomposition into dioxygen and an oxygen radical, as represented by the chemical equation provided below.
O3 + hν → O2 + O.