Decomposition
Definition and meaning of Decomposition in chemistry.
Decomposition is a chemical reaction in which a single compound breaks down into two or more simpler substances, which may be elements or simpler compounds.
In more detail
Decomposition reactions are the reverse of synthesis (combination) reactions and generally require an input of energy, usually heat, light, or electricity, to break the bonds holding the reactant together. Depending on the energy source, chemists distinguish thermal decomposition (thermolysis), light-driven decomposition (photolysis), and electrically driven decomposition (electrolysis). These reactions are important industrially (e.g., producing lime from limestone) and biologically (e.g., breakdown of hydrogen peroxide by catalase), and they follow the general pattern AB → A + B.
Key facts
| Field | General Chemistry |
|---|---|
| General form | AB → A + B |
| Common triggers | heat, light, or electric current |
| Example reaction | CaCO3 → CaO + CO2 |
Heating calcium carbonate drives off carbon dioxide gas and leaves solid calcium oxide (quicklime): CaCO3(s) → CaO(s) + CO2(g). This thermal decomposition is the basis of industrial lime production in cement kilns.
Frequently asked questions
How is decomposition different from combustion?
Combustion is a specific type of reaction where a substance reacts rapidly with oxygen to release heat and light, whereas decomposition simply breaks one compound into simpler products and does not require oxygen. Some combustion reactions do produce decomposition-like products, but the defining feature of decomposition is a single reactant splitting apart.
Is decomposition endothermic or exothermic?
Most decomposition reactions are endothermic because energy must be supplied to break the bonds in the reactant compound, though a few, like the decomposition of some unstable peroxides or explosives, release energy.