A decomposition reaction is a type of chemical reaction in which a compound breaks down into two or more simpler substances. It is the opposite of a combination reaction, where two or more substances combine to form a more complex compound. In a decomposition reaction, the starting substance is called the reactant, and the resulting substances are called products.
Decomposition reactions can be classified into three categories:
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Thermal decomposition: These reactions are triggered by heat and often require an input of energy. An example is the decomposition of potassium chlorate (KClO3) into potassium chloride (KCl) and oxygen gas (O2) when heated.
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Electrolytic decomposition: These reactions occur in the presence of an electric current and are commonly observed in electrolysis processes. For example, the electrolysis of water (H2O) produces hydrogen gas (H2) and oxygen gas (O2).
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Photolytic decomposition: These reactions are initiated by light. An example is the photolytic decomposition of certain ketenes, where the molecules containing two carbon atoms and an oxygen atom joined by double bonds break down into simpler substances.
Decomposition reactions are essential in various applications, such as:
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Airbags: The decomposition of sodium azide (NaN3) in airbags produces nitrogen gas (N2), which rapidly inflates the airbag and protects the occupants during a collision.
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Thermite welding: The decomposition of metal oxides, such as iron(III) oxide (Fe2O3), in a thermite reaction generates a large amount of heat, which is used for welding.
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Relief from acid indigestion: Antacid tablets contain baking soda (sodium bicarbonate, NaHCO3), which decomposes in the stomach to produce carbon dioxide gas (CO2), water (H2O), and sodium ions (Na+), providing relief from acid indigestion.
