Chemical decomposition or analysis is the fragmentation of a chemical compound into elements or smaller compounds. It is sometimes defined as the opposite of a chemical synthesis. Chemical decomposition is often an undesired chemical reaction. The stability that a chemical compound ordinarily has is eventually limited when exposed to extreme environmental conditions like heat, radiation, humidity or the acidity of a solvent. The details of decomposition processes are generally not well defined, as a molecule may break up into a host of smaller fragments. Chemical decomposition is exploited in several analytical techniques, notably mass spectrometry, traditional gravimetric analysis, and thermogravimetric analysis.
A broader definition of the term decomposition also includes the breakdown of one phase into two or more phases.
The generalized reaction formula for chemical decomposition is:
- AB → A + B
- 2H2O → 2H2 + O2
An example of spontaneous decomposition is that of hydrogen peroxide, which will slowly decompose into water and oxygen:
- 2H2O2 → 2H2O + O2
Carbonates will decompose when heated, a notable exception being that of carbonic acid, H2CO3. Carbonic acid, the "fizz" in sodas, pop cans and other carbonated beverages, will decompose over time (spontaneously) into carbon dioxide and water:
- H2CO3 → H2O + CO2
- MCO3 → MO + CO2
A specific example of this involving calcium carbonate:
- CaCO3 → CaO + CO2
- MClO3 → MCl + O2
A common decomposition of a chlorate to evolve oxygen utilizes potassium chlorate as follows:
- 2 KClO3 → 2 KCl + 3 O2HOT
- ↑ International Union of Pure and Applied Chemistry. "decomposition". Compendium of Chemical Terminology Internet edition.
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