Chemical decomposition

Chemical decomposition or analysis is the separation 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.

There are broadly 3 types of decomposition reactions: thermal,elecrolytic and catalytic.

Reaction formulas

The generalized reaction formula for chemical decomposition is:

AB → A + B

with a specific example being the electrolysis of water to gaseous hydrogen and oxygen:

2H₂O → 2H₂ + O₂

Additional examples

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

Other carbonates will decompose when heated producing the corresponding metal oxide and carbon dioxide. In the following equation M represents a metal:

MCO₃ → MO + CO₂

A specific example of this involving calcium carbonate:

CaCO₃ → CaO + CO₂

Metal chlorates also decompose when heated. A metal chloride and oxygen gas are the products.

MClO₃ → MCl + O₂

A common decomposition of a chlorate to evolve oxygen utilizes potassium chlorate as follows:

2KClO₃ → 2KCl + 3O₂

See also

• Analytical chemistry
• Thermal decomposition

External links

• Biodegradation database

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