Chemical decomposition

Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. It is sometimes defined as the exact 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.^[1]

There are three broad types of decomposition reactions: thermal, electrolytic and catalytic.^{[citation needed]}

Reaction formula

The generalized reaction for chemical decomposition is:

AB → A + B

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

2H₂O(I) → 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.

2MClO₃ → 2MCl + 3O₂

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

2KClO₃ → 2KCl + 3O₂

Many metal carbonates decompose to form metal oxides and carbon dioxide when heated.

See also

• Analytical chemistry
• Thermal decomposition

References

1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "decomposition".

External links

• Biodegradation database