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GIVE 5 EXAMPLES ON DECOMPOSITION REACTION.
Decomposition Reactions
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When a compound undergoes a decomposition reaction, usually when heated, it breaks down into its component elements or simpler compounds. The products of a decomposition reaction are determined largely by the identity of the anion in the compound. The ammonium ion also has characteristic decomposition reactions.

A few binary compounds decompose to their constituent elements upon heating. This is an oxidation-reduction reaction since the elements undergo a change in oxidation number. For example, the oxides and halides of noble metals (primarily Au, Pt, and Hg) decompose when heated. When red solid mercury(II) oxide is heated, it decomposes to liquid metallic mercury and oxygen gas:
2HgO (s) --->?? 2Hg (l) + O2 (g)

Some nonmetal oxides, such as the halogen oxides, also decompose upon heating:
2Cl2O5 (g) ---->?? 2Cl2 (g) + 5O2 (g)

Other nonmetal oxides, such as di-nitrogen pent-oxide, decompose to an element and a compound:
2N2O5 (g) --->?? O2 (g) + 4NO2 (g) .

Many metal salts containing oxo-anions decompose upon heating. These salts either give off oxygen gas, forming a metal salt with a different nonmetal anion, or they give off a nonmetal oxide, forming a metal oxide. For example, metal nitrates containing Group 1A or 2A metals or aluminum decompose to metal nitrites and oxygen gas:

Mg(NO3)2 (s) --->?? Mg(NO2)2 (s) + O2 (g) .
2SO3 (g) --->?? 2SO2 (g) + O2 (g) .


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