Why are decomposition reactions called the opposite of combination reactions ? Write equations for these reactions.

Explanation

Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy. For examples : Decomposition reaction-
`CaCO_(3)(s) overset("heat") to CaO(s)+CO_(2)(g)`
Combination reaction-
`CaO(s)+H_(2)O(I) to Ca(OH)_(2)(aq)`