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.
Decomposition reaction :
`AB +"Energy" to A+B`
`2H_(2)O (l) overset("Electrolysis")to 2H_(2)(g) +O_(2)(g)`
Combination reaction
`A+B to AB +` Energy
`2CO + O_(2) to 2CO_(2) +` Energy