Q.11: Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Decomposition reactions are those reactions in which a compound is broken into two or more new compounds.
Combination reactions are those reactions in which two substances are combined to form a new substance.
CaO + CO2 —> CaCO3 + energy
In above examples, both the reactions are same but show opposite directions, so decomposition reaction is called the opposite of combination reaction.