Define a combination reaction. Give one example of a combination reaction which is also exothermic.
In combination reactions, two or more substances combine to form a new compound. Only one product is obtained in such reactions. The reactants in such reaction can be elements as well as compounds. The general equation used to represent a combination reaction is:
A + Z → AZ
For example; calcium oxide reacts vigorously with water to produce calcium hydroxide
CaO(s) + H2O(l) → Ca(OH)2(aq)
A large amount of heat is also evolved during this process, which increases the temperature of the system. Hence, the combination of calcium oxide and water is exothermic in nature.