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 reactions 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. 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.
It is a reaction in which two or more atoms combine to form a single product.