A reaction which has an equal no.of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation. the law of conservation of mass states that mass can neither be created nor destroyed. hence,in a chemical reaction,the total mass of reactants should be equal to the total mass of the means that the total no.of atoms of each element should be equal on both sides of a chemical equation.hence,it is for this reason that chemical equation should be balanced