'Molecularity' applies only to elementary reactions However 'order' applies to both elementary as well as complex reactions. Explain.

Explanation

An elementary reaction is a single molecular event in which reactant molecules collide simultaneously to form Product molecules. So, we can determine the number of reacting species or molecularity of an elementary reaction from the balanced chemical equation of the reaction. A complex reaction involves a sequence of elementary steps each of which has its own molecularity. Hence, it is meaningless to talk about the overall molecularity of a reaction. On the other hand, reaction order is purely an experimental quality, which expresses how the reaction-rate affected due to change in concentration of the reactants. So, the term 'order' is equally important for both elementary and complex reactions.