Why molecularity is applicable only for elementary reactions and order is applicable for elementary as well as complex reactions?

Answer

N/a

Explanation

 A complex reactlon occurs through a number cf steps i.e, elementary reactions. Number of molecules irvclved in each elernentary reaction may be different,i.e, the molecularity of each step may be different. Therefore, It Is meaningless to talk of molecularity of the overall complex reaction.
On the other hand, orcer of ccmplex reaction depends upon the molecularity of the slowest step, Hence, it is not meaningless to talk of the crder of a complex reaction.