Molecularity is considered as theoretical concept

But molecularity of complex reaction is know by slowest step for which we have to know the mechanism which is experimentally determined.Then why you cannot consider molecularity as experimentally determined

concept

DEAR STUDENT,
DETERMINING RATE OF REACTION BASED ON MOLECULARITY IS A HYPOTHESIS, SINCE THE MOST PRECISE VALUE WAS OBTAINED ONLY WHEN SCIENTISTS TOOK MOLECULARITY OF THE RATE DETERMINING STEP IN CONSIDERATION.
AND NOT THE COMPLETE REACTION’s MOLECULARITY.

EVEN WHEN THE MOLECULARITY OF SLOWEST STEP IS CONSIDERED THE RATE OF REACTION IS NOT EXACTLY ACCURATE, BUT A VALUE VERY CLOSE TO IT.