It can be zero and
even a fraction but molecularity cannot be zero or a non integer (ii) Order is applicable to elementary as well as complex reactions
whereas molecularity is applicable only for elementary reactions For complex reaction molecularity has no meaning Rationalised 2023-24
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Chemical Kinetics
(iii) For complex reaction, order is given by the slowest step and
molecularity of the slowest step is same as the order of the overall
reaction