Which of the following statements is correct ?

Options

A. Order of a reactoin is an experimental quantity. It can be zero and even a fraction but molecularity cannot be zero or a non-integer.
B. Order is applicable to elementary as well as complex reactions whereas molecularity is applicable only for elementary reactions. For a complex reaction molecularity has no meaning.
C. For a complex reaction, order is given by the slowest step and generally, molecularity of the slowest step is same as the order of the overall reaction
D. All of these

Answer

D

Explanation

Decomposition of ammonia on a hot tungsten or platinum surface is a zero order reaction. oMolecularity can't be zero or a non-integer because the number of molecules reaction in an elementary step determines the molecularity of a reaction. For a complex reaction, molecularity is meaningless because such a reareaction takes place in two or more elementary steps. The required rate law can be found easily for a mechanism that includes a rate determining step (i.e. the slowest step in the reaction mechanism).