What is the molecularity of each of the following elementary reactions?

A. O+O2+N2----> O3+N2+
B. NO2Cl + Cl---> NO2 + Cl2
C. Cl + H2 ---> HCl + H
D. CS2----> CS + S

To determine the molecularity of a reaction, we need to identify the number of reactant particles involved in the rate-determining step of the reaction. The rate-determining step is the slowest step in a reaction mechanism and often involves the breaking or formation of chemical bonds.

Let's analyze each reaction:

A. O + O2 + N2 ---> O3 + N2

In this reaction, the rate-determining step involves the collision of O atoms with O2 and N2 molecules. As we can see, there is one O atom and two molecules (O2 and N2) involved in this step. Therefore, the molecularity of this reaction is three.

B. NO2Cl + Cl ---> NO2 + Cl2

The rate-determining step in this reaction involves the collision between NO2Cl and Cl molecules. Since there are two reactant particles (NO2Cl and Cl) involved in this step, the molecularity of this reaction is two.

C. Cl + H2 ---> HCl + H

In this reaction, the rate-determining step involves the collision between Cl and H2 molecules. Since there are two reactant particles (Cl and H2) involved in this step, the molecularity of this reaction is two.

D. CS2 ---> CS + S

In this reaction, the rate-determining step involves the decomposition of CS2 into CS and S. Since only one reactant (CS2) is involved in this step, the molecularity of this reaction is one.

In summary:
A. Molecularity = 3
B. Molecularity = 2
C. Molecularity = 2
D. Molecularity = 1