Question

Define molecularity of a reaction?

Answer 1

Molecularity of a reaction:

• The molecularity of a reaction is defined as the number of reacting molecules that collide simultaneously to bring about a chemical reaction.
• In other words, the molecularity of an elementary reaction is defined as the number of reactant molecules taking part in the reaction.
• The Molecularity of a reaction is a theoretical concept.
• The Molecularity of a reaction can never be zero.

For example, consider the reaction :

$\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Iodine}\mathrm{gas}}{{\mathrm{I}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Hydrogen}\mathrm{Iodide}}{2\mathrm{HI}\left(\mathrm{g}\right)}$

The molecularity of this reaction is 2 because there are two reactant molecules in this reaction.