Question

The molecularity of a reaction is:
a.) Is same as its order
b.) Is different from order
c.) May be same or different as compared to order
d.) Is always zero

Answer 1

Hint: To answer the correct option, we should know about the molecularity of a reaction. We should know that molecularity is always a positive whole number and it can't be zero & fractional.


Complete step by step solution:
First of all we should know about molecularity. We should know that the molecularity of a reaction is defined as the number of reacting molecules which collide simultaneously to bring about a chemical reaction. In other words we can say that the molecularity of an elementary reaction is defined as the number of reactant molecules taking part in the reaction. Let us know about elementary reactions. We should know that a chemical reaction that takes place in one and only one step or we can say that all reactions that occur in a single step is called elementary reaction. Let us know about different types of molecularity:
The following reaction is unimolecular:

\[\text{PC}{{\text{l}}_{\text{5}}}~\text{ }\to ~\text{ PC}{{\text{l}}_{\text{3}}}~+\text{ C}{{\text{l}}_{\text{2}}}~\]
The following reaction is bi-molecular gaseous reaction:
\[{{O}_{\text{3}}}\left( g \right)+O\left( g \right)\to \text{2}{{O}_{\text{2}}}\left( g \right)\]
The following reaction is a bimolecular gaseous reaction.
\[\text{2}NO+{{H}_{\text{2}}}\to {{N}_{\text{2}}}+{{H}_{\text{2}}}{{O}_{\text{2}}}\]
Now, we will answer our question. We should note that for an elementary reaction or simple reaction the order and the molecularity will be the same. So, we can say that option C is the correct answer.


Note: We should note that molecularity and order of reaction are identical if the reaction is elementary. They may become different when the reaction is complex and has a mechanism.