Question

Explain the molecularity of reaction with example.

Hint:

Molecularity is different from the order of reaction; molecularity is applicable to elementary reactions, while the order of reaction is a broader concept.

Answer 1

Step 1: Define Molecularity
Molecularity refers to the number of reactant molecules involved in an elementary reaction step. It is the number of particles (atoms, molecules, or ions) that collide to produce a reaction.
Step 2: Types of Molecularity
- **Unimolecular**: A reaction involving the collision of a single molecule, e.g., the decomposition of N₂O₅: \[ \text{N}_2\text{O}_5 \rightarrow 2\text{NO}_2 + \text{O}_2 \] - **Bimolecular**: A reaction involving the collision of two molecules, e.g., the reaction between hydrogen and iodine: \[ \text{H}_2 + \text{I}_2 \rightarrow 2\text{HI} \] - **Trimolecular**: A reaction involving the collision of three molecules, e.g., a reaction between two nitrogen dioxide molecules and one oxygen molecule: \[ 2\text{NO}_2 + \text{O}_2 \rightarrow 2\text{NO}_2 \] Final Answer: Molecularity refers to the number of molecules or ions involved in an elementary reaction. Correct Answer: The number of molecules or ions involved in an elementary reaction.