Question

Explain with suitable example, how the molecularity of a reaction is different from the order of the reaction.

Answer 1

The order is the total of the exponents of the concentration variables in the rate law equation. Molecularity refers to the quantity of reacting entities that must collide simultaneously to start a chemical reaction. To discern between the two, let us consider the reaction.

\[\ce{CH3COOC2H5 + H2O ->[H+] CH3COOH + C2H5OH}\]

If ethyl acetate and water are the two interacting species in this instance, the reaction's molecularity is two. However, as a significant amount of water is added to the process, the concentration of just ethyl acetate changes.

Therefore, rate of reaction = k[CH₃COO₂H₅]

Thus order of reaction is one.