Question

Explain why the reactions having molecularity greater than 2 are rare.

Answer 1

Reactions having molecularity greater than 2 are rare because:

• Molecularity refers to the number of reacting species (atoms, ions, or molecules) that collide simultaneously in a single elementary step to bring about a reaction.
• When more than two particles are required to collide at the same time, the probability of such a collision happening with proper orientation and sufficient energy is extremely low.
• The chances that three or more molecules will collide at the same place, at the same time, and with the correct orientation and enough energy are very rare in practice.

Hence, elementary reactions with molecularity 3 or more are seldom observed, and most complex reactions occur via multiple simpler steps, each with molecularity 1 or 2.