What is molecularity?

Molecularity refers to the number of molecules that participate in a particular elementary reaction step. It is an important concept in the study of chemical kinetics, as it helps determine the rate of a chemical reaction.

There are three types of molecularity: unimolecular, bimolecular, and termolecular.

• Unimolecular reactions involve the collision of a single molecule and are characterized by first-order rate laws.
• Bimolecular reactions involve the collision of two molecules and are characterized by second-order rate laws.
• Termolecular reactions involve the collision of three molecules and are relatively rare due to the low probability of three molecules colliding simultaneously in the correct orientation. Termolecular reactions are characterized by third-order rate laws.

The molecularity of a reaction can be determined by examining the rate law for the reaction. The rate law is a mathematical expression that relates the rate of the reaction to the concentration of the reactants, and the order of the rate law is equal to the overall molecularity of the reaction.

Overall, molecularity is an important concept in understanding the mechanisms and rates of chemical reactions. By determining the molecularity of a reaction, chemists can better understand and predict the behavior of chemical systems.