Question

What do you understand by molecularity of a reaction?

Answer 1

1. The collision theory states that when molecules of reactants collide with one another, a reaction occurs. The molecularity of a reaction is determined by the number of molecules that collide simultaneously.
2. The number of reacting species (atoms, ions or molecules) which must collide simultaneously in order to bring about a chemical reaction is called the molecularity of the reaction. The molecularity of a reaction is a whole number and may have values 1, 2, 3, etc.
3. The reaction is referred to as a unimolecular reaction because it involves only one molecule of the reactant, meaning that its molecularity is 1.
4. A reaction is referred to as a bimolecular reaction when two molecules of reactants meet to produce a chemical change, and the molecularity of the reaction is assumed to be equal to 2.
5. When three molecules of reactants meet at the same time to produce a chemical change, the reaction is said to be trimolecular or tennolecular if its molecularity is 3.
6. Because it is extremely unlikely that more than three molecules will collide at the same time, reactions with molecularities greater than three are extremely uncommon.