For a chemical reaction to begin, the reacting molecules must approach and collide. The bonds between the interacting molecules are severed as a result of these collisions, and the product is created with new bonds.
To explain the reaction rates in a gaseous state, Arrhenius presented a simple collision theory. Kinetic molecular theory or reaction rate collision theory is the name given to this theory.
Arrhenius equation is given by rate where A is a pre-exponential factor or orientation factor which tells the orientation of the molecule.
For reaction , the Pre exponential factor is also given by A where P represents the probability factor, ZAB represents collision frequency, Ea represents activation energy, R represents gas constant, and T represents temperature.
Therefore, the collision frequency of the reactants A and B are represented by ZAB.