Q.Define collision frequency and effective collisions on the basis of collision theory.

Collision theory explains reaction rate in terms of how often molecules collide (collision frequency) and how many of those collisions actually result in a reaction (effective collisions).

Collision frequency (Z): the number of collisions taking place per second per unit volume of the reaction mixture between the reactant molecules. It depends on the concentration of reactants and their average speed (temperature).

Effective collisions: not every collision between reactant molecules results in the formation of products. Only those collisions in which (i) the colliding molecules possess energy equal to or greater than the threshold energy (i.e., sufficient energy to cross the energy barrier, supplying the activation energy), AND (ii) the molecules are oriented favourably (proper orientation so that the reacting parts of the molecules can interact) at the moment of collision, lead to the formation of products. Such collisions ar …