Fraction of effective collisions (f) is given by the following expression
\(f = e^{-E_a/RT}\)
To understand the magnitude of collision factor (f), Let us calculate the collision factor (f ) for a reaction having an activation energy of 100 kJ mol-1 at 300K.
Thus, out of 1018 collisions, only four collisions are sufficiently energetic to convert reactants to products.