The number of collisions per
second per unit volume of the reaction mixture is known as
collision frequency (Z) Another factor which affects the rate of
chemical reactions is activation energy (as we have already studied) For a bimolecular elementary reaction
A + B   ®   Products
rate of reaction can be expressed as
a /
AB
Rate
Z
e E
RT
−
=
(3 23)
where ZAB represents the collision frequency of reactants, A and B
and e
-Ea /RT represents the fraction of molecules with energies equal to
or greater than Ea