Define the terms:
(i) Activation Energy (ii) Molecularity .
(iii) Rate Constant.

Explanation

(1) Activation Energy : It is the excess energy which must be supplied to the reacting species in addition to energy already possesed by them so that their energy becomes equal to the threshold energy.
(i) Molecularity : It is the total number of reacting species which must collide together to bring about a simple reaction.
(ii) Rate Constant : It is equal to the rate of the reaction when molar concentration of cach reactant is unity