(a) Explain the following terms :
(i) Order of a reaction
(ii) Molecularity of a reaction
(b) The rate of a reaction increases four times when the temperature changes from 300 K to 320 K. Calculate the energy of activation of the reaction, assuming that it does not change with temperature. `(R = 8.314 J K^(-1) mol^(-1))`

Explanation

The number of reacting species (atoms, ions or molecules, taking part in an elementary reaction, which must collide simultaneously in order to bring about a chemical reaction is called as molecularity of a reaction.