NEET Chemistry Chemical Kinetics Questions Solved


(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 )

(a) (i)  Order of a reaction : It is the sum of powers of the molar concentrations of reacting species in the rate equation of the reaction.

(ii) Molecularity of a reaction:

 1. It is the total number of reacting species (molecules, atoms or ions) which bring the chemical change.

 2. It is always a whole number.

 3. It is theoritical concept.

 4. It is meaningful only for simple reactions or individual steps of a  complex reaction. It is meaningless for overall complex reaction.

(b) Given : T1= 300K       T2= 320 K

                K1 =K (Consider)

                K2= 4K           R= 8.314    Ea= ?

Substituting these values in the formulae,

          log k2k1=Ea2.303RT2-T1T1T2

        log4KK =Ea2.303×8.314320-300320×300


   or  log 4 =Ea19.1471×2096000

   or  0.6020 =Ea19.1471×2096000

   or  Ea0.6020×19.1471×9600020= 55327.46

 Energy of activation, Ea = 55327.46

                                        =55.3 K J mol-1

Difficulty Level: