Q.

For a reaction taking place in three steps at same temperature, overall rate constant K=K1K2K3. If Ea1Ea2 and Ea3 are 40, 50 and 60 kJ/mol respectively, the overall Ea is ________ kJ/mol.                [2024]


Ans.

(30)

             k=k1k2k3

            Ae(-EaRT)=A1e(-Ea1RT)A2e(-Ea2RT)A3e(-Ea3RT)  [Arrhenius equation]

             Ae(-EaRT)=A1e(-40RT)A2e(-50RT)A3e(-60RT)

             Ae(-EaRT)=A1A2A3e(-40-50+60RT)

             Ae(-EaRT)=A1A2A3e(-30RT)

            Thus Ea for overall reaction is 30 kJ/mol.