Question

4. Suppose that a reaction R → P proceeded according to the energy diagram shown. a. [4 pts] A catalyst lowers the activation barrier of a reaction from 125 kJ/mol to 55 kJ/mol. Write out a reaction mechanism for the catalyzed reaction. b. [6 pts] Sketch what the catalyzed reaction pathway would look like on an energy diagram. All relative heights should make sense for catalyzed pathways for full credit. c. [6 pts] By what factor would you expect the reaction rate to increase at 25 °C, assuming that the frequency factors for the catalyzed and uncatalyzed reactions are the same? Exn progress

Answer 1

A . a) The reaction mechanism for catalysed reaction we can write as a Ŕ te ä .RC .(c is the catalyst) Re p te (RC is a reactant-catalyst complex) 6) In case of catalysed reaction, there is formation of reactant - Catayst. complex as an intermediate which at has comparatively lower :

energy than the trasition state of uncatalysed reaction to this Theiss, the catalyst lowers reaction activation energy and the energy diagram looks like -

- uncatalysed rxh. I ...... Catalysed 86 uca 125kJlnis ole 2.55 kJ/mol. reno progress at Acc ...to Arrhenius equation. the rate constant of a reaction k. A é balry - Ea= Activation energy i fos corresponds to energy Gramer . A 2 pre exponential factor, - . for Eatalysed uncatalysed reaction. The 2 42-(125x109 I. nusī' /R72

- For catalysad reaction, The e Àe é (SJK (035-noi(Rt.) According to the se question , Aue a dei The rate will rea increase by ä tieten .-(558103 J.most /RT) kauc - e-1125x103 9. na' /RT) 1. : ke a e

- ke exp{- 56 xlo? simer ex. PT 8.314.5.x. not x 2984 ť 125*103 of not (T = 28% 2 98k) : 8.314 5x mort x 2984 1. * the **.(-22.20 4.50-45) 1:2) det er 22825 iske 1186 X1012 : increase .. The rate of the reaction factor 1.8.6 x 1.012