1. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 1 Generalised Expectations A + B C + D Chemical kinetics is interested in knowing 1.How fast A and B are disappearing to produce C and D 2.The mechanism by which A and B are disappearing 3.The mechanism by which C and D are appearing

2. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 2 Reaction Rates The aim is to establish this plot. Depending on the “velocity” of the reaction, different techniques have to be employed.

3. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 3 First-Order Kinetics In a) raw concentration data is plotted vs. time for a first-order reaction for various k values. In b) The slope is –k.

4. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 4 Integrated Rate Laws

5. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 5 Approach to Equilibrium for A  B

6. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 6 Arrhenius Parameters from Plot of ln k vs 1/T

7. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 7 Activation Energy

8. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 8 Effect of a Catalyst on the Activation Energy

9. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 9 Consecutive Elementary Reactions (A) Decays according to first order kinetics. The intermediate (I) starts to build up as soon as (A) starts to decay. Concentration of (I) increases at the initial stages of the reaction, but later starts to decrease as (P) formation starts. Concentration of (P) is always on the increase.

10. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 10 Basis for QSSA

11. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 11 Comparison of Exact and QSSA Treatment Exact SS and QSSA treatment of data gives two nearly-coinciding curves. The error is within permissible limits. Curve for A does not change.

12. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 12 Rate Determining Step

13. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 13 The Lindemann-Hinshelwood Mechanism

14. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 14 Absorption of Radiation When a suitable material is irradiated with some radiation, it forms an exited state. Depending on conditions, the excited species can follow any of the two paths. It may decay back to the original state, or it may give rise to some other product(s).

15. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 15 Some Photophysical Processes

16. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 16 Enzymes – Active Site Models

17. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 17 Rate of Enzyme-Catalysed Reaction

18. Chemical Kinetics Physical Chemistry CHM 351Dr Erdal OnurhanSlide 18 A Lineweaver-Burk Plot