AdvancedKineticsDynamics - Advanced class Kinetics and...

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Advanced class – Kinetics and Reaction Dynamics Q1. Advanced Physical Chemistry 1998, Q9 Explain each of the following concepts in collision dynamics: i) impact parameter ii) centrifugal barrier iii) total cross section iv) differential cross section. Answer THREE of the following parts: a) Discuss the behaviour of the collision cross section in elastic collisions. How can such cross sections be used to provide detailed information on the intermolecular potential energy function? b) What is meant by the harpoon mechanism of chemical reactions? How can it be used to explain the large reaction cross-section and the product angular distribution? Given that the electron affinity of Br 2 is 246 kJ mol -1 and the ionisation energy of Rb is 403 kJ mol -1 , estimate the reaction cross-section for the Rb + Br 2 reaction. c) The following diagram shows the angle-velocity distribution of KI, produced by the collision of K atoms with CH 3 I. Discuss the appearance of this diagram and comment on the fact that the majority of the energy available appears as product translational energy. How might the influence of the orientation of the CH 3 I molecule on the collision dynamics be investigated? K CM CHI 3 d) How do the shape of the potential energy surface, the position of the barrier to reaction and the masses of the particles involved affect the course of a reaction between an atom and a diatomic molecule? How can measurements of the vibrational, rotational or translations distributions of the product molecules be used to provide information on reaction dynamics? Q2. Advanced Physical Chemistry 1999, Q8 a) Explain what is meant by kinetic isotope effect and how it is related to zero point energy. b) Consider the following gas-phase reactions:
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1. H+D 2 k 1 HD + D 2. D+H 2 k 2 DH + H Estimate the ratio of the rate constants k 2 /k 1 at 300 K using the vibrational wavenumbers given below. Assume that the effect of isotopic substitution is limited to changes in the zero
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AdvancedKineticsDynamics - Advanced class Kinetics and...

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