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The decomposition of ozone (03) in the atmosphere into oxygen is given by the following reaction: 203 (9) ► 302 (g) The proposed mechanism consists of two elementary reactions as follows: 03 = 02 +0 (2) 0 + 03 → 202 The forward and backward rate constants for elementary reaction (1) are ki and kí, respectively. The rate constant for elementary reaction (2) is k. (1) (a) Briefly explain the concepts of quasi-steady state approximation (QSSA), pre-equilibrium, and the rate determining step (RDS). Do QSSA and pre-equilibrium assumptions refer to the RDS? (4 marks) (b) Derive the following expression for the rate of reaction as a function of the rate constants and concentrations of oxygen and ozone. You may apply the steady-state approximation. d[03] 2kk2[03] dt k [02] + kz [03] (8 marks) (c) Under what conditions will the overall reaction exhibit kinetics that are (i) first order with respect to [03] (ii) second order with respect to [03] Discuss in terms of pre-equilibrium and specify the RDS for (i) and (ii). (4 marks) (d) Assuming that the overall reaction rate is 2nd order with respect to [03], find the rate constant of the reaction if the pressure of the reactant 03 drops by a factor of four in 2 x 104 s. The reaction is conducted in a closed reactor. The initial pressure of Oz is 103 kPa, and temperature is 200 K. (4 marks) PAGE 11 OF 12 SEE NEXT PAGE