Kinetics Questions - CHEM 2PD3 ASSIGNMENT DUE 5 APRIL 2010...

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CHEM 2PD3 ASSIGNMENT DUE: 5 APRIL, 2010 QUESTION 1 “Mechanisms governing the kinetics of a reaction in a homogeneous system differ from those governing the kinetics of a reaction in a heterogeneous system.” Is this statement correct? Justify your answer, including in the case of heterogeneous systems, differences between gaseous and liquid reactants. QUESTION 2 The unimolecular decomposition of A after it adsorbs onto a vacant site S on a surface. Write the three elementary steps of this decomposition, using the rate constants k 1 , k -1 and k 2 . Write the expression for the rate of the decomposition reaction. (C AS is the concentration of adsorbed species/m 2 , C s is the total concentration of active surface sites, θ is the fraction of surface sites occupied by A and C S is the concentration of vacant sites). Using the steady-state assumption, show that the rate of the reaction can also be written as: 2 1 1 1 2 k k c k c c k k A A s + + = ν [1] QUESTION 3 In the limiting case of [1], where the rate of decomposition is very small compared to the rate of adsorption and desorption, Show how θ can be written as the Langmuir isotherm (i.e. express θ in terms of the equilibrium constant of adsorption K). How does the rate of the reaction in this limiting case compare to [1]? Include an expression for the rate of the
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This note was uploaded on 03/26/2012 for the course CHEM CHEM 2PD3 taught by Professor K during the Winter '12 term at McMaster University.

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Kinetics Questions - CHEM 2PD3 ASSIGNMENT DUE 5 APRIL 2010...

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