Chem_215_Lect_29_Color

Chem_215_Lect_29_Color - Temperature Dependence of k Rate...

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1 Temperature Dependence of k • Rate constants (k) for many reactions vary with temperature according to the Arrhenius Equation: RT E a Ae k / = RT E A k a = ln ln Plot of ln k vs 1/T is linear. Slope = -E a /R and intercept = ln A E a = Activation Energy A = “A factor” = Pre- exponential factor
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2 Why don’t all exothermic reactions occur immediately? 2BrNO (g) 2NO(g) + Br 2 (g)
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Reaction Mechanism Sequence of elementary (single step) reactions. Elementary Reactions may be: Unimolecular: CH 3 Cl* CH 3 + Cl or Bimolecular: H + Cl 2 HCl + Cl Notes : Exponents in rate law are the stoichiometric coefficients. Elementary processes are reversible, may reach eq’m with equal rates of forward and reverse reactions. Reaction intermediates may be formed and consumed in elementary steps. They cannot appear in the overall chemical equation or in the overall rate law expression. The “rate determining step” occurs much more slowly than
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This note was uploaded on 03/05/2009 for the course CHEM 2150 taught by Professor Chirik,p during the Fall '08 term at Cornell.

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Chem_215_Lect_29_Color - Temperature Dependence of k Rate...

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