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Unformatted text preview: 1 Chapter 16 Kinetics: Rates and Mechanisms of Chemical Reactions Kinetics: Rates and Mechanisms of Chemical Reactions 16.1 Factors That Influence Reaction Rates 16.2 Expressing the Reaction Rate 16.3 The Rate Law and Its Components 16.4 Integrated Rate Laws: Concentration Changes over Time 16.7 Reaction Mechanisms: Steps in the Overall Reaction 16.8 Catalysis: Speeding Up a Chemical Reaction 16.5 The Effect of Temperature on Reaction Rate 16.6 Explaining the Effects of Concentration and Temperature Reaction Kinetics: Basic Concepts Need to know if reaction will occur or not (spontaneous) G Need to know how fast a reaction will occur kinetics Factors that affect reaction rates: Collision frequency (concentrations of reactants) Orientation factors (must have correct aligment) Energy of collision must be sufficient to overcome energy barriers to reaction (e.g. bond breaking) Kinetics provide microscopic information on how reactions occur reaction mechanisms = control Review of Previous Lecture Elementary reactions are either unimolecular or bimolecular (ternary 3 body collisions are virtually non-existent) Reaction rate constants relate probability that the molecules have energy in the correct atomic motions (modes) to react Unimolecular decays have constant probability for reaction and therefore follow exponential relaxation processes [A = A exp(-kt)] ln[A] vs. t gives straight line test for first order unimolecular 2 Review of Previous Lecture (cont.) Reaction rates of bimolecular processes slow down as reactants consumed probability of reaction decreases with time as [A] decreases.1/A - 1/A = -kt plot of 1/A gives straight linetest for bimolecular process Overall reactions generally involve many different steps one of which will be Rate Limiting. The rate limiting step can be related to either bimolecular or unimolecular processes. More complex orders for reactions involve intermediate steps that are not clearly determined by one rate limiting step or involve intermediates not connected to overall reaction....
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