Principles of Chemistry II © Vanden BoutTodayReviewing Rate LawsArrhenius TheoryTemperature dependence of rate constantsKinetic Theory of ReactionsWhy is there a barrier?Principles of Chemistry II © Vanden Boutrate∆[C]c∆t-∆[A]a∆t===k[A]x[B]ydifferential rate lawrate lawrate expressionrate is changing with time and concentrationthe rate constant is constantPrinciples of Chemistry II © Vanden BoutRate ExpressionIndependent of Initial AmountPrinciples of Chemistry II © Vanden BoutWhat is the reaction order for the following reaction?" A." " zeroth" B." " first" C." " second"Principles of Chemistry II © Vanden BoutWhat is the reaction order for the following reaction?" A." " zeroth order" B." " first" C." " second"Principles of Chemistry II © Vanden BoutWhat are the units for the rate constant?" A." " M s-1" B." " s-1" C." " M-1 s-1"rate = k[N2O5]M s-1 = k x Mk must be s-1Principles of Chemistry II © Vanden BoutWhat is the rate constant for the following reaction?" A." " 8 x 10-3 s-1" B." " -8 x 10-3 s-1" C." " 8 x 10-1 s-1"slope = (0.8/100)slope = -kPrinciples of Chemistry II © Vanden BoutHalf lifeHalf-life for first order reactions is independent of the initial concentrationPrinciples of Chemistry II © Vanden BoutIntegrated Rate LawsRelates the order and k to the concentration at any timeSecond Order1/[A] = 1/[A]o + ktA given reaction is second order with a rate constant of 10-3 M-1 s-1, at what time has 99% of initial concentration reacted?Principles of Chemistry II © Vanden BoutIncreasing the Temperature makes Reaction FasterPrinciples of Chemistry II © Vanden BoutPrinciples of Chemistry II © Vanden BoutPrinciples of Chemistry II © Vanden BoutArrhenius LawThe rate constant k is a function of temperaturek = A e-Ea/RTArrhenius Lawpre-factorbarriertemperatureThe higher the temperature the more molecules that have enough energy to make it over the barrierPrinciples of Chemistry II © Vanden BoutBoltzmann Distributionnumber of moleculesAs T increases, more molecules have enough energy to transition over the barrierPrinciples of Chemistry II © Vanden BoutArrhenius Plotk = A exp(-Ea/RT)lnk = lnA -Ea/RTstraight line plot y = b + mxy = lnkx = 1/Tb = lnAm = -Ea/RPlot lnk vs 1/T, slope = -Ea/R intercept = lnAPrinciples of Chemistry II © Vanden Boutgo to Henkelman webpagePrinciples of Chemistry II © Vanden BoutPre-exponential Factork = A exp(-Ea/RT)This is the rate constant if T = infinity (no barrier)Even with enough energy, you don't always reactPrinciples of Chemistry II © Vanden BoutPrinciples of Chemistry II © Vanden BoutPrinciples of Chemistry II © Vanden BoutPrinciples of Chemistry II © Vanden Bout Kinetics ProblemsSee
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