18.4 Kinetics-Rxn Mechanism and Rate-2020 (1).pdf -...

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2020/4/301Chapter18:ChemicalKinetics18.1RatesofChemicalReactions18.2RateLaws18.3ReactionMechanisms18.4ReactionMechanismsandRate18.5EffectofTemperatureonReactionRates18.6MolecularTheoriesofElementaryReactions18.7ReactionsinSolution18.8CatalysisCumulativeExercise:SulfiteandSulfateKineticsinAtmosphericChemistryContentsChapter18.4:ReactionMechanismsandRateSummary18.4&18.4ReactionMechanismsandRateContentsReactionMechanismandRateTomakeaconnectionofthemacroscopicallydeterminedreactionrate(experiment)totherationinthemolecularlevelreactionrateIfthereactionisonlyaelementarystep(molecularlevel),thenaA + bBcC + dDmRate = k[A][B]ma,nbn,mRate = k[A][B]ma,nbn,ReactionMechanismandRateForexample,theelementarystepsForamacroscopicreaction,breakintomanyelementarystepsAproducts,Rate = k[A]2A + Aproducts,Rate = k[A]A + Bproducts,Rate = k[A][B]1234
2020/4/302ReactionMechanismandRateInmanyreactionmechanisms,onestepissignificantlyslowerthanalltheothers:Thatslowstepistherate‐determiningstepThemostimportantstepofallAlwaysstartwiththatstepforanalysisReactionMechanismandRateIftherate‐determiningstepisthefirstone,theanalysisisparticularlysimple,e.g.ApossiblemechanismTheoverallrate(fromslowstep#1)   2222NOg+ Fg2NO F gobs22The experiment observed rate = kNOF[]       1k22k22NOg+ FgNOFg+ FgslowNOg+ FgNO F gfast2122rate = kNOF[]ReactionMechanismandRateTherate‐determiningstepisnotthefirststep,i.e.thefirststepisnottheslowstepCouldbeareactionofordergreaterthan2,CouldbeaninverseconcentrationdependenceononeofthespeciesCouldbeanon‐integralreactionorderForexampletheexperimentalratelawis   222NOg+ Og2NOgobs22[Nrate = kO ] []O2ReactionMechanismandRate:ExampleIForexampletheexperimentalratelawisWhatistheratelawfromaproposedmechanism?

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Term
Fall
Professor
DINNER
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Trigraph, BR postcode area, Bromine

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