物理化学厦门大学课件.ppt

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1、Chapter8ChemicalKinetics-28.7Elementaryandcomplexreactions8.8ReactionKineticsandequilibriumstate8.10Speculationofreactionmechanism8.19Activationenergyforelementary&complexreactions2021/8/38.7Elementary&ComplexReactionsFocusesElementaryreactions基元反应Molecularity分子数Overallre

2、actions总包反应Reactionorder反应级数Reactionmechanism反应机理I.ConceptsII.KineticsoftypicalcomplexreactionsIII.Steady-StateApproximationIV.Pre-equilibria2021/8/3I.ElementaryReactions&OverallReactionsAnelementaryreactionreferstoasingle-stepreactioninvolvingasmallnumberofmoleculesorion

3、s.Forexamples：AnoverallreactionisareactioncombinedwithaseriesofelementaryreactionsForexamples：2021/8/3MolecularityofElementaryReactionThemolecularityofanelementaryreactionisthenumberofmoleculescomingtogethertoreactinanelementaryreaction.ElementaryreactionUnimolecularreact

4、ion单分子反应MolecularityBimolecularreaction双分子反应Trimolecularreaction三分子反应2021/8/3LawofMassActionratelawElementaryreactionForanelementaryreaction,therateisproportionaltotheconcentrationofofthereactantmoleculesthatmeettogether.2021/8/3ReactionMechanismForanoverallreaction,theco

5、mbinationofaseriesofelementary-reactionstepsisthereactionmechanism.同一反应在不同的条件下，可有不同的反应机理。了解反应机理可以掌握反应的内在规律，从而更好的驾驭反应。一个反应机理需要经得起实验和理论的考验，有时需要作长期的大量的动力学研究。2021/8/3TypicalCombinationsofElementaryReactionsReversible(Opposing)reactions对峙反应Parallelreactions平行反应Consecutivereact

6、ion连续反应k1ABk-1ABCDk1k2k32021/8/3II.KineticsoftypicalcomplexreactionsReversible(Opposing)reactions对峙反应Parallelreactions平行反应Consecutivereaction连续反应k1ABk-1ABCDk1k2k32021/8/3Reversible(Opposing)ReactionsMorecommonsituationisthattheforwardandthebackreactionsmaynotbeelementaryr

7、eactions,andmaybefirst-,second-orthird-orderreactionsForexampleskfABkbkfA+BCkbkfAB+Ckb2021/8/3ReversibleFirst-OrderReactions:Differentialequationt=0[A]0[B]0t=t[A]0–x[B]0+xt=te[A]0–xe[B]0+xek1ABk-1[A]0+[B]0=[A]+[B]=[A]e+[B]ek1/k-1=[B]e/[A]e[B]=[A]e+[A]ek1/k-1－[A]Differenti

8、alequation2021/8/3ReversibleFirst-OrderReactions:Integratedequation∫0td[A][A]﹣[A]e∫[A]0[A](k1+k-