级物理化学-4、参考已双语chemical kinetics

PhysicalChemistry—ChemicalBasictheoretical Disciplinary(Statisticalthermodynamics)(Direction&equilibriumofreactions)(Rates&Quantum&structural

ColloidandinterfacesMolecularreactionMaiBackIntroductiontoChemicalThelimitationsofTheobjectsofchemicalBriefhistoryofchemicalMaiBackThermodynamics:Ondirectionsofspontaneousreaction,equilibrium,andthefactorsinfluencingtheequilibrium.PredictingpossibilityofareactionFor 1

3 NH (g) 3 1 HO(l) Thermodynamics:can’tanswer(1)howtomakethemhappen(2)howfasttheywilltakeplace(timeasavariable)(3)thereactionMaiBackChemicalKinetics:MainChemicalThestudyofreactionrates(consideringtime),theinfluencesofvariablessuchastemperature,pressureandcatalystontherates,andthereactionmechanisms.1N

3H(g)NH

Chemical2 T,P,H(g)+1O(g)H Tor MaiBackChemicalKinetics:MainReactionratesandtheinfluencesofvariablesonratesForexamples:>700H2+Cl2→ r∝H2+Br2→ r∝H2+ → r∝ReactionWhysodifferent？DifferentreactionRateofelementaryreactionsandmolecularMaiBackChemicalKinetics:BriefEmpiricalchemical kA Elementarychemicalkinetics-rate Eyring:activatedcomplexState-to-Statedynamics-Molecularreaction Cross-beamD.R.Herschbach-J.C.Polanyi-Y.Lee1986NobelMaiBackChapter1EmpiricalChemicalChapter1EmpiricalChemicalChapter2Elementary&ComplexChapter3RateTheoryforElementaryChapter4ChainReactionChapter5CatalyticReactionChapter6SolutionReactionChapter7PhotochemicalReactionMaiBackChapter1EmpiricalChemical1.1Theratesof1.2 awsandreaction1.3Integrated 1.4Half-1.5Thedeterminationofthe 1.6ThetemperaturedependenceofreactionMaiBackTheRateofReactionratesandtheir反应速率及其单位、各表达形式间的MaiBackVelocityand vector,with scalar,withoutdirection,allFor R 速 d[R] d[P] d[R]d[P]0 MaiBackExtentofConsidera eE+fF→gG+0= (B,stoichiometricnumberofB nB(t)– Unit:dBMaiBackRateofConversion&RateofConsidera0 d Rateof 1

ols B Rateof1

1r = V VB

oldmsMaiBackRateofReactionatConstantAtconstantr1 (d1dnBV B 1d(nB/V)1B B mol·dm-3·s-Foranyreactions：eEfFgGr1d[E]1d[F]1d[G]1 MaiBackRateofReactionExpressedwithForgaseousreactions,piseasyto r 量纲:分压· Unit:Pa·s-1orkPa·s-Forexample：N2+3H2→r’

13

12Foridealgas,pB=cBRTr’=(RT)rMaiBackInstantaneousRate&InitialRRPrRrpInthecurveshowingthevariationofconcentrationwithInstantaneousrateistheslopeoftheAtInitialrate:r0=-MaiBackReactionRateMeasurements-DrawingKineticKineticcurvesarechangesinconcentrationsofreactantsorproductswithtime.Withkineticcurves,wecangettherateofMaiBackTechniquesformonitoringtheChemicalAtdifferenttimes,samplingacertainamountofreactants,stop thereactionbycooling,dilutionandremovingcatalyst,thenmaking MaiBackTechniquesformonitoringthePhysicalMonitoringthechangesinconcentrationsusingvariousphysicalproperties(totalpressure旋光、折etc.)orspectroscopicmethods(IR、UV-VIS、ESR、NMR、ESCAetc.)MaiBack aws&Reaction aws速率Integrated Reactionorder反应Ratecoefficientrateconstant)反应速率常数(系数MaiBack Inabroadsense,theraawisanequationthatexpressestherateofreactionasafunctionofallaffectingfactorsr1d=f(c,T,catalyst, Incommonsense,thera awreferstoanequationthatexpressestherateofreactionasafunctionoftheconcentrationsofallspeciesr1d=1dci= mustbeV i fromMaiBackIntegrated 1 = differentialiIntegrated c=Forrd[A]/dt aw速率方程 = Integrated MaiBackReactionsPossessingReactionTher=f(c)mustbedeterminedbykineticFormanyaA+bB→eE+r=f(c)=kcAcBcEcF=k∏c iOnlyinthiscase,reactionordersMaiBackReactionThepowertowhichtheconcentrationofaspeciesisraisedistheorderwiththisspeciesA,B,E,Theoverallorderofareaction(n)isthesumoftheindividualordersn=A+B+E+MaiBack Onlywhenr=f(c)= Reactionorder

∏= ∏ReactionorderisnotthestoichiometricItmaybepositive,negative,integer,fractionorReactionorderisdeterminedbyItmaybechangedwithexperimentalMaiBackReactionOrder:rrrrSecond-rkA2Br Third-r NegativeFirst-r 1.5- NosimpleMaiBackRateThecoefficientinthera awiscalledratecoefficientorrateconstant(k).kisindependentofconcentrationsofreactants.Itisgenerallyisafunctionoftemperature(ifcatalystisTheunitofkdependsonreactionorder(n)，mol1-ndm3(n-1)s-1(3)Whenpisusedinsteadofconcentration,kp=kc(RT)1-MaiBackPseudoReactionInaws,iftheconcentrationofonereactantislargeexcess,itcanbeincorporatedintothecoefficientterm,theapparentreactionordercalledpseudoreactionorder,willbedecreasedandsimplified.Forrrkrk[Hk'k[A])H为催化rk'(k'k[H MaiBackIntegrated awsaredifferentialequations,wemustintegratethemifwewanttofindtheconcentrationsasafunctionoftime.Also,theintegratedra awsaregenerallyusedforobtainingthereactionorderandthe MaiBackThissectionisveryimportant,thefocusistograspthefeaturesofthereactionswithdifferentorders.Theusuallyusedintegrated aws积分Theunitof half-life Forasetofexperimentaldata,howtogetnandMaiBackTherateofreactionisproportionaltotheconcentrationofreactant226Ra222Rn4 rk[226 N N 1 rk[NO MaiBackFirst-OrderReactions:Differential Consider：A t t Differential rdA rdxk(Ax) MaiBackFirst-OrderReactions:Integrated t–ln[A]=kt+ First-orderreaction:-ln[A]vsMaiBackln[A]0=First-Orderln[A]0= dAkdt [A]0 MaiBackHalf-Firstorder ln[A]0=t1/2=t1/2=t1/2iscalledthehalf-life半衰For1storder t1/2=t3/4=t7/8=3ln2/kt1/2:t3/4:t7/8=1:2:MaiBackTime

Firstorder = iscalledtimeisalsocalledrelaxationMaiBack一级反应的特t2.t

1

1

半衰期(half-lifetimet1/2无关的常数t1/2t1/2:t3/4:t7/81:2: , MaiBackAnExampleforFirst-Order(1)蜕变常数，(2)半衰期，(3)分解掉90%解：(1)k1ln 1ln 0.00507d-1 100t1/2ln2/k1t1 1 1 1MaiBackABP r2A rk2[A]2MaiBackSecond-OrderReactions:Integrated aw- r1dAkA2 Define:kA dAk 1A1

k oMaiBackSecond-OrderReactions:Features-11

k Half-[A]1 tt1/t1/t1/1[A]

tSecond-orderreaction:

vsMaiBackSecond-OrderReactions:Integrated aw- Differential t0 ttA 0AxB If

x

tkdt 0 01 1

oMaiBackSecond-OrderReactions:Features-11

kHalf-[A]1 tt1/tt1[A]o

tSecond-orderreaction:

vsMaiBackSecond-OrderReactions:Integrated aw- dt If[A]o x dt x x 00

0 0

Bx o BB B/BAAAA B A/A oMaiBack1 t成线性关系，斜率为k或kAkAak)1[1-1]=k或k,k的量纲为[浓度-1[时间-0 [A] 0 1/ [A] 对ab的二级反应，t1/2t34t78=1：3：7MaiBack二级反应（a≠b）的特1lnb(a- t成线性关系，斜率为(b-1

kk的单位为[浓度-1[时间-MaiBacknth-orderreaction:Integrated Consider：aA→ r=Differential kA[A]dA t[A]0 k k Integrated n1 [A]n1 oMaiBacknth-OrderReaction:Half- k n1 [A]n1 o[A]1[A]o,tt1/22 n

[A]

kAt1/t2n1t2n1(n1)k[A]Ao

1/ MaiBackn级反应的1[A]n-

k或kk的量纲为[浓度]1-n[时间 (n-1)t[A]n- [A]n-0半衰期的表示式为： 2n- (n-1)kA[A]n-0MaiBackTheDeterminationofthe FromintegratedFromintegrated Fromdifferential Methodofinitialrates—MethodMethodofHalf-life—IsolationIsolationmethod(pseudo-reactionorder)—MaiBackThemostimportantthingfortheempiricalchemicalkineticsistoestablishthera awsfromexperiments.Generally,thereactionorderisdeterminedinthefirststep,thentheratecoefficientisworkerout.MaiBackFromIntegrated 积分法又称尝试法。当实验测得了一系列[A]~tx～t的动力学数据后，作以下两种尝Putthedataof[A]~tintotheintegratedra awsfordifferent-orderreactions,thencalculatethekIftheobtainedkisaconstant,thentheassumedreactionorderiscorrect.Plot,ln[A]~t,[A]-1~t,[A]-2~tlinear[A]~t linear linear[A]- MaiBackSummaryofIntegrated k k 1 k=1[11 [A]= k=1lna(b- [A]0(a)≠t(b- b(a- k [ ][A]=[B](n-1)t[A]n- [A]0n- *如反应物的计量系数为,则右边应除以MaiBack FromDifferential →t t rdAkdPlotcurveofDrawthetangent,workout–d[A]/dtPlotln(-d[A]/dt)vs.lnr }lnknlnALargererrors, suitablePlotln{dA}vs. reactionswithdt integerTheslopeofthestraightlinewillbeMaiBackMethodofInitialrodAkAolnr0=lnk+Plotlnr0versusln[A]0,theslopeofthestraightlinewillbenMaiBackTheinitialrateofthereaction(A+B→P)dependedontheinitialconcentrationsofAandBasfollows: DeterminetheofthereactioncAAnswer:Assumer=kc BcA

calculatetherateFromthefirst3group,weknow,Fromthelast2groups,n=0;sor=kcA;k=0.15s-MaiBackExpressionsofhalf- Independentof 10 t1/2= 0 = 2k[A]0nth- 2n- (n-1)k[A]n-0如反应物的计量系数为,则右边应用MaiBackACommonWayoftheMethodofHalf-Foranth-order 1/ [A]o[A]to1/'[A]o[A]to1/'[A]on1ln(t1/2/t1/2')ln([A]o'lntlnt1/2=lnC+(1-n)2.Plotlnt1/2versusln[A]o,evaluatenfromtheMaiBackMethodofThismethodisforthesimplificationofexperiments,andmustbeusedwithothermethodsrk[A]Doexperimentr DetermineβDoexperimentatrk DetermineαMaiBackExample:CombinationwithIsolationwithHalf-Life Foragas-phasereaction,2NO+H2→N2O+H2O,thera awcanbeexpressedasr=kp b,calculatea,bandk Answer:Forthefirsttwogroups,pNO>>pH2,sopNOcanbeviewedunchanged,r=kpNO pH2=k’pH2 Thust1/2isforBecauset1/2isindependentofpH20,weknowbFromthelattertwogroups,pH2>>pNOr=kpH20 a=k”Thust1/2isforBecauset1/2isproportionalto(pNOo)-1,wegetaMaiBackRelationshipofPhysicalPropertywithInkineticexperiments,monitoringthechangesinconcentrationsusingaphysicalproperty()isasimpleway,therequirementsforthephysicalpropertyare:MaiBackConsidera 0=设、及∞分别是时间为0,t及∞时体系中某物理量的值；[B]0[B]为0及t时刻的某物种的浓度；A为某反应物,∑fB[B]﹣0=–∞ = +∑f([B] [﹣0=–∞ = +∑f([B] [A] ﹣ =[A]·∑f﹣ =[A]·∑f· / ﹣∞=[A]·∑fB·/MaiBackFirst-OrderReaction:UsingPhysical ﹣[A]=﹣0Propertymayinclude：总压、膨胀值、旋光度、吸Forfirst-order=ln