Physical chemistr Reaction Kinetics(7) Xuan Cheng Xiamen University
1 Reaction Kinetics (7) Xuan Cheng Xiamen University Physical Chemistry
Ch ical chemistr Reaction Kinetic Thermodynamic Aspects Activated Complex Theory: structure of the activated complex(? The concepts: an equilibrium between the reactants and the activated complex The activation process is expressed in terms of thermodynamic function 二≠/NA re h T (2324 (EB/NAVEC/NAV) /NAV K f=BIC]…(=B/N4(=c/N) (23.10 1(2m7ck)28 h (23.15) 1/2 Kr=K h (2325)
2 Physical Chemistry Thermodynamic Aspects Activated Complex Theory: structure of the activated complex (?) The concepts: an equilibrium between the reactants and the activated complex The activation process is expressed in terms of thermodynamic function k T (23.24) B A C A A c e z N V z N V z N V K − 0 ( / )( / ) / ' h m k T K K rc c f 1/ 2 2 = (23.25) k T B A C A f A f e z N V z N V z N V B C X K − = 0 ( / )( / ) / [ ][ ] (23.10) (23.15) ' 1/ 2 (2 ) 2 1 = z h m kT z rc Reaction Kinetics
Ch ical chemistr Reaction Kinetic Thermodvnamic aspects kT kr =Ko (2326) In terms of AGO=-RT hn Ko =-RT In concentration 0\An/mot (2327) For the process B+c+…→少 △/mol=1-n By analogy to(23.27), define Gibbs energy of activation△G*=- RT ktc(°y-1 23.28 kT Rate constant kr (c0)1-n-△GO=/RT h (2329) Thermodynamic version of the tst expression for the rate constant
3 Physical Chemistry Thermodynamic Aspects = − = − o n mol o c c o c c K G RT K RT / ( ) ln ln (23.27) n/mol =1−n → B +C + X f For the process (23.28) 1 ln ( ) − − o n c o c G RT K c By analogy to (23.27), define r = Kc h kT k (23.26) In terms of concentration Gibbs energy of activation o n G RT r o c c e h k T k 1 / ( ) − − = (23.29) Thermodynamic version of the TST expression for the rate constant. Rate constant Reaction Kinetics
choical Chemistry Reaction Kinetic Thermodvnamic aspects KdE RTc 23.30 Enthalpy of activation aho+=AHo*= dhn Kp (2331) Entropy of activation △S≠=△HO≠-△G≠/T 9i6 gy of activation△G2=△H2-T^S2 (23.32) kr O1-n-△G/RT (2329) .、kTo1-na-AS/R-△He=/RT h (23.33)
4 Physical Chemistry Thermodynamic Aspects (23.30) n o o o c o P P RTc K K − 1 dT d K H H RT o o o P c = 2 ln (23.31) S ( H G ) T o c o c o c / Entropy of activation − (23.32) = − o c o c o Gc H T S o n G RT r o c c e h k T k 1 / ( ) − − = (23.29) o n S R H RT r o c o c c e e h k T k 1 / / ( ) − − − = (23.33) Enthalpy of activation Gibbs energy of activation Reaction Kinetics
choical Chemistry Reaction Kinetic Thermodynamic Aspects a=Rr2 dInk 17.68) En≡RT dn k dhKO≠ -RT+rT d T' K (2326) dhn kc dIn kox KB≡K O≠ (23.30) =△HO/R2+(n-1)T T =△HO≠=RT 2dIn kp (2331) dT Ea=△HO≠+ nr Gas-phase reaction(23.34) △HO≠=△U0+(1-n)RT (5.10) E=△U+RT
5 Physical Chemistry Thermodynamic Aspects dT d k Ea RT 2 ln (17.68) r = Kc h kT k (23.26) dT d K RT RT dT d k E RT o r c a = + 2 ln 2 ln (23.30) n o o o c o P P RTc K K − 1 dT d K H H RT o o o P c = 2 ln (23.31) H RT n T T n dT d K dT d K o o P o c / ( 1) ln ln 1 2 = + − − = + E H nRT o a = + Gas-phase reaction (23.34) RT (5.10) H U n o o = + (1− ) E U RT o a = + Reaction Kinetics