Ch ical chemistr Reaction Kinetic Theories of reaction rates Hard-Sphere Collision Theory of Gas-Phase reactions l/2 k=Nar(rB+C aRt E/RT forB≠C(23.3) 1/2 2(8Rr 1/2 VATdB MB e Ethr/RT for B=C(23. 4) Ink= const +-Int--inr RT Ea=Rtt Ea= rr2 dhn k (17.68) a- ethr +-Rt (235)
6 Physical Chemistry Theories of Reaction Rates Hard-Sphere Collision Theory of Gas-Phase Reactions (23.4) E RT B A B thr e M RT k N d / 1/ 2 2 1/ 2 8 2 1 − = for B = C (23.3) E RT B C A B C thr e M M RT k N r r / 1/ 2 2 8 1 1 ( ) − = + + for B C RT E k const T thr = + ln − 2 1 ln dT d k Ea RT 2 ln (17.68) = + 2 2 2 1 RT E E RT T thr a Ea Ethr RT 2 1 = + (23.5) Reaction Kinetics
Ch ical chemistr Reaction Kinetic Theories of reaction rates Hard-Sphere collision Theory of Gas-Phase reactions aRT k=NaI(rB+rO thr/ for B≠C(233) U/2RT is small ea >>rt Ea= Ethr+RT (23.5) En≈En E a=kert (17.69) 1/2 A=M1n八8RT(11 1/2 forB≠C(23.6) The hard-sphere threshold energy is nearly the same as the activation energy. The simple collision theory gives only the pre-exponential factor A(but not for the calculation of ethr)
7 Physical Chemistry Theories of Reaction Rates Hard-Sphere Collision Theory of Gas-Phase Reactions RT Ea A ke (17.69) Ea Ethr RT 2 1 = + (23.5) (23.6) 1/ 2 1/ 2 2 8 1 1 ( ) − = + + e M M RT A N r r B C A B C for B C (23.3) E RT B C A B C thr e M M RT k N r r / 1/ 2 2 8 1 1 ( ) − = + + for B C 1/2RT is small Ea Ethr The hard-sphere threshold energy is nearly the same as the activation energy. The simple collision theory gives only the pre-exponential factor A (but not for the calculation of Ethr) Ea RT 2 1 Reaction Kinetics
Chical chemistr Reaction Kinetico a comparison of theoretic calculation and experimental measurement E ko(theo Reaction 10uldm3·mol1·s-l K|kJ·mol ca measured ca K+Br2→KBr+Br6000 10 2.1 4.8 CH3+ CH3 2Hb3000 0.24 1.10.22 2NOC→→2NO+Cl24701020.0940.590.16 CHO cHo 500831.5×10-5305×10-6 H2+C,H4→→CH。8001801.24×10-57317×10-6
8 K + Br2 KBr + Br 600 0 10 2.1 4.8 CH3 + CH3 C2H6 300 0 0.24 1.1 0.22 2NOCl 2NO + Cl2 470 102 0.094 0.59 0.16 500 83 1.5×10 -5 3.0 5×10- 6 H2 + C2H4 C2H6 800 180 1.24×10 -5 7.3 1.7×10- 6 Reaction T E K kJ· mol-1 k0 (theo) k0 (cal) k0 1011dm3 · mol-1 · s-1 measured cal. A comparison of theoretic calculation and experimental measurement + CHO CHO Physical Chemistry Reaction Kinetics