山东大学：《物理化学》课程教学资源（讲义资料）9.2 Rate and rate equation

89.2 Reaction rate and rate equation I.R. Levine, pp 528-533 17.1 reaction kinetics 17.2 measurement of reaction rates

§9.2 Reaction rate and rate equation I. R. Levine, pp. 528-533 17.1 reaction kinetics; 17.2 measurement of reaction rates

89.2 Reaction rate and rate equation (1) Expression of reaction rate △[A] H2+L2=2HI H2+ Cl2=2 HCI △t r=[H2][2]】r=k[H2C12 0.5 [A] t Logical method? ac c dt

(1) Expression of reaction rate §9.2 Reaction rate and rate equation 2 1 2 1 [A] = c c r t t t      d[A] r dt  dt d J   dt d c r i i 1 [ ]   H2 + I2 = 2 HI 1 1 2 2 r k  [H ] [I ] H2 + Cl2 = 2 HCl 1 0.5 2 2 r k  [H ] [Cl ] A A B C dc r kc c c dt       Logical method?

89.2 Reaction rate and rate equation (4)Rate equation In 1895, Noyes defined a, Bas the partial H 2+C2=2 HCI order of the reaction with respect to A or B r=k[H,1[CLI respectively, and the sum of the partial order n=a+B+r+. the overall order of the 2SO2+O2→>2SO3 reaction, or more simply, the reaction order. dso 2kISO,[so 2 a, B % etc, different from the Rate law must be determined from stoichiometric coefficient, may be integers, measurements of reaction rate and cannot decimals, of plus or minus values be deduced from the reaction stoichiometry

1 0.5 2 2 r k  [H ] [Cl ] (4) Rate equation §9.2 Reaction rate and rate equation 2SO2 + O2  2SO3 1 3 2 2 3 [SO ] 2 [SO ][SO ] d r k dt    , , , etc., different from the stoichiometric coefficient, may be integers, decimals, of plus or minus values. Rate law must be determined from measurements of reaction rate and cannot be deduced from the reaction stoichiometry. H2 + Cl2 = 2 HCl In 1895, Noyes defined ,  as the partial order of the reaction with respect to A or B, respectively, and the sum of the partial order n =  +  +  +… the overall order of the reaction, or more simply, the reaction order.

89.2 Reaction rate and rate equation (5) The law of mass action Exercise For elementary reaction such as 21+H2=2HI k 2 at k[][H 2A B +C E Partial order= stoichiometric coefficient daI db dc dd de Reaction order= number of molecules involved in the reaction Law of mass action valid only for elementary reaction

For elementary reaction such as A A B C dc a b c r kc c c dt    Partial order = stoichiometric coefficient Reaction order = number of molecules involved in the reaction 2I + H2 = 2HI 2 2 1 [I] [I] [H ] 2 d r k dt    Law of mass action valid only for elementary reaction (5) The law of mass action §9.2 Reaction rate and rate equation 2A k1 k2 B + C D E k3 k4 dt d[A] dt d[B] dt d[C] dt d[D] dt d[E] Exercise

89.2 Reaction rate and rate equation (3) Rate equation and the law of mass action Group work-I third-order First-order second-order zeroth-order a+B 3A-k3>P a-ko >P P 2A—k2>P 2A +B A+B+c-ka>P (1) Write the differential form of rate equation (2) Write their integration rate equation

Group work-1: First-order second-order third-order zeroth-order A P 1 k 2 2 A + B P 2A P k k   3 3 3 3A P 2A + B P A + B + C P k k k    A P 0 k (3) Rate equation and the law of mass action §9.2 Reaction rate and rate equation (1) Write the differential form of rate equation; (2) Write their integration rate equation