Ch ical chemistr Reaction Kinetic R ate laws For many reactions r=k[4y[B2…[y (175) k: rate constant (rate coefficient),kfT, P) as B,.n: order or partial order a+B+..+h=n: overall order The expression for ras a function of concentrations at a fired temperature is called the rate law
6 Physical Chemistry Rate Laws For many reactions r = k A B L (17.5)* k: rate constant (rate coefficient), k = f (T, P) , , : order or partial order + + + n : overall order The expression for r as a function of concentrations at a fixed temperature is called the rate law. Reaction Kinetics
Ch ical chemistr Reaction Kinetic Reaction orders ero -or de er k First-order r=k乎Pr=[4B Se econd-order r=kAP[B] r=kAIBP Third-order k[AIB」 Negative First-order KAIB]/2 1. 5-order r=A42) No simple order
7 Physical Chemistry Reaction Orders o r = k r = kA 2 r = k A r = kAB r kA B 2 = 2 r = k A B −2 r = k A B 1/ 2 r = k A B ( ) 1/ 2 r = k A B / 1− B Zero-order First-order Second-order Third-order Negative First-order 1.5-order No simple order Reaction Kinetics
Ch ical chemistr Reaction Kinetic Rate laws Reaction Rate law klh, Br 1/2 H+B→2HB 1+jHBr[Br2 H2+2→>2团 kle2ll21 2N2O5>4MO2+02 CH2CHO→CH4+CO r=k[cH3CHOF/2
8 Physical Chemistry Rate Laws Reaction Rate Law H Br 2HBr 2 + 2 → 2 1/ 2 2 2 1 j HBr / Br k H Br r + = 2N2 O5 → 4NO2 +O2 H I 2HI 2 + 2 → 2 2 r = k H I N2 O5 r = k CH3 CHO →CH4 +CO 3/ 2 r = k CH3 CHO Reaction Kinetics
Ch ical chemistr Reaction Kinetic Reaction mechanisms Reaction actually occurs 2SO2+O2-A,2O3 02+2AO→O (177) intermediate (O2)+SO2→MO+SO3 2N2O5>4MO2+O2 Elementary reaction Step(a) N2O令→NO2+MO3 Step(b NO2+NO3→NO+O2+NO2 (178) Step(c) NO+NO3→>2NO2
9 Physical Chemistry Reaction Mechanisms NO2 + SO2 → NO+ SO3 O2 + 2NO →2NO2 (17.7) 2SO2 O2 2SO3 NO + ⎯ ⎯→ intermediate 2N2 O5 → 4NO2 +O2 N2 O5 NO2 + NO3 NO+ NO3 → 2NO2 NO2 + NO3 → NO+O2 + NO2 (17.8) Step (a) Step (b) Step (c) Elementary reaction Reaction actually occurs Reaction Kinetics
choical Chemistry Reaction Kinetic Measurement of reaction rates The concentration of a reactant or product as a function of time Chemical method Cooling the sample removing a catalyst Diluting the mixture At constant T Adding a species At intervals Slows down or stop the reaction Rapidly analyze chemical Reaction vessels compositions of the mixture
10 Physical Chemistry Measurement of Reaction Rates Chemical Method The concentration of a reactant or product as a function of time Reaction vessels At constant T At intervals Slows down or stop the reaction Rapidly analyze chemical compositions of the mixture Cooling the sample removing a catalyst Diluting the mixture Adding a species Reaction Kinetics