1Week 15 CHEM 1310 - Sections L and M 1Ch. 15: Kinetics 15.1 Reaction Rates 15.2 Rate Laws 15.3 Forms of Rate Laws 15.4 Integrated Rate Law 15.5 Rate Laws: A Summary 15.6 Reaction Mechanisms 15.7 Steady-State Approximation 15.8 A Model for Chemical Kinetics 15.9 CatalysisWeek 15 CHEM 1310 - Sections L and M 2Reaction Rates: Example Recap: Avg. Reaction rate = +∆[Product]/∆t Avg. Reaction rate = -∆[Reactant]/∆tButane, C4H10, burns in oxygen to give CO2 and H2O vapor.If the butane concentration is decreasing at a rate of 0.20M/s, what is the rate at which the oxygen is decreasing?What is the rate at which the products are increasing?2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(g)Week 15 CHEM 1310 - Sections L and M 3Reaction Rates: ExampleButane, C4H10, burns in oxygen to give CO2 and H2O vapor.If the butane concentration is decreasing at a rate of 0.20M/s, what is the rate at which the oxygen is decreasing?What is the rate at which the products are increasing?2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(g)0.20 M/s ???For oxygen:0.20 mol C4H10xL s 2 mol C4H1013 mol O2= 1.3 M O2/s2Week 15 CHEM 1310 - Sections L and M 4Reaction Rates: ExampleButane, C4H10, burns in oxygen to give CO2 and H2O vapor.If the butane concentration is decreasing at a rate of 0.20M/s, what is the rate at which the oxygen is decreasing?What is the rate at which the products are increasing?2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(g)0.20 M/s 1.3M/s??For CO2:0.20 mol C4H10xL s 2 mol C4H108 mol CO2= 0.80 M CO2/sWeek 15 CHEM 1310 - Sections L and M 5Reaction Rates: ExampleButane, C4H10, burns in oxygen to give CO2 and H2O vapor.If the butane concentration is decreasing at a rate of 0.20M/s, what is the rate at which the oxygen is decreasing?What is the rate at which the products are increasing?2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(g)0.20 M/s 1.3M/s 0.80 M/s ?For H2O:0.20 mol C4H10xL s 2 mol C4H1010 mol CO2= 1.0 M H2O/sWeek 15 CHEM 1310 - Sections L and M 6Reaction Rates: Example2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(g)0.20 M/s 1.3M/s 0.80 M/s 1.0 M/sNotice that rxn rates are stoichiometrically proportionaltDdtCctBbtAarateDDDDDDDD][1][1][1][1˜¯ˆÁËÊ=˜¯ˆÁËÊ+=˜¯ˆÁËÊ-=˜¯ˆÁËÊ-=3Week 15 CHEM 1310 - Sections L and M 7Rate Laws Types of Rate Laws Differential: depends on [reactants] Integrated: depends on time and [reactants] Both involve expressions with the rate constant Rate Constants A proportionality constant in a specific rateequation (i.e. chemical reaction)Week 15 CHEM 1310 - Sections L and M 8Differential Rate Law Differential rate laws are expressed interms of the concentration of a reactant Differential rate laws correspond to theorder of the reactionOrder of Reaction Rate Law0 Rate = k1 Rate = k [A]2 Rate = k [A]2 or k[B]2 orRate = k [A] x [B]Week 15 CHEM 1310 - Sections L and M 9Integrated Rate Laws Integrated rate laws express the rate interms of time.Rate of Disappearance of A- d[A]dt= k [A] first order rxnRearranging…d[A][A]= - k dtA products4Week 15 CHEM 1310 - Sections L and M 10Integrated Rate LawsRearranging…d[A][A]= - k dtIntegrate onboth sidesof eqn: Ú[A]0[A]t 1[A]dA=  Ú- k dt(ln [A]t + constant) - (ln [A]0 + constant) = - kt ln [A]t - ln [A]0 = - ktWeek 15 CHEM 1310 - Sections L and M 11Integrated Rate Lawsln [A]t - ln [A]0 = - ktRearranging:ln [A]t[A]0= - ktTake exponentof both sides:[A]t[A]0= e -kt[A]t = [A]0 e -ktfirst order rxnfirst order rxnWeek 15 CHEM 1310 - Sections L and M 12Integrated Rate Laws How does the integrated rate law change ifthe order of the reaction is second order?A productsRate of Disappearance of A- d[A]dt= k [A]2second order rxnRearranging…d[A][A]2= - k dtShow result on board5Week 15 CHEM 1310 - Sections L and M 13Integrated Rate Laws How does the integrated rate law change ifthe order of the reaction is zeroth order?A productsRate of Disappearance of A- d[A]dt= k zeroth order rxnRearranging…d[A]= - k dtShow result on boardWeek 15 CHEM 1310 - Sections L and M 14Half-Life The half-life of a chemical reaction is thetime required for a reactant to reach half ofits original concentration.Show derivations on boardWeek 15 CHEM 1310 - Sections L and M 15Kinetics Summary6Week 15 CHEM 1310 - Sections L and M 16Final Week of Classes On Monday, Dec 3 Reaction Mechanisms Activation Energy Applications in Kinetics Wed and Friday, Dec 5 & 7 Review for Final