CHEM 135 1st Edition Lecture 13 Outline of Last Lecture I. Factors affecting the rate of a reactiona. Concentration b. Temperaturec. Surface areaII. Demo observationsa. Glow sticksb. Blue solution c. Corn starchOutline of Current Lecture I. Activation in a chemical reactiona. Definitionb. Arrhenius equationc. ExamplesII. Reaction mechanism and reaction intermediatea. Unimolecularb. Bimolecularc. TermolecularIII. Rate determining step and rate lawa. ExampleCurrent LectureActivation energy in a chemical reaction (Ea)- Lower the activation energy, faster the rate of reaction- REMEMBER: frequent collisions + energetic collision + correct orientation= productArrhenius equation- Takes into account all factors that affect the rate of a reactionk =Ae− EaRTThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.k= rate constantAe= Arrhenius factor: collision frequency and orientation factorR= gas constantT= temperature in kelvinEa= energy barrier to be surmounted in going from reactants to products- The Arrhenius equation has two derivatives:ln(k)=−EaR(1T)+ln ⁡( A )lnk2k1=EaR(1T1−1T2)Ex. If the activation energy for a given compound is found to be 42.0 kJ/mol with a frequency factor of 8.0x1010 s-1, what is the rate constant for this reaction at 298K?Given:Ea= 42.0 kJ/molA= 8.0x1010 s-1T= 298KR= 0.008314 kJ/molln(k)=−EaR(1T)+ln ⁡( A )ln(k)=−420.008314×1298+ln 8.0 × 1010ln(k)=8.15k =e8.15k=3.5x103 s-1Reaction Mechanism and Reaction IntermediateUnimolecular: Aproduct rate= k[A]1Bimolecular: 2A product rate= k[A]2Termolecular: A+B product rate= k[A]![B]13A product rate= k[A]3A+B+C product rate= k[A]![B]1[C]1Reaction intermediates appear in the elementary steps but not in the final balanced overall reaction.Ex. Overall reaction: NO2 + CO NO + CO2Elementary Steps: 1. NO2 + NO2 NO3 + NO 2. NO3 + CO NO2 + CO2Rate= k[NO3]![CO2]1Intermediate=NO3 (consumed element)Ex.H2 + 2ICl  2HCl + I2rate=k[H2]m[ICl]n1. H2 + ICl  HCl + HI rate= k[H2]1[ICl]1 (bimolecular)2. HI + ICl HCl + I2rate= k[HI]1[ICl]1 (bimolecular) H2 + 2ICl  2HCl + I2Intermediate= HIRate Determining Step- Rate determining step (slow step) determines the rate law of the overall reactionEx.NO2 + CO NO + CO Rateabs= k[NO2]21. NO2 + NO2 NO3 + NO Rate= k[NO2]2 (slow)2. NO3 + CO NO2 + CO2Rate= k[NO3][CO] (fast)Rate law of slow step= rate law of overall