CHEM 135 1st Edition Lecture 11 Outline of Last Lecture I Rate vs reaction concentration II Complex rate law and reaction order a Overall reaction order b Examples III Integrated Rate Law Outline of Current Lecture I Integrated Rate Law a Graphs b Equations c Examples II Half life a Equations b Examples Current Lecture Integrated Rate Law Zero order graph A on y axis and time on x axis slope k First order graph ln A on y axis and time on x axis slope k Second order graph 1 A on y axis and time on x axis slope k Equations Zero order A kt A initial These 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 First order ln A kt ln A initial Second order 1 A kt 1 A initial Examples The reaction is first order in cyclopropane and has a measured rate constant of 3 36 x 10 5s 1 at 720K If the initial cyclopropane concentration is 0 0445 M what will be the cyclopropane concentration after 235 0 min Given k 3 36 x 10 5s 1 A 0 0 0445 M A t t 235min 14100 seconds ln A kt ln A o ln A 3 36 x 10 5 14100 ln 0 0445 ln A 3 585 A e 3 585 A 0 0277 M Half Life Time it takes for the concentration of the reactant to fall to one half its original value Zero order reaction t1 2 Ainitial 2k First order reaction t1 2 0 693 k Second order reaction t1 2 1 k A0 Ex A substance decays with second order kinetics What is the half life given a rate constant that is 0 37 M 1s 1 and an initial concentration of 0 75 M t1 2 1 k A0 1 2 0 37 x 75 3 6s Carbon 14 has a half life of 5720 years and this is a first order reaction If a piece of wood has converted 25 of the carbon 14 then how old is it T1 2 5720 years 75 remains A 0 75 A0 find k t1 2 0 693 k 5720 0 693 k k 1 21 x 10 4 ln A A0 kt ln 0 75 A0 1 21 x 10 4t 0 287 1 21x10 4 t time 2372 years
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