CHM 104 1st Edition Lecture 7 Outline of Last Lecture I Reaction Mechanism Outline of Current Lecture II Reaction Mechanism where rate determining step is not the first step III IV V VI Homogeneous Catalysis Heterogeneous Catalysis Hydrogenation of ethylene Enzymatic catalysis Current Lecture Reaction Mechanism Example Rate k2 N2O2 1 H2 1 To compare to exponentially determined rate law we need to rewrite in an equivalent for our intermediate need rate law without intermediate present Strategy A lot of N2O2 will build up causes the reverse process to speed up Equilibrium eventually reach a point where NO is formed as fast as N2O2 is formed Rate step 1 forward rate step 2 backward K1 NO 2 k 1 N2O2 NO 2 k 1 N2O2 k1 k 1 NO 2 N2O2 Substitute k1 k 1 NO 2 for N2O2 1 Rate k2 k1 k 1 NO 2 H2 1 k2 k1 k 1 is the overall rate constant Rate k NO 2 H2 1 Factors that influence rates of reaction 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 reactant concentration temperature catalyst substance that increases reaction rates by providing different reaction mechanism which has a lower activation energy Catalysts are recycled Homogeneous used in 1 step and regenerated in another step Heterogeneous platform for molecules to come together Homogeneous Catalysis Example Ozone decomposition catalyzed by chlorine Uncatalyzed reaction O3 g O g 2 O2 g Catalyzed reaction 1 O3 Cl ClO O2 FAST 2 ClO O O2 Cl FAST ClO is the intermediate formed and consumed within mechanism Cl is the catalyst used and regenerated within the mechanism Heterogeneous Catalysis Catalyst is in a different state of matter to the reactants Example Automobile Catalytic Converter CO O2 NO CO2 N2 O2 CxHy O2 CO2 H2O Catalyst in a mix of Pt and Rh dispersed on a high surface area material Exhaust fumes pass over catalyst Hydrogenation of ethylene Enzymatic catalysis
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