Kinetics PS16 Wrap Up PDF

Slides for 12/6 and 12/9 Wrap up–PS16 & Review Mechanisms (a little harder) If the slow step has an intermediate, we cannot include the intermediate in the reaction’s Rate Law. We instead need to substitute it from it’s rxn where it was formed with a reactant. Example: The reaction between NO and...

Slides for 12/6 and 12/9 Wrap up–PS16 & Review Mechanisms (a little harder) If the slow step has an intermediate, we cannot include the intermediate in the reaction’s Rate Law. We instead need to substitute it from it’s rxn where it was formed with a reactant. Example: The reaction between NO and H2 is believed to occur in the following three step process. From this mechanism, what is the rate law for the rxn? NO + NO < --> N2O2 (fast) N2O2 + H2 --> N2O + H2O (slow) N2O + H2 --> N2 + H2O (fast) Rate Laws from Mechanisms The following are three steps in a mechanism for :Cl2 + CHCl3 → HCl + CCl4 Step 1: Cl2 < -- > 2Cl(g) fast Step 2: Cl(g) + CHCl3(g) → HCl(g) + CCl3(g) slow Step 3: Cl(g) + CCl3(g) → CCl4(g) fast a) What is the predicted rate law? Wrap up PS16 Collision Theory -- Big Idea: Reactions are the result of effective collisions between reacting molecules Factors that affect the rate of reaction? Where are those factors seen in the Rate Law? Temperature, Rate, Ea and k Let’s think a bit… how does temp affect Rate, affect k, affect Ea? Which of these shows Change in temp?  Collision Theory Recall… How does changing temp impact collisions? Impact rate constant? Record Relate rate constant to k, to temp, to activation energy Activation Energy and Catalysts! As the reaction progresses (from R to P) there is a progression of Energy. Discuss the following about energy: What happens when bonds are broken? What happens when bonds are formed? During a rxn, when are bonds broken vs when are bonds formed? So how could we graph this energy exchange? Energy Profiles Energy Profiles with catalyst Record Activation Energy (and energy profiles) w/ Mechanisms You can see the Ea for each step. You can see which step is slow step? Let’s record & practice Practice Review time Let’s work on preparing for the test: PPCs Quiz–learn from mistakes Lab–read over feedback Old FRQs