CHEM 102 1nd Edition Lecture 15 Outline of Last Lecture I. Rate Constant KII. Kinetics So FarIII. Concentration vs Time: Integrated Rate LawsIV. Zero-Order ReactionsV. First-Order ReactionsVI. Second-Order ReactionsVII. Use What You Now KnowOutline of Current Lecture I. Transition State Theory II. Arrehenius EquationIII. Reaction MechanismCurrent LectureI. Transition State Theory -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.- The activation energy of the reaction will equal the topmost part of the curve – the energy of the reactants- The energy of the reaction is the energy of the products – the energy of the reactants- If the equation were switched, then the reactants would become the products and the products the reactants.- The top of the curve is the activation complex This point is the there is finally enough energy in the reaction to activate the reaction Two-part reaction: one part of the molecule must leave before the other part of the molecule can attach- Ea cannot be predicted from the enthalpy of the reaction- If the temperature increases, then the rate increases because the number of molecules that can reach the activation energy has increased due to the increase of energy from the increase in temperature.- Catalyst reduce the activation energy.- If the graph of the catalyst has two humps, then there it is a two-step reaction.- Example 1-- What is the ΔE of this reaction 80 J -100 J -75 J -80 J ** ΔE = Ep - Er ΔE = 20 – 100 = -80 J- What is the ΔE of the reverse reaction? 80 J ** -100 J -75 J -80 J Because the original way of the reaction is -80 J, then the reverse would be the opposite sign or 80 J ΔE = Ep - Er ΔE = 100 – 20 (because the reactants and products would be switched) = 80 J- What is the ΔEa (activation energy) of the reverse reaction? 155 J ** 100 J 75 J 80 J ΔEa = Top - Er ΔE = 175 – 20 = 155 J- What is the ΔEa of the reaction? 155 J 100 J 75 J ** 80 J ΔEa = Top - Er ΔEa = 175 – 100 = 75 JII. Arrehenius Equation-K = A e− Ea/ RT-lnK =−EaRT1T+lnA, so that the equations resembles y = mx + b K = specific rate constant A = frequency factor Ea = activation energy R = 8.314 j/molK T = absolute temp (K) E-Ea/rt = fraction of moles availableIII. Reaction Mechanism- The set of steps that contribute to the overall reaction- These steps shows bonds breaking and forming- Reactions can occur in one step- Does not include intermediate compounds (compounds formed then used right away)- Only include products if specified- Elementary reactions Single even at a molecular level Reaction order = the number of reactant molecules Unimolecular = one – molecule reaction Br2 2Br Bimolecular = two – molecular
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