5 CHEM 117 Exam #3 Study Guide Chapter 13: The Effect of Temperature on Reaction RateSection 13.5Arrhenius Equation: k= Ae^(-Ea/RT)- where “k” is the constant rate, A is a frequency factor related to the number of times that reactants approach the energy barrier per unit time and with the proper orientationfor a successful reaction to occur, Ea is the activation energy, R is the gas constant (8.314 J/mol*K), and T is the temperature in Kelvin. - Higher T leads to larger k which increases the rateNew relationship derived from Arrhenius equation:ln(k2/l1) = -Ea/R [1/T2 – 1/T1)Section 13.6- Reaction Mechanisms1. Two types of molecular transformations:-unimolecular- the structure of a single particle rearranges to produce a different particle or particles.-bimolecular- two particles collide and rearrange into products; new bonds may be formed between the reactants, and existing bonds may be broken. **Study Table 13.3 “Rate Laws for Elementary Steps” (Need to memorize, not on test)Rules for Mechanism Elementary Steps:a.the individual, elementary steps of a mechanism must add up to the overall reaction.b.The individual elementary steps cannot be broken down into simpler steps.c. There is a reaction intermediate. HI (g), in this mechanistic schemed.In most mechanistic schemes, one of the elementary steps is slower than the others and iscalled the rate-determining step**Study page 626 in textbook!Section 13.7: Catalysts- The primary function of a catalyst is to alter the mechanism so that the activation energy for the rate-limiting step is decreased, which has the effect of increasing the rate constant for that step. **Study Energy Diagram on page 628.Chapter 14: Chemical EquilibriumDynamic Equilibrium: The condition in which the rate of the forward reaction equals the rate of the reverse reaction.Expressing the equilibrium constant in terms of pressure, KpExpression for Kp: Kp= Products/Reactants = P(C)^c x P(D)^d / P(A)^a x P(B)^b-The values of Kc and Kp are not necessarily the same because of the difference in units: Kc= Kp If Δn = 0. Heterogeneous Equilibria:-the concentrations of pure solids and pure liquids do not change during the course of a reaction.-because their concentration doesn’t change, solids and liquids are not included in the equilibrium constant expression.The Reaction QuotientQc= [C]^c[D]^d / [A]^a[B]^b*If Q < K reaction will proceed to the right. *If Q > K reaction will proceed to the left. Le Chatelier’s Principle-When a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance. -Guides us in predicting the effect various changes in conditions have on the position of equilibrium.Effects of Volume change on Equilibrium:-When volume decreases, the pressure is increased and therefore shifts to the right because there are more moles on the left. -Increasing the volume causes the reaction to shift in the direction that has the great number of moles of gas particles. -If a reaction has an equal number of moles of gas on both sides of the chemical equation, then a change in volume produces no effect on the equilibrium.-adding an inert gas to the mixture at a fixed volume has no effect on equilibrium. The Effect of Temperature Changes on Equilibrium position:Exothermic Reactions:-When the temperature decreases the reaction shifts to the right.-When the temperature increases the reaction shifts to the left. Endothermic Reactions:-When the temperature decreases the reaction shifts to the left.-When the temperature increases the reaction shifts to the