Question

Model 1 - Potential Energy Diagrams 1) The energy (enthalpy) change of a reaction can be determined by the following expression: Activated Complex Transition State AH = Energy products - Energy reactants Activation Energy, E Reactants Consider the energy change for the reaction in Model 1 (the graph to the left). Potential Energy (kJ/mol) Energy change (AH) Products a) The energy change shown is (positive/negative). b) This reaction is (endothermic / exothermic). c) These (reactants / transition state) has more potential energy. d) These (reactants/products) have more potential energy. Reaction Progress 2) The activated complex (also called the transition state) is an intermediate (in-between) stage between reactant and products. How does the energy of the activated complex compare to the energy of the reactants and the products? 3) Reactions are theoretically reversible (although they may not be reversible under normal conditions). In a reverse reaction, the products turn back into the reactants, but the energy of the activated complex remains the same. Using Model 1 calculate the following a) the enthalpy change for the forward reaction b) the enthalpy change for the reverse reaction c) the activation energy for the forward reaction d) the activation energy for the reverse reaction_ 4) Sketch a Potential Energy diagram for the reverse reaction of the one shown in Model 1. a) b) The energy change of the reverse reaction will be (positive / negative) Calculate the c) The reverse reaction will be (exothermic / endothermic). potential reaction progress →

Answer 1

3407 A 3207 Activated complex \ Transition state (TS) t activation Energy. 1300+ I Ea Energy 1 small squaren = 20 Kylmol A Reactant 0 1. (kJ/mol &nеx9 AH change Potenzial 1 Product V 00+ - Reaction - Progress → As, 5 small division = 100 kylmol Ý 1 Small division - 100 = 20 kg/mol. S llet Energy Reactan tl FR (a) AH = fnergy product an. (Ep? - AS, Ep < ER

E 50 AH = Energy Change shown ins Negative. (6) As, OH = ove sy This is Exothermic. (C) These Transition state (340 kJ/mo) has more potential Energy (than Meactant 240 kJ/mola (d) These Reactants have more Potential energy T ER240 kylmol] t Ep 120 kJ mol ) (2) This activated complex has higher energy than energy of reactants and products: 3403 (240 or 120) IETS (3) the enthalpy change of forward (a) reaction = Ep-ÉR = (120 - 240) = -120 kylmol (Answer) (b) the enthalpy . Change of reverse CO Hy) reaction c Endothermic) = 120 hylmol le = - oH forward. (C) Activation Energy for forward ... reaction - Ets - ER ETs Energy = 340 – 240 of Transition = 100 kg/mol state. Answer icts: 340 Ep

. (d) Activation Energy of reverse reaction ( Product Reactant) = A Hot Fa = 120 + 100) Reveraction = 220 kylmol. Alternately or FalReverse) = Ets - Ep = 340 - 120 = 220 kg Imus (4) Potential Energy diagram . for the reverse reaction il product to reactant (Now, product Tisch Model 9 is Meactant) - 340 320+ 300+ . reverse - Activation eneron at Energy of reaction. Energy (kylmol) - » Product 40 - -Yh Ar (Reactant) Enthalpy change of Meverse - reaction 120 product)> Reactant - Reaction Progress (9) DHy = Ep - ER = Hove (Positive) As, Ep> ER. (8) (C) The reverse reaction will be Endothermic (As DHy = (tive) Nowy reactant af Model 1 is the product of reverse reaction modely Sketch