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CHM 130 GCC

Chapter 16. CHM 130 GCC. 16.1 Collision Theory. Molecules must hit/collide in order to react and make products A successful collision results in reactant bonds breaking and/or product bonds forming To increase the # of successful collisions: you need more collisions.

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CHM 130 GCC

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  1. Chapter 16 CHM 130 GCC

  2. 16.1 Collision Theory • Molecules must hit/collide in order to react and make products • A successful collision results in reactant bonds breaking and/or product bonds forming • To increase the # of successful collisions: • you need more collisions. • you need enough energy, Ea, activation energy. • the molecules must be oriented correctly. http://www.mhhe.com/physsci/chemistry/animations/chang_2e/orientation_of_collision.swf

  3. To Increase the Rate of Reaction • Increase [reactant], more reactants = more collisions • Increase temperature, molecules move faster = more collisions AND more energy • Add a catalyst which provides an alternate reaction pathway with lower Ea Activation Energy, Ea, is the minimum energy needed to react (turn reactants to products)

  4. 16.2 Energy Profiles • Transition state = in between reactants and products, the reactant bonds are ½ broken and product bonds ½ formed, so this is a very high energy and unstable species, exists less than a millisecond • DH = change in heat energy = product’s heat – reactant’s heat • Endothermic = reactants gain or absorb heat, heat is a reactant, heat enters the rxn • Reactants + Heat g Products • Exothermic = reactants lose or release heat, heat is a product, heat exits the rxn • Reactants g Products + Heat

  5. - Exothermic, is DH + or -?

  6. Draw the energy profile for an endothermic reaction • Label the • TS • DH • Reactants • Products • EA

  7. + Endothermic, is DH + or -?

  8. With Catalyst

  9. Self Test • Page 477 • Try 1-2, 10 • Answers in Appendix J

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