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  • 1. RATE THEORIES
  • 2. RATE THEORIES
    • Collision Theory
    • Transition State Theory
    • Catalysts
  • 3. RATE THEORIES COLLISION THEORY: The rate of rxn is proportional to the number of effective/successful collisions per second between reactant molecules. What factors determine whether reactants could form a molecule? (e.g. is bumping into each other enough?)
  • 4. Not all collisions are effective. Effective collision: A collision that actually results in the production of product molecules In a game of pool, what are the two conditions that are required for an effective collision? RATE THEORIES COLLISION THEORY:
  • 5. WRONG ORIENTATION RATE THEORIES COLLISION THEORY: Not all collisions are effective 8 3
  • 6. CORRECT ORIENTATION! RATE THEORIES COLLISION THEORY: 3 8
  • 7. INCORRECT SPEED! RATE THEORIES COLLISION THEORY: Not all collisions are effective 3 8
  • 8. CORRECT SPEED!!! RATE THEORIES COLLISION THEORY: 3 8
  • 9. RATE THEORIES
    • COLLISION THEORY:
    • For a collision to be effective, the molecules must collide with the proper:
      • orientation
      • kinetic energy
    8 SCORE
  • 10. RATE THEORIES
    • Orientation : H 2 + I 2  2 Hl
    COLLISION THEORY:
  • 11. RATE THEORIES
    • Orientation : NO + NO 3  2 NO 2
    COLLISION THEORY:
  • 12. RATE THEORIES
    • Kinetic energy : A minimum kinetic energy, called activation energy (E a ), is required between reactants for a reaction to proceed.
      • E a is unique to each reaction
    • Higher temperatures result in a higher percentage of reactants with enough energy to react.
    COLLISION THEORY:
  • 13. RATE THEORIES
    • Kinetic energy :
    COLLISION THEORY:
  • 14. RATE THEORIES
    • Kinetic energy :
    COLLISION THEORY: number of particles energy Only a fraction of the reactant molecules collide with enough kinetic energy
  • 15. RATE THEORIES COLLISION THEORY:
    • Factors affecting effective collisions:
      • molecule orientation
      • molecule energy
    • Collision Theory Animation
    • Collision Theory Applet
  • 16. RATE THEORIES TRANSITION STATE THEORY: Potential energy Reaction coordinate Potential energy diagrams Reactants Products E a Δ H The transition state complex (or activated complex) is formed at this peak
  • 17. RATE THEORIES TRANSITION STATE THEORY: Potential energy diagrams The transition state complex (bonds break and form at the same time) Potential energy Reaction coordinate Reactants Products E a Δ H
  • 18. RATE THEORIES TRANSITION STATE THEORY: Potential energy diagrams
  • 19. RATE THEORIES TRANSITION STATE THEORY: Potential energy Reaction coordinate Draw the potential energy diagram for the reverse reaction Reactants Products E a Δ H
  • 20. RATE THEORIES TRANSITION STATE THEORY: Examine the E a for both reactions. What does that suggest? E a is different between the forward and reverse directions of a given reaction. Generally, endothermic reactions are slower than exothermic reactions due to a higher E a .
  • 21. RATE THEORIES TRANSITION STATE THEORY:
    • Identify E a ,  H and transition state.
    • What are the values of E a and  H? 50kJ, -100kJ
    • Endothermic or exothermic? Exothermic
    • What are E a and  H for the reverse rxn? 150kJ, 100kJ
  • 22. RATE THEORIES CATALYST: catalyst - a substance that increases the rate of a chemical reaction without being consumed homogeneous catalyst - exist in the same phase as the reactants heterogeneous catalyst - exist in a different phase as the reactants
  • 23. RATE THEORIES CATALYST: Catalysts lower the E a of a reaction
  • 24. RATE THEORIES CATALYST: Catalysts lower the E a of a reaction
  • 25. RATE THEORIES CATALYST:
    • Catalysts:
    • bend or stretch bonds to make them easier to break / react
    • reduce E A (make transition state easier)
    • bring two reactants close together
    • provide a microenvironment for reactions
  • 26. RATE THEORIES CATALYST: Inhibitors - bind with the reactant or the catalyst to prevent the reaction from occurring and reducing reaction rate