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Factors affecting reaction rates

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Factors affecting chemical reaction rate

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Factors affecting reaction rates

  1. 1. Tuesday, 14 February 2017
  2. 2.  Concentration  The higher the level of concentration (or pressure in gases) the faster the reaction.  This is due to increased collisions between reacting particles. Factors affecting reaction rates
  3. 3.  Surface area in solids  The larger the surface area of a solid the faster the reaction. Finely divided substances have much larger surface areas than large chunks of a solid.  This is due to increased collisions between reacting particles. Factors affecting reaction rates
  4. 4.  Temperature  The higher the temperature the faster the reaction.  This is due to increased and more energetic collisions between reacting particles.  A 10oC rise in temperature often results in a doubling of the reaction rate.  Key point: at a higher temperature more molecules have energy greater than the activation energy. Factors affecting reaction rates
  5. 5. Maxwell Boltzman distribution
  6. 6. Temperature effect
  7. 7.  Only molecules with enough activation energy will react to form the products. Temperature effects explained
  8. 8. The Arrhenius equation
  9. 9. The Arrhenius equation
  10. 10.  Catalysts  Catalysts increase the rates of chemical reactions.  This is due a lowering of the activation energy for the reaction.  Catalysts are not consumed in the reaction so in theory they can be used over and over again. In practice they are often contaminated and/or some is lost in a process. Factors affecting reaction rates
  11. 11. Catalyst effect
  12. 12. Catalyst effect
  13. 13. Catalyst effect
  14. 14. Hetrogeneous catalysts
  15. 15. Hetrogeneous catalysts
  16. 16. Homogeneous catalysts
  17. 17. Homogeneous catalysts
  18. 18. Relating mechanisms to the rate determining step
  19. 19. SN 1
  20. 20. Hydrolysis of halogenoalkanes  This is a SN2 reaction:
  21. 21. SN 2
  22. 22. Reaction of iodine with propanone
  23. 23. Reaction of iodine with propanone

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