The document discusses several factors that affect the rate of chemical reactions: 1) Concentration and surface area - Increasing concentration and surface area increases the number and frequency of collisions between reacting particles, speeding up reactions. 2) Temperature - Higher temperatures cause particles to collide more energetically, increasing reaction rates. A 10 degree rise often doubles the rate. More particles have energy exceeding the activation energy at higher temperatures. 3) Catalysts - Catalysts increase reaction rates by lowering the activation energy needed, allowing reactions to proceed more quickly without being consumed in the process.

1. Tuesday, 14 February 2017

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.  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.  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. Maxwell Boltzman distribution

6. Temperature effect

7.  Only molecules with enough activation energy will
react to form the products.
Temperature effects explained

8. The Arrhenius equation

9. The Arrhenius equation

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. Catalyst effect

12. Catalyst effect

13. Catalyst effect

14. Hetrogeneous catalysts

15. Hetrogeneous catalysts

16. Homogeneous catalysts

17. Homogeneous catalysts

18. Relating mechanisms to the rate
determining step

19. SN 1

20. Hydrolysis of halogenoalkanes
 This is a SN2 reaction:

21. SN 2

22. Reaction of iodine with propanone

23. Reaction of iodine with propanone