1. Reaction Rates and Le Chatelier’s Principle

2. Rate of Reaction The rate of a chemical reaction
The number of particles that react in a certain amount of time to form products
Describes how rapidly a chemical change takes place
They are determined by measuring changes in physical properties
Volume, Temperature, Color, Mass, or pH

3. Five Factors that Effect Reaction Rate
1. Nature of the reactants
2. Temperature
3. Concentration
4. Surface Area
5. Catalysts

4. Which INCREASE Reaction Rates?
Increasing Temperature
Increasing Concentration
Increasing Surface Area
Adding a Catalyst.
How are these factors related to Reaction Rates?
DIRECTLY

5. Nature of Reactants
Reaction rates are affected by the complexity of the bonds that must be broken and formed in the chemical reaction
The state of a reactant can also affect the reaction rate
Gases have the fastest and solids the slowest reaction rats
Because the frequency at which particles collide and the amount of energy they possess increase with increasing motion.

6. Continued
The faster particles are moving, the more frequent they will collide
Collide with greater kinetic energy.
Because of this TEMPERATURE and REACTION RATE are directly related

7. Chemical Equilibrium
At equilibrium the forward reaction and the reverse reaction happen at the same time
There is no change in the amount of any substance in the reaction
Le Chatelier’s principle can be used to predict the effect of a change in conditions on a chemical equilibrium

8. Le Chatelier’s Principle Summarized
If a chemical system at equilibrium experiences a change (also called a stress) in concentration, temperature, volume, or total pressure; the equilibrium will shift in order to minimize that change.

9. See Saw
H2O H OH

10. Add More Hydrogen H2O OH H H
Which way does the see saw have to shift to reach equilibrium again?

11. Add More Hydrogen H2O OH H H
Which way does the see saw have to shift to reach equilibrium again?

12. Add More Hydrogen H2O OH SHIFT LEFT H H
More H2O is produced due to the shift in equilibrium

13. Synthesis of Ammonia H2 H2
NH3
NH3 N2 H2
N2 (g) + 3H2 (g)  2NH3 (g)

14. SHIFT will occur to side with the least number of MOLES
Increase Pressure
SHIFT RIGHT H2
NH3
NH3 H2 H2 N2
SHIFT will occur to side with the least number of MOLES
N2 (g) + 3H2 (g)  2NH3 (g)

15. SHIFT will occur to side with the least number of MOLES
Increase Pressure
SHIFT RIGHT H2
NH3
NH3 H2 H2 N2
SHIFT will occur to side with the least number of MOLES
N2 (g) + 3H2 (g)  2NH3 (g)

16. Decreasing Volume (Think about how P and V relate with Boyle’s Law)
NH3
NH3 N2 H2
N2 (g) + 3H2 (g)  2NH3 (g)

17. Decrease Volume = Increase Pressure
SHIFT RIGHT H2
NH3
NH3 H2 H2 N2
SHIFT will occur to side with the least number of MOLES
N2 (g) + 3H2 (g)  2NH3 (g)

18. Change in Temperature
Depends if reaction is Endothermic or Exothermic.
Endothermic: Heat on LEFT
Exothermic: Heat on RIGHT

19. Exothermic Increase Temperature… which way will the see saw tip? D A C
HEAT D A C B

20. Which way will the reaction shift?
Exothermic A
HEAT B C D
Which way will the reaction shift?

21. Reaction will SHIFT LEFT
Exothermic A
HEAT B C D
Reaction will SHIFT LEFT

22. Exothermic DecreaseTemperature… which way will the see saw tip? D A C
HEAT D A C B
DecreaseTemperature… which way will the see saw tip?

23. Which way will the reaction shift?
Exothermic
HEAT D C B A
Which way will the reaction shift?

24. Reaction will SHIFT Right
Exothermic
HEAT D C B A
Reaction will SHIFT Right

25. Endothermic Increase Temperature… which way will the see saw tip? D A
HEAT D A C B

26. Which way will the reaction SHIFT?
Endothermic
Which way will the reaction SHIFT?
HEAT D C B A

27. Reaction will SHIFT Right
Endothermic
Reaction will SHIFT Right
HEAT D C B A

28. Endothermic Decrease Temperature… which way will the see saw tip? D A
HEAT D A C B

29. Which way will the reaction SHIFT?
Endothermic
HEAT
Which way will the reaction SHIFT? A B C D

30. Reaction will SHIFT Left
Endothermic
HEAT
Reaction will SHIFT Left A B C D

31. Reaction Rates
Concentration
Temperature
Pressure
Volume