1. LeChâtelier's Principle
If a stress is applied to a system at equilibrium, the system will shift in the direction which helps alleviate the stress and find a NEW EQUILIBRIUM position.

2. Stress causes the opposing rates to no longer be equal
change in concentration
change in temperature
change in pressure gases ONLY
adding a catalyst

3. Concentration Changes
Increasing the concentration of a substance will shift the equilibrium in the direction which consumes that substance
A + B ↔ C + D A
A & B have more effective collisions between them and produce more C & D

4. A decrease in concentration will shift the equilibrium in the direction which produces that substance A
A + B C + D

5. [N2] increases [NH3] increases [H2] decreases
Which way will the equilibrium shift if:
[N2] increases
[NH3] increases
[H2] decreases
Answers 

6. Which way will the equilibrium shift if:
[N2] increases RIGHT to use up extra N2
[NH3] increases LEFT to use up extra NH3
[H2] decreases RIGHT to use up extra H2

7. Common Ion Effect
A substance containing chloride ions (ex. NaCl) is added to this equilibrium system.
Which way will the equilibrium shift?
Left to consume the excess Cl-1 ions
What will happen to [Ag+1]?
Decrease to make AgCl

8. Temperature Changes
Increasing temperature will shift the equilibrium in the endothermic direction
As heat E is added
the system absorbs it

9. Which way will equilibrium shift if E in increased?
ΔH = 53.0 kJ

10. Decreasing temperature will shift the equilibrium in the exothermic direction
As heat E is decreased
the system releases
heat E

11. Which way will equilibrium shift if temp is decreased?
ΔH = kJ

12. Pressure Changes GASES ONLY
An increase in pressure on the system will shift the equilibrium in the direction which produces fewer TOTAL gas molecules
2 moles gas
1 mole gas
+ 3 moles gas
4 moles gas

13. 2Fe(s) + 3H2O(l) ↔ Fe2O3(s) + 3H2(g)
It is NOT necessary for ALL substances to be gases for pressure to have an effect.
2Fe(s) + 3H2O(l) ↔ Fe2O3(s) + 3H2(g)
Which way will the equilibrium shift if the pressure is increased?

14. 2Fe(s) + 3H2O(l) ↔ Fe2O3(s) + 3H2(g)
It is NOT necessary for ALL substances to be gases for pressure to have an effect.
2Fe(s) + 3H2O(l) ↔ Fe2O3(s) + 3H2(g)
Which way will the equilibrium shift if the pressure is increased? LEFT: to the side with less gas (in this case there is NO gas on the left and 3 moles on the right. )

15. Decrease pressure
Increase pressure

16. LeChatelier’s Principle Practice
Relieve the stress

17. THE ↔ END