1. Mr. Quinn & Ms. Tom March 24, 2014 Aim: How does chemical equilibrium correct itself? Do Now:
What will happen to the size of the balloon on the right when the balloon on the left is squeezed?

2. Introduction Le Châtlier’s Principle:
When we ADD to one side of an equilibrium, it shifts to the other side.
When we REMOVE from one side of an equilibrium, it shifts to that side.

3. Introduction
Which way does the equilibrium above shift when H3O+ is added?
Which way does the equilibrium above shift when H3O+ is removed?
To the left
To the right

4. Introduction
Which way does the equilibrium above shift when H2O is added?
Which way does the equilibrium above shift when H2O is removed?
To the right
To the left

5. Let’s try it out!
Which way does the equilibrium above shift when C2H4O2 is added?
What two molecules are formed when C2H4O2 is added?
What SIDE (left or right) will be favored when C2H3O2- is removed?
To the right
C2H3O2- and H3O+
Right

6. Let’s try it out! CH4O (g) ⇌ CH4O (l) + heat
Which side contains the heat term? Which way does the equilibrium above shift when heat is added?
What phase do molecules favor when heat is added?
Why does the equilibrium shift to the right when heat is removed?
To the left
Gas
Le Châtlier’s Principle

7. Your Turn!

8. NaCl (s) ↔ Na+ (aq) + Cl– (aq)
Your Turn!
Given the system at equilibrium:
NaCl (s) ↔ Na+ (aq) + Cl– (aq)
When NaCl (s) is added to the system, the equilibrium will shift to the
right and the concentration of NaCl (s) will decrease
right and the concentration of NaCl (s) will increase
left and the concentration of Na+ (aq) will decrease
left and the concentration of Na+ (aq) will increase

9. PbCO3(s) ↔ Pb2+(aq) + CO32–(aq)
Your Turn!
Given the equilibrium system:
PbCO3(s) ↔ Pb2+(aq) + CO32–(aq)
Which changes occur as Pb2+ (aq) is added to the system at equilibrium?
The equilibrium shifts to the right and the amount of PbCO3 (s) decreases.
The equilibrium shifts to the left and the amount of PbCO3 (s) increases.
The equilibrium shifts to the left and the amount of PbCO3(s) increases.

10. N2 (g) + 2 O2 (g) ↔ N2O4 (g) + heat
Your Turn!
Given the reaction at equilibrium:
N2 (g) + 2 O2 (g) ↔ N2O4 (g) + heat
Which change will shift the equilibrium to the right?
decreasing [N2]
adding a catalyst
increasing [O2]
increasing the temperature

11. 2 HI(g)⇌ H2(g) + I2(g) + heat
Your Turn!
Given the equilibrium reaction in a closed system:
2 HI(g)⇌ H2(g) + I2(g) + heat
What will be the result of an increase in temperature?
The equilibrium will shift to the left and [H2] will increase.
The equilibrium will shift to the left and [H2] will decrease.
The equilibrium will shift to the right and [I2] will increase.
The equilibrium will shift to the right and [HI] will increase.

12. Your Turn! Given the equilibrium reaction: A + B + heat ↔ C + D
What change in the reaction system will shift the equilibrium to the left?
an increase in the concentration of A and B
an increase in the concentration of C and D
an increase in temperature
adding a catalyst

13. 2 HBr (g) + 17.4 kcal ↔ H2 (g) + Br2 (g)
Your Turn!
Given the equilibrium reaction at constant pressure:
2 HBr (g) kcal ↔ H2 (g) + Br2 (g)
When the temperature is increased, the equilibrium will shift to the
right, and the concentration of HBr (g) will decrease
right, and the concentration of HBr (g) will increase
left, and the concentration of HBr (g) will decrease
left, and the concentration of HBr (g) will increase