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Mr. Quinn & Ms. Tom
March 19, 2014
Aim: What happens when chemical equilibrium is disturbed?
Do Now:
What happens when homeostasis is disrupted?
Introduction
Homeostasis is a type of equilibrium. When equilibrium is disrupted, it
shifts to the other side.
This is called Le Châtlier’s Principle.
Introduction
Which way does the equilibrium above shift when H3O+ is added?
• To the left
What two molecules are formed when H3O+ is added?
• H3PO4 and H2O
Are we still together?
In a dynamic equilibrium, which of the following must be true?
1. A catalyst is present
2. The rates of the forward and reverse reactions are equal
3. No reaction is taking place
4. Heat is released
Let’s try it out!
Which way does the equilibrium above shift when H2O is added?
• To the right
What two molecules are formed when H2O is added?
• C2H3O2- and H3O+
What SIDE (left or right) will be favored when H3O+ is removed?
• Right
Let’s try it out!
H2O (l) + 2260 J ⇌ H2O (g)
Which way does the equilibrium above shift when heat is added?
• To the right
What phase do molecules favor when heat is added?
• Gas
What phase do molecules favor when heat is removed?
• Liquid
Are we still together?
Consider the following balanced chemical equation:
A+B⇌C
What will happen when more C is added?
1.
2.
3.
4.
The equilibrium shifts to the right and A increases
The equilibrium shifts to the right and A decreases
The equilibrium shifts to the left and A increases
The equilibrium shifts to the left and A decreases
Your Turn!
Your Turn!
Given the system at equilibrium:
AgCl (s) ↔ Ag+ (aq) + Cl– (aq)
When AgCl (s) is added to the system, the equilibrium will shift to the
1. right and the concentration of AgCl (s) will decrease
2. right and the concentration of AgCl (s) will increase
3. left and the concentration of Ag+ (aq) will decrease
4. left and the concentration of Ag+ (aq) will increase
Your Turn!
Given the equilibrium system:
PbCO3(s) ↔ Pb2+(aq) + CO32–(aq)
Which changes occur as CO32- (aq) is added to the system at equilibrium?
1. The equilibrium shifts to the right and the amount of PbCO3 (s) decreases.
2. The equilibrium shifts to the left and the amount of PbCO3 (s) increases.
3. The equilibrium shifts to the right and the amount of PbCO3 (s) decreases.
4. The equilibrium shifts to the left and the amount of PbCO3(s) increases.
Your Turn!
Given the reaction at equilibrium:
2 SO2(g) + O2(g) ↔ 2 SO3(g) + heat
Which change will shift the equilibrium to the right?
1. decreasing [SO2]
2. decreasing the pressure
3. increasing [O2]
4. increasing the temperature
Your Turn!
Given the equilibrium reaction in a closed system:
H2(g) + I2(g) + heat ⇌ 2 HI(g)
What will be the result of an increase in temperature?
1. The equilibrium will shift to the left and [H2] will increase.
2. The equilibrium will shift to the left and [H2] will decrease.
3. The equilibrium will shift to the right and [HI] will increase.
4. The equilibrium will shift to the right and [HI] will decrease.
Your Turn!
Given the equilibrium reaction:
A + B ↔ C + D + heat
What change in the reaction system will shift the equilibrium to the left?
1.
2.
3.
4.
an increase in the concentration of A and B
an increase in the concentration of C and D
an increase in temperature
an increase in pressure
Your Turn!
Given the equilibrium reaction at constant pressure:
2 HBr (g) + 17.4 kcal ↔ H2 (g) + Br2 (g)
When the temperature is increased, the equilibrium will shift to the
1. right, and the concentration of HBr (g) will decrease
2. right, and the concentration of HBr (g) will increase
3. left, and the concentration of HBr (g) will decrease
4. left, and the concentration of HBr (g) will increase