1. Catalyst

2. Drill Baby Drill Quiz in 45 minutes
Integrated Practice will by homework

3. Quiz 2 SO2(g) + O2(g) ⇌ 2 SO3(g)
1. Two moles of SO2(g) and seven moles of O2(g) are introduced into a 1.00 L reaction vessel and allowed to react to form SO3(g). At equilibrium, the vessel contains four moles of SO3(g). Calculate Keq for this reaction
2 SO2(g) + O2(g) ⇌ 2 SO3(g)
2. Hydrogen and iodine gases react to form hydrogen iodide gas. If 6.00 mol of H2 and 3.00 mol of I2 are placed in a 3.00 L vessel and allowed to come to equilibrium at 250°C calculate the equilibrium concentrations of all species. The Keq for the reaction is at 250 °C.
H2 (g) + I2 (g) ⇌ 2 HI (g)

4. Cobalt Chloride Again!

5. Justify – TPS ⇌ Pink Purple
The cobalt chloride equilibrium is as follows:
Co(H2O) Cl CoCl H2O
Based on this do you believe the heating/cooling of cobalt chloride indicates that the reaction is endothermic or exothermic? Justify your reasoning. ⇌
Pink
Purple

6. Lecture 7.3 – Le Chatelier’s Principle

7. Today’s Learning Targets
LT 7.7 – I can describe and calculate the shift of a chemical reaction using the reaction quotient (Q)
LT 7.8 – I can describe the shift of a chemical reaction using Le Chatelier’s principle. Furthermore, I can explain this shift in terms of the reaction quotient and common ion effect.

8. Predicting the Direction of Reactions
Oftentimes, we examine reactions prior to them achieving equilibrium.
How do we know the direction a reaction needs to move in order to achieve equilibrium?
We use the reaction quotient (Q) to determine this
Q is calculating the equilibrium constant prior to equilibrium:
a A + b B c C + d D ⇌

9. Value of Q and Direction
There are three possible results of our Q calculation:
Q = K: Reaction is at equilibrium
Q > K: Amount of products is too large, reaction needs to shift towards reactants
Q < K: Amount of reactants is too large, reaction needs to shift towards products

10. Class Example ⇌ At 1000 K the value of Kp for the reaction:
2 SO3 (g) SO2 (g) + O2 (g)
is Calculate the value for Qp and predict the direction in which the reaction proceeds toward equilibrium if the initial partial pressures are PSO3 = 0.16 atm; PSO2 = 0.41 atm; PO2 = 2.5 atm. ⇌

11. Table Talk ⇌ At 100 oC the equilibrium constant for the reaction:
COCl2 (g) CO (g) + Cl2 (g)
has the value Kc = 2.19 x Are the following mixtures of COCl2, CO, and Cl2 at 100 oC at equilibrium? [COCl2] = 2.00 x 10-3 M; [CO] = 3.3 x 10-6 M; [Cl2] = 6.62 x 10-6 M ⇌

12. Le Chatelier’s Principle
“If a system at equilibrium is disturbed by a change in temperature, pressure, or a component concentration, the system will shift its equilibrium position so as to counteract the effect of the disturbance”
When you calculate Q you are doing the math behind Le Chatelier’s Principle

13. Le Chatelier’s Principle and Concentration
If we add more of a product/reactant, then our reaction will shift to the other side in order to compensate for this new amount.
Think back to the relationship between Q and K as the reasoning for this.

14. Le Chatelier’s Principle and Volume/Pressure
Changes in pressure can alter the side of the reaction that is favored.
If we increase pressure, the reaction will shift to the side that produces less molecules
If we decrease pressure, the reaction will shift to the side that produces more molecules

15. Le Chatelier’s Principle and Temperature
When a reaction is endothermic, heat is listed as a reactant.
Heat + Reactants  Products
When a reaction is exothermic, heat is listed as a product.
Reactants  Products + Heat
Therefore we can treat heat like a reactant or a product depending where it is listed.

16. Class Example ⇌ Consider the equilibrium:
In which direction will the equilibrium shift when:
N2O4 (g) NO2 (g) ΔHo = 58.0 kJ
N2O4 is added
NO2 is removed
The pressure is increased by addition of N2 (g)
The volume is increased
The temperature is decreased ⇌

17. PCl5 (g) PCl3 (g) + Cl2 (g) ΔHo = 87.9 kJ
Table Talk
For the reaction:
PCl5 (g) PCl3 (g) + Cl2 (g) ΔHo = 87.9 kJ
In which direction will the equilibrium shift when:
Cl2 (g) is removed
The temperature is decreased
The volume of the reaction system is increased
PCl3 (g) is added ⇌

18. Le Chat. and Catalysts
A catalyst increases the rate of reaction, but does not impact final concentrations.
Therefore, a catalyst does not impact the value of the equilibrium constant

19. Relay Race

20. Relay Race Questions
1. Calculate the reaction quotient for the following equilibrium given that [SO2Cl2] = M, [SO2] = M, and [Cl2] = M. Given that K = Which direction must the reaction shift in order to achieve equilibrium?
2 SO2 (g) + O2 (g) SO3 (g)
2. For the same equation in problem 1, calculate the reaction quotient given that that [SO2Cl2] = M, [SO2] = 0.52 M, and [Cl2] = M. Given that K = Which direction must the reaction shift in order to achieve equilibrium?
State whether it will shift to the left, right, or stay the same based on the given conditions
NaOH (aq) + HCl (aq)  NaCl (s) + H2O (l)
Add HCl
Remove NaOH
React NaOH with HNO3
NaCl (aq)  Na+ (aq) + Cl- (aq) kJ
Decrease the temperature
Increase the pressure ⇌

21. Exit Ticket
1. At 448 oC the equilibrium constant Kc for the reaction: H2 (g) + I2 (g)  2 HI (g) is Predict in which direction the reaction proceeds to reach equilibrium if we start with 2.0 x 10-2 mol of HI, 1.0 x 10-2 mol of H2, and 3.0 x 10-2 mol of I2 in a 2.00 L container. 2. Using the equilibrium in question 1, if the reaction above is exothermic, then in which direction will it shift when the reaction vessel is heated.

23. Closing Time
Read: 15.5, 15.6, and 15.7
Homework: Integrated Free Response Questions