2. 15.4 What does it mean if Keq is large? Small?
Apply stoichiometry to determine Keq’s
HW: 15.5 form

3. Quick review What is equilibrium? What is Keq, conceptually?
What is the Keq expression for:
2SO3(g)  2SO2(g) + O2(g)

6. Packet O’ Practice
8,10,11,12,13,14, 41

7. Chem. 116 Prof. T.L. Heise

8. Chem. 116 Prof. T.L. Heise

9. Chem. 116 Prof. T.L. Heise

11. Do Now
What were the big ideas for 15.5? Be prepared to share. Don’t be afraid to consult your notes/summary.

12. Objectives
Use Keq to predict direction of reaction based on initial reactions
Determine equilibrium concentrations based on initial conditions

13. 2SO3(g)  2SO2(g) + O2(g) Keq= 4.08 x 10-3
Initial concentrations are: [SO3] = 2 x 10-3 M, [SO2] = 5 x 10-3 M, and [O2] = 3 x 10-2 M?
Which way will the reaction proceed in order to reach equilibrium?

14. 2SO3(g)  2SO2(g) + O2(g) Keq= 4.08 x 10-3
Initial concentrations are: [SO3] = 2 x 10-3 M, [SO2] = 5 x 10-3 M, and [O2] = 3 x 10-2 M?
What will the equilibrium concentrations be?

15. Your turn: Packet O’ Practice:
38 (and actually determine EQ concentrations for each compound), 39, 40, 41

16. Todays goals Practice ICE box type problems
Discuss Le Chatelier’s principle
Test is Wednesday
Please complete 15.6 form
Lab on Monday (hopefully…)
Kinetics lab due tomorrow

17. Packet o’ practice
38 (and actually determine EQ concentrations for each compound), 39, 40, 41

22. Chem. 116 Prof. T.L. Heise

23. Chem. 116 Prof. T.L. Heise

24. Chem. 116 Prof. T.L. Heise

25. Chem. 116 Prof. T.L. Heise

26. Le Chatelier’s principle
Changing the following will disturb an equilibrium:
Changing [reactant/product]
Add-> away
Remove -> replace
Changing pressure
Favors side with less moles of gas
Changing temperature
Treat it like a chemical…

27. Remember A catalyst increases the forward AND reverse reactions rates…
No change overall…

28. 58
Sample Exercise: For the reaction PCl5(g) + energy  PCl3(g) + Cl2(g) in what direction will the equilibrium shift when (a) Cl2(g) is added (b) the temperature is increased (c ) the volume is decreased (d) PCl5(g) is added
Chem. 116 Prof. T.L. Heise
Chem 116: Prof. T.L. Heise
Chem 15.6

29. How would Keq change with increasing the temperature?
2POCl3(g) + energy  2PCl3(g) + O2(g) use this result to determine how the equilibrium constant for the reaction should change with temperature Keq = [PCl3]2[O2] [POCl3]2

30. Chem. 116 Prof. T.L. Heise

31. Chem. 116 Prof. T.L. Heise

32. Do Now Turn in Kinetics Lab
The decay of a radioactive isotope is first order and has a half-life of 10days. How long will it take for 65% of it to decay?

33. Whats the rate law?

34. Quick rundown by chapter:
CH14 stuff:
Overview
Rxn order from data
Stoich and rxn rates
Rxn mech and rate law (intermediates, catalysts, etc)
Mechanism general info
[X]left after time
½ life problems…
Catalyst and what they do…
Factors affecting rxn rate
Graphing and rate order

35. Ch 15 Big idea stuff Keq expression and determining value
Heterogenous eq…
Determining direction of reaction (Q vs Keq)
ICE question, new conc from Keq
Determining [x] given Keq and data
High vs low Keq, whats it tell you
Le chat, determine changes and ID stress from changes
Catalysts and their effects…

36. Review by looking at the lab
Determining Keq given one of the concentrations…

37. Review by looking at the lab
What happened when we added NH4Cl?
Why? (Le Chaet’ and Keq)

38. Review by looking at the lab
Determining eq concetrations of NH3, NH4+, OH- (use the accepted keq)
Initial? Change? Eq?

39. 3. The half-life of a radioisotope is found to be 4. 55 minutes
3. The half-life of a radioisotope is found to be 4.55 minutes. If the decay follows first order kinetics, what percentage of isotope will remain after 2.00 hours?

40. Chem. 116 Prof. T.L. Heise