1. Drill: A 0.100 M solution of HZ ionizes 20.0 %. Calculate: KaHZ

2. Review Drill & Discuss Exam (Writing on it) (A Mistake)

3. Second Semester Syllabus

4. The SSS is on Poly’s Website

5. Equilibrium will be a major of the second semester. Review PP-20-22

6. CHM II HW
Review PP-23
Complete the attached assignment & turn it in tomorrow

7. Buffer Solutions

8. A solution that resists changes in pH
Buffer Solution
A solution that resists changes in pH

9. Made from the combination of a weak acid & its salt
Buffer Solution
Made from the combination of a weak acid & its salt

10. Made from the combination of a weak base & its salt
Buffer Solution
Made from the combination of a weak base & its salt

11. Buffer Examples Mix acetic acid & sodium acetate
Mix ammonia & ammonium chloride

12. A buffer solution works best when the acid to salt ratio is
1 : 1

13. A buffer solution works best when the base to salt ratio is
1 : 1

14. Buffer Solution
The buffering capacity of a solution works best when the pH is near the pKa

15. pKa or pKb
pKa = - log Ka
pKb = - log Kb

16. Buffer Equilibria

17. To solve buffer equilibrium problems, use the same 5 steps

18. 5 Steps of Equilibrium Problems
1) Set up & balance reaction

19. 5 Steps of Equilibrium Problems
2) Assign Equilibrium amounts in terms of x
(ICE)

20. 5 Steps of Equilibrium Problems
3) Write the equilibrium expression (K = ?)

21. 5 Steps of Equilibrium Problems
4) Substitute Equilibrium amounts into the K

22. 5 Steps of Equilibrium Problems
5) Solve for x

23. Calculate the pH of a solution containing
Buffer Problems
Calculate the pH of a solution containing
0.10 M HAc in 0.10 M NaAc: Ka = 1.8 x 10-5

24. Calculate the pH of 0.10 M NH3 in
Buffer Problems
Calculate the pH of 0.10 M NH3 in
0.20 M NH4NO3:
Kb = 1.8 x 10-5

25. Calculate the pH of a solution containing
Buffer Problems
Calculate the pH of a solution containing
0.10 M HBz in 0.20 M NaBz: Ka = 6.4 x 10-5

26. Calculate the pH of a solution containing
Drill:
Calculate the pH of a solution containing
0.30 M HZ in 0.10 M NaZ: Ka = 3.0 x 10-5

27. Review Drill & Check HW

28. CHM II HW
Review PP-23
Complete the attached assignment & turn it in tomorrow.

29. Calculate the pH of a solution containing
Buffer Problem
Calculate the pH of a solution containing
0.50 M R-NH2 in 0.10 M R-NH3I: Kb = 4.0 x 10-5

30. Derivations from an equilibrium constant

31. HA H+ + A-
[H+][A-]
[HA]
Ka =

32. Cross multiply to isolate [H+]
HA H+ + A-
[H+][A-]
[HA]
Ka =
Cross multiply to isolate [H+]

33. HA H+ + A-
[Ka][HA]
[A-]
[H+]=

34. HA H+ + A-
[HA]
[A-]
[H+] = (Ka)

35. HA H+ + A-
[HA]
[A-]
[H+] = (Ka)
Take –log of each side

36. pH =
[HA]
[A-]
pKa - log

37. Henderson-Hasselbach Eq
pH = pKa + log

38. Henderson-Hasselbach Eq
pOH = pKb+ log

39. Buffer Problems
Calculate the salt to acid ratio to make a buffer solution with pH = 5.0
Ka for HBZ = 2.0 x 10-5

40. Derivations from an equilibrium constant

41. HA H+ + A-
[H+][A-]
[HA]
Ka =

42. [H+][A-]
[HA]
Ka =
Divide both sides by [H+]

43. You Get the Salt to Acid Ratio
Ka [A-]
[H+] [HA] =
You Get the Salt to Acid Ratio

44. Drill:
Calculate the salt to acid ratio to make a buffer solution with pH = 5.0
Ka for HBZ = 2.0 x 10-5

45. Review & Collect Drill & HW

46. CHM II HW
Review PPs 23 & 24
Complete the attached assignment & turn it in tomorrow.

47. Buffer Problems
Calculate the salt to base ratio to make a buffer solution with pH = 9.48
Kb for MOH = 2.0 x 10-5

48. Point at which the # of moles of the two titrants are equal
Equivalence Point
Point at which the # of moles of the two titrants are equal

49. Titration Curves

51. [HA]=[OH-]
[HA]=[A-]

52. Drill:
Calculate the pH of a buffer solution containing 0.50 M HX in 0.25 M KX.
Ka = 2.5 x 10-5

53. Test
End of next week

55. Calculate the HCO3- to H2CO3 ratio in blood with pH = 7.40
Ka1 for H2CO3 = 4.4 x 10-7

56. 150 ml of 0. 10 M NaOH is added to 100. 0 ml of 0. 10 M H2CO3
150 ml of 0.10 M NaOH is added to ml of 0.10 M H2CO3. Calculate pH.
Ka1 for H2CO3 = 4.4 x 10-7
Ka2 for H2CO3 = 4.8 x 10-11