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

2. Buffer Solutions

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

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

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

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

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

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

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

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

11. 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

12. AP CHM HW
Problem: 9
Page: 421

13. CHM II HW
Problem: 11
Page: 818

14. 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

15. 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

16. 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

17. 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

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

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

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

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

22. Henderson-Hasselbach Eq
pH = pKa + log

23. Henderson-Hasselbach Eq
pOH = pKb+ log

24. 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

25. AP CHM HW
Read: Chapter 14
Problem: 23
Page: 421

26. CHM II HW
Read: Chapter 19
Problem: 21
Page: 819

27. 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

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

29. Test
Friday

30. 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

31. Titration Curves

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

35. 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

36. AP CHM HW
Read: Chapter 14
Problem: 33
Page: 422

37. CHM II HW
Read: Chapter 19
Problem: 31
Page: 819