1. Schedule Today (3/1): Continue Chapter 8
Should have read Sections 8.7 (at least)
Monday (3/4): Continue Chapter 8
Should have read through Section 8.7 (at least)
Wednesday (3/6): Continue Chapter 8
Should have read through Section 8.8 (at least)
Friday (3/8): Continue Chapter 8
Should have read all of Chapter 8
Monday (3/11): Finish Chapter 8

2. Slowly adding a base to a weak acid…
Start with 1.00-L of 1.00M HA (Ka = 1.00 x 10–6)
Added NaOH pH
change in pH
(see earlier work)
3.00 --
0.05
4.72
1.72
0.10
5.05
0.33
0.15
5.25
0.20
5.40
0.25
5.52
0.12
0.30
5.63
0.11

3. Slowly adding a base to a weak acid…
Start with 1.00-L of 1.00M HA (Ka = 1.00 x 10–6)
Added NaOH pH
change in pH
0.35
5.73
0.10
0.40
5.82
0.09
0.45
5.91
0.50
6.00
0.55
6.09
0.60
6.18
0.65
6.27

4. Slowly adding a base to a weak acid…
Start with 1.00-L of 1.00M HA (Ka = 1.00 x 10–6)
Added NaOH pH
change in pH
0.70
6.37
0.10
0.75
6.47
0.80
6.60
0.13
0.85
6.75
0.15
0.90
6.95
0.20
095
7.27
0.32
1.00
(see earlier work)
10.00
2.73

5. Slowly adding a base to a weak acid…
Initial jump in pH, buffer region, jump at equivalence

6. Best Buffers? It depends on pH!
Acid Ka
pKa HF
7.2 x 10–4
3.14 ( !)
HC2H3O2
1.8 x 10–5
4.74
HCN
6.2 x 10–10
9.21
How would we make a buffered solution at pH = 3.00?

7. Clicker Question
We have added the same (excess) mass of baking soda to 30.0 mL of 3.0M HCl, 30.0 mL of 3.0M HC2H3O2, and 30.0 mL of 3.0M HC2H3O2/NaC2H3O2. All reactions generate CO2. (Ka for HC2H3O2 = 1.8 x 10–5) Which balloon will be the largest? a) The one using HC2H3O2 will be the largest. b) The one using HCl will be the largest. c) The one using HC2H3O2/NaC2H3O2 will be the largest d) They will all be essentially the same size.

8. Slowly adding a base to an acid…
While pH remains ~same with a strong acid, it is not a “buffered solution”.

9. Titrations with 0.100M NaOH
25.0 mL of 0.100M HCl 25.0 mL of 0.100M HC2H3O2 (Ka=1.8 x 10–5; pKa=4.74)