Worksheet 5. Acids, Bases and Buffers
.
I. Complete the table
pH
[ H3O+ ] or [H+]
pOH
[ OH– ]
ACID or BASE?
11.86
1.38 x 10-12 M
2.14
7.24 x 10-3 M
BASE
3.36
4.37 x 10-4 M
10.64
2.31 x 10–11 M
ACID
10.91
1.23 x 10-11 M
3.09
8.13 x 10-4 M
BASE
5.13
7.49 x 10–6 M
1.34 x 10-9 M
ACID
8.87
II. Determine the conjugate acid for the following bases:
1.
2.
3.
OH- O
HSO4-1 H2SO4
ClO4-1 HClO4
III. Determine the conjugate base for the following acids:
1. HPO4-2 PO4-3
2. HCO3-1 CO3-2
3. HBrO2 BrO2-1
1. Calculate the pH of an acetic acid (HAc) buffer with [H+] = 0.15 and [Ac-] = 0.18 if the pka
of acetic acid is 4.75.
Acid: 0.15 M
Base: 0.18 M
pH = pKa + log B/A
pH = 4.75 + log 1.2
pH = 4.83
b. if 0.01M of HCl is added to this solution, what will be the new pH?
Acid: 0.15 + 0.01 = 0.16 M
Base: 0.18 - 0.01 = 0.17 M
pH = pKa + log B/A
pH = 4.75 + log 1.06
pH = 4.78
c. if 0.01M of NaOH is added to this solution, what will be the new pH?
Acid: 0.15 - 0.01 = 0.14 M
Base: 0.18 + 0.01 = 0.19 M
pH = pKa + log B/A
pH = 4.75 + log 1.36
pH = 4.88
d. Is this a good buffer? Justify your answer.
Buffer Range: 4.83-1 = 3.83
4.83+1= 5.83
Yes, it is a good buffer because it is in the buffer range.