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120 Special Topic I
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2. By mixing the appropriate amounts of acetic acid and sodium hydroxide and adding water to
obtain a final volume of 100 mL.
Sodium hydroxide is used to convert some of the acetic acid into sodium acetate. This means that acetic
acid will be the source of both acetic acid and sodium acetate.
The concentrations needed:
3
CH
3
COOH
4
=
1.00 M
3
NaOH
4
=
0.23 M
The amount of acetic acid needed:
3
CH
3
COOH
4
=
1.00 M
x
x
mmol
mL
M
100 mmol
100
1 00
=
=
.
To obtain 100 mmol of acetic acid from a 1.50 M solution of acetic acid:
100
1 50
66 7
mmol
mL
M
mL
y
y
=
=
.
.
The amount of sodium hydroxide needed:
3
NaOH
4
=
0.23 M
x
x
mmol
100 mL
M
mmol
=
=
0 23
23
.
To obtain 23 mmol of sodium hydroxide from a 1.50 M solution of NaOH:
23
1 50
15 3
mmol
mL
M
mL
y
y
=
=
.
.
The desired buffer solution can be prepared using: 66.7 mL 1.50 M acetic acid
15.3 mL 1.50 M NaOH
18.0 mL H
2
O
100.0 mL
3. By mixing the appropriate amounts of sodium acetate and hydrochloric acid and adding water to
obtain a final volume of 100 mL.
Hydrochloric acid is used to convert some of the sodium acetate into acetic acid.
This means that sodium acetate will be the source of both acetic acid and sodium acetate.
The concentrations needed:
3
CH
3
COONa
4
=
1.00 M
3
HCl
4
=
0.77 M