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Special Topic I
121
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The amount of sodium acetate needed:
3
CH
3
COONa
4
=
1.00 M
x
x
mmol
mL
M
100 mmol
100
1 00
=
=
.
To obtain 100 mmol of sodium acetate from a 1.50 M solution of sodium acetate:
100
1 50
66 7
mmol
mL
M
mL
y
y
=
=
.
.
The amount of hydrochloric acid needed:
[
]
.
.
HCl
M
mmol
100 mL
M
mmol
=
=
=
0 77
0 77
77
x
x
To obtain 77 mmol of hydrochloric acid from a 1.50 M solution of HCl:
77
1 50
51 3
mmol
mL
M
mL
y
y
=
=
.
.
100 mL of a 1.00 M acetic acid/acetate buffer cannot be made from these reagents, because the volumes
needed
1
66.7 mL
+
51.3 mL
2
add up to more than 100 mL. To make this buffer using sodium acetate
and hydrochloric acid, you need to use a more concentrated solution
1
7
1.50 M
2
of sodium acetate
and/or a more concentrated solution
1
7
1.50 M
2
of HCl.