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Chem 100
Dr. Anna ToyPalmer
Ch 13 Problems
1.
What is the mass percent of a solution when 15.4 g of sodium phosphate is dissolved
in 56.5 g of water?
4
3
PO
Na
%
4
.
21
%
100
)
g
4
.
15
g
5
.
56
(
g
4
.
15
Percent
Mass
=
+
=
X
2.
How many milliliters of a 15.5% mass percent potassium carbonate solution to obtain
3.65 g of potassium carbonate?
(Assume the density of the solution is 1.00 g/ml)
3
2
3
2
3
2
CO
K
g
.5
23
solution
g
1.00
solution
ml
1.00
X
CO
K
g
15.5
solution
g
100
X
CO
K
g
3.65
=
3.
What is the mass percent of a 0.15 M sucrose (C
12
H
22
O
11
) solution?
(Assume that the
density of the solution is 1.00 g/ml)
C
12
H
22
O
11
: [(12 X 12.011)+(22 X 1.00794)+(11 X 15.9994)] g/mol = 342.30 g/mol
solution
sucrose
5.1%
%
100
sucrose
mol
1
sucrose
g
342.30
solution
g
1.00
solution
ml
1.00
X
solution
ml
1000
solution
L
1
X
solution
L
1
sucrose
mol
0.15
=
X
X
4.
25.3 ml of a 3.5% mass percent sodium hydroxide solution is neutralized by 18.7 ml
of an acetic acid solution.
What is the mass percent concentration of the acetic acid
solution?
(Assume that the density of solution for both the sodium hydroxide
solution and the acetic acid solution is 1.00 g/ml)
NaOH (aq) + HC
2
H
3
O
2
(aq)
H
2
O (l) + NaC
2
H
3
O
2
(aq)
Equivalence:
1 NaOH ≡ 1 HC
2
H
3
O
2
Molar mass:
NaOH:
(22.989 + 15.9994 + 1.00794)g/mol = 39.996 g/mol
HC
2
H
3
O
2
:
(4X1.00794 + 2X12.011 + 2X15.9994) g/mol = 60.053 g/mol
Obtain moles of NaOH from mass percent and convert to grams of acetic acid.
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 Spring '09
 Palmer

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