Chemistry Worksheets Page 2
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2
313. What is the molar solubility of Ca
(PO
)
in a 0.20 M Na
PO
solution? Ksp for Ca
(PO
)
= 1.3 x
3
4
2
3
4
3
4
2
-32
-11
10
. Ans. 2.3 x 10
mol/L
Predicting Precipitate Formation
14. Water from a well is found to contain 3.0 mg of calcium ion per liter (Ca, 40. g/mol). If 0.5 mg of
sodium sulfate (142 g/mol) is added to one liter of the well water without changing its volume, will a
-5
-10
precipitate of CaSO
form? Ksp for CaSO
= 7.1 x 10
. Ans. P = 2.6 x 10
< Ksp, no
4
4
15. Before lead in paint was discontinued, lead chromate was a common pigment in yellow paint. A
1.0-L solution is prepared by mixing 0.50 mg of lead nitrate (331.2 g/mol) with 0.020 mg of
potassium chromate (K
CrO
, 194.2 g/mol). Will a precipitate of PbCrO
form? Ksp for PbCrO
=
2
4
4
4
-14
-13
2 x 10
. Ans. P = 1.6 x 10
> Ksp, yes
16. Will a precipitate form when 75.0 mL of 0.020 M BaCl
and 125 mL of 0.040 M Na
SO
are mixed
2
2
4
-10
-4
together? Ksp for BaSO
= 1.1 x 10
. Ans. P = 1.9 x 10
> Ksp, yes
4
17. A solution is prepared by mixing 35.00 mL of a 0.061 M solution of zinc nitrate with 20.0 mL of
-17
KOH with a pH of 9.00. Will a precipitate of zinc hydroxide form? Ksp = 4 x 10
. Ans. P = 5.13
-13
x 10
, yes.
2+
18. Solid Ba(NO
)
is added to a solution of 0.025 M NaF. At what concentration of Ba
does a
3
2
precipitate start to form? Assume that the volume does not change when Ba(NO
)
is added. Ksp
3
2
-7
-4
for BaF
= 1.8 x 10
. Ans. 2.9 x 10
2
2+
19. Solid CdCl
is added to a solution of KOH with a pH of 9.62. At what concentration of Cd
does a
2
precipitate first start to form? Assume that the volume does not change when CdCl2 is added. Ksp
-14
-5
for Cd(OH)
= 2.5 x 10
. Ans. 1.4 x 10
2
Dissolving Precipitates in Acid
20. Which substances listed below show increased solubility as the pH of a solution becomes more
acidic? Write equations for the reactions that occur to increase the solubility.
a. Ag
PO
b. CaCO
c. PbI
d. CdCO
e. Sr
(PO
)
f. AgF
g. AgBr
h. Pb(OH)
3
4
3
2
3
3
4
2
2
i. Sr(NO
)
j. Sr(NO
)
k. Ni(CN)
l. Cu
S
3
2
2
2
2
2
Answers:
+
+
a. Ag
PO
+ 3H
3Ag
+ H
PO
3
4
3
4
+
2+
2+
Ca
Ca
b. CaCO
+ 2H
+ H
CO
+ CO
+ H
O
3
2
3
2
2
c. no reaction
+
2+
2+
Cd
Cd
d. CdCO
+ 2H
+ H
CO
+ CO
+ H
O
3
2
3
2
2
+
2+
e. Sr
(PO
)
+ 6H
3Sr
+ 2H
PO
3
4
2
3
4
+
+
Ag
f. AgF + H
+ HF
g. no reaction
+
2+
Pb
h. Pb(OH)
+ 2H
+ 2H
O
2
2
i. no reaction
+
2+
Sr
j. Sr(NO
)
+ 2H
+ 2HNO
2
2
2
+
2+
k. Ni(CN)
+ 2H
Ni
+ 2HCN
2
+
+
2Cu
l. Cu
S + 2H
+H
S
2
2
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