Solubility

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Solubility Lesson 5 Trial Ion Product
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 When two ionic solutions are mixed and if one
product has low solubility, a precipitate will
form.
Pb(NO3)2(aq) 2NaCl(aq) ?
PbCl2(s) 2NaNO3(aq)
low solubility
The solubility chart on page 4 predicts this
reaction, if the ions are gt 0.10 M.
A trial ion product is required if the ion
concentrations are lt 0.10 M.
3
The capacity of a solution to dissolve a solid is
described by the Ksp.
Pb(NO3)2
NaCl
PbCl2(s) ? Pb2 2Cl-
The Ksp represents the limit of the solution to
dissolve PbCl2.
Pb2 and Cl- will dissolve until the ion
concentrations are equal to the Ksp.
The solution is saturated- any more ions will
form a solid.
4
1. 200.0 mL 0.10 M Pb(NO3)2 is mixed with 300.0
mL of 0.20 M NaCl, will a precipitate occur?
PbCl2(s) ? Pb2 2Cl-
200
300
0.10 M
0.20 M
500
500
0.040 M
0.12 M
TIP Pb2Cl-2
TIP 0.0400.12 2
5.8 x 10-4
Ksp 1.2 x 10-5
TIP gt Ksp ppt forms
5
2. Will a precipitate form if 20.0 mL of 0.010M
CaCl2 is mixed with 60.0 mL of 0.0080 M Na2SO4?
CaSO4(s) ? Ca2 SO42-
20
0.010 M
60
0.0080 M
80
80
0.0025 M
0.0060 M
TIP Ca2SO42-
TIP 0.00250.0060
1.5 x 10-5
Ksp 7.1 x 10-5
TIP lt Ksp no ppt forms
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3. Will a precipitate form when equal volumes of
0.020 M AlCl3 and 0.040 M AgNO3 are mixed.

AgCl(s) ? Ag Cl-
1
1
0.060 M
0.040 M
2
2
0.020 M
0.030 M
TIP AgCl-
TIP 0.0200.030
6.0 x 10-4
Ksp 1.8 x 10-10
TIP gt Ksp ppt forms
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4. Consider the two saturated solutions AgCl and
Ag2CrO4. Which has the greater Ag concentration?
Ag2CrO4 ? 2Ag CrO42-
AgCl ? Ag Cl-
s 2s s
s s s
Ksp s2
Ksp 4s3
1.1 x 10-12 4s3
1.8 x 10 -10 s2
s 6.5 x 10-5 M
s 1.3 x 10-5 M
Ag 2s 1.3 x 10-4 M
Ag 1.3 x 10-5 M
Ag2CrO4 has the greater Ag concentration