We have learned that when two ionic solutions are mixed and if one product has low solubility , then there is a reaction where a precipitate will form .
Pb(NO
3
)
2(aq)
+ 2NaCl
(aq)
→ PbCl
2(s)
+ 2NaNO
3(aq) low solubility
The solubility chart on page 4 predicts this reaction, but only if the solution is 0.10 M or greater . If the molarity is less than 0.10 M , then the reaction may or may not happen.
A trial ion product must be calculated to predict the reaction of all solutions less than 0.10 M .

The capacity of a solution to dissolve a solid is described by the
Ksp.
Pb (NO
3
)
2
Na Cl
Pb 2+ 2Cl -
PbCl
2(s)
⇌
Pb 2+ + 2Cl -
The Ksp represents the limit of the solution to dissolve PbCl
2
.
You can add Pb 2+ and Cl until the ion concentrations are equal to the
Ksp .
The solution is saturated and addition PbCl
2 not dissolved.
must sit on the bottom

1.
200.0 mL 0.10 M Pb(NO
3
)
2 is mixed with 300.0 mL of 0.20 M
NaCl, will a precipitate occur?

1.
200.0 mL 0.10 M Pb(NO
3
)
2 is mixed with 300.0 mL of 0.20 M
NaCl, will a precipitate occur?
PbCl
2(s)
⇌
Pb 2+ + 2Cl -
Write a dissociation equation for the compound with low solubility.

1.
200.0 mL 0.10 M Pb(NO
3
)
2 is mixed with 300.0 mL of 0.20 M
NaCl, will a precipitate occur?
PbCl
2(s)
⇌
Pb 2+ + 2Cl -
0.10 M 0.20 M
Write a dissociation equation for the compound with low solubility.
List the initial molarities of each ion.

1.
200.0 mL 0.10 M Pb(NO
3
)
2 is mixed with 300.0 mL of 0.20 M
NaCl, will a precipitate occur?
PbCl
2(s)
⇌
Pb 2+ + 2Cl -
200 0.10 M
500
0.040 M
300
500
0.20 M
0.12 M
Write a dissociation equation for the compound with low solubility.
List the initial molarities of each ion.
Reduce each molarity by the dilution factor: V
1
/V
2
.

1.
200.0 mL 0.10 M Pb(NO
3
)
2 is mixed with 300.0 mL of 0.20 M
NaCl, will a precipitate occur?
PbCl
2(s)
⇌
Pb 2+ + 2Cl -
200 0.10 M
500
0.040 M
300
500
0.20 M
0.12 M
TIP
TIP
=
=
=
[Pb 2+ ][Cl ] 2
[ 0.040
][ 0.12] 2
5.8 x 10 -4
Write a dissociation equation for the compound with low solubility.
List the initial molarities of each ion.
Reduce each molarity by the dilution factor: V
1
/V
2
.
Write the Ksp or TIP (trial ion product) and solve.

1.
200.0 mL 0.10 M Pb(NO
3
)
2 is mixed with 300.0 mL of 0.20 M
NaCl, will a precipitate occur?
PbCl
2(s)
⇌
Pb 2+ + 2Cl -
200 0.10 M
500
0.040 M
300
500
0.20 M
0.12 M
TIP
TIP
Ksp
=
=
=
=
[Pb 2+ ][Cl ] 2
[ 0.040
][ 0.12] 2
5.8 x 10 -4
1.2 x 10 -5 TIP > Ksp ppt forms
Write a dissociation equation for the compound with low solubility.
List the initial molarities of each ion.
Reduce each molarity by the dilution factor: V
1
/V
2
.
Write the Ksp or TIP (trial ion product) and solve.
Compare to real Ksp

2. Will a precipitate form if 20.0 mL of 0.010M CaCl
2 mixed with 60.0 mL of 0.0080 M Na
2
SO
4
? is
CaSO
4(s)
⇌
Ca 2+ + SO
4
2-
20 0.010 M
80
0.0025 M
60 0.0080 M
80
0.0060 M
Ksp
TIP =
TIP =
=
=
[Ca 2+ ][SO
4
2]
[ 0.0025
][ 0.0060]
1.5 x 10 -5
7.1 x 10 -5 TIP < Ksp no ppt forms

3.
Will a precipitate form when equal volumes of 0.020 M CaCl
2 and 0.040 M AgNO
3 are mixed.
The Cl is doubled
AgCl
(s)
⇌
Ag + + Cl -
1
2
0.040 M
0.020 M
1
2
0.040 M
0.020 M
TIP
TIP
=
=
=
[Ag + ][Cl ]
[ 0.020
][ 0.020]
4.0 x 10 -4
Ksp =
TIP > Ksp
1.8 x 10 -10 ppt forms

4.
Consider the two saturated solutions AgCl and Ag
2
CrO
4
.
Which has the greater Ag + concentration?
AgCl
⇌
Ag + + Cl s s s
Ag s
2
CrO
4
⇌
2Ag + + CrO
2s s
4
2-
Ksp =
1.8 x 10 -10 = s 2 s 2 Ksp
1.1 x 10
=
-12 =4s 3
4s 3 s = 1.3 x 10 -5 M
[Ag + ] = 1.3 x 10 -5 M s = 6.5 x 10
[Ag +
-5
Ag
2
CrO
4 has the greater Ag + concentration
M
] = 2s = 1.3 x 10 -4 M