Solubility

1
Solubility Lesson 7 Changing solubility
2
When to and When not to Multiply the
Molarity   1. The molar solubility of Ba(OH)2
is 2. Equal volumes of 0.0010 M Ba(NO3)2 and
0.0010 M. Ksp ? 0.0010 M NaOH are mixed.
Will a precipitate occur?
Ba(OH)2(s) ? Ba2 2OH-
Ba(OH)2(s) ? Ba2 2OH-
s s 2s
0.0010 M 0.0010 M
0.00050 M 0.00050 M
Ktrial Ba2OH-2
Ksp Ba2OH-2

Ksp s2s2
Ktrial 0.000500.000502
Ksp 4s3
Ktrial 1.25 x 10-10
Ksp 40.00103
Ktrial lt Ksp No ppt.
Ksp 4.0 x 10-9
3
3. AgNO3(s) is added to 1.0 L of a solution
containing Cl- in order to precipitate out the
Cl- as AgCl(s). After the AgCl(s) is filtered out
what is the remaining concentration of Cl-?

AgCl(s) ? Ag Cl-
s s s
Ksp s2
1.8 x 10-10 s2
s Cl- 1.3 x 10-5 M
4
The molar solubility is the amount of PbCl2(s) in
moles per litre that dissolves into ions to form
a saturated solution.
increases the molar solubility
energy PbCl2(s) ? Pb2 2Cl-
decreases the molar solubility
Solid equilibriums are endothermic.
Only changing the temperature changes the Ksp.
5
Changing the Solubility of a Salt
energy AgCl(s) ? Ag
Cl-
Substance Added Molar Solubility Ksp Effect
AgNO3
Decrease
none
NaCl
Decrease
none
Increase
none
Na2S
2Ag S2- ? Ag2S(s)
Pb(NO3)2
Increase
none
Pb2 2Cl- ? PbCl2(s)
6
Changing the Solubility of a Salt
energy AgCl(s) ? Ag
Cl-
Substance Added Molar Solubility Ksp Effect
moles/L does not change
H2O
none
none
none
AgCl
none
solid
Increase Temperature
Increase
Increase
Decrease
Decrease
Decrease Temperature
7
Changing the Solubility of a Salt   Ca(OH)2(s)
? Ca2 2OH-
Substance Added Effect on Molar
Solubility Effect on Ksp
none
Decrease
Ca(NO3)2
Increase
Na2SO4
none
NaOH
Decrease
none
none
HCl
Increase
none
NaCl
none
none
none
Ca(OH)2
Increase Temperature
Increase
Increase
Decrease Temperature
Decrease
Decrease
8
1. Mg(OH)2 will have the greatest solubility
in Mg(OH)2(s) ? Mg2 2OH- A. NaOH
B. Mg(NO3)2 C. H2O
OH- lowers solubility
Mg2 lowers solubility
No effect solubility
Ag increases solubility by reacting with OH-
D. AgNO3