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 M Ba(NO3)2 and M. Ksp = ? M NaOH are mixed. Will a precipitate occur?
Do not multiply by 2 because of NaOH
Ba(OH)2(s) ⇌ Ba OH-
Ba(OH)2(s) ⇌ Ba OH- 1 2 1 2
s s s
M M
Multiply by 2 because of Ba(OH)2(s)
M M
TIP = [Ba2+][OH-]2
Ksp = [Ba2+][OH-]2
Ksp = [s][2s]2
TIP = [ ][ ]2
Ksp = 4s3
TIP = x
Ksp = [0.0010]3
Ksp = 4.0 x 10-9
TIP < Ksp No ppt.

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 = s2
s = [Cl-] = 1.3 x 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
Na2S
Increase
2Ag S → Ag2S(s)
none
Pb(NO3)2
Increase
Pb Cl- → PbCl2(s)
none

6. Changing the Solubility of a Salt
energy AgCl(s) ⇄ Ag Cl-
Substance Added Molar Solubility Ksp Effect
H2O
none
moles/L does
not change
none
AgCl
none
solid
none
Increase Temperature
Increase
Increase
Decrease Temperature
Decrease
Decrease

7. Changing the Solubility of a Salt Ca(OH)2(s) ⇄ Ca2+ + 2OH-
Ca(OH)2(s) ⇄ Ca OH-
Substance Added Effect on Molar Solubility Effect on Ksp
none
Ca(NO3)2
Decrease
Na2SO4
Increase
none
NaOH
Decrease
none
HCl
Increase
none
NaCl
none
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) ⇌ Mg OH-
A. NaOH
B. Mg(NO3)2
C. H2O
OH- lowers solubility
Mg2+ lowers solubility
No effect solubility
D. AgNO3
Ag+ increases solubility by reacting with OH-