1. Solubility
Unit III
Lesson 1

2. Solubility is a measure of the maximum amount of solid that will dissolve in a volume of water.
Units: g/L mol/L g/100mL
Or even: mL/L for CO2(g) in water
The unit must have an amount on the top and volume on the bottom!
In order to determine the solubility you must completely fill or saturate the solution!
To saturate the solution you must add weighed portions of the solid to a given volume of water and stir until no more will dissolve. A small amount of excess solid will be present in the saturated solution.

3. Determining The Solubility of NaCl
Add measured portions of NaCl and stir to dissolve
NaCl
10.0 g
Take 100 mL of water

4. Determining The Solubility of NaCl

5. Determining The Solubility of NaCl
The solution is stirred and it all dissolves
NaCl

6. Determining The Solubility of NaCl
The solution is stirred and it all dissolves
NaCl

7. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Rate of dissolving > Rate of crystallization
Na+
Cl-

8. Determining The Solubility of NaCl
Add more since the solution is not full
Amount NaCl Dissolved
10.0 g
NaCl
10.0 g
Na+
Cl-

9. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
NaCl
Na+
Cl-

10. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Na+
Cl-
NaCl

11. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Na+
Cl-
NaCl

12. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Rate of dissolving > Rate of crystallization
Na+
Cl-

13. Determining The Solubility of NaCl
Add more since the solution is not full
Amount NaCl Dissolved
10.0 g
NaCl
10.0 g
Na+
Cl-

14. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
NaCl
Na+
Cl-

15. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Na+
Cl-
NaCl

16. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Na+
Cl-
NaCl

17. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Rate of dissolving > Rate of crystallization
Na+
Cl-

18. Determining The Solubility of NaCl
Add more since the solution is not full
Amount NaCl Dissolved
10.0 g
NaCl
3.0 g
Na+
Cl-

19. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
NaCl
Na+
Cl-

20. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Na+
Cl-
NaCl

21. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
The solution is stirred and it all dissolves
Na+
Cl-
NaCl

22. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
3.0 g
The solution is stirred and it all dissolves
Rate of dissolving > Rate of crystallization
Na+
Cl-

23. Determining The Solubility of NaCl
Add more since the solution is not full
Amount NaCl Dissolved
10.0 g
3.0 g
NaCl
1.0 g
Na+
Cl-

24. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
3.0 g
NaCl
Na+
Cl-

25. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
3.0 g
Na+
NaCl
Cl-

26. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
3.0 g
33.0 g/100 mL
The solution is stirred and it does not dissolve!
The solution is full or saturated.
Na+
Cl-
A bit of solid (1 g)
sits on the bottom
NaCl(s)
Rate of dissolving = Rate of crystallization

27. Determining The Solubility of NaCl
Amount NaCl Dissolved
10.0 g
3.0 g
33.0 g/100 mL
The solution is stirred and it does not dissolve!
The solution is full or saturated.
Na+
Cl-
NaCl(s)
A bit of solid sits on the bottom
This tells you that the solution is saturated and that it is in equilibrium
Rate of dissolving = Rate of crystallization

28. Calculate the solubility in units of g/L and mole/L.
Solubility = 33.0 g
0.100 L
= 330. g/L
s = molar solubility = the molarity to saturate
= 33.0 g x 1 mole
58.5 g
= 5.60 M

29. Na+
Cl-
NaCl(s)
33.0 g/100 mL
A bit of solid sits on the bottom
This tells you that the solution is saturated and that it is in equilibrium
Since this is an equilibrium lets write the Equilibrium
Equation: NaCl(s) ⇌ Na Cl-
Expression: Keq = [Na+][Cl-] do not count a solid!
Because this Keq is special and based on the solubility of a solid it is
called a solubility product or Ksp.
Ksp = [Na+][Cl-]

30. This unit is all about the Ksp and the solubility of saturated solutions.

31. Equilibrium Expressions for Saturated Solutions
Write the equation for equilibrium present in a saturated solution of Al2(SO4)3 solution.
Al2(SO4)3(s) ⇌ 2Al3+ + 3SO42-
Write the equilibrium expression or solubility product
Solubility Product = Ksp = [Al3+]2[SO42-]3

32. Equilibrium Expressions for Saturated Solutions
Write the equation for equilibrium present in a saturated solution of Al2(SO4)3 solution.
Ca3(PO4)2(s) ⇌ 3Ca2+ + 2PO43-
Write the equilibrium expression or solubility product
Solubility Product = Ksp = [Ca2+]3[PO43-]2

33. There are three types of solutions.
Unsaturated
Contains less than the maximum amount of dissolved solid
Not at equilibrium
Add more solid and it will dissolve
The rate of dissolving > the rate of crystallizing

34. There are three types of solutions.
Saturated
Contains the maximum amount of dissolved solid
At equilibrium
Add more solid and it does not dissolve
The rate of dissolving is equal to the rate of crystallization

35. There are three types of solutions.
Supersaturated
Contains more than the usual maximum amount of dissolved solid
Not at equilibrium
Add more solid and more solid precipitates
The rate of dissolving is less than the rate of crystallization

36. What we just calculated was exact solubility.
The data book page 4 gives us relative solubility.
High Solubility means > .1 M
Low Solubility means  .1M
Classify as high or low solubility.
Na3PO4

37. What we just calculated was exact solubility.
The data book page 4 gives us relative solubility.
High Solubility means > .1 M
Low Solubility means  .1M
Classify as high or low solubility.
Na3PO4 High
H2SO4

38. What we just calculated was exact solubility.
The data book page 4 gives us relative solubility.
High Solubility means > .1 M
Low Solubility means  .1M
Classify as high or low solubility.
Na3PO4 High
H2SO4 High
Ca(NO3)2  

39. What we just calculated was exact solubility.
The data book page 4 gives us relative solubility.
High Solubility means > .1 M
Low Solubility means  .1M
Classify as high or low solubility.
Na3PO4 High
H2SO4 High
Ca(NO3)2 High
CaSO4

40. What we just calculated was exact solubility.
The data book page 4 gives us relative solubility.
High Solubility means > .1 M
Low Solubility means  .1M
Classify as high or low solubility.
Na3PO4 High
H2SO4 High
Ca(NO3)2 High
CaSO4 Low
FeSO4

41. What we just calculated was exact solubility.
The data book page 4 gives us relative solubility.
High Solubility means > .1 M
Low Solubility means  .1M
Classify as high or low solubility.
Na3PO4 High
H2SO4 High
Ca(NO3)2 High
CaSO4 Low
FeSO4 High

42. Classify as high or low solubility.
Ag2SO4

43. Classify as high or low solubility.
Ag2SO4 low
CuSO4

44. Classify as high or low solubility.
Ag2SO4 low
CuSO4 high
CuCl2

45. Classify as high or low solubility.
Ag2SO4 low
CuSO4 high
CuCl2 high
CuCl

46. Classify as high or low solubility.
Ag2SO4 low
CuSO4 high
CuCl2 high
CuCl low
BaS

47. Classify as high or low solubility.
Ag2SO4 low
CuSO4 high
CuCl2 high
CuCl low
BaS high
K2CO3  

48. Classify as high or low solubility.
Ag2SO4 low
CuSO4 high
CuCl2 high
CuCl low
BaS High
K3CO3   high

49. See notes “Solubility Charts/Qualitative Analysis”
Do Hebden p #21, 22, 24
Hebden p. 90 #26, 27,31,32,35, 37,38”