Section 18.3 Lecture for Honors Chem Bellwork for is for Prep & Honors

1. Bellwork- Le Chat
The system described by the equation
2H2(g) + O2(g)  2H2O(g) ΔH= -241.8kJ
is at equilibrium.
a)How does the concentration of H2 gas
change?
b)Do H2 molecules react?
c)What happens to the H2 concentration if the
container’s volume is reduced?
d)What happens to the H2 concentration if
temperature is increased?

2. Solubility
The final concentration of ions in
solution is different for every substance.
Insoluble very few ions in solution

3. The solubility product constant (Ksp), equals the
product of the concentrations of the ions, each raised
to a power equal to the coefficient of the ion in the
dissociation equation.
Example-
PbCl2(s)  Pb2+(aq) + 2Cl-(aq)
Ksp= [Pb2+][Cl-]2= 1.7x10-5
The smaller the solubility
product constant (Ksp), the lower
the solubility of the compound.

4. 18.3

5. 18.3

6. 18.3
Silver chloride is slightly soluble in water.

7. 18.3
Scale, formed by the precipitation of slightly
soluble salts, builds up around faucets.

8. 18.3

9. 18.3

10. 18.3

11. 18.3

12. for Sample Problem 18.3

13. 18.3
PbCl2(s)  Pb2+(aq) + 2Cl-(aq)
Ksp= [Pb2+][Cl-]2= 1.7x10-5
If the product of the
concentrations is greater than
the Ksp, a precipitate will form.

14. 18.3 The Common Ion Effect
A common ion is an ion that is found
in both salts in a solution.
Common ion effect- solubility lowers
when a common ion is added

15. The Common Ion Effect
A saturated When a few drops
solution of of lead nitrate are
lead(II) added to the
chromate is solution, more
pale yellow. lead(II) chromate
precipitates.

16. The Common Ion Effect
Precipitation
occurs until
Ksp is again
satisfied
Ksp = [Pb2+][CrO42+]
A When This
constant this must
goes go
up↑ down↓

17. 18.3 The Common Ion Effect
Le Chatelier’s Principle
PbCrO4(s)  Pb2+(aq) + CrO42+(aq)
More Increase
solid is Shift left to Pb2+
remove Pb2+
formed

18. 18.3 Section Quiz.
1. What is the concentration of a saturated
solution of silver sulfide?
The Ksp of Ag2S is 8.0 × 10-51.
a. 2.0 × 10-17M
b. 8.9 × 10-26M
c. 8.9 × 10-25M
d. 2.0 × 1017M

19. 18.3 Section Quiz.
2. Adding which of these solutions to a saturated
solution of BaSO4 will cause the solubility of
BaSO4 to decrease?
I. BaCl2(aq)
II. Na2SO4 (aq)
a. (I) only
b. (II) only
c. (I) and (II)
d. neither solution

20. 18.3 Section Quiz.
3. The Ksp of AgBr is 5.0 × 10-13. When 7.1 × 10-6
mol/L solutions of NaBr(aq) and AgNO3(aq)
are mixed, we would expect
a. no precipitate to form.
b. a definite precipitation reaction.
c. no reaction.
d. a saturated solution but no visible
precipitation.

21. 18.3 Section Quiz.
4. After the common ion effect causes a
precipitate to form in a solution,
a. the solution will no longer be saturated.
b. the solution will again be saturated.
c. the solution will be supersaturated.
d. there will be no solute left in the solution.