Transcript Chemistry 18.3

Chemistry 18.3
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18.3
Solubility Equilibrium
Barium sulfate is ingested by a
patient before X-ray images of
the digestive tract are taken.
Barium sulfate absorbs the Xrays, thereby producing light
areas on the developed X-ray
film. However, barium salts are
usually toxic. You will learn why
patients can ingest this
poisonous substance without
harm.
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18.3
Solubility Equilibrium
> The Solubility Product Constant
The Solubility Product Constant
What is the relationship between the
solubility product constant (Ksp) and the
solubility of a compound?
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18.3
Solubility Equilibrium
> The Solubility Product Constant
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.
The smaller the numerical value of the
solubility product constant, the lower the
solubility of the compound.
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Solubility Equilibrium
>
e.g. Write the Ksp expression for:
(i) AgCl
(ii) BaSO4
(i) Ionization Equation: AgCl(s)
(iii) PbCl2
Ag+(aq) + Cl-(aq)
Ksp = [Ag+(aq)] [Cl-(aq) ]
(ii) Ionization Equation: BaSO4(s)
Ba2+(aq) + SO42-(aq)
Ksp = [Ba2+(aq) ] [SO42-(aq)]
(iii) Ionization Equation: PbCl2(s)
Pb2+(aq) + 2 Cl-(aq)
Ksp = [Pb2+(aq) ] [Cl-(aq)]2
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18.3
Solubility Equilibrium
> The Solubility Product Constant
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18.3
Solubility Equilibrium
> The Solubility Product Constant
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18.3
Solubility Equilibrium
> The Solubility Product Constant
Silver chloride is slightly soluble in water.
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18.3
Solubility Equilibrium
>
The Solubility Product Constant
Scale, formed by the precipitation of slightly
soluble salts, builds up around faucets.
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SAMPLE PROBLEM 18.3
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SAMPLE PROBLEM 18.3
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SAMPLE PROBLEM 18.3
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SAMPLE PROBLEM 18.3
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Practice Problems for Sample Problem 18.3
Problem Solving 18.17 Solve
Problem 17 with the help of an
interactive guided tutorial.
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Practice Problems
More difficult problem :
What will be the Pb2+ ion concentration and Clion concentration in a saturated solution of lead
(II) chloride? (Ksp = 1.7 x 10-5)
Let’s try it on the board…
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18.3
Solubility Equilibrium
> The Common Ion Effect
The Common Ion Effect
How can you predict whether
precipitation will occur when two salt
solutions are mixed?
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18.3
Solubility Equilibrium
> The Common Ion Effect
If the product of the concentrations of
two ions in the mixture is greater than
the Ksp of the compound formed from the
ions, a precipitate will form.
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Solubility Equilibrium
>
Sample Problem (taken from p.565):
Will a precipitate form when 0.500L of 0.002M
Ba(NO3 )2 reacts with 0.500L of 0.008M Na2SO4?
[Ksp (BaSO4) = 1.1 x 10-10]
Let’s go to the board…
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18.3
Solubility Equilibrium
> The Common Ion Effect
A common ion is an ion that is found in both
salts in a solution. The lowering of the solubility
of an ionic compound as a result of the addition
of a common ion is called the common ion
effect.
Example: adding lead (II) nitrate to an
existing saturated solution of lead (II)
chromate (see next page).
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18.3
Solubility Equilibrium
A saturated solution
of lead(II) chromate
is pale yellow.
> The Common Ion Effect
When a few drops of
lead nitrate are added
to the solution, more
lead(II) chromate
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precipitates.
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SAMPLE PROBLEM 18.4
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SAMPLE PROBLEM 18.4
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SAMPLE PROBLEM 18.4
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SAMPLE PROBLEM 18.4
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Practice Problems for Sample Problem 18.4
Problem Solving 18.19 Solve
Problem 19 with the help of an
interactive guided tutorial.
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18.3 Section Quiz.
Assess students’ understanding
of the concepts in Section 18.3.
Continue to:
-or-
Launch:
Section Quiz
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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
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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
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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.
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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.
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