Solubility Products Constants Data Sheet

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• Solubility Products Constants Data Sheet
• Sample page from the
• Handbook of Chemistry and Physics

Heterogeneous Equilibria Problem Set
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Heterogeneous Equilibria

• Edward A. Mottel
• Department of Chemistry
• Rose-Hulman Institute of Technology

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Heterogeneous Equilibria

• Reading assignment
• Chang Chapters 4.2, 4.6, 16.1, 16.6-16.11
• Sparingly soluble salts
• Solubility product
• Common ion effect
• Molar solubility
• Applications

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Some Salts are Soluble

• Soluble salts
• Group IA, NH4, NO3, ClO3, ClO4
• Most halides (Cl, Br, I)
• except Ag, Cu, Hg22, Pb2
• Most sulfates
• except CaSO4, BaSO4, Ag2SO4, HgSO4, PbSO4

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Some Salts are Not Very Soluble

• Sparingly soluble salts
• Most hydroxides
• except Group IA, Ba(OH)2
• Carbonates, phosphates, sulfides
• except Group IA, NH4

• Solubility depends on
• Temperature and solvent
• Strong electrolyte

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Sparingly Soluble Salts

• The solubility product of silver chloride is
• 1.8 x 10-10, how can it be a strong electrolyte?

This indicates that the amount of AgCl which
dissolves ionizes extensively. (strong
electrolyte)
This indicates that AgCl isnt very
soluble. (sparingly soluble)
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Solubility Product, Ksp

• Products over reactants with simplifications

Ag Cl Kc AgCl(s)
Ag Cl
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For Each of the Following Determine the
Solubility Product Expression

• lead(II) carbonate
• calcium fluoride
• iron(III) hydroxide

• iron(II) sulfide
• lead(II) iodide
• silver sulfate

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For Each of the Following Determine the
Solubility Product Expression

• Pb2 CO32
• Ca2 F2
• Fe3 OH3

• Fe2 S2
• Pb2 I2
• Ag2 SO42

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How to Determine If a Compound is Soluble or Not?

• Solubility Rules
• Table of Solubility Product Constants
• Handbook of Chemistry and Physics
• Physical Constants of Inorganic Compounds

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Physical Constants of Inorganic Compounds

• Name
• Formula
• Molecular Weight
• Crystalline Form
• Color
• Density

• Melting Point
• Boiling Point
• Solubility
• Cold Water
• Hot Water
• Other Solvents

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Copper(II) Formate

• Formula and Molecular Weight
• Cu(HCOO)2, 153.58 amu
• Color
• blue, monoclinic crystals
• Is copper(II) formate soluble in water?
• yes, 12.5 grams per 100 mL of water
• greater than 1 gram per 100 mL water

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Group Activity

• An aqueous solution of copper(II) nitrate is
  mixed with aqueous sodium iodate.
• Write an equation for this process and use
  appropriate tables to determine if a reaction
  occurs.
• What observations are expected to be made?
• Is Cu(NO3)2 soluble?
• Is NaIO3 soluble?

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Copper(II) Iodate
Ionic Equation
Cu(IO3)2(s) 2 NO3(aq) 2 Na(aq)
Net Ionic Equation
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Copper(II) Iodate

• Sparingly soluble
• less than 1 gram per 100 mL of water
• 0.136 grams per 100 mL of water at 15 C
• Green, monoclinic crystals

What is its solubility and color ?
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Pre-laboratory Assignment

• Experiment P Qualitative Reactions
• Complete the Predicted Reactions grid on page P-4
  in laboratory manual
• Predict double displacement reactions, use
• Solubility Rules
• Table of Solubility Product Constants
• Handbook of Chemistry and Physics

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NR
AlCl3 ZnSO4
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BaSO4 white ppt
BaCl2
AlCl3 BaSO4
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Molar Solubility
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Two Beakers Each Contain500 mL of Water
Some of the solid dissolves.
In which beaker will more lead(II) fluoride
dissolve?
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Solubility Product
What is the solubility of lead(II) fluoride in
pure water?

• Write the chemical equation for the dissolution
  process.
• Let x be the moles per liter of lead(II) ion
  that is produced.
• Write the mass-action expression.
• Substitute variables and solve the solubility
  product mass-action expression.

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Lead(II) Fluoride
-x
x
2x
Ksp Pb2 F2 3.7 x 108 M3
(x) (2x)2 3.7 x 108 M3
4x3 3.7 x 108 M3
x 2.1 x 103 M
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Lead(II) Fluoride
x 2.1 x 103 M

• What does 2.1 x 103 M represent?
• Molar solubility of PbF2 in pure water
• Molarity of lead(II) ion in solution

• What is the molarity of the fluoride ion?

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How many grams of lead(II) fluoride will dissolve
in 500 mL of water?

• Molar solubility of PbF2 (FW 245.2 amu) in pure
  water is 2.1 x 103 M

0.500 liter
0.26 g PbF2
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Each beaker contains 500 mL of water.In which
beaker will more lead(II) fluoride dissolve?
If there is excess solid at equilibrium, the same
amount dissolves!
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Common Ion Effect
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Two beakers each contain500 mL of solution

• 50 grams of PbF2 is added to pure water

• 50 grams of PbF2 is added to 0.0200 M sodium
  fluoride

H2O
H2O
F-
Na
Into which solution will more lead(II) fluoride
dissolve?
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Common Ion Effect

• Equilibrium concentrations of each ion depend on
  the number of those ions in solution, regardless
  of the source.
• What is the molar solubility of lead(II) fluoride
  in a solution containing 0.0200 M sodium
  fluoride?
• Assume one liter of solution

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lots
0
lots
0
0
Assume one liter of solution
0.0200
Start with the initial conditions, assume one
liter of solution
Use moles or millimoles
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-0.0200
0.0200
0.0200
0
0
Is NaF a strong electrolyte? Does it dissociate
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Is PbF2 very soluble?
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Cross-ReactionsWhich of these reactions are
favorable?

• Na Na
• Na F-
• Na PbF2
• Na H2O
• F- F-
• F- PbF2
• F- H2O

• PbF2 PbF2
• PbF2 H2O
• H2O H2O

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Equilibrium ReactionWhich of these reactions are
favorable?
K 1
K gt 1
K lt 1
Na Na
Na F-
Na PbF2
Na H2O
F- F-
F- PbF2
F- H2O
PbF2 PbF2
PbF2 H2O
H2O H2O
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Assume one liter of solution
Assume one liter of solution
0.0200
0.0200
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What was the goal of the calculation?
The molar solubility of lead(II) fluoride in a
solution containing 0.0200 M sodium fluoride.
That is, how many moles of lead(II)
fluoride dissolve in a liter of solution
containing 0.0200 M sodium fluoride?
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-x
x
2x
lots
x
lots-x
0.0200
.02002x
Let -x equal the moles of PbF2 which dissolve per
liter of solution.
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The Molar Solubility of Lead(II) Fluoridein
0.0200 M Sodium Fluoride
0.0200
Ksp Pb2 F2 3.7 x 108 M3
Ksp (x) (0.0200 2x)2 3.7 x 108 M3
x 9.2 x 105 M
x 0.023 g in one liter
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Group Activity

• Why is the molar solubility of lead(II) fluoride
  different in a solution containing sodium
  fluoride?

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Group Activity

• Why is the molar solubility of lead(II) fluoride
  different in a solution containing sodium
  fluoride?
• Explain in terms of Le Châteliers Principle

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Applications
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Selective Precipitation
A solution contains 0.100 M cadmium ion 0.050 M
iron(III) ion 0.200 M nickel(II) ion
If sodium hydroxide is slowly added to the
solution
What precipitates will form?
In what order will the precipitates form?
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Selective Precipitation Strategy

• Determine the hydroxide ion concentration needed
  to precipitate each metal.

• Determine the order in which those hydroxide ion
  concentrations will be reached.
• 0.100 M cadmium ion
• 0.050 M iron(III) ion
• 0.200 M nickel(II) ion

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Hydroxide Ion Concentration Neededto Precipitate
0.100 M Cd2
Cd2 OH2 Ksp
0.100 OH 2 2.0 x 1014 M3
OH 4.5 x 107 M
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Hydroxide Ion Concentration Neededto Precipitate

• 0.100 M Cd2
• OH 4.5 x 107 M
• 0.050 M Fe3
• OH 1.1 x 1012 M
• 0.200 M Ni2
• OH 2.8 x 108 M

Cd(OH)2
Ni(OH)2
Fe(OH)3
As the solution is slowly made basic, which
precipitates first?
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Selective Precipitation
At what pH will the last metal ion begin to
precipitate?
7.65
When the cadmium ion begins to precipitate how
much of the iron(III) ion is still in solution?
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Selective Precipitation

• 0.100 M cadmium ion begins to precipitate when
  the hydroxide ion concentration is 4.5 x 107 M.
• What is the maximum iron(III) ion concentration
  under these conditions?

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Selective Precipitation
Fe3 OH3 Ksp
Fe3 (4.5 x 107 M)3 6.0 x 1038 M4
Fe3 6.6 x 1019 M
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Determination ofMolar Solubility and Ksp

• The Handbook of Chemistry and Physics indicates
  that the solubility of zinc fluoride (FW 103.37)
  is 1.62 grams per 100 mL of water.
• What is the molar solubility of zinc fluoride?
• What is the solubility product of zinc fluoride?

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Zinc FluorideMolar Solubility
1.62 g /100 mL water
16.2 g /1000 mL water
_at_ 16.2 g /1000 mL solution
16.2 g /103.37 gmol1 0.157 mol ZnF2
The molar solubility of zinc fluoride is 0.157 M.
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Zinc FluorideSolubility Product
Ksp Zn2 F2
Ksp (0.157 M) (2 x 0.157 M)2
Ksp (0.157 M) (0.314 M)2
Ksp 1.54 x 102 M3
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Please Pick Up

• Solubility Products Constants Data Sheet
• Heterogeneous Equilibria Problem Set
• Sample page from the
• Handbook of Chemistry and Physics