Solubility Equilibria
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Transcript of Solubility Equilibria
Solubility Equilibria
• Write solubility product (Ksp) expressions from balanced chemical equations for salts with low solubility.
• Solve problems involving Ksp.
Additional KEY TermsDissociation Saturated
C6H12O6(s) C6H12O6(aq)
There are 3 actions that affect solubility:
1. Nature of the solute and solvent“like dissolves like”
Polar / ionic solute dissolve in polar solvent.Non-polar dissolve in non-polar.
Even the most insoluble ionic solids are actually soluble in water to a limited extent
2. Temperature
Solids in liquids: ↑ temperature - ↑ solubility.Gases in liquids: ↑ in temperature - ↓ solubility.
3. Pressure
Does not affect the solubility of (s)/(l).(g): ↑ pressure ↑ solubility.
AaBb(s) aA+(aq) + bB¯(aq)
Ksp, called the solubility product constant.
Ksp = [A+]a[B-]b
Product of ion concentrations in a saturated solution.
Kc =
[A+]a[B-]b [AaBb]
Write the dissociation and the product constant equation for the solubility of calcium hydroxide.
Ksp = [Ca2+][OH-]2
Ca(OH)2 (s)
Pb3(PO4)2(s) 3 Pb2+(aq) + 2 PO4
3-(aq)
Ksp = [Pb2+]3[PO43-]2
Write a solubility product expression for Pb3(PO4)2.
Ca2+(aq) + OH-
(aq)2
At equilibrium, the [Ag+] = 1.3 x 10-5 M and the [Cl-] = 1.3 x 10-5 M, what is the Ksp of silver chloride?
Ksp = [Ag+][Cl-]
Ksp =(1.3 x 10-5)(1.3 x 10-5)Ksp = 1.7 x 10-10
AgCl (s) Ag+(aq) + Cl-
(aq)
*NOTE: Ksp has no units.
SolubilityAnd
I.C.E. Tables(Yeah!)
Calculate Ksp of lead (II) chloride if a 1.0 L saturated solution has of lead ions.
I --- 0 0C -x +x +2xE 0
Ksp = [Pb+2][Cl -]2
Ksp = [1.62 x 10 -2][ 3. 24 x 10 -2]2
Ksp = 1.70 x 10 -5
PbCl2(s) Pb2+(aq) + 2 Cl-
(aq)
1.62 x 10-2 M
2(1.62 x 10-2)
1.62 x 10-2 M
The solubility of PbF2 is . What is the value of the solubility product constant?
PbF2(s) Pb2+(aq) + 2 F¯(aq)
0.466 g1 L 245.2 g
1 mol= 1.90 x 10-3 M PbF2
0.466 g/L
207 + 2 (19) = 245g/mol
Ksp = [Pb2+][F-]2
Ksp = [Pb2+][F-]2
Ksp = (1.90 x 10-3)(3.80 x 10-3)2
Ksp = 2.74 x 10-8
PbF2(s) Pb2+(aq) + 2 F¯(aq)
[E] 0 1.9 x 10-3 M
[I] 1.9 x 10-3 M 0 0
[C] - x + x + 2x
3.8 x 10-3 MSaturated – all solid reactant dissociates.
Calculate Ksp if 50.0 mL of a saturated solution was found to contain 0.2207 g of lead (II) chloride.
I 0.0159 M 0 0C -x +x +2xE 0 0.0159 M 0.0318 M
Ksp = [Pb2+][Cl-]2
0.2207 g278.1g1 mol = 0.0159 M PbCl20.05 L
PbCl2(s) Pb2+(aq) + 2 Cl-
(aq)
Ksp = [0.0159][0.0318]2 = 1.61 x 10-5
Ksp of magnesium hydroxide is 8.9 x 10-12. What are the [equilibrium] of ions in saturated solution?
I --- 0 0C -x +x +2xE 0 x 2x
Mg(OH)2 (s) Mg2+(aq)
+ 2 OH-(aq)
Ksp = [Mg2+][OH-]2
8.9 x 10-12 = [x][2x]2
8.9 x 10-12 = [x]4x2
8.9 x 10-12 = 4x3
[Mg2+] = x = 1.3 x 10-4 mol/L
[OH-] = 2x = 2.6 x 10-4 mol/L
8.9 x 10-12 = 4x3
44
2.23 x 10-12 = x33√ 3√
1.3 x 10-4 = x
Precipitation
Compare value of Q, with given Ksp to determine if an aqueous solution is saturated or unsaturated.
Q = Ksp Saturated solution, no precipitate.
Q >Ksp Precipitate forms (“oversaturated”)
Q < Ksp Solution is unsaturated.
Qsp = [A+]a[B¯]b
· Substances which are insoluble are actually slightly soluble.
· The solubility product, Ksp, describes the product of ion concentrations in saturated solutions.
· Solubility can be determined from the solubility product.
CAN YOU / HAVE YOU?
• Write solubility product (Ksp) expressions from balanced chemical equations for salts with low solubility.
• Solve problems involving Ksp.
Additional KEY TermsDissociation Saturated