-5 -1 -1
0.00
0.00100
0.00500
0.0100
1.278
1.325
1.385
1.427
Salt effect：The salt effect is the increase in the
solubility of a sparingly soluble salt by the addition of a strong soluble electrolyte.
13
6.2.1 The product solubility rule
A n Bm (s) nA
m+
m+
(aq) + mB (aq)
nm
n-
J = {c(A
)} {c(B )}
n
The product solubility rule: The reaction quotient criterion for precipitation—solubility equilibria. ☆ J > Ksp the equilibrium position shifts to left, so a precipitate will form； ☆ J =Ksp the system is at equilibrium, the solution is saturated； ☆ J < Ksp the equilibrium position shifts to the right, the solution is not saturated. 14
Answer：We know Mr(AgCl) = 143.3 -3 1.92× 10 -1 -3 -1 = = S mol L 1.34× 10 mol L 143.3 + AgCl(s) Ag (aq) + Cl (aq)
Equilibrium / mol.L-1
S
S
+ -10 2 = = = Ksp (AgCl) {c(Ag )}{c(Cl )} S 1.80×10
c0 - ceq c0
100%
pH of a buffer solution c(HA) pH = pK a (HA) - lg c( A ) c(B) pH = 14 - pK b (B) + lg + c(BH ) Dissociation / stability constant for complexes
Example： BaCO3 (s)
23
Ba (aq) + CO (aq)
2+
23
2① Adding acids: 2H+ + CO3 H 2 O + CO2
c (CO ) J J < Ksp
Adding acids is beneficial to dissolving BaCO3 ② Adding BaCl2 or Na2CO3
Initial/(m ol L-1 ) Equilibrium/(mol L-1 ) 0 2x 0.010 0.010+ x
(2x) 2 (0.010+ x) = Ksp = 1.110-12
x is verysmall,so
x = 5.2 10
-1
0.010+ x 0.010
S = 5.2 10 mol L
2+ 2= Ksp (BaSO4 ) [c(Ba )/c ][c(SO4 )/c ]
or simply： Ksp(BaSO4 ) = {c(Ba )}{c(SO )} Ksp — solubility product constant
For general precipitation reactions：
S = 6.510 mol L
-5 -1
-6
-6 -1
In 0.010mol L K 2CrO4
In pure water
20
2. Salt effect The solubility of AgCl in a KNO3 solution (25℃ )
c(KNO3 ) /(mol L ) S (AgCl) /10 (mol L )
6.1.1 Solubility
6.1.2 Solubility product
6.1.3 Relationship between solubility and solubility product
5
6.1.1 Solubility
Solubility is the maximum amount of solute that will dissolve in a given quantity of solvent when dynamic equilibrium is established between undissolved solute and the solution at
Ksp = 1.110
2+
-10
24
Ba (aq) + SO (aq)
16
17
18
6.2.2 The common ion effect and salt effect
1.The common ion effect
The common ion effect is the reduction
in the solubility of a sparingly soluble salt by the addition of a soluble salt that has an ion in common with it.
6.2.1 The solubility product rule
6.2.2 The common ion effect and salt effect 6.2.3 The effect of pH on solubility
6.2.4 The effect of complex ions formation on solubility
Inorganic Chemistry – 2016 Fall
Review for Previous Chapter 5. Acid-Base Equilibrium：

Bronsted acid / base
Lewis acid / base
Ion product constant of water
1 Kf = Kd
2
Inorganic Chemistry – 2016 Fall
Chapter 6
Precipitation-Solubility Equilibria
How to dissolve precipitate?
3
Chapter 6 Precipitation-Solubility Equilibria
6
6.1.2 Solubility product
The process which involves the dissolution and precipitation of an insoluble electrolyte occurs when it is added to water at a certain temperature.
c(Ba ) or c (CO ) J J > Ksp
BaCO3 will precipitate out.
15
2+
23
Example： Suppose 10.0L of 0.010mol· L-1 BaCl2 is added to 40.0L of a solution that contains SO42- ion with a concentration of 6. 0×10-4 mol· L-1 at 25℃. Does BaSO4 precipitate? If so, how many grams of BaSO4 are formed? What is the concentration of SO42- in the final solution? Answer: BaSO4 (s)
21
c(Na2SO4)/ 0 0.001 0.01 0.02 0.04 0.100 0. 200 -1 molL S(PbSO4)/ -1 0.15 0.024 0.016 0.014 0.013 0.016 0.023 mmolL
2+
24
A n Bm (s)
n+ nA (aq) mB (aq) m+ n n-
m+
Ksp (AnBm ) = {c(A )} {c(B )}m
8
6.1.3 Relationship between solubility and the solubility product
The conversion between Ksp and solubility Because concentrations in the Ksp expression must in molarity and the unit of solubility is g solute /100g water, So we need convert the solubility data to molarity(mol· L－1).
KW ={c(H 3O )} {c (OH )}
Ka Kw = , Kb or : K a K b = K w
+
-
pH scale pH + pOH = p KW = 14
250 C , pK a + pK b = 14
1
percent ionization (a)