PRINCE GEORGE’S COMMUNITY COLLEGE
CHM1020(SHAH)
Solubility product constant (Ksp)
SPRING 2011
1. Lead II sulfate’s solubility in water at 25°C is 4.25 x 10-3 g/100mL.
What is the Ksp of lead II sulfate? (Answer: 1.96 x 10-8)
2. When lead II fluoride is shaken with pure water at 25°C, the solubility
is found to be 0.64g/L. Calculate the Ksp for lead II fluoride.
(Answer: 7.0 x 10-8)
3. Calculate the solubility of Ca(OH)2 in water if Ksp is 6.5 x 10-6.
(Answer: 1.2 x 10-2M)
4. If 1.5 x 10-4 g CaF2 is dissolved in pure water to make 10mL of
solution at 18°C, what is the Ksp of this solution?
5. What is the solubility of Ca(OH)2 in 0.10M Ca(NO3)2 solution?
(Ksp for Ca(OH)2 is 6.5 x 10-6)
(Answer: 4.0 x 10-3M)
6. Does a precipitate form when 0.100L of 0.30M Ca(NO3)2 is mixed with
0.200L of 0.060M NaF? (Ksp for CaF2 is 3.2 x 10-11)
Qsp > Ksp
Qsp = Ksp
Qsp< Ksp
precipitate will occur until the solution becomes saturated.
precipitate will NOT occur, the solution is saturated
precipitate will NOT occur, the solution is unsaturated
The effect of pH on solubility
a. If the compound contains the anion of a weak acid, addition of
hydronium ion (H3O+) from a strong acid increases its solubility.
Cu(OH)2(s) addition of hydronium ion will increase the solubility.
OH- an anoin is from very weak acid H2O.
CaCO3(s) addition of hydronium ion will increase the solubility.
CO3-- an anion is from weak acid H2CO3.
BaF2
Ca(OH)2(s) addition of hydronium ion will increase the solubility.
OH- an anoin is from strong base H2O.
b. Addition of hydronium ion to a saturated solution of a compound
with a strong acid anion, no effect on solubility.
PbBr2(s) addition of hydronium ion will have no effect because
anoin Br- is from strong acid HBr.
AgI(s) addition of hydronium ion will have no effect because anoin
I- is from strong acid HI.
Another example AgCl
Complex ion: A complex ion contains a central metal ion bound to
one or more ligand.
A ligand is a neutral molecule or ion that acts as a Lewis base with
the central metal ion.
Examples: Ag(H2O2)2+
Cu(NH3)42+
Ag(NH3) 2+