KSP – Solubility Product Constant
Example
KSP = 3.2 x 10-7 for CuCl. What is [Cu+] in a saturated solution CuCl?
Example
What mass of CuCl will dissolve in 10 L of water?
Example
A saturated solution of Ag2CO3 can be made by dissolving 1.27 x 10-4 mol of solid
Ag2CO3 in 1.0 L of water. What is the KSP for Ag2CO3?
Example
KSP = 8.3 x 10-9 for PbI2. What is the concentration of Pb2+ in a saturated solution
of PbI2?
Exercises
1. The solubility of PbSO4 in water is 0.038 g/L. Calculate the solubility
product constant for Lead (II) Sulfate.
2. The concentration of silver ions in a saturated solution of silver oxalate
(Ag2C2O4) is 2.2 x 10-4 M. Compute the KSP for Silver Oxalate.
3. The solubility product constant for Pb(IO3)2 is 2.5 x 10-13. What is the
solubility of Lead (II) Iodate in mol/L and in g/L.
4. Given that the KSP of BaSO4 is 1.5 x 10-9, how many grams of Barium Sulfate
can you dissolve in 1000 L of water?
5. Given the KSP of AgC2H3O2 is 2.5 x 10-3, how many grams of silver acetate
can be dissolved in 10 L of water at 25 ˚C?
Precipitation
• So far we have considered solids dissolving in solutions.
• Now we will consider the reverse process - the formation of a solid from solution.
• We will use the ion product, Q, which is defined just like the expression for KSP for a
given solid except that initial concentrations are used instead of equilibrium
concentrations.
• For solid CaF2, the expression for the ion product Q is written as
Q = [Ca2+][F-]
• If we add a solution containing Ca2+ ions to a solution containing F- ions, a precipitate
may or may not occur, depending on the concentrations of these ions in the resulting
mixed solution.
• If Q is greater than KSP, precipitation occurs and will continue until the concentrations
are reduced to the point that the satisfy KSP.
• If Q is less than KSP, no precipitation occurs.
Example
Predict whether a precipitate will form when 20 mL of 0.0020 M Ag+ is added to 30 mL
of 0.0020 M Cl-.
Example
A solution is prepared by adding 750.0 mL of 4.00 x 10-3 M Ce(NO3)3 to 300.0 mL of
2.00 x 10-2 M KIO3 (KSP = 1.9 x 10-10) precipitate from this solution?
Practice Problems
1. A solution contains a magnesium ion concentration of 0.0010 M. Will Mg(OH)2
precipitate if the OH- ion concentration is:
a) 1.0 x 10-5 M
b) 1.0 x 10-3 M
The KSP for magnesium hydroxide is 1.1 x 10-11.
2. If 50.0 mL of a 0.200 M silver nitrate solution and 50.0 mL of a 0.00400 M solution of
sodium chloride are mixed, what substance might precipitate? Will a precipitate
form is the substance has a KSP of 1.7 x 10-10?
3. Would a precipitate form if 20.0 mL of 0.010 M barium chloride solution were mixed
with 20.0 mL of 0.00050 M sodium sulfate solution. The KSP for barium sulfate is
1.1 x 10-10.
4. Would you expect a precipitate of barium fluoride if 20.0 mL of 0.010 M barium
chloride solution is mixed with 30.0 mL of 0.010 M sodium fluoride. The KSP for
barium fluoride is 2.4 x 10-5.
5. The KSP for AgCl is 1.60 x 10-10. How many moles of AgCl will dissolve in 8.0 L of
water?
6. The KSP for barium chromate is 1.6 x 10-8. How many grams of this substance are
present in 5.0 L of a saturated solution.
7. A solution in equilibrium with a precipitate of Lead (II) phosphate was found to
contain 5.4 x 10-4 M phosphate ions and 2.4 x 10-2 M of lead ions. Calculate the KSP
for lead (II) phosphate.