Solubility Equilibria (McGuire)

1.) Calculate the Ksp for each of the salts whose solubility is listed below.  Show units!

1. CaSO4 = 5.0 x 10-3 mol/L

1. MgF2 = 2.7 x 10-3 mol/L

1. AgC2H3O2 (silver acetate) = 1.02 g/100 mL

1. SrF2 = 12.2 mg/100 mL

2.) Calculate the solubility in moles/L of each of these salts in pure water and the concentration of the cations in ppm in each of the saturated solutions.

salt

Ksp

Solubility (M)

Conc. cation (ppm)

AgCN

2.0 x 10-12

BaSO4

1.5 x 10-9

FeS

3.7 x 10-19

Mg(OH)2

9.0 x 10-12

Ag2S

1.6 x 10-49

CaF2

4.9 x 10-11

3.) For each of these substances, calculate the milligrams of metallic ion per liter that can remain at equilibrium in a buffered solution at pH = 10.

1. Cu(OH)2     Ksp = 1.6 x 10-9

1. Fe(OH)3     Ksp = 6.0 x 10-38

1. Mg(OH)2     Ksp = 6.0 x 10-12

4.) Which salt — CaCO3 or Ag2CO3 — is more soluble in water in units of moles per liter?

CaCO3:     Ksp = 2.8 x 10-9

Ag2CO3:     Ksp = 8.1 x 10-12

5.) If 55 mg of lead (II) sulfate, PbSO4, is placed in 250.0 mL of pure water, how much PbSO4 will remain undissolved?  Ksp for PbSO4 is 2.53 x 10-8.

6.) Will a precipitate form when 0.150 L of 0.10 M lead (II) nitrate and 0.100 L of 0.20 M NaCl are mixed? For PbCl2, Ksp = 1.2x10-5.

7.) What is the molar solubility of Pb(IO3)2 in a solution of 0.10 M Pb(NO3)2?  Ksp for Pb(IO3)2  = 3.69 x 10-13.   Justify any approximations you make.

8.) Would it be possible to separate a solution containing 0.0020 M Pb2+ and 0.030 M Ag+ by adding drops of Na2CO3 solution? (Ksp for lead carbonate = 1.5 x 10-13 and Ksp for silver carbonate = 8.2 x 10-12)

9.) You wish to separate the metals in 100 mL of a solution of 0.10 M Ag+ and 0.10 M Pb2+.

1. Which metal will precipitate first if you add a solution of 0.10 M Br- is small increments?

AgBr               Ksp=3.3 x 10-13

PbBr2               Ksp=6.3 x 10-6

1. What is the concentration of Br- when the second metal just begins to precipitate?

1. What is the concentration of the first metal (identified in part a) that will be left in solution at the point that the second metal begins to precipitate?