Workshop CHE 168
Problem Set #8
1. A saturated solution of MgF2 (aq) in contact with undissolved solid is prepared. The concentration of Mg2+ ions in the solution is found to be 1.2 x 10-3 M. What is the value of Ksp for MgF2?
2. Calculate the molar solubility of CaF2 in water? What is this value in grams per liter?
3. The Ksp for copper(II) azide, Cu(N3)2, is 6.3 x 10-10. What is the solubility of this compound in water in grams per liter?
4. Calculate the molar solubility of CaF2 in a solution containing
(a) 0.010 M Ca(NO3)2 (aq)
(b) 0.010 M NaF (aq)
5. Will a precipitate form when ).100 L of 3.0 x 10-3 M Pb(NO3)2 (aq) is added to 0.400 L of 5.0 x 10-3 M Na2SO4 (aq)?6. Assume that 0.10 M NaF (aq) solution is added slowly, with stirring to a solution that contains 0.10 M Cr(NO3)3 (aq) and0.10 M Ca(NO3)2. Which salt, CrF3 or CaF2, precipitates first?
7. What concentration of OH- (aq) must be exceeded in a 0.010 M solution of Ni(NO3)2 (aq) in order to precipitate Ni(OH)2?
8. The solubility product for gadolinium hydroxide, Gd(OH)3, is 1.8 x 10-23. If a solution is 0.010 M in Gd3+ ion and the pH of the solution is slowly increased, at what pH will this compound begin to precipitate?
9. Calculate the concentration of free Cr3+ ion when 0.010 mol of Cr(NO3)3 is dissolved in a liter of solution buffered at pH 10.00.