Chem_222_Solubility_Homework

Chem_222_Solubility_Homework - best separation? In the best...

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Chem 222 Analytical Chemistry Additional Homework on Solubility Doing this homework you will understand in depth the concepts we discussed in the lectures. 1. An aqueous solution at 25 o C is 0.010 M in both Mg 2+ and Pb 2+ ions. We need to separate the two kinds of metal ions by taking advantage of the different solubilities of their oxalates, MgC 2 O 4 ( K sp = 8.6 x 10 -5 ) and PbC 2 O 4 . ( K sp = 2.7 x 10 -11 ). a. What is the highest possible oxalate ion concentration that allows only one solid oxalate salt to be present at equilibrium? Which ion is present in the solid Mg 2+ or Pb 2+ ? b. What fraction of the less soluble ion still remains in solution under the conditions of part (a)? 2. The cations in an aqueous solution that contains 0.100 M Hg 2 (NO 3 ) 2 and 0.0500 M Pb(NO 3 ) 2 are to be separated by taking advantage of the different solubilities of their iodides K sp (PbI 2 ) = 1.4 x 10 -8 and K sp (Hg 2 I 2 ) = 1.2 x 10 -28 . What should be the concentration of iodide ion for the
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Unformatted text preview: best separation? In the best separation, one of the cations should remain entirely in solution and the other should precipitate as fully as possible. 3. Calculate the [Zn 2+ ] in a solution that is in equilibrium with ZnS( s ) and in which [H 3 O + ] = 1.0x10-3 M and [H 2 S] = 0.10 M. 4. What is the highest pH at which 0.10 M Fe 2+ will remain entirely in a solution that is saturated with H 2 S at a concentration of [H 2 S] = 0.10 M? At this pH, what would be the concentration of Pb 2+ in equilibrium with solid PbS in this solution? ( K of FeS (s) = Fe 2+ + S 2-is 5.0 x 10-19 and K a1 of H 2 S is 9.1 x 10-8 ) 5. Suppose 140 mL of 0.0010 M Sr(NO 3 ) 2 is mixed with enough 0.0050 M NaF to make 1.0 L of solution. Will SrF 2 ( s ) ( K sp = 2.8 x 10-9 ) precipitate at equilibrium? Explain....
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