388
Solubility Product and Precipitation
42. A 100 ml sample of 0.250 M NH 3 is added to 100 ml of 0.0200 M Mn(NO 3 ) 2
solution. What is the minimal number of grams of NH 4 C1 that must be added
to prevent the precipitation of Mn(OH) 2 ?
43. What volume of 3.00 M NH 3 must be added to 100 ml of a solution containing
1.00 g of Mn(NO 3 ) 2 and 75.0 g of NH 4 C1 in order to commence the precipitation of Mn(OH) 2 ?
44. How many grams of NaCN must be added to 1.00 liter of 0.0100 M Mg(NO 3 ) 2
in order to commence precipitation of Mg(OH) 2 ?
45. What will be the molar concentration of the following ions remaining in solutions saturated with H 2 S and adjusted to a final pH of 2.00?
(a) Ag
+
(d) Mn
2+
(b) Bi
3+
(e) T1+
(c) Ni
2+
Initial concentrations are 0.0100 M.
46. Is it possible to precipitate PbS from a suspension of PbI 2 in 2.00 M HC1 by
saturation with H 2 S? Explain.
47. (a) To what final pH must a solution saturated with H 2 S be adjusted in order
to precipitate SnS without precipitating any FeS? (This solution is originally 0.100 M with respect to each metal ion.)
(b) How much Sn
2+ will be left in solution when the Fe
2+ begins to precipitate?
48. What must be the final pH of an HC1 solution in order to just dissolve 0.200
mole FeS in 1.00 liter of solution?
49. What is the lowest pH that will permit the sulfide of each of the following
metals to precipitate from a 1.00 x 10~
4 M solution saturated with H 2 S?
(a) Tl
+
(c) Ni
2+
(b) Cd
2+
(d) Sn
2+
50. What volume of saturated Ag 2 S solution would you have to take in order to
obtain, statistically, one Ag
+ ion? (Neglect hydrolysis of the sulfide ion.)
51. A 100 ml sample of a solution contains 10.0 g of NaC 2 H 3 O 2 , 5.00 ml of 6.00 M
HC 2 H 3 O 2 , and 50.0 mg of Fe
2+ . When the solution is saturated with H 2 S, how
many milligrams of Fe
2+ remain in solution?
52. A solution that is 0.0500 M in Cd
2+ , 0.0500 M in Zn
2+ , and 0.100 M in H
+ is
saturated with H 2 S. Calculate the concentration of Zn
2+ and Cd
2+ remaining in
solution after saturation. (Do not neglect the H
+ formed on precipitation.)
53. Calculate the solubility in water of (a) MnS and (b) Ag 2 S. (Do not neglect
hydrolysis of the sulfide ion.)
54. Which will precipitate first when solid Na 2 S is slowly added to a 0.0200 M
CdCl 2 solution: CdS or Cd(OH) 2 ? Explain.
Solubility Product and Precipitation
42. A 100 ml sample of 0.250 M NH 3 is added to 100 ml of 0.0200 M Mn(NO 3 ) 2
solution. What is the minimal number of grams of NH 4 C1 that must be added
to prevent the precipitation of Mn(OH) 2 ?
43. What volume of 3.00 M NH 3 must be added to 100 ml of a solution containing
1.00 g of Mn(NO 3 ) 2 and 75.0 g of NH 4 C1 in order to commence the precipitation of Mn(OH) 2 ?
44. How many grams of NaCN must be added to 1.00 liter of 0.0100 M Mg(NO 3 ) 2
in order to commence precipitation of Mg(OH) 2 ?
45. What will be the molar concentration of the following ions remaining in solutions saturated with H 2 S and adjusted to a final pH of 2.00?
(a) Ag
+
(d) Mn
2+
(b) Bi
3+
(e) T1+
(c) Ni
2+
Initial concentrations are 0.0100 M.
46. Is it possible to precipitate PbS from a suspension of PbI 2 in 2.00 M HC1 by
saturation with H 2 S? Explain.
47. (a) To what final pH must a solution saturated with H 2 S be adjusted in order
to precipitate SnS without precipitating any FeS? (This solution is originally 0.100 M with respect to each metal ion.)
(b) How much Sn
2+ will be left in solution when the Fe
2+ begins to precipitate?
48. What must be the final pH of an HC1 solution in order to just dissolve 0.200
mole FeS in 1.00 liter of solution?
49. What is the lowest pH that will permit the sulfide of each of the following
metals to precipitate from a 1.00 x 10~
4 M solution saturated with H 2 S?
(a) Tl
+
(c) Ni
2+
(b) Cd
2+
(d) Sn
2+
50. What volume of saturated Ag 2 S solution would you have to take in order to
obtain, statistically, one Ag
+ ion? (Neglect hydrolysis of the sulfide ion.)
51. A 100 ml sample of a solution contains 10.0 g of NaC 2 H 3 O 2 , 5.00 ml of 6.00 M
HC 2 H 3 O 2 , and 50.0 mg of Fe
2+ . When the solution is saturated with H 2 S, how
many milligrams of Fe
2+ remain in solution?
52. A solution that is 0.0500 M in Cd
2+ , 0.0500 M in Zn
2+ , and 0.100 M in H
+ is
saturated with H 2 S. Calculate the concentration of Zn
2+ and Cd
2+ remaining in
solution after saturation. (Do not neglect the H
+ formed on precipitation.)
53. Calculate the solubility in water of (a) MnS and (b) Ag 2 S. (Do not neglect
hydrolysis of the sulfide ion.)
54. Which will precipitate first when solid Na 2 S is slowly added to a 0.0200 M
CdCl 2 solution: CdS or Cd(OH) 2 ? Explain.