(cmb3744) byrne H10: Solubility mccord (51620) This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page nd all choices before answering. 001 10.0 points The compound M2 X3 has a molar solubility of 0.0280 M. What is the value of Ksp for M2 X3 ? 1. 1.66 105 2. 6.2 107 3. 1.72 108 4. 0.000132 5. 1.86 10
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2. Ksp = x2 3. Ksp = 2 x3 4. Ksp = 4 x2 5. Ksp = 2 x2 Explanation: The equation for the dissociation of Ag2 CrO4 is written as Ag2 CrO4 2 Ag+ + CrO . 4
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The expression for Ksp = Ag+ CrO . 4 Since the molar solubility is x, Ksp can be rewritten (in terms of x) as correct Ksp = [2 x]2 [x] = 4 x3 . Ag+ = 2 x because for every salt molecule that dissociates, 2 Ag+ ions are produced. 004 10.0 points Which of the following compounds has the LOWEST molar solubility in water? 1. PbSO4 , Ksp = 1.3 108 2. Sn(OH)2 , Ksp = 3 1027 3. MgC2 O4 , Ksp = 8.6 105 4. Al(OH)3 , Ksp = 2 1032 5. CdS, Ksp = 1.0 1028 correct Explanation: 005 10.0 points The value of Ksp for CuI is 1 1012 . What is the solubility for CuI? 1. 9.0 106 g/L 2. 1.0 1012 g/L 3. 1.0 106 g/L 4. 2.4 104 g/L 5. 1.9 104 g/L correct
Explanation: 002 10.0 points A solution in equilibrium with solid barium phospate is found to have a barium ion concentration of 5 104 mol/L and a Ksp of 5 1023 . Calculate the concentration of phosphate ion. 1. 3.16 1010 mol/L 2. 4.64 107 mol/L 3. 6.32 107 mol/L correct 4. 5.77 1011 mol/L 5. 2.50 10
64
mol/L
Explanation: 003 10.0 points Assume the molar solubility of silver chromate (Ag2CrO4 ) is represented as x. Which of the following expressions correctly expresses the relationship between the molar solubility of silver chromate and the solubility product constant (Ksp ) for this compound? 1. Ksp = 4 x3 correct
byrne (cmb3744) H10: Solubility mccord (51620) Explanation: Ksp = 1 1012 CuI Cu+ + I Let x = molar solubility, so Ksp = [Cu+ ] [I] = 1 1012 = x2 x= (1 1012 ) = 1.0 106 mol/L
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008 10.0 points M+ is added to a solution of 0.0038 M X and 0.002 M Z . MX has Ksp = 7.7 109 , while MZ has Ksp = 1.7 1010 . What percentage of the Z is still in solution (not precipitated) when the MX just starts to precipitate? Correct answer: 4.19%. Explanation: [X ] = 0.0038 M Ksp MX = 7.7 109 [Z ] = 0.002 M Ksp MZ = 1.7 1010
molecular weight of CuI = 63 + 127 = 190 g/mol. solubility = (1.0 106 mol/L) (190 g/mol) = 1.9 104 g/L 006 10.0 points The solubility product constant of PbCl2 is 1.7 105 . What is the maximum concentration of Pb2+ that can be in ocean water that contains 0.0500 M NaCl? 1. 3.4 103 M 2. 6.8 103 M correct 3. 4.2 108 M 4. 8.5 107 M 5. 1.7 103 M Explanation: Ksp of PbCl2 = 1.7 105 PbCl2 Pb
2+
The two relevant equilibria here are M+ + X Ksp = [M+ ] [X] MX(s) M+ + Z Ksp = [M+ ] [Z ] MZ(s) MX would precipitate when Ksp = [M+ ] [X ] 7.7 109 = [M+ ] (0.0038 M) [M+ ] = 2.02632 106 M This corresponds to a [Z ] of Ksp = [M+ ] [Z] 1.7 1010 = (2.02632 106 M) [Z ] [Z ] = 8.38961 105 M The percentage of [Z ] still in solution is 8.38961 105 M (100 %) = 4.19% 0.002 M 009 10.0 points How many mL of a 0.001 M chloride solution must be added to a 100 mL solution of 7.2 105 M Ag+ solution for AgCl to precipitate? Ksp (AgCl) = 1.8 1010 (Neglect dilution by the added Cl solution.) 1. 2.6 mL 2. 0.03 mL 3. 40.6 mL 4. Need to know the solution pH to solve this problem
+ 2FCl
Ksp = [Pb2+ ] [Cl]2 105 1.7 = [Pb2+ ] (0.05)2 [Pb2+ ] = 0.0068 007 10.0 points A saturated solution of MX3 (of MW 145 g/mol) contains 0.0225 grams per liter. What is the solubility product constant of MX3 ? Correct answer: 1.57 1014 . Explanation:
byrne (cmb3744) H10: Solubility mccord (51620) 5. 0.25 mL correct Explanation: 010 10.0 points The solubility product constant of AgCl is 1.8 1010 and that of AgBr is 3.3 1013 . Solid AgNO3 is slowly added to a solution containing 0.0010 M each of NaCl and NaBr. What concentration of Br would remain in solution when AgCl begins to precipitate? 1. 5.5 101 M 2. 1.8 104 M 3. 1.8 1010 M 4. 1.8 106 M correct 5. 5.5 104 M Explanation: 011 10.0 points A solution is 0.01 M BaCl2 and 0.02 M SrCl2 . Which cation can be selectively precipitated rst with a concentrated Na2 SO4 solution? Ksp is 1.5 109 for BaSO4 , and 7.6 107 for SrSO4 . 1. Sr+2 2. Both will precipitate at the same time. 3. Ba+2 correct Explanation: Before addition of Na2 SO4 ... [Ba2+ ] = 0.01 M [Sr2+ ] = 0.02 M Cl is a spectator ion to be ignored. Each of the two cation concentrations listed above have a corresponding concentration of SO2 that will cause each of these cations to 4 precipitate (shown as ) as the sulfate salt. We must calculate these two SO2 concen4 trations and note which of the two is smaller (since well get to that one rst as we increase the SO2 concentration from zero). 4 SrSO4 Sr2+ + SO2 4 Ksp = [Sr2+ ] [SO2 ] 4 7.6 107 = (0.02 M) [SO2 ] 4 [SO2 ] = 3.8 105 M for SrSO4 4 BaSO4 Ba2+ + SO2 4 Ksp = [Ba2+ ] [SO2 ] 4 1.5 109 = (0.01 M) [SO2 ] 4
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[SO2 ] = 1.5 108 M for BaSO4 4 The concentration of sulfate ion that will cause BaSO4 to precipitate is smaller than the concentration that will cause SrSO4 to precipitate. Therefore, Ba+2 will be precipitated rst. 012 10.0 points A uoridated water supply contains F at a concentration of 8.2 ppm. What is the maximum concentration of Mg2+ that can exist in this water supply without causing precipitation? The Ksp for MgF2 is 6.4 109. Correct answer: 0.834992 grams/L. Explanation: 013 10.0 points If a solution is 1.0 105 M in Mn(NO3 )2 and 1.5 103 M in aqueous ammonia, will Mn(OH)2 precipitate? Kb for NH3 = 1.8 105 Ksp for Mn(OH)2 = 2.0 1013 1. no, because Ksp > Qsp . 2. yes, because Ksp > Qsp . 3. yes, because Qsp > Ksp . correct 4. no, because Qsp > Ksp . Explanation: 014 10.0 points Fe(OH)3 (s) is very insoluble in water (Ksp = 1.6 1039 ; however, Fe3+ forms a strong complex with EDTA (FeEDTA , Kf =
byrne (cmb3744) H10: Solubility mccord (51620) 1.3 1025 ). For a solution which is at equilibrium and contains Fe(OH)3 (s) precipitate, which of the following occurs if EDTA is added to the solution? 1. More Fe(OH)3 (s) precipitates because [Fe3+ ] decreases. 2. No more Fe(OH)3 (s) dissolves, but Fe3+ complexes with EDTA. 3. More Fe(OH)3 (s) dissolves. correct 4. Nothing happens because Ksp is much smaller than Kf . Explanation: 015 10.0 points What is the concentration of CN ion in a 0.400 molar solution of K4 Fe(CN)6? Kd for (Fe(CN)6)4 is 1.3 1037 . 1. 5.00 106 M 2. 1.02 106 M 3. 2.83 106 M 4. 6.09 106 M correct 5. 8.33 107 M Explanation: 016 10.0 points Ferrous hydroxide is a slightly soluble base. In which of the following would Fe(OH)2 be most soluble? It is not necessary to know Ksp for Fe(OH)2 . 1. 0.1 M FeCl2 2. 0.1 M KOH 3. 0.1 M HCl correct 4. 0.1 M Ca(OH)2 Explanation:
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