Solubility Homework Set Worked Out Solutions

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Unformatted text preview: d for AgCl to ppt. AgCl(s) *Lowest concentration will precipitate first: AgCl precipitates first, then Ag2CrO4, then Ag2CO3. 70. In which one of the following solutions is silver chloride the most soluble? a) 0.181 M HCl solution b) 0.0176 M NH3 solution c) Pure water d) 0.744 M LiNO3 solution e) 0.181 M NaCl solution AgCl(s) Ag+(aq) + Cl‐(aq) a) HCl: common‐ion effect, decreases solubility b) NH3: ­ Ag+ forms the complex ion Ag(NH3)2+, increasing solubility. c) Water: no change in solubility d) LiNO3: both ions are conjugate salts of strong base/acid (LiOH and HNO3) and therefore do not affect solubility. e) NaCl: common‐ion effect, decreases solubility. 71. Given the following Ksp values, which statement about solubility in water is correct? PbCrO4 = 2.0 x 10‐16 Zn(OH)2 = 4.5 x 10‐17 Pb(OH)2 = 1.2 x 10‐15 MnS = 2.3 x 10‐13 a) PbCrO4, Zn(OH)2, and Pb(OH)2 have the same solubilities in water. b) PbCrO4 has the lowest solubility in water. c) The solubility of MnS in water will not be pH dependant d) MnS has the highest molar solubility in water. e) A saturated PbCrO4 solution will have a higher [Pb2+] that a saturated Pb(OH)2 solution. 21 Dr. Fus CHEM 123 a) Because the cation‐to‐anion ratios are the same for Zn(OH)2 and Pb(OH)2, we can directly compare their Ksp values. Because they differ, their solubilities in water cannot be the same, making this statement FALSE. b) Because the cation‐to‐anion ratios are the same for PbCrO4 and MnS, we can directly compare their Ksp values. Because Ksp is lower for PbCrO4, we know it is less soluble than MnS. However, to compare the solubility of PbCrO4 to those of Zn(OH)2 and Pb(OH)2, we must use ICE tables to calculate molar solubilities: Pb2+(aq) + CrO42‐(aq) PbCrO4(s) ____ Initial ‐‐‐‐‐ 0 M 0 M Change ‐‐‐‐‐ +1x M +1x M Equilibrium ‐‐‐‐‐ +x M +x M Ksp=[ Pb2+] [CrO42‐]= (x)(x)= x2= 2.0 x 10‐16 x= 1.4 x 10‐8 M Zn(OH)2(s) ____Zn2+(aq) + 2OH‐(aq) Initial ‐‐‐‐‐ 0 M 0 M Change ‐‐‐‐‐ +1x M +2x M Equilibrium ‐‐‐‐‐ +x M +2x M Ksp=[ Zn2+] [OH‐]2= (x)(2x)2= 4x3= 4.5 x 10‐17 x= 2.2 x 10‐6 M ____Pb2+(aq) + 2OH‐(aq) Pb(OH)2(s) Initial ‐‐‐‐‐ 0 M 0 M Change ‐‐‐‐‐ +1x M +2x M Equilibrium ‐‐‐‐‐ +x M +2x M Ksp=[ Pb2+] [OH‐]2= (x)(2x)2= 4x3= 1.2 x 10‐15 x= 6.7 x 10‐6 M *PbCrO4 has the lowest x‐value (molar solubility) in water, making this statement TRUE. c) MnS(s) Mn2+(aq) + S2‐(aq) *Both ions are the conjugate acid/base of a WEAK base/acid, making them both subject to the effects of pH, making this statement FALSE. d) Because the cation‐to‐anion ratios are the same for PbCrO4 and MnS, we can directly compare their Ksp values. Because Ksp is higher for MnS, we know it is more soluble than PbCrO4. However, to compare the solubility of MnS to those of Zn(OH)2 and Pb(OH)2, we must use ICE tables to calculate molar solubilities: MnS(s) ____ Mn2+(aq) + S2‐(aq) Initial ‐‐‐‐‐ 0 M 0...
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