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Unformatted text preview: m expression and see how the various reagents will influence the equilibrium. Remember, a common‐ion will decrease solubility, the effect of a change in pH will depend on the particular equilibrium, and formation of a complex ion will increase solubility, trumping both the common‐ion and pH effects: Ag+(aq) + C2H3O2‐(aq) AgC2H3O2 (s) NaC2H3O2‐common ion, therefore decreases solubility. HNO3‐ C2H3O2‐ is the conjugate base of a weak acid (HC2H3O2), and is therefore a weak base itself. It can be neutralized by HNO3, a strong acid, thereby decreasing the concentration of C2H3O2‐ and shifting the equilibrium to the right, increasing solubility. NH3‐ Ag+ forms the complex ion Ag(NH3)2+, increasing solubility. AgNO3‐ common ion, therefore decreases solubility. 48. How many of the following salts would be more soluble in acidic solution that in pure water? CaS AuCl3 PbF2 ZnCO3 BaC2O4 For an acidic solution to increase solubility, it must neutralize a weak base. Therefore the anion must be the conjugate base of a weak acid. Remember, conjugate salts of strong acids/bases are NOT influenced by addition of acids/bases or pH changes: BaC2O4‐ C2O4‐ is the conjugate base of the weak acid HC2O4. Solubility increases. CaS‐ S2‐ is the conjugate base of the weak acid HS‐. Solubility increases. 13 Dr. Fus CHEM 123 AuCl3‐ Cl‐ is the conjugate base of the strong acid HCl. Solubility is NOT affected. PbF2‐ F‐ is the conjugate base of the weak acid HF. Solubility increases. ZnCO3‐ CO32‐ is the conjugate base of the weak acid HCO3‐. Solubility increases. 49. Would each of the following reagents increase, decrease, of have no effect on the solubility of Cu(OH)2? HCl NH3 NaOH CuCl2 Cu2+(aq) + 2OH‐(aq) Cu(OH)2 (s) CuCl2‐common ion, therefore decreases solubility. HCl‐ H+ neutralizes OH‐, decreasing the concentration of OH‐ and shifting the equilibrium to the right, increasing solubility. NH3‐ Cu2+ forms the complex ion Cu(NH3)42+, increasing solubility. NaOH‐ common ion, therefore decreases solubility. 50. Which salt solubility would be most sensitive to pH? CaF2 CaCl2 Ca(NO3)2 CaBr2 CaI2 All of the cations are Ca2+, the conjugate salt of the strong base Ca(OH)2. It cannot be neutralized by changes in pH. Of all the anions, only F‐ is the conjugate base of a weak acid. The rest are conjugate bases of strong acids. Therefore CaF2 is most sensitive to pH. 51. The solubility of which of the listed salts would be unaffected by the presence of a strong acid? BaF2 FePO4 SnI2 KClO4 Conjugate bases of strong acids will be unaffected by addition of a strong acid. The salts with this type of conjugate base include KClO4 (HClO4 is a strong acid) and SnI2 (HI is a strong acid). BaF2 and FePO4 contain conjugate bases of weak acids and are therefore influenced by a strong acid addition. 52. How many of the following reagents, when added to a solution in contact with solid NiCO3 would change the solubility of NiCO3? NaCl Na2CO3 NH3 HCl NiCl2 Ni2+(aq) + CO32‐(a...
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This homework help was uploaded on 03/28/2014 for the course CHEM 123 taught by Professor Larosa during the Spring '06 term at Ohio State.
- Spring '06