Factors That Affect Solubility 1. For solids, as temperature increases, solubility common-ion effect Use Le Chatelier’s principle. For example, with... CaF 2 (s) Ca 2+ (aq) + 2 F – (aq) 3. pH and solubility Compounds with anions exhibiting basic properties (e.g., Mg(OH) 2 / OH –, CaCO 3 / CO 3 2–, CaF 2 / F – ) ____ in solubility as solution becomes more acidic. If you add Ca 2+ or F –, shift. (Sol. )

4. presence of complex ions: metal ions and the Lewis bases bonded to them In general, the solubility of metal salts __ in the presence of suitable Lewis bases (e.g., NH 3, CN –, OH – ) if the metal forms a complex ion with the bases. AgCl(s) Ag + (aq) + Cl – (aq) e.g., In a soln of AgCl, we have the equilibrium: Ag + (aq) + 2 NH 3 (aq) Ag(NH 3 ) 2 + (aq) If ammonia is added, we get… As Ag + forms the complex ion w /NH 3, Le Chatelier dictates that more AgCl will dissolve into the soln to replenish the decreased [ ] of Ag +. complex ion

Qualitative Analysis for Metallic Elements Steps: (1) (2) separate ions into broad groups by solubility specific ions are then separated from the group and identified by specific tests determines the presence or absence of a particular ion (as opposed to quantitative analysis)

aqueous solution containing “god-knows- what” metal ions insoluble chlorides (AgCl, Hg 2 Cl 2, PbCl 2 ) ppt out. Filter and test for a specific ion. acid-insoluble sulfides (CuS, Bi 2 S 3, CdS, PbS, HgS, As 2 S 3, Sb 2 S 3, SnS 2 ) ppt out. Filter and test for a specific ion. Bubble H 2 S(g) in. Add HCl. aqueous solution containing “god-knows- what” metal ions (but not much Ag +, Hg 2 2+, or Pb 2+ )

aqueous solution w /even fewer metal ions base-insoluble sulfides and hydroxides (Al(OH) 3, Fe(OH) 3, Cr(OH) 3, ZnS, NiS, CoS, MnS) ppt out. Filter and test for a specific ion. insoluble phosphates (Ba 3 (PO 4 ) 2, Ca 3 (PO 4 ) 2, MgNH 4 PO 4 ) ppt out. Filter and test for a specific ion. Add (NH 4 ) 2 PO 4. aqueous solution w /even FEWER metal ions Add (NH 4 ) 2 S. alkali metal ions still remain in soln.