L21_Solub2_115b08

L21_Solub2_115b08 - L21: Solubility and precipitation...

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L21: Solubility and precipitation equilibria Solubility: the greatest amount that will dissolve in a specified volume of a solvent at particular conditions (T, pH, presence of oth ions, etc). Solubility product: equilibrium constant For an ionic solid A n B m : A n B m (s) <−> nA +x (aq) + mB -y (aq) K sp =[A +x ] n [B -y ] m TODAY: Common ion effect: Add one of the ions Æ Concentration of second ion diminishes Æ Solubility diminishes Selective Precipitation: Separate two metal ions
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(1) CaF 2 (s) <-> Ca 2+ (aq) + 2F - (aq) F- is the conjugate base of a weak acid (2) F - + H 2 O <-> HF + OH - Lowering the pH means adding H+, which would push reactions (2) and (1) to the right, thereby increasing solubility. For CaF 2 ( s ), K sp = 3.9 × 10 -11 . As the pH is lowered, the solubility of CaF 2 in water should increase or decrease?
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Common ion effect: Compare the solubility of AgCl, K sp =1.6x10 -10 , in water and in 0.1 M solution of NaCl (a) in water AgCl(s) <-> Ag + + Cl - K sp =[Ag + ][Cl - ] -y
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This note was uploaded on 07/22/2008 for the course CHEM 115b taught by Professor Reisler during the Spring '08 term at USC.

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L21_Solub2_115b08 - L21: Solubility and precipitation...

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