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Solubility Equilibria Lead (II) iodide precipitates when potassium iodide is mixed with lead (II) nitrate. Graphic: Wikimedia Commons user PRHaney.

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Presentation on theme: "Solubility Equilibria Lead (II) iodide precipitates when potassium iodide is mixed with lead (II) nitrate. Graphic: Wikimedia Commons user PRHaney."— Presentation transcript:

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2 Solubility Equilibria Lead (II) iodide precipitates when potassium iodide is mixed with lead (II) nitrate. Graphic: Wikimedia Commons user PRHaney

3 K sp Values for Some Salts at 25  C

4 Solving Solubility Problems For the salt AgI at 25  C, K sp = 1.5 x AgI(s)  Ag + (aq) + I - (aq) I C E O O +x x x 1.5 x = x 2 x = solubility of AgI in mol/L = 1.2 x M

5 Solving Solubility Problems For the salt PbCl 2 at 25  C, K sp = 1.6 x PbCl 2 (s)  Pb 2+ (aq) + 2Cl - (aq) I C E O O +x +2x x 2x 1.6 x = (x)(2x) 2 = 4x 3 x = solubility of PbCl 2 in mol/L = 1.6 x M

6 Solving Solubility Problems For the salt AgI at 25  C, K sp = 1.5 x AgI(s)  Ag + (aq) + I - (aq) I C E O O +x x x 1.5 x = x 2 x = solubility of AgI in mol/L = 1.2 x M

7 Predicting Precipitate Formation Use the initial concentrations of ions in solution in the solubility product constant expression to calculate Q sp. If Q sp < K sp the solution is unsaturated and no precipitate will form. If Q sp = K sp the solution is saturated and no change will occur.

8 Predicting Precipitate Formation, continued… If Q sp > K sp a precipitate will form, reducing the concentrations of the ions in the solution until the product of their concentrations in the K sp expression equals the numerical value of K sp.

9 Predicting Precipitate Formation, continued… Do practice problems on pg. 619

10 Predicting Precipitate Formation, continued… Answers: 25. a. Qsp > Ksp so a precipitate of PbF2 will form. b. Qsp < Ksp so no precipitate will form 26. A precipitate will form.

11 The Common Ion Effect Why is PbCrO 4 less soluble in aqueous solution of K 2 CrO 4 than in pure water? The K 2 CrO 4 solution contains CrO 4 2– ions before any PbCrO 4 dissolves.

12 The Common Ion Effect (cont.) A common ion is an ion that is common to two or more ionic compounds.common ion The lowering of the solubility of a substance because of the presence of a common ion is called the common ion effect.common ion effect

13 Solving Solubility with a Common Ion For the salt AgI at 25  C, K sp = 1.5 x What is its solubility in 0.05 M NaI? AgI(s)  Ag + (aq) + I - (aq) I C E 0.05 O +x 0.05+x x 1.5 x = (x)(0.05+x)  (x)(0.05) x = solubility of AgI in mol/L = 3.0 x M

14 Precipitation and Qualitative Analysis


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