the S”) indicates the point of maximum buffering of the second buffering “second zone where [HA-] / [A2-] = 1. The middle of the S” is the second “second equivalence point where [HA-] = 0. The top part of the S” levels off at “second the pH of the base solution. 22. Solubility Product (Ksp) Example 1: Co(OH)2(s) Co2+ + 2OH- = [Co2+][]2 Ksp (don’t forget concentration of is twice the solubility) – Example 2: Solubility of Ag2SO4 is 0.016 mol L-1 (5.0 g L-1). Find the of Ksp Ag2SO4. (Answer: = 1.5 × 10-5) Ksp 23. Ion product (Qi) equivalent to the quotient” – “reaction < all ions in solution; more will dissolve Qi Ksp = equilibrium solution is saturated Qi Ksp – > precipitation will occur until = Qi Ksp Qi Ksp 24. Solubility of any salt which contains a basic anion is influenced by pH: Example: Consider a solution which is 1 in each of Fe3+ and H+. Will M Fe(OH)3 precipitate? Answer: NO! Fe(OH)3 Fe3+ + 3 = [Fe3+][] Qi If [H+] = 1 then [] = 10-14 M, = (1) (10-14)3 = 10-42 Qi Since for Fe(OH)3 = 3 × 10-39; precipitation does not occur. Ksp However, what if [H+] = 10-5? Then [] = 10-9 = (1) (10-9)3 = 10-27 Qi Since > Fe(OH)3 will precipitate! Qi Ksp; Free Response Questions 2007 #1 1. HF(aq) + H2O(l) H3O+(aq) + F-(aq) = 7.2 × 10-4 Ka Hydrofluoric acid, HF(aq), dissociates in water as represented by the equation above.
the “second S”) indicates the point of maximum buffering of the second buffering zone where [HA-] / [A2-] = 1. The middle of the “second S” is the second equivalence point where [HA-] = 0. The top part of the “second S” levels off at the pH of the base solution. 22. Solubility Product (Ksp) Example 1: Co(OH)2(s) Co2+ + 2OH- Ksp = [Co2+][]2 (don’t forget – concentration of is twice the solubility) Example 2: Solubility of Ag2SO4 is 0.016 mol L-1 (5.0 g L-1). Find the Ksp of Ag2SO4. (Answer: Ksp = 1.5 × 10-5) 23. Ion product (Qi) – equivalent to the “reaction quotient” Qi < Ksp all ions in solution; more will dissolve Qi = Ksp equilibrium – solution is saturated Qi > Ksp precipitation will occur until Qi = Ksp 24. Solubility of any salt which contains a basic anion is influenced by pH: Example: Consider a solution which is 1 M in each of Fe3+ and H+. Will Fe(OH)3 precipitate? Answer: NO! Fe(OH)3 Fe3+ + 3 Qi = [Fe3+][] If [H+] = 1 M, then [] = 10-14 Qi = (1) (10-14)3 = 10-42 Since Ksp for Fe(OH)3 = 3 × 10-39; precipitation does not occur. However, what if [H+] = 10-5? Then [] = 10-9 Qi = (1) (10-9)3 = 10-27 Since Qi > Ksp; Fe(OH)3 will precipitate! Free Response Questions 2007 #1 1. HF(aq) + H2O(l) H3O+(aq) + F-(aq) Ka = 7.2 × 10-4 Hydrofluoric acid, HF(aq), dissociates in water as represented by the equation above.
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