1 / 27

16.6 Solubility Equilibria

16.6 Solubility Equilibria. Solubility Equilbria. Many ionic cmpds are very soluble in water (as NaCl) but others have limited solubility--p 109 table 4.2.

trisha
Download Presentation

16.6 Solubility Equilibria

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 16.6 Solubility Equilibria

  2. Solubility Equilbria • Many ionic cmpds are very soluble in water (as NaCl) but others have limited solubility--p 109 table 4.2

  3. Let’s envision what happens when make a saturated solution of some ionic cmpd of limited solubility, as CaCO3. Assume that the solvent is water and the temp is 25oC. • CaCO3(s)  Ca2+(aq) + CO32-(aq)  CaCO3(aq) • A certain quantity of CaCO3 goes into solution and immediately dissociates into ions. _______________

  4. A saturated solution has ___________ • Remember in writing equil expressions that pure solids, pure liquids--______.

  5. Solubility Product • CaCO3(s)  Ca2+(aq) + CO32-(aq) • Ksp = _____________ • Ksp is called the _______________ (equil constant) (Implies ideal behavior) • [Ca2+] implies conc units in _________ • Ksp values tabulated in book, p 672, table 16.2

  6. Relationship btn molar sol’y (s) and Ksp • Define molar solubility, s ,as the ________ • Let us examine the stoichiometrically different salts and their relationship to molar solubility.

  7. 1:1 salt as AgCl, CaCO3 • AgCl(s)  Ag+(aq) + Cl-(aq) • Ksp = ____________ • [Ag+] = [Cl-] = ____

  8. 2:1 or 1:2 salt as CaF2 or Ag2SO4 • CaF2(s)  • Ksp = ________ • [F-] = __ [Ca2+] = __

  9. 1:3 or 3:1 salt as Fe(OH)3 or Ag3PO4 • Ag3PO4(s) • Ksp = • [Ag+] = ___ [PO43-]= ___

  10. 2:3 or 3:2 salt as Bi2S3 or Ca3(PO4)2 • Bi2S3(s)  • Ksp = • [Bi3+] = ___ [S2-] = _____ • Remember this assumes ideal behavior (as complete ionization--no ion pair formation, no hydrolysis of ions as Al3+ )

  11. Ksp and Q (ion-product) • Remember Ksp refers to a saturated sol’d, Q refers to any sol’n, not just an equilibrium system. • Ag3PO4(s)3Ag+(aq) + PO43-(aq) • Ksp = [Ag+]3[PO43-] • Q = [Ag+]3[PO43-] : these need not be equil concs

  12. If • Q < Ksp ______ • Q = Ksp ______ • Q > Ksp _______

  13. Problems: Ksp to s and s to Ksp • What are the molar solubilities of CaCO3(Ksp = 8.7 x 10-9) and Ag2CO3 (Ksp = 8.1 x 10-12) • Calc Ksp of Ag3PO4, given the sol’y of Ag3PO4 is 6.7 x 10-3 g/L

  14. 16.45: The sol’y of an ionic cmpd, M2X3 (molar mass=288g) , is 3.6 x 10-17 g/L. What’s the Ksp? • 16.47:What is the pH of a saturated zinc hydroxide sol’n? • 16.48: The pH of a sat’d sol’n of a metal hydroxide, MOH, is 9.68. Calc. the Ksp.

  15. Mix two sol’s together, do you get a ppt (predicting ppt rxns) • Do you get a ppt if mix • 10 mL of 0.0010M AgNO3 and 10 ml of 0.0010M Na2SO4 • 10 mL of 1.0 x 10-6M iron(II) chloride and 20 ml of 3.0 x 10-4M barium hydroxide

  16. 16.50: A volume of 75 mL of 0.060 M NaF is mixed with 25 mL of 0.15 M Sr(NO3)2. Calc the concs in the final soln of NO3-, Na+, Sr2+, and F-. Ksp for SrF2 is 2.0 x 10-10.

  17. 16.8: The common ion effect and solubility • What does Le Chatelier say about the presence of a common ion and solubility • AgI(s)  Ag+(aq) + I-(aq)  add Ag+ from AgNO3 • ___________

  18. Calculate the molar sol’y of SrF2 (Ksp = 2.0 x 10-10) in • water • in 0.010 M Sr(NO3)2 • in 0.010 M NaF • _________ • 16.56 similar

  19. 16.55: How many grams of CaCO3 will dissolve in 300 mL of 0.050 M Ca(NO3)2?

  20. What’s the solubility of Fe(OH)3 in HOH? Ksp for Fe(OH)3 =1.1 x 10-36. • So does changing pH affect solubility of insoluble hydroxides? • 16.62: Calc the pH of Fe(OH)2 in water and at a pH of 7.00, at a pH of 8.00 and at a pH of 10.00. • 16.61: Compare the molar soly of Mg(OH)2 in water and in a soln buffered at a pH of 9.00 .

  21. Factors that affect solubility • 1. _______ • 2. common ion ____________ • 3. pH: salt contains anion (conj base of WA): ____________ • CaF2(s)  Ca2+(aq) + 2F-(aq)  H+

  22. 4. hydroxides--pH: ___ • Except for amphoteric hydroxides as Al(OH)3, Pb(OH)2, Cr(OH)3, Zn(OH)2, Cd(OH)2 • Al(OH)3 + OH-  Al(OH)4-(aq) • As pH increases (add more OH-), tie up the hydroxide salt as a soluble complex,

  23. 5.Complex ion formation • Cu2+(aq) +2OH- Cu(OH)2(s) • Cu(OH)2(s) + 4NH3(aq)  Cu(NH3)42+(aq) complex ion • Cu2+(aq) + 4NH3(aq)Cu(NH3)42+(aq) • Kf = [Cu(NH3)42+] = 5.0 x 1013 [Cu][NH3]4 • Table of formation constants Kf, p 685, table 16.4

  24. 16.67: If 2.50 g of CuSO4 are dissolved in 900 mL of 0.30 M NH3, what sre the concs of Cu2+, Cu(NH3)42+ and NH3 at equilibrium? • 16.70: Calc the molar soly of AgI in a 1.0 M NH3 soln.

  25. Which of the following will be more soluble in acid solution than in water? • BaSO4 • PbCl2 • Fe(OH)3 • CaCO3 • Ca3(PO4)2 • AgBr

  26. 16.54: The molar soly of AgCl in 6.5x10-3M AgNO3 is 2.5 x 10-8 M. In deriving Ksp from these data which of the following assumptions are reasonable? • Ksp is the same as soly. • Ksp of AgCl is the same in 6.5x10-3M AgNO3 as in pure water. • Soly of AgCl is independent of the conc of AgNO3.

  27. [Ag+] in soln does not change significantly upon the addition of AgCl to 6.5x10-3M AgNO3. • [Ag+] in soln after the addition of AgCl to 6.5x10-3M AgNO3 is the same as it would be in pure water.

More Related