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Solubility

Solubility. Not all ionic compounds are completely soluble in water. All will dissolve up to saturation. Remaining solid added doesn’t dissolve. No matter how much extra solid you add the amount dissolved remains constant. Solubility – grams solid per Liter of solution.

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Solubility

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  1. Solubility Not all ionic compounds are completely soluble in water All will dissolve up to saturation Remaining solid added doesn’t dissolve No matter how much extra solid you add the amount dissolved remains constant Solubility – grams solid per Liter of solution Molar solubility – mol solid per Liter of solution

  2. Solubility Rules 1) Group I (& NH4+) ionic cpds are soluble 2) NO3-, CH3COO-, ClO3-, and ClO4- cpds soluble 3) Cl- cpds soluble except AgCl, Hg2Cl2, and PbCl2 4) SO42- cpds soluble except Pb and Ba 5) OH- cpds insoluble except GroupI & Group II Ca & higher 6) CO32-, PO43-, and AsO43- cpds insoluble except #1 Precipitation reactions AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)formula unit equation Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) → AgCl(s) + Na+(aq) + NO3-(aq)total ionic equation Ag+(aq) + Cl-(aq) → AgCl(s) net ionic equation

  3. Ksp values of some poorly soluble compounds (A-16) CaCO3 4.8 x 10-9 AgCl 1.8 x 10-10 Al(OH)3 1.9 x 10-33 Mg(OH)2 1.5 x 10-11 Ca3(PO4)2 1.0 x 10-25 BaSO4 1.1 x 10-10 ‘Insoluble’ compounds exist in equilibrium with dissolved ions. Be able to represent this in the form of a reaction. The solubility product is the result of writing the equilibrium expression for a solubility ‘reaction’.

  4. Solubility Rules 1) Group I (& NH4+) ionic cpds are soluble 2) NO3-, CH3COO-, ClO3-, and ClO4- cpds soluble 3) Cl- cpds soluble except AgCl, Hg2Cl2, and PbCl2 4) SO42- cpds soluble except Pb and Ba 5) OH- cpds insoluble except GroupI & Group II Ca & higher 6) CO32-, PO43-, and AsO43- cpds insoluble except #1 Ksp values of some poorly soluble compounds (A-16) CaCO3 4.8 x 10-9 AgCl 1.8 x 10-10 Al(OH)3 1.9 x 10-33 Mg(OH)2 1.5 x 10-11 Ca3(PO4)2 1.0 x 10-25 BaSO4 1.1 x 10-10 solubility (g L-1) molar solubility (mol L-1)solubility product 1. Determine Molar solubility and Ksp from solubility Problem 8d: SnI2 solubility = 10.9 g L-1

  5. Ksp values of some poorly soluble compounds (A-16) CaCO3 4.8 x 10-9 AgCl 1.8 x 10-10 Al(OH)3 1.9 x 10-33 Mg(OH)2 1.5 x 10-11 Ca3(PO4)2 1.0 x 10-25 BaSO4 1.1 x 10-10 2. Determine solubilityandMolar solubility from Ksp AgCl Ksp = 1.8 x 10-10 Mg(OH)2 Ksp = 1.5 x 10-11 also: what is pH?

  6. Solubility Product – Common Ion effect an application of LeChatelier’s Principle What is the solubility of CaCO3 …. KSP = 4.8 x 10-9 In water? Ksp = [Ca2+][CO32-] Molar Solubility (x) = 4.8 x 10-9 = x2 In 0.5M Na2CO3 ? Molar Solubility: 4.8 x 10-9 = x (0.5 + x) will x be small compared to 0.5?

  7. Fractional Precipitation If you have multiple ions in solution that all precipitate with the same counterion, which one will precipitate 1st? How much of that ion will remain when the 2nd ion begins to precipitate? # 36 (pg 838) - 0.010 M of Cu+, Ag+, and Au+ slowly add solid NaBr (neglect volume change) pptKspKsp expression AgBr 3.3 x 10-13 [Ag+][Br-] AuBr 5.0 x 10-17 [Au+][Br-] CuBr 5.3 x 10-9 [Cu+][Br-] 2nd 1st 3rd

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