CH 302 1st Edition Lecture 5Outline of Last Lecture I. Important RemindersII. Thermodynamics of Solutions(a) Effects of pressure and temperatureIII. Colligative Properties(a) Boiling Point Elevation (VP lowering)(b) Freezing Point Depression(c) OsmosisOutline of Current Lecture I. Important RemindersII. Concept of SolubilityIII. Modeling Ionic ReactionsIV. Solubility Product ConstantCurrent LectureImportant Reminders:- When comparing the free energy of the pure solvent to the free energy of a solution formed by adding a solid solute to the solvent, the free energy of the solution is lower- Which would you expect to have the lowest vapor pressure: 4 M sugar aqueous solution,0.75 M KCl aqueous solution, 0.25 M CaCl2 aqueous solution, or 1.5 M MgCl2 aqueous solution?o 1.5 M MgCl2 aqueous solution because there is 4.5 M of “bits”- What will happen if I add more solid slat to a saturated solution?o The concentration of salt will remain the same because it is in dynamic equilibrium (we dissolved as much as we can already)Concept of Solubility:- Solubility: g solute/ 100 g solutionWhat is the molar solubility of CaCl2?1. Write the formula equation down: CaCl2 (s) Ca2+ (aq) + 2 Cl- (aq)2. Given g solute/ 100 g H2O (solvent), we now have 64.7 g solute/ 164.7 g solutiono Solution = solvent + solute so 100 g H2O (solvent) + 64.7 g solute = 164.7 g solution3. Dimensional analysis to achieve moles/L64.7 g CaCl2 x 1 mole CaCl2 x 1.435 g CaCl2 solution x 1000 mL = 5.08 moles/L164.7 g soln. 111.07 g CaCl2 1 mL solution 1 LModeling Ionic Reactions:The net ionic equation for the following is: (NH4)2CO3 (aq) + CaCl2 - NH4+ + CO3 2- + Ca2+ +2 Cl- NH4+ + 2 Cl - + CaCO3 (s)- Spectator Ions go away: NH4+, Cl-- So the net ionic equation becomes: CO32- (aq) + Ca2+(aq) CaCO3(s)To determine whether or not a compound dissociates into two, follow the solubility rules:1. All common compounds of Group I and ammonium ions are soluble. 2. All nitrates, acetates, and chlorates are soluble. 3. All binary compounds of the halogens (other than F) with metals are soluble, except those of Ag, Hg(I), and Pb. Pb halides are soluble in hot water.) 4. All sulfates are soluble, except those of barium, strontium, calcium, lead, silver, and mercury (I). The latter three are slightly soluble. 5. Except for rule 1, carbonates, hydroxides, oxides, silicates, and phosphates are insoluble. Sulfides are insoluble except for calcium, barium, strontium, magnesium, sodium, potassium, and ammoniumSolubility Product Constant:Set up the Ksp expression and solve for the molar solubility of CaCO3. Ksp = 8.7 x 10^-9- Ksp = [Ca2+][CO3 2-]- Brackets shows molar concentration (moles/L)- Since x = [Ca2+] = [CO3 2-], Ksp = x^2- So the molar solubility is Ksp = x^2- 8.7 x 10^-9 = x^2- x = 9.3 x
View Full Document
Unlocking...