10A solution contains 5.0 g of toluene (C7H8) and 225 g of benzene (C6H6) and has a density of g/mL.Calculate the mass percent and mole fraction of C7H8, andthe molarity and molality of the solution.2.2 %, 0.018, 0.21 mol/L, 0.24 mol/kgPractice on Example 12.4 andcompare your results with the answers.
21i ― electrolyte or nonelectrolyte Boiling point elevation can be used to find molar mass of solute.∆Tb ― experimentsi ― electrolyte or nonelectrolyteKb ― table or reference book
22A solution was prepared by dissolving 18.00 g glucose in 150.0 g water. The resulting solution was found to have a boiling point of°C. Calculate the molar mass of glucose. Glucose ismolecular solid that is present as individual molecules in solution.180 g/mol
23Four properties of solutions (1) Boiling point elevation(2) Freezing point depressionSolution compared to pure solventwater = solventfreezing point = 0 °Cwater + salt = solutionfreezing point < 0 °C
24∆Tf = Tf,solvent − Tf,solution = i Kf m i: van’t Hoff factor of solutem: molalityKf: freezing-point depression constantUnitsKf is characteristic of the solvent. Does notdepend on solute.
27i ― electrolyte or nonelectrolyte Freezing point depression can be used to find molar mass of solute.∆Tf ― experimentsi ― electrolyte or nonelectrolyteKf ― table or reference book
28A chemist is trying to identify a human hormone that controls metabolism by determining its molar mass. A sample weighing0.546 g was dissolved in 15.0 g benzene, and the freezing-pointdepression was determined to be °C. Calculate the molarmass of the hormone.776 g/mol
32Experiment 23 this Thursday Read the lab manual before coming to the labBring the manual, a copy of the data form,a pair of goggles, and an apron to the labWash your apron before ThursdayDress properly according to the syllabus
33Four properties of solutions (1) Boiling point elevation(2) Freezing point depression(3) Osmotic pressure
37i ― electrolyte or nonelectrolyte Osmotic pressure can be used to find molar mass of solute.Π ― experimentsi ― electrolyte or nonelectrolyteR ― constantT ― experiments
38To determine the molar mass of a certain protein, 1.00 x 10−3 g of it was dissolved in enough water to make 1.00 mL of solution.The osmotic pressure of this solution was found to be 1.12 torrat 25.0 °C. Calculate the molar mass of the protein.1.66 x 104 g/mol
39Practice on Example 12.10 and compare your results with the answers.
49Raoult’s Law: Case 1 ― vapor pressure of solution Nonvolatile solute in a Volatile solvent― vapor pressure of solution― vapor pressure of pure solvent― mole fraction of solvent
50For a Solution that Obeys Raoult's Law, a Plot of Psoln Versus Xsolvent, Give a Straight Line
51Example 12.6Calculate the vapor pressure at 25 °C of a solution containing99.5 g of sucrose (C12H22O11) and 300 mL of water. The vaporpressure of pure water at 25 °C is 23.8 torr. Assume thedensity of water to be 1.00 g/mL.molar mass of sucrose = g/mol23.4 torr
5622.1 torr Predict the vapor pressure of a solution prepared by mixing 35.0 g solid Na2SO4 (molar mass = 142 g/mol) with 175 gwater at 25 °C. The vapor pressure of pure water at 25 °C is23.8 torr.22.1 torrTry Example 12.12
58Raoult’s Law: Case 2 Volatile solute in a Volatile solvent Recall Dalton’s law of partial pressures
59Vapor Pressure for a Solution of Two Volatile Liquids XA + XB = 1
60A mixture of benzene (C6H6) and toluene (C7H8) containing 1.0 mol of benzene and 2.0 mol of toluene. At 20 °C the vaporpressures of pure benzene and toluene are 75 torr and 22 torr,respectively. What is the vapor pressure of the mixture?What is the mole fraction of benzene in the vapor?
62A solution that obeys Raoult’s Law is called an ideal solution.
63Chapter 12, Figure 12.15ABehavior of Nonideal Solutions
64What kind of solution is ideal if viewed at a molecular level?
65pure solvent10%P0# of molecules in vapor = 100 x 1 x 10% = 10χ
66P0 χ Psln solvent + solute 15%solvent + solute5%10%P0# of molecules in vapor = 100 x 0.8 x 10% = 8χPslnRaoult’s law:# of molecules in vapor = 100 x 0.8 x 5% = 4Deviate fromRaoult’s law# of molecules in vapor = 100 x 0.8 x 15% = 12
67What kind of solution is ideal? Solute-solute, solvent-solvent, and solute-solventinteractions are very similar.
68Chapter 12, Figure 12.15Behavior of Nonideal Solutions
70What kind of solution is ideal? Solute-solute, solvent-solvent, and solute-solventinteractions are very similar.Comparison to ideal gas.
71Four Colligative properties of solutions (1) Boiling point elevation: ∆Tb = i Kb m(2) Freezing point depression: ∆Tf = i Kf m(3) Osmotic pressure: Π = iMRT(4) Lowering the vapor pressure:Colligative: depend on the quantity (number of particles,concentration) but not the kind or identity of the solute particles.
72Quiz 3 Find van’t Hoff factors from formulas Use osmotic pressure to find molarmass of a soluteRaoult’s law, ideal solution