1. Chapter 11 Properties of Solutions

2. Chapter 11 Table of Contents Copyright © Cengage Learning. All rights reserved 2 11.1 Solution Composition 11.2 The Energies of Solution Formation 11.3 Factors Affecting Solubility 11.4 The Vapor Pressures of Solutions 11.5 Boiling-Point Elevation and Freezing-Point Depression 11.6Osmotic Pressure 11.7Colligative Properties of Electrolyte Solutions 11.8Colloids

3. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 3 Various Types of Solutions Example State of SolutionState of Solute State of Solvent Air, natural gasGas Vodka, antifreezeLiquid BrassSolid Carbonated water (soda)LiquidGasLiquid Seawater, sugar solutionLiquidSolidLiquid Hydrogen in platinumSolidGasSolid

4. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 4 Solution Composition

5. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 5 Molarity

6. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 6 Exercise You have 1.00 mol of sugar in 125.0 mL of solution. Calculate the concentration in units of molarity. 8.00 M

7. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 7 Exercise You have a 10.0 M sugar solution. What volume of this solution do you need to have 2.00 mol of sugar? 0.200 L

8. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 8 Exercise Consider separate solutions of NaOH and KCl made by dissolving 100.0 g of each solute in 250.0 mL of solution. Calculate the concentration of each solution in units of molarity. 10.0 M NaOH 5.37 M KCl

9. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 9 Mass Percent

10. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 10 Exercise What is the percent-by-mass concentration of glucose in a solution made my dissolving 5.5 g of glucose in 78.2 g of water? 6.6%

11. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 11 Mole Fraction

12. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 12 Exercise A solution of phosphoric acid was made by dissolving 8.00 g of H 3 PO 4 in 100.0 mL of water. Calculate the mole fraction of H 3 PO 4. (Assume water has a density of 1.00 g/mL.) 0.0145

13. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 13 Molality

14. Section 11.1 Solution Composition Return to TOC Copyright © Cengage Learning. All rights reserved 14 Exercise A solution of phosphoric acid was made by dissolving 8.00 g of H 3 PO 4 in 100.0 mL of water. Calculate the molality of the solution. (Assume water has a density of 1.00 g/mL.) 0.816 m

15. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 15 Formation of a Liquid Solution 1.Separating the solute into its individual components (expanding the solute). 2.Overcoming intermolecular forces in the solvent to make room for the solute (expanding the solvent). 3.Allowing the solute and solvent to interact to form the solution.

16. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 16 Steps in the Dissolving Process

17. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 17 Steps in the Dissolving Process Steps 1 and 2 require energy, since forces must be overcome to expand the solute and solvent. Step 3 usually releases energy. Steps 1 and 2 are endothermic, and step 3 is often exothermic.

18. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 18 Enthalpy (Heat) of Solution Enthalpy change associated with the formation of the solution is the sum of the ΔH values for the steps: ΔH soln = ΔH 1 + ΔH 2 + ΔH 3 ΔH soln may have a positive sign (energy absorbed) or a negative sign (energy released).

19. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 19 Enthalpy (Heat) of Solution

20. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 20 Concept Check Explain why water and oil (a long chain hydrocarbon) do not mix. In your explanation, be sure to address how ΔH plays a role.

21. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 21 The Energy Terms for Various Types of Solutes and Solvents H1H1 H2H2 H3H3  H soln Outcome Polar solute, polar solventLarge Large, negativeSmallSolution forms Nonpolar solute, polar solventSmallLargeSmallLarge, positiveNo solution forms Nonpolar solute, nonpolar solvent Small Solution forms Polar solute, nonpolar solventLargeSmall Large, positiveNo solution forms

22. Section 11.2 Atomic MassesThe Energies of Solution Formation Return to TOC Copyright © Cengage Learning. All rights reserved 22 In General One factor that favors a process is an increase in probability of the state when the solute and solvent are mixed. Processes that require large amounts of energy tend not to occur. Overall, remember that “like dissolves like”.

23. Section 11.3 The MoleFactors Affecting Solubility Return to TOC Copyright © Cengage Learning. All rights reserved 23 Structural Effects:  Polarity Pressure Effects:  Henry’s law Temperature Effects:  Affecting aqueous solutions

24. Section 11.3 The MoleFactors Affecting Solubility Return to TOC Copyright © Cengage Learning. All rights reserved 24 Pressure Effects Henry’s law:C = kP C = concentration of dissolved gas k = constant P =partial pressure of gas solute above the solution Amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution.

25. Section 11.3 The MoleFactors Affecting Solubility Return to TOC Copyright © Cengage Learning. All rights reserved 25 A Gaseous Solute

26. Section 11.3 The MoleFactors Affecting Solubility Return to TOC Copyright © Cengage Learning. All rights reserved 26 Temperature Effects (for Aqueous Solutions) Although the solubility of most solids in water increases with temperature, the solubilities of some substances decrease with increasing temperature. Predicting temperature dependence of solubility is very difficult. Solubility of a gas in solvent typically decreases with increasing temperature.

27. Section 11.3 The MoleFactors Affecting Solubility Return to TOC Copyright © Cengage Learning. All rights reserved 27 The Solubilities of Several Solids as a Function of Temperature

28. Section 11.3 The MoleFactors Affecting Solubility Return to TOC Copyright © Cengage Learning. All rights reserved 28 The Solubilities of Several Gases in Water

29. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 29 An Aqueous Solution and Pure Water in a Closed Environment

30. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 30 Liquid/Vapor Equilibrium

31. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 31 Vapor Pressure Lowering: Addition of a Solute

32. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 32 Vapor Pressures of Solutions Nonvolatile solute lowers the vapor pressure of a solvent. Raoult’s Law: P soln =observed vapor pressure of solution solv =mole fraction of solvent =vapor pressure of pure solvent

33. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 33 A Solution Obeying Raoult’s Law

34. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 34 Nonideal Solutions Liquid-liquid solutions where both components are volatile. Modified Raoult’s Law: Nonideal solutions behave ideally as the mole fractions approach 0 and 1.

35. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 35 Vapor Pressure for a Solution of Two Volatile Liquids

36. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 36 Summary of the Behavior of Various Types of Solutions Interactive Forces Between Solute (A) and Solvent (B) Particles  H soln  T for Solution Formation Deviation from Raoult’s Law Example A  A, B  B  A  B Zero None (ideal solution) Benzene- toluene A  A, B  B < A  B Negative (exothermic) PositiveNegative Acetone- water A  A, B  B > A  B Positive (endothermic) NegativePositive Ethanol- hexane

37. Section 11.4 The Vapor Pressures of Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 37 Concept Check For each of the following solutions, would you expect it to be relatively ideal (with respect to Raoult’s Law), show a positive deviation, or show a negative deviation? a)Hexane (C 6 H 14 ) and chloroform (CHCl 3 ) b)Ethyl alcohol (C 2 H 5 OH) and water c)Hexane (C 6 H 14 ) and octane (C 8 H 18 )

38. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 38 Depend only on the number, not on the identity, of the solute particles in an ideal solution:  Boiling-point elevation  Freezing-point depression  Osmotic pressure Colligative Properties

39. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 39 Nonvolatile solute elevates the boiling point of the solvent. ΔT = K b m solute ΔT = boiling-point elevation K b = molal boiling-point elevation constant m solute = molality of solute Boiling-Point Elevation

40. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 40 Boiling Point Elevation: Liquid/Vapor Equilibrium

41. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 41 Boiling Point Elevation: Addition of a Solute

42. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 42 Boiling Point Elevation: Solution/Vapor Equilibrium

43. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 43 When a solute is dissolved in a solvent, the freezing point of the solution is lower than that of the pure solvent. ΔT = K f m solute ΔT = freezing-point depression K f = molal freezing-point depression constant m solute = molality of solute Freezing-Point Depression

44. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 44 Freezing Point Depression: Solid/Liquid Equilibrium

45. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 45 Freezing Point Depression: Addition of a Solute

46. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 46 Freezing Point Depression: Solid/Solution Equilibrium

47. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 47 Changes in Boiling Point and Freezing Point of Water

48. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 48 Exercise A solution was prepared by dissolving 25.00 g glucose in 200.0 g water. The molar mass of glucose is 180.16 g/mol. What is the boiling point of the resulting solution (in °C)? Glucose is a molecular solid that is present as individual molecules in solution. 100.35 °C

49. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 49 Exercise You take 20.0 g of a sucrose (C 12 H 22 O 11 ) and NaCl mixture and dissolve it in 1.0 L of water. The freezing point of this solution is found to be -0.426°C. Assuming ideal behavior, calculate the mass percent composition of the original mixture, and the mole fraction of sucrose in the original mixture. 72.8% sucrose and 27.2% sodium chloride; mole fraction of the sucrose is 0.313

50. Section 11.5 Boiling-Point Elevation and Freezing-Point Depression Return to TOC Copyright © Cengage Learning. All rights reserved 50 Exercise A plant cell has a natural concentration of 0.25 m. You immerse it in an aqueous solution with a freezing point of –0.246°C. Will the cell explode, shrivel, or do nothing?

51. Section 11.6 Osmotic Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 51 Osmosis – flow of solvent into the solution through a semipermeable membrane. = MRT =osmotic pressure (atm) M=molarity of the solution R= gas law constant T=temperature (Kelvin)

52. Section 11.6 Osmotic Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 52

53. Section 11.6 Osmotic Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 53 Osmosis

54. Section 11.6 Osmotic Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 54

55. Section 11.6 Osmotic Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 55 Exercise When 33.4 mg of a compound is dissolved in 10.0 mL of water at 25°C, the solution has an osmotic pressure of 558 torr. Calculate the molar mass of this compound. 111 g/mol

56. Section 11.7 Colligative Properties of Electrolyte Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 56 The relationship between the moles of solute dissolved and the moles of particles in solution is usually expressed as: van’t Hoff Factor, i

57. Section 11.7 Colligative Properties of Electrolyte Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 57 Ion Pairing At a given instant a small percentage of the sodium and chloride ions are paired and thus count as a single particle.

58. Section 11.7 Colligative Properties of Electrolyte Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 58 The expected value for i can be determined for a salt by noting the number of ions per formula unit (assuming complete dissociation and that ion pairing does not occur).  NaCli = 2  KNO 3 i = 2  Na 3 PO 4 i = 4 Examples

59. Section 11.7 Colligative Properties of Electrolyte Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 59 Ion pairing is most important in concentrated solutions. As the solution becomes more dilute, the ions are farther apart and less ion pairing occurs. Ion pairing occurs to some extent in all electrolyte solutions. Ion pairing is most important for highly charged ions. Ion Pairing

60. Section 11.7 Colligative Properties of Electrolyte Solutions Return to TOC Copyright © Cengage Learning. All rights reserved 60 Modified Equations

61. Section 11.8 Colloids Return to TOC Copyright © Cengage Learning. All rights reserved 61 A suspension of tiny particles in some medium. Tyndall effect – scattering of light by particles. Suspended particles are single large molecules or aggregates of molecules or ions ranging in size from 1 to 1000 nm.

62. Section 11.8 Colloids Return to TOC Copyright © Cengage Learning. All rights reserved 62 Types of Colloids

63. Section 11.8 Colloids Return to TOC Copyright © Cengage Learning. All rights reserved 63 Destruction of a colloid. Usually accomplished either by heating or by adding an electrolyte. Coagulation