1. Chapter 13 – Properties of Solutions Jennie L. Borders

2. Section 13.1 – The Solution Process A solution is a homogeneous mixture.A solution is a homogeneous mixture. The solvent is present in the largest amount.The solvent is present in the largest amount. The solutes are the other components.The solutes are the other components. Aqueous solutions are have water as the solvent.Aqueous solutions are have water as the solvent. Solutions can be solids, liquids, or gases.Solutions can be solids, liquids, or gases.

3. Solutions The ability of substances to form solutions depends on two factors:The ability of substances to form solutions depends on two factors: 1.The intermolecular forces involved. 2.The tendency of the substance to spread into larger volumes.

4. Intermolecular Forces Ion-dipole forces are present when ionic substance dissolve in water.Ion-dipole forces are present when ionic substance dissolve in water. Dispersion forces are present when nonpolar substances form solutions.Dispersion forces are present when nonpolar substances form solutions. Solutions form when the attractive forces between the solute and solvent particles are comparable to the forces that exist between 2 solute particles or 2 solvent particles.Solutions form when the attractive forces between the solute and solvent particles are comparable to the forces that exist between 2 solute particles or 2 solvent particles.

5. Solvation and Hydration Solvation is the interaction between the solute and solvent particles.Solvation is the interaction between the solute and solvent particles. Hydration is the interaction between the solute and solvent particles when the solvent is water.Hydration is the interaction between the solute and solvent particles when the solvent is water.

6. Energy Changes  H soln =  H 1 +  H 2 +  H 3  H soln is the energy change when the solution forms.  H 1 is the energy required to separate the solute particles (endothermic).  H 2 is the energy required to separate the solvent particles (endothermic).  H 3 is the energy released when the solute and solvent particles attract (exothermic).

7. Energy Changes

8. Will a solution form? Processes that are exothermic tend to be spontaneous, but endothermic processes still occur.Processes that are exothermic tend to be spontaneous, but endothermic processes still occur. Ex: ammonium nitrate spontaneously dissolves in water even though  H soln = 26.4 kJ/mol

9. Entropy Spontaneous processes involve two factors:Spontaneous processes involve two factors: 1. energy (exothermic) 2. tendency to spread out Entropy is the degree of randomness or disorder of a system.Entropy is the degree of randomness or disorder of a system. Processes in which the entropy (randomness) of the components increases tend to be spontaneous.Processes in which the entropy (randomness) of the components increases tend to be spontaneous.

10. Solutions The formation of solutions involves enthalpy (energy change) and entropy (randomness).The formation of solutions involves enthalpy (energy change) and entropy (randomness).

11. Sample Exercise 13.1 The picture below shows the following reaction:The picture below shows the following reaction: Na 2 SO 4(s) + 10H 2 O (g)  Na 2 SO 4. 10H 2 O (s) Essentially all of the water vapor in the closed container is consumed in this reaction.

12. Sample Exercise 13.1 con’t If we consider our system to consist initially of Na 2 SO 4(s) and 10H 2 O (g)If we consider our system to consist initially of Na 2 SO 4(s) and 10H 2 O (g) a. does the system become more or less ordered in the process? b. does the entropy of the system increase or decrease?

13. Practice Exercise Does the entropy of the system increase or decrease when the stopcock is opened to allow mixing of the two gases in the apparatus?Does the entropy of the system increase or decrease when the stopcock is opened to allow mixing of the two gases in the apparatus?

14. Section 13.2 – Saturated Solutions and Solubility Dissolving and crystallization are opposite processes.Dissolving and crystallization are opposite processes. Solute + solvent  solution

15. Solubility The maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature is the solubility.The maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature is the solubility.

16. Unsaturated An unsaturated solution contains less than the maximum amount of solute at a given temperature.An unsaturated solution contains less than the maximum amount of solute at a given temperature. If more solute is added, then itIf more solute is added, then it will dissolve. will dissolve.

17. Saturated A saturated solution contains the maximum amount of solute at a given temperature.A saturated solution contains the maximum amount of solute at a given temperature. If more solute is added, thenIf more solute is added, then it will not dissolve and it will it will not dissolve and it will settle at the bottom. settle at the bottom.

18. Supersaturated A supersaturated solution contains more than the maximum amount of solute at a given temperature.A supersaturated solution contains more than the maximum amount of solute at a given temperature. A supersaturated solution is made by heating the solvent to a higher temperature so that more solute can be dissolved.A supersaturated solution is made by heating the solvent to a higher temperature so that more solute can be dissolved. The solution is then carefully cooled so that crystallization does not occur.The solution is then carefully cooled so that crystallization does not occur.

19. Supersaturated If more solute is added, then rapid crystallization occurs.If more solute is added, then rapid crystallization occurs. Supersaturated solutions areSupersaturated solutions are extremely unstable. extremely unstable.

20. Section 13.3 – Factors Affecting Solubility The stronger the attractions between the solute and solvent molecules, the greater the solubility.The stronger the attractions between the solute and solvent molecules, the greater the solubility. Polar solvents tend to dissolve polar or ionic solutes.Polar solvents tend to dissolve polar or ionic solutes. Nonpolar solvents tend to dissolve nonpolar solutes.Nonpolar solvents tend to dissolve nonpolar solutes. “Like dissolves like.”“Like dissolves like.”

21. Miscible vs. Immiscible Liquids that are miscible will dissolve one another. Ex: water and rubbing alcoholLiquids that are miscible will dissolve one another. Ex: water and rubbing alcohol Liquids that are immiscible will not dissolve one another. Ex: water and oilLiquids that are immiscible will not dissolve one another. Ex: water and oil

22. Hydrocarbon Molecules C-H bonds are considered nonpolar due to the small difference in electronegativity.C-H bonds are considered nonpolar due to the small difference in electronegativity. Hydrocarbons tend to be insoluble in polar solvents.Hydrocarbons tend to be insoluble in polar solvents. One way to increase the solubility is to increase the number of polar groups. Ex: an alcohol group –OH.One way to increase the solubility is to increase the number of polar groups. Ex: an alcohol group –OH.

23. Alcohols As the carbon chain of an alcohol increases, the solubility decreases due to the increased London dispersion forces. The molecule starts to act more nonpolar.As the carbon chain of an alcohol increases, the solubility decreases due to the increased London dispersion forces. The molecule starts to act more nonpolar.

24. Network Solids Network solids are not soluble in polar or nonpolar substances due to the strong bonding forces within the solid.Network solids are not soluble in polar or nonpolar substances due to the strong bonding forces within the solid.

25. Sample Exercise 13.2 Predict whether each of the following substances is more likely to dissolve in the nonpolar solvent carbon tetrachloride or water: C 7 H 16, Na 2 SO 4, HCl, and I 2.Predict whether each of the following substances is more likely to dissolve in the nonpolar solvent carbon tetrachloride or water: C 7 H 16, Na 2 SO 4, HCl, and I 2.

26. Practice Exercise Arrange the following substances in order of increasing solubility in water:Arrange the following substances in order of increasing solubility in water:

27. Pressure The solubilities of liquids and solids are not affected by pressure, but the solubility of a gas is affected.The solubilities of liquids and solids are not affected by pressure, but the solubility of a gas is affected. The solubility of a gas increases when pressure is increased.The solubility of a gas increases when pressure is increased.

28. Henry’s Law Henry’s Law shows the relationship between pressure and solubility of a gas:Henry’s Law shows the relationship between pressure and solubility of a gas: S g = kP g S g = solubility of a gas (M = molarity) k = Henry’s law constant (different for each solute-solvent pair and changes with temperature) (mol/L. atm) P g = partial pressure of the gas (atm) P g = partial pressure of the gas (atm)

29. Sample Exercise 13.3 Calculate the concentration of CO 2 in a soft drink that is bottled with a partial pressure of CO 2 of 4.0 atm over the liquid at 25 o C. The Henry’s law constant for CO 2 in water at this temperature is 3.1 x 10 -2 mol/L. atm.Calculate the concentration of CO 2 in a soft drink that is bottled with a partial pressure of CO 2 of 4.0 atm over the liquid at 25 o C. The Henry’s law constant for CO 2 in water at this temperature is 3.1 x 10 -2 mol/L. atm.

30. Practice Exercise Calculate the concentration of CO 2 in a soft drink after the bottle is opened and equilibrates at 25 o C under a CO 2 partial pressure of 3.0 x 10 -4 atm.Calculate the concentration of CO 2 in a soft drink after the bottle is opened and equilibrates at 25 o C under a CO 2 partial pressure of 3.0 x 10 -4 atm.

31. Temperature The solubility of most solids increases as temperature increases.The solubility of most solids increases as temperature increases. The solubility of most gases decreases with increasing temperature.The solubility of most gases decreases with increasing temperature.

32. Section 13.4 – Ways of Expressing Concentration We do not need to cover parts per million (ppm), parts per billion (ppb), mass percent, molality, or normality.We do not need to cover parts per million (ppm), parts per billion (ppb), mass percent, molality, or normality.

33. Mole Fraction and Molarity Mole Fraction = mole of componentMole Fraction = mole of component total moles total moles Molarity = moles of soluteMolarity = moles of solute liters of solution liters of solution

34. Molarity The molarity of a solution does change with temperature because the contraction or expansion of the solution changes the volume.The molarity of a solution does change with temperature because the contraction or expansion of the solution changes the volume.

35. Sample Exercise 13.6 An aqueous solution of hydrochloric acid contains 36% HCl by mass. Calculate the mole fraction of HCl in the solution.An aqueous solution of hydrochloric acid contains 36% HCl by mass. Calculate the mole fraction of HCl in the solution.

36. Practice Exercise A commercial bleach solution contains 3.62 mass % NaOCl in water. Calculate the mole fraction of NaOCl in the solution.A commercial bleach solution contains 3.62 mass % NaOCl in water. Calculate the mole fraction of NaOCl in the solution.

37. Section 13.5 – Colligative Properties Colligative properties are properties of a solvent that change when solute particles are added.Colligative properties are properties of a solvent that change when solute particles are added. Colligative properties are only based on the number of solute particles, not the identity of the solute.Colligative properties are only based on the number of solute particles, not the identity of the solute.

38. Vapor Pressure The vapor pressure of a substance lowers when solute particles are added because the solvent particles are attracted to the solute particles.The vapor pressure of a substance lowers when solute particles are added because the solvent particles are attracted to the solute particles.

39. Boiling Point The boiling point of a solvent elevates when solute particles are added because the solvent particles are attracted to the solute particles.The boiling point of a solvent elevates when solute particles are added because the solvent particles are attracted to the solute particles.

40. Freezing Point The freezing point of a solvent depresses (lowers) when solute particles are added because the solvent particles are attracted to the solute particles.The freezing point of a solvent depresses (lowers) when solute particles are added because the solvent particles are attracted to the solute particles.

41. Osmosis Materials that only allow some molecules to pass through are called semipermeable.Materials that only allow some molecules to pass through are called semipermeable. For example, a membrane may allow small water molecules to pass through but not larger solute particles.For example, a membrane may allow small water molecules to pass through but not larger solute particles. Osmosis is the net movement of solvent toward the solution with theOsmosis is the net movement of solvent toward the solution with the higher solute concentration. higher solute concentration.

42. Colligative Properties Colligative properties are considered prior knowledge and should not be directly assessed on the AP exam, so I have just provided a brief overview to make sure that you are familiar with them.Colligative properties are considered prior knowledge and should not be directly assessed on the AP exam, so I have just provided a brief overview to make sure that you are familiar with them.

43. Section 13.6 - Colloids Solutions contain very small solute particles.Solutions contain very small solute particles. Colloids contain intermediate (medium- sized) solute particles. Colloid particles are between 5 to 1000 nm.Colloids contain intermediate (medium- sized) solute particles. Colloid particles are between 5 to 1000 nm. Suspension contain large solute particles that settle over time.Suspension contain large solute particles that settle over time.

44. Colloids Colloids particles are small enough to seem uniform, but they are large enough to scatter light.Colloids particles are small enough to seem uniform, but they are large enough to scatter light. The scattering of light by colloid particles is called the Tyndall effect.The scattering of light by colloid particles is called the Tyndall effect.

45. Hydrophilic and Hydrophobic Hydrophilic colloids are “water loving.”Hydrophilic colloids are “water loving.” Hydrophobic colloids are “water fearing.”Hydrophobic colloids are “water fearing.”

46. Adsorption vs. Absorption Adsorption means to adhere to a surface.Adsorption means to adhere to a surface. Absorption means to pass into the interior.Absorption means to pass into the interior.

47. Biology … INFERIOR! Biology … INFERIOR! In the body, hydrophobic colloids can mix with water by adsorbing ions onto the surface.In the body, hydrophobic colloids can mix with water by adsorbing ions onto the surface.

48. Removal of Colloid Particles Colloid particles are too small to be removed by filtration.Colloid particles are too small to be removed by filtration. Coagulation is a process of enlarging the colloid particles so that they can be removed.Coagulation is a process of enlarging the colloid particles so that they can be removed. Heating a colloid or adding electrolytes can bring about coagulation.Heating a colloid or adding electrolytes can bring about coagulation.

49. Coagulation

50. Sample Integrative Exercise A 0.100L solution is made by dissolving 0.441g of CaCl 2(s) in water. The enthalpy of solution for CaCl 2 is  H = - 81.3 kJ/mol. If the final temperature of the solution is 27.0 o C, what was the initial temperature? (Assume that the density of the solution is 1.00 g/mL, that its specific heat is 4.18 J/g. K, and that the solution loses no heat to its surroundings.)A 0.100L solution is made by dissolving 0.441g of CaCl 2(s) in water. The enthalpy of solution for CaCl 2 is  H = - 81.3 kJ/mol. If the final temperature of the solution is 27.0 o C, what was the initial temperature? (Assume that the density of the solution is 1.00 g/mL, that its specific heat is 4.18 J/g. K, and that the solution loses no heat to its surroundings.)