1. Copyright © Houghton Mifflin Company. All rights reserved.7–17–1 Solutions Homogeneous Mixtures of Compounds

2. Copyright © Houghton Mifflin Company. All rights reserved.7–27–2 7.1 Characteristics of Solutions Definitions: Solution: A homogeneous combination of two or more substances, in which each substance retains its chemical identity Solvent: The component of a solution present in the greatest amount Solute(s): The component(s) of a solution present in smaller amount(s) than the solvent

3. Copyright © Houghton Mifflin Company. All rights reserved.7–37–3 7.1 Characteristics of Solutions Solutions have variable compositions; the ratio of solvent to solute(s) can be varied. The properties of the solution change as the ratio of solvent to solute(s) is varied. Solutes are present as individual molecules, atoms, or ions. The composition of a solution is constant through space. Solute(s) can be separated from the solvent by physical means such as evaporation.

4. Copyright © Houghton Mifflin Company. All rights reserved.7–47–4 7.2 Solubility Solids and liquids are usually more solu- ble at high temperatures than at low temperatures Gases are usually more soluble at low temperatures than at high temperatures Gases are more soluble at high pressures than at low pressures.

5. Copyright © Houghton Mifflin Company. All rights reserved.7–57–5 Table 7.1 Solubilities of Various Compounds in Water at 0  C, 50  C, and 100  C.

6. Copyright © Houghton Mifflin Company. All rights reserved.7–67–6 7.2 Solubility Saturated solutions contain the maximum amount of solute that the solvent can hold at a given temperature. Undis- solved solute is usually present. Unsaturated solutions contain less than the maximum amount of solute that can be dissolved at a given temperature.

7. Copyright © Houghton Mifflin Company. All rights reserved.7–77–7 Figure 7.3 In a saturated solution, the dissolved sol- ute is in a dynamic equilibrium with the undissolved solute.

8. Copyright © Houghton Mifflin Company. All rights reserved.7–87–8 7.2 Solubility Aqueous solutions have water as the solvent. Nonaqueous solutions have substances other than water as the solvent.

9. Copyright © Houghton Mifflin Company. All rights reserved.7–97–9 7.3 Solution Formation To form a solution, two sets of intermolecular forces must be overcome Forces between solvent molecules Forces between solute molecules or ions Attractive forces between solute and solvent particles must compensate for disrupting the other forces.

10. Copyright © Houghton Mifflin Company. All rights reserved.7–10 Figure 7.5 Hydration of ions in an aqueous solution

11. Copyright © Houghton Mifflin Company. All rights reserved.7–11 7.4 Solubility Rules Like dissolves like In water, ionic compounds are more likely to be soluble if the charge on individual ions is low NaCl (Na 1+ + Cl 1– ) is soluble Na 3 PO 4 (3 Na 1+ + PO 4 3– ) is soluble Ca 3 (PO 4 ) 2 (3 Ca 2+ + 2 PO 4 3– ) is not soluble Ca 10 (PO 4 ) 6 (OH) 2 is not soluble

12. Copyright © Houghton Mifflin Company. All rights reserved.7–12 Table 7.2 Solubility Guidelines for Ionic Compounds in Water.

13. Copyright © Houghton Mifflin Company. All rights reserved.7–13 7.5 Solution Concentration Units Concentration: Amount of solute in a specified amount of solution Percent concentrations Percent by mass (m/m) Percent by volume (v/v) Mass-volume percent (m/v) Molarity: Moles Solute per Liter Solution

14. Copyright © Houghton Mifflin Company. All rights reserved.7–14 7.5 Solution Concentration Units Molarity: Moles solute = mol = M Liter solution L Molarity is a conversion factor, like molar mass, that allows us to convert between moles and an easily measurable quantity, volume.

15. Copyright © Houghton Mifflin Company. All rights reserved.7–15 7.5 Solution Concentration Units What is the molarity of a solution of NaCl if 50.0 g of NaCl is dissolved in 1.00 L of water? How many moles of NaCl are present in 250 mL of 0.100 M solution? How many milliliters of 0.250 M NaCl will contain 0.500 mol of NaCl?

16. Copyright © Houghton Mifflin Company. All rights reserved.7–16 7.5 Solution Concentration Units H 3 PO 4 + 3 NaOH  Na 3 PO 4 + 3 H 2 O How many milliliters of 0.0500 M NaOH will react with 15.0 mL of 0.0300 M H 3 PO 4 ? What is the molarity of H 3 PO 4 if 15.05 mL of 0.1500 M NaOH react with 10.00 mL of the H 3 PO 4 solution?

17. Copyright © Houghton Mifflin Company. All rights reserved.7–17 7.5 Solution Concentration Units Percent by Mass: %(m/m), %(w/w) Mass of solute x 100% Mass of solution What is the percent by mass of a solution made by combining 8.5 g of sucrose with 73.8 g of water? How many grams of sucrose and how many grams of water must be used to prepare 250 g of solution that is 5.0%(m/m)?

18. Copyright © Houghton Mifflin Company. All rights reserved.7–18 7.5 Solution Concentration Units Percent by Volume: %(v/v) Volume of solute x 100% Volume of solution What is the percent by volume of a solution in which 15 mL of glacial acetic acid is diluted to 100 mL with water? Could you do this by combining 15 mL of acetic acid and 85 mL of water?

19. Copyright © Houghton Mifflin Company. All rights reserved.7–19 Figure 7.7 When volumes of two different liquids are combined, the volumes are not additive.

20. Copyright © Houghton Mifflin Company. All rights reserved.7–20 Figure 7.8 Volumetric flasks are filled to the 50.0 mL mark with ethanol and with water. The liquids are combined in a 100 mL volu- metric flask, and the volume is 96.5 mL.

21. Copyright © Houghton Mifflin Company. All rights reserved.7–21 7.5 Solution Concentration Units Mass-volume percent: %(m/v) Grams of solute x 100% Milliliters of solution mg/dL Milligrams of solute Deciliters of solution 1 mg = 0.001 g1 dL = 100 mL

22. Copyright © Houghton Mifflin Company. All rights reserved.7–22 7.6 Dilution Calculations It is common to make dilute solutions from concentrated solutions (a.k.a. stock solutions) C 1 V 1 = C 2 V 2 A nurse must prepare 100 mL of 1.0 % (m/v) AgNO 3. She has a 3.0% (m/v) stock solution. How much stock solution should she use? How should she prepare the solution?

23. Copyright © Houghton Mifflin Company. All rights reserved.7–23 7.7 Colligative Properties of Solutions Colligative properties of a solution depend on the concentration of solute particles, not their chemical identity Lowering of vapor pressure Freezing point depression Boiling point elevation Osmotic Pressure

24. Copyright © Houghton Mifflin Company. All rights reserved.7–24 Figure 7.10Close-ups of the surface of a solvent (a) pure liquid (b) with nonvolatile solute

25. Copyright © Houghton Mifflin Company. All rights reserved.7–25 7.7 Colligative Properties of Solutions Nonvolatile solutes: Lower the vapor pressure of the solution relative to that of the pure solvent Raise the boiling point of the solution relative to that of the pure solvent Lower the freezing point of the solution relative to that of the pure solvent.

26. Copyright © Houghton Mifflin Company. All rights reserved.7–26 7.8 Osmosis and Osmotic Pressure Osmosis is the passage of solvent through a semipermeable membrane from a dilute solution or pure liquid to a concentrated solution. Semipermeable membranes have very small pores, and allow only certain small molec-ules to pass from one side to the other.

27. Copyright © Houghton Mifflin Company. All rights reserved.7–27 Figure 7.12(a) Osmosis, the flow of solvent through a semipermeable membrane from a dilute to a concentrated solution (b) At equilibrium, the molecules move back and forth at equal rates.

28. Copyright © Houghton Mifflin Company. All rights reserved.7–28 Figure 7.13A semipermeable membrane separating (a) pure water and solute-water solution (b) dilute solute-water solution and a concentrated solute-water solution.

29. Copyright © Houghton Mifflin Company. All rights reserved.7–29 Figure 7.14 Osmotic pressure is the amount of pressure needed to prevent the solution in the tube from rising as a result of the process of osmosis.

30. Copyright © Houghton Mifflin Company. All rights reserved.7–30 Isotonic, Hypertonic, and Hypotonic Solutions Isotonic solutions have the same osmotic pressure as intracellular fluids Red blood cells are stable Hypertonic solutions have higher osmotic pressure that intracellular fluids Red blood cells undergo crenation Hypotonic solutions have lower osmotic pressure than intracellular fluids Red blood cells undergo hemolysis

31. Copyright © Houghton Mifflin Company. All rights reserved.7–31 Isotonic, Hypertonic, and Hypotonic Solutions

32. Copyright © Houghton Mifflin Company. All rights reserved.7–32 7.9 Dialysis Dialysis is the process in which a semi- permeable membrane permits the passage of solvent and small solute particles (ions and molecules) but blocks the passage of large molecules. Cell membranes permit dialysis

33. Copyright © Houghton Mifflin Company. All rights reserved.7–33 Figure 7.17In dialysis, there is a net movement of ions from a region of higher concentra- tion to a region of lower concentration. (a) Before dialysis. (b) After dialysis.

34. Copyright © Houghton Mifflin Company. All rights reserved.7–34 Figure 7.18 Impurities (ions) can be removed from a solution by using a dialysis procedure.