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Bellringer …

Bellringer …. Describe the steps used for determining the solubility constant of a reaction when only the initial concentrations and the change in concentration are known. How would you set up an ICE chart? State Le Chatelier’s Principle. **Review for your quiz today**. Bellringer ….

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Bellringer …

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  1. Bellringer… • Describe the steps used for determining the solubility constant of a reaction when only the initial concentrations and the change in concentration are known. • How would you set up an ICE chart? • State Le Chatelier’s Principle. **Review for your quiz today**

  2. Bellringer… Define the following using ch. 11 in your textbook Henry’s law Thermal pollution Raoult’s law Ideal solution Colligative properties Semipermeable membrane osmosis 8. Osmotic pressure 9. Dialysis 10. Isotonic solution 11. Reverse osmosis 12. Desalination 13. van’t Hoff factor 14. Tyndall effect 15. Colloid 16. coagulation

  3. Properties of Solution AP Chemistry

  4. Solution composition • Molarity = • Mass Percent =( ) x 100% • Mole Fraction of A = • Molality =

  5. Example • Refer to problem 28 (a and b) and 30 on pg. 548 • Complete c and do on your own for practice!

  6. Bellringer… • Complete problem 27 from pg. 548 in your textbook.

  7. Finding concentration of ions in aqueous solution • Write out the balanced ionic equation. • Multiply the number of moles of each ion present by the initial concentration. Examples: a. State the concentration, in moles per liter, of each ion in 1.0 mol Al(NO3)3.b. State the concentration, in moles per liter, of each ion in 0.20 mol K2CrO4.

  8. The Energies of Solution Formation • “Likes dissolve likes” • 1. Polar molecules and ionic compounds tend to dissolve in polar solvents • 2. Nonpolar molecules dissolve in nonpolar compounds

  9. Factors affecting solubility • Structure Effects • 1. Polar (hydrophilic) dissolves in polar • a. Water soluble vitamins • 2. Nonpolar (hydrophobic) in nonpolar • a. Fat soluble vitamins

  10. Factors affecting solubility Pressure Effects • 1. Henry’s Law • a. The amount of a gas dissolved in a solution is directly proportional to the pressure of the gas above the solution • b. P = kC • (1) P = partial pressure of the gaseous solute above the solution • (2) C = concentration of the dissolved gas • (3) k = constant characteristic of a particular solution • c. Henry’s Law works best for dilute solutions of gases that do not dissociate or react with the solvent • Refer to sample exercise 11.4 in your textbook.

  11. Factors affecting solubility Temperature Effects 1. Solids a. Increases in temperature always cause dissolving to occur more rapidly b. Increases in temperature usually increases solubility (the amount that can be dissolved) 2. Gases a. Solubility of gases always decreases with increasing temperature

  12. The Vapor Pressure of Solutions • A. Nonvolatile Solutes • 1. Nonvolatile electrolytes lower the vapor pressure of a solute • a. Nonvolatile molecules do not enter the vapor phase • b. Fewer molecules are available to enter the vapor phase • B. Raoult's Law • 1. Pso ln= X solvent P0solventwhere Xsolventis the mole fraction of the solvent in the solution • a. a linear equation (y = mx) • 2. Molar mass of a solute can be calculated from experimental results for vapor pressure lowering

  13. Example • Refer to problem 46 on pg. 549

  14. Practice Problems • Beginning on pg. 548 • 25, 29, 31, 43, 45

  15. Bellringer… • As you come in grab a Ch. 17 Reading guide and a BRADY book! Complete both sides.

  16. Vapor pressure of solutions • C. Ionic solutes • 1. Dissociation of ionic compounds has nearly two, three or more times the vapor pressure lowering of nonionic (nonelectrolyte) solutes. • D. Non-ideal Solutions • 1. Liquid-liquid solutions in which both components are volatile • 2. Modified Raoult'sLaw: • PTOTAL= PA+ PB= XA P0A+ XB P0B • a. P0is the vapor pressure of the pure solvent • b. PAand PBare the partial pressures

  17. Example (nonideal) • Acetone is a solvent for both water and molecular liquids that do not dissolve in water, like benzene. At 20oC, acetone has a vapor pressure of 162 torr. The vapor pressure of water at 20oC is 17.5 torr. Assuming that the mixture obeys Raoult’s law, what would be the vapor pressure of a solution of acetone and water with 50.0 mol% of each?

  18. Vapor pressure of solution • E. Ideal Solutions • 1. Liquid-liquid solution that obeys Raoult's law • a. No solution is perfectly ideal, though some are close • 2. Negative deviations from Raoult's law (lower than predicted vapor pressure for the solution) • a. Solute and solvent are similar, with strong forces of attraction • 3. Positive deviations from Raoult's law (higher than predicted vapor pressure for the solution) • a. Solute and solvent are dissimiliar, with only weak forces of attraction • b. Particles easily escape attractions in solution to enter the vapor phase

  19. Boiling point elevation and freezing point depresion • A. Colligative Properties • 1. Properties dependent on the number of solute particles but not on their identity • a. Boiling-Point elevation • b. Freezing-Point depression • c. Osmotic Pressure

  20. Boiling point elevation and freezing point depression • B. Boiling-Point Elevation • 1. Nonvolatile solutes elevate the boiling point of the solvent • DT = Kbmsolute • a. DT is the boiling point elevation • b. Kb is the molal boiling point elevation constant of the solvent • c. msoluteis the molality of the solute in the solution • C. Freezing-Point Depression • 1. Solutes depress the freezing point of the solvent • DT = Kf msolute • a. DT is the freezing point depression • b. Kfis the molal freezing point depression constant of the solvent • c. msoluteis the molality of the solute in the solution

  21. Example • Estimate the freezing point of a permanent-type of antifreeze solution made up of 100.0 g of ethylene glycol, C2H6O2 (molecular mass 62.07), and 100.0 g of water (molecular mass 18.0) • Kf water = 1.86oCm-1

  22. Bellringer… • Complete problem #61 on pg. 550 • Use table 11.5 on pg. 532 for Kf and Kb values.

  23. Example • A solution made by dissolving 5.65 g of an unknown molecular compound in 110.0 g of benzene froze at 4.39oC. What is the molecular mass of the solute? • Kf = 5.07oC/m • Melting ponit: 5.45oC

  24. solution • Given: 5.65 g unknown compound in 110.0 g benzene; T = 4.39oC • ΔT = 5.45oC – 4.39oC • ΔT = 1.06oC • Determine molality • m = = • m = 0.209 m Result means there is a ratio of 0.209 mol solute per 1 kg of benzene (110.0 g = 0.1100 kg) *# of moles of solute found by (0.1100 kg benzene)(0.209 mol solute/1kg) = 0.0230 mol solute *Detetermine molecular mass: = 246 g/mol

  25. Bellringer… • Pg. 550 • 57, 59, 63

  26. Osmotic pressure • Osmosis • 1. The flow of solvent molecules into a solution through a semipermeable membrane

  27. Osmotic pressure • 1. The pressure necessary to keep water from flowing across a semipermeable membrane • 2. Osmotic pressure can be used to characterize solutions and determine molar masses • p = MRT • a. p is osmotic pressure in atmospheres • b. M is the molarity of the solution • c. R is the gas law constant • d. T is the Kelvin temperature

  28. Bellringer… • Complete problem 67 on pg. 550.

  29. example • A very dilute solution, 0.0010 M sugar in water, is separated from pure water by an osmotic membrane. What osmotic pressure in torr develops at 25oC or 298 K?

  30. Another one  • An aqueous solution with a volume of 100 mL and containing 0.122 g of an unknown molecular compound has an osmotic pressure of 16.0 torr at 20.0oC. What is the molecular mass of the solute?

  31. Osmotic pressure • C. Dialysis • Transfer of solvent molecules as well as small solute molecules and ions • D. Isotonic Solutions • 1. Solutions that have the same osmotic pressure • E. Osmotic Pressure and Living Cells • 1. Crenation • a. Cells placed in a hypertonic solution lose water to the solution, and shrink • 2. Hemolysis • a. Cells placed in a hypotonic solution gain water from the solution and swell, possibly bursting

  32. Osmotic pressure • F. Reverse Osmosis • 1. External pressure applied to a solution can cause water to leave the solution • a. Concentrates impurities (such as salt) in the remaining solution • b. Pure solvent (such as water) is recovered on the other side of the semipermeable membrane

  33. Colligative properties of electrolyte solutions • A. van't Hoff factor i: 1. i = 2. For ionic compounds, the expected value of iis an integer greater than 1 • a. NaCl, i= 2 • b. BaCl2, i= 3 • c. Al2(SO4)3, i= 5

  34. Colligative properties of electrolyte solutions • B. Actual values of i • 1. Values of iare less than expected due to ion pairing (clustering) • 2. Refer to table11.6 • 3. Values of iare closer to the expected the more dilute the solution becomes • C. Incorporation of van't Hoff factor in Problem Solving • 1. Boiling-elevation and freezing-point depression • a. DT = imK • 2. Osmotic pressure • A. p = iMRT • Refer to eample 11.13 in textbook.

  35. colloids • A. Colloidal Dispersions (Colloids) • 1. Tiny particles suspended in some medium • 2. Particles range in size from 1 to 1000 nm. • B. Tyndall Effect • 1. Scattering of light by particles • a. Light passes through a solution • b. Light is scattered in a colloid Refer to table 11.7 (p. 543) for Types of Colloids

  36. Practice problems • Pg. 551 • 71-73, 75

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