2. Solutions and Colloids Homogeneous (or nearly homogeneous) Mixtures

3. Solutions n Homogeneous mixtures n Solvent = dissolving medium –often liquid; frequently water –gas in air and other gas solutions –rarely a solid n Solute(s) = dissolved material(s) –solids, liquids, and/or gases –often more than one solute

4. Water as Solvent n Form aqueous solutions n Many biological fluids are solutions or have solution components n One of best solvents for dissolving ionic substances n Poor solvent for non-polar covalent substances.

5. WaterH H O ---- ++++ OHH ++++ ---- O H H ++++ ---- O H H ---- O H H ++++ ---- “H-bonding” binds water molecules tightly.

6. Water n Water is one of best solvents for ionic material (electrolytes) n Water’s polar molecular structure interacts strongly with charged ions n Water---Ion attractions replace and water---water attractions with little net energy change n Water---Ion attractions replace ion---ion and water---water attractions with little net energy change

7. Water Na + Cl - Crystal’s +/- attractions cause lattice energy, which must be overcome to break up crystal.

8. Water Na + Cl -

9. Water Na + Cl - Several more H 2 O molecules may associate “Void” weakens crystal and makes it more likely to break up in vicinity.

10. Water Na + Cl -

11. Water Na + Cl -

12. Water Na + Cl - Positive Note: Positive ions associate with negative ends of waters, and negative ions associate with positive ends of waters. +/- forces release energy

13. Water n In similar fashion, the entire crystal dissolves –positive ions link to oxygen of water –negative ions link to hydrogen of water –process call hydration n Hydration releases energy n Hydration energy compensates for lattice energy.

14. Water

15. Water An exothermic dissolving process. Hydration energy is greater than lattice energy.

16. Water

17. Water An endothermic dissolving process. Lattice energy is greater than hydration energy.

18. Water n Exothermic processes release energy –Temperature of surroundings increase. –Hydration energy grater than lattice energy. n Endothermic processes absorb energy. –Temperature of surroundings decrease. –Lattice energy greater than hydration energy.

19. Solution Concentrations n Dilute –Small amount of solute for given solvent n Concentrated –Large amount of solute for given solvent n Saturated –Maximum amount of solute for given solvent n But these terms are qualitative, not quantitative, and are open to interpretation.

20. Solution Concentrations. 20 gal.

21. Solution Concentrations. Dilute or Concentrated???

22. Solution Concentrations Dilute or Concentrated???..

23. Solution Concentrations n It depends, of course, on one’s point of view. –It’s only a teaspoon in 20 gallons. –Dilute?? –But this concentration is far beyond the lethal dose for the fish. –Concentrated???

24. Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Expressed as a ratio of the amount of solute to the total amount of solution: Concentration = Amount of solute Total amount of solution grams mL (%, w/v)

25. Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Expressed as a ratio of the amount of solute to the total amount of solution: Concentration = Amount of solute Total amount of solution mass (grams) mass unit (grams) (%, w/w)

26. Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Expressed as a ratio of the amount of solute to the total amount of solution: Concentration = Amount of solute Total amount of solution dL ( mg %) mg

27. Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Expressed as a ratio of the amount of solute to the total amount of solution: Concentration = Amount of solute Total amount of solution moles Liters ( molarity, M)

28. Solution Concentrations % Concentration has multiplier of 100 to place ratio on “parts per 100” basis: % Concentration has multiplier of 100 to place ratio on “parts per 100” basis: Grams of solute mL of solution %, w/v = X 100

29. Solution Concentrations Concentration has multiplier of 1000 to place ratio on “parts per 1000 total” basis: ‰ Concentration has multiplier of 1000 to place ratio on “parts per 1000 total” basis: Grams of solute mL of solution ‰ =‰ = X 1000

30. Solution Concentrations ppm concentration has multiplier of 10 6 to place ratio on “parts per million total” basis: ppm concentration has multiplier of 10 6 to place ratio on “parts per million total” basis: Grams of solute mL of solution ppm = X 10 6

31. Solution Concentrations Practice situation: 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution? Grams of solute mL of solution %, w/v = X 100 % = 4.75 g 750 mL X 100 = 0.633 % The g/mL units are understood but not included.

32. Solution Concentrations 0.633% NaCl The concentration is 0.633 % (w/v). 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution? 750 mL

33. Solution Concentrations Another: 12.5 grams of H 2 SO 4 is dissolved in sufficient water to make 0.500 liters of solution. What is the % (w/v) concentration of this solution? Grams of solute mL of solution %, w/v = X 100 % = 12.5 g 500 mL X 100 = 2.50 % The g/mL units are understood but not included. Solution volume units must be converted from liters to mL before doing calculations: 0.500 L = 500 mL.

34. Solution Concentrations n Once known, the solution concentration works as a conversion factor. –Establishes the “relationship” between amount of solute and volume of solution. –For % (w/v) concentrations, conversion factors derive from this relationship: “%-Value” grams of solute = 100 mL solution

35. Solution Concentrations Once known, the solution concentration work as a conversion factor. Examples (all are wt/vol percents): 0.85 % NaCl means… 0.85 g NaCl = 100 mL solution and the conversion factors are… 0.85 g NaCl 100 mL solution or 0.85 g NaCl 100 mL solution

36. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What mass of NaCl is present in 2000 mL of 0.85% NaCl solution? 0.85% NaCl How much dissolved NaCl is in this 2000 mL of saline solution?

37. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): 0.85 g NaCl 100 mL solution What mass of NaCl is present in 2000 mL of 0.85% NaCl solution? 2000 mL soln X = 17.0 g NaCl

38. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What mass of NaCl is present in 2000 mL of 0.85% NaCl solution? 0.85% NaCl 17.0 grams of dissolved NaCl is present in 2000 mL of this solution

39. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl? 0.85% NaCl What volume will contain 2.50 grams of dissolved NaCl?

40. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl? 2.50 g NaCl X = 294 mL soln 0.85 g NaCl 100 mL solution

41. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl? 0.85% NaCl 294 mL of this solution contains 2.50 grams of dissolved NaCl.

42. Solution Concentrations n Given the amount of solute and total solution, determine the concentration. n Given the concentration and amount of solution, find the amount of solute. n Given the concentration and the amount of solute, determine the amount of solution. Three types of calculations dealing with concentrations:

43. Solution Concentrations Three types of calculations dealing with concentrations: Concentration = Amount of solute Total amount of solution 1 3 2

44. Solution Concentrations Given any two, be able to calculate the third: Concentration = Amount of solute Total amount of solution 1 3 2

45. Solution Concentrations Molarity M = M = Moles of solute Liters of solution 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the molarity of NaCl in this solution? We previously determined this solution to be 0.633%; what is its molarity?

46. Solution Concentrations Molarity M = M = Moles of solute Liters of solution The 4.75 grams of NaCl will need to be converted to moles before the calulations are done. Similarly, to make units match, the 750 mL will be converted to liters.

47. Solution Concentrations Molarity M = M = Moles of solute Liters of solution 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. M = ? 4.75 g NaCl X = 0.0812 mole NaCl 58.5 g NaCl 1 mole NaCl 1 mole NaCl 750 mL X = 0.750 L 1000 mL 1 Liter 1 Liter

48. Solution Concentrations 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. M = ? 0.0812 mole NaCl 0.750 L M = M = Moles of solute Liters of solution = 0.108 M NaCl = 0.108 moles NaCl/L M = M = 0.0812 moles NaCl 0.750 Liters of solution

49. Solution Concentrations 0.633% 0.108 M NaCl The concentration is 0.633 % (w/v) and… and… is 0.108 M 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution and what is its molarity? 750 mL

50. Solution Concentrations Given any two, be able to calculate the third: Concentration = Amount of solute Total amount of solution 1 3 2

51. Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): How many moles of NaCl is present in 2000 mL of 0.225-M NaCl solution? 0.225M NaCl How much dissolved NaCl is in this 2000 mL of saline solution?

52. Solution Concentrations Using the concentration as a conversion factor: 0.225 moles NaCl 1 L solution 1 L solution How many moles of NaCl is present in 2000 mL of 0.225-M NaCl solution? 2000 mL soln x = 0.450 moles x 1 L 1 L 1000 mL 0.225 moles NaCl 1000 mL solution 1000 mL solution 2000 mL soln = 0.450 moles NaCl x Or…

53. Solution Concentrations Using the concentration as a conversion factor: 1000 mL 1 L 1 L What volume of 0.225-M NaCl solution will contain 0.0175 moles of dissolved NaCl? 0.0175 moles x = 77.8 mL x 1 L 1 L 0.225 Moles 1000 mL solution 0.225 moles NaCl 0.225 moles NaCl 0.0175 moles NaCl = 77.8 mL soln x Or…

54. Solution Stoichiometry n Just as grams of a pure substance and its FW determine moles of the substance, so do volulme and molarity of a substance in its solution. n As for “pure substance” stoichiometry, solution stoichiometry usually involves a three-step approach:

55. Solution Stoichiometry 2HCl + Na 2 CO 3  2NaCl + CO 2 + H 2 O Consider reaction of 0.200-M HCl with sodium carbonate: How many grams of Na 2 CO 3 will react with 25.0 mL of 0.200-M HCl solution? 25.0 mL ? moles ? g Use volume and HCl molarity Use Equation Coefficients Use moles and FW of Na 2 CO 3

56. Solution Stoichiometry 2HCl + Na 2 CO 3  2NaCl + CO 2 + H 2 O Consider reaction of 0.200-M HCl with sodium carbonate: 25.0 mL ? moles ? g Use volume and HCl molarity Use Equation Coefficients Use moles and FW of Na 2 CO 3 25.0 mL HCl x 1000 mL HCl 0.200 mole HCl x 2 mole HCl 1 mole Na 2 CO 3 x 106 g Na 2 CO 3 1 mole Na 2 CO 3 = 0.265 grams Na 2 CO 3

57. Solution Stoichiometry 2HCl + Na 2 CO 3  2NaCl + CO 2 + H 2 O Consider reaction of 0.200-M HCl with sodium carbonate: What volume of 0.200-M HCl solution is required for reaction with 5.00 grams of Na 2 CO 3 ? 5.00 g ? moles ? mL Use grams and FW Use Equation Coefficients Use moles and HCl molarity

58. Solution Stoichiometry 2HCl + Na 2 CO 3  2NaCl + CO 2 + H 2 O Consider reaction of 0.200-M HCl with sodium carbonate: 5.00 g ? moles ? mL Use grams and FW Use Equation Coefficients Use moles and HCl molarity 5.00g Na 2 CO 3 x 106 g Na 2 CO 3 1 mole Na 2 CO 3 x 2 mole HCl x = 472 mL HCl solution 0.200 mole HCl 1000 mL HCl

59. Solutions vs Colloids n Solution –Solute particle are of ionic or molecular size (a few nm across) –Transparent to ordinary light –Stable unless solvent evaporated n Colloids –Solute (called “dispersed phase”) typically 1000 nm or more per particle –Giant molecules (or “clumps” of smaller ones) –Not totally transparent – Tyndall Effect –Dispersed phase may separate out (similar to separation of mayonnaise).

60. Solutions vs Colloids ColloidalMixtureTrueSolution The Tyndall Effect

61. Solutions vs Colloids ColloidalMixtureTrueSolution The Tyndall Effect

62. Semipermeable membrane Pure H 2 O Solution (H 2 O + Solutes) Transmembrane Diffusion Only water passes through osmotic membranes and faster from the side on which water is more concentrated.

63. Semipermeable membrane Pure H 2 O Solution (H 2 O + Solutes) Transmembrane Diffusion Diffusion rates tend to equalize as flow continues.

65. Pure H 2 O H 2 O + Solutes Osmotic Pressure If applied pressure is too low, H 2 O flows into the region of higher solute concentration... “Down the concentration gradient” for H 2 O. P Membrane P

66. Pure H 2 O H 2 O + Solutes Osmotic Pressure If applied pressure is too high, H 2 O flows into the region of lower solute concentration... Against the natural concentration gradient for H 2 O. --Reverse Osmosis P Membrane P

67. Pure H 2 O H 2 O + Solutes Osmotic Pressure Minimum pressure required to maintain equal flow rates (to prevent infusion of H 2 O). Proportional to solute concentration differences across membrane. P Membrane P

68. Solutions vs Colloids n Solution –Solute particles are of ionic or molecular size –Transparent to ordinary light –Stable unless solvent evaporated –May pass through dialytic, but not true osmotic, membranes n Colloids –Typically 1000 nm or more per particle –Not totally transparent – Tyndall Effect –May separate out –Particles too large to pass through most membranes

69. Dialytic membrane Pure H 2 O Mixture (H 2 O, Na + Cl -, protein) Transmembrane Diffusion Water and solutes pass down concentration gradient through dialytic membrane. Colloids do not cross membrane. H2OH2OH2OH2O NaCl H 2 O more concentrated here NaCl more concen- trated here

70. Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Expressed as a ratio of the amount of solute to the total amount of solution: Concentration = Amount of solute Total amount of solution Osmoles (total moles) Liters ( Osmolarity, osM) For certain solutes, osM will equal M.

71. Osmolarity n Calculating –Total of molarities of all types of solute particles in the solution. –For ionic solutes, the ions are separated; and each ion has a separate molarity to be totaled. –Molecular solutes have same molarity and osmolarity, but each different solute needs to be included. n Impact –Osmolarity determines osmotic pressure –Useful in determining net direction of H 2 O flow across membranes.

72. Osmolarity Solute, M Osmolarity 0. 25-M C 6 H 12 O 6 (molecular) 0. 25-osM 0. 25-M NaCl (ionic) 0. 50-osM (0.25-M Na + + 0.25-M Cl - ) 0. 10-M CaBr 2 (ionic) 0. 30-osM (0.10-M Ca + + 0.20-M Br - ) 0. 05-M Fe 2 (SO 4 ) 3 (ionic) 0. 25-osM (0.10-M Fe 3+ + 0.15-M SO 4 2- )

73. H2OH2OH2OH2O Dialytic membrane Transmembrane Diffusion Cl - 0.1-M NaCl 0.1-M CaCl 2 0.1-M C 6 H 12 O 6 1% starch 0.1-M NaCl 0.2-M CaCl 2 0.2-M C 6 H 12 O 6 2% starch A B C 6 H 12 O 6 Ca 2+ 1.0 osM + 2% colloid 0.2 osM 0.6 osM 0.2 osM 0.3 osM 0.1 osM 0.6 osM + 1% colloid

74. H2OH2OH2OH2O Dialytic membrane Transmembrane Diffusion Cl - 0.1-M NaCl 0.1-M CaCl 2 0.1-M C 6 H 12 O 6 1% starch 0.1-M NaCl 0.2-M CaCl 2 0.2-M C 6 H 12 O 6 2% starch A B C 6 H 12 O 6 Ca 2+ 1.0 osM + 2% colloid 0.6 osM + 1% colloid Hypotonic Hypertonic Water flows into hypertonic fluid (where water is less concentrated).

75. Transmembrane Diffusion “Head pressure” -- High “Head pressure” -- Low Tissue Cell Nutrients Wastes Venous End Arterial End Hypertonic blood “draws” wastes into blood (P OSMOTIC >P BLOOD ). Head pressure of heart “pushes” nutrients and water into cell (P BLOOD > P OSMOTIC ).

76. Solution Concentrations 0.633% NaCl The concentration is 0.633 % (w/v). 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution? 750 mL