Solutions and Colloids

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

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

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

4. - O H H + - O H - H O H + + - H O H - H O + H H Water “H-bonding” binds water molecules tightly.

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

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

7. Water Na+ Cl-

8. Water “Void” weakens crystal and makes it more likely to break up in vicinity. Several more H2O molecules may associate Na+ Cl-

9. Water Na+ Cl-

10. Water Na+ Cl-

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

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

13. Water

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

15. Water

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

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

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

19. . Solution Concentrations 20 gal.

20. . Solution Concentrations Dilute or Concentrated???

21. . . Solution Concentrations Dilute or Concentrated???

22. Solution Concentrations • 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???

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

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

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

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

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

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

29. Grams of solute ppm = mL of solution Solution Concentrations ppm concentration has multiplier of 106 to place ratio on “parts per million total” basis: X 106

30. Grams of solute %, w/v= mL of solution % = X 100 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? 4.75 g X 100 = 0.633 % 750 mL The g/mL units are understood but not included.

31. 0.633% NaCl Solution Concentrations 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? The concentration is 0.633 % (w/v). 750 mL

32. Grams of solute %, w/v= mL of solution % = X 100 Solution Concentrations Another: 12.5 grams of H2SO4 is dissolved in sufficient water to make 0.500 liters of solution. What is the % (w/v) concentration of this solution? Solution volume units must be converted from liters to mL before doing calculations: 0.500 L = 500 mL. 12.5 g X 100 = 2.50 % 500 mL The g/mL units are understood but not included.

33. Solution Concentrations • 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

34. 100 mL solution 0.85 g NaCl 0.85 g NaCl 100 mL solution 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… or

35. 0.85% NaCl 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? How much dissolved NaCl is in this 2000 mL of saline solution?

36. 0.85 g NaCl 100 mL solution 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? 2000 mL soln X 17.0 g NaCl =

37. 0.85% NaCl 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? 17.0 grams of dissolved NaCl is present in 2000 mL of this solution

38. What volume will contain 2.50 grams of dissolved NaCl? 0.85% NaCl 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?

39. 100 mL solution 0.85 g NaCl 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 =

40. 294 mL of this solution contains 2.50 grams of dissolved NaCl. 0.85% NaCl 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?

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

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

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

44. Moles of solute Liters of solution M = Solution Concentrations Molarity 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?

45. Moles of solute Liters of solution M = Solution Concentrations Molarity 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.

46. Moles of solute Liters of solution M = 1 Liter 1 mole NaCl 58.5 g NaCl 1000 mL Solution Concentrations Molarity 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 = 750 mL X 0.750 L =

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

48. 0.633% 0.108 M NaCl Solution Concentrations 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? The concentration is 0.633 % (w/v) and… is 0.108 M 750 mL

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

50. 0.225M NaCl 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? How much dissolved NaCl is in this 2000 mL of saline solution?