1. Chapter 7: Solutions and Colloids Suggested Problems: 4, 16, 20-28, 46, 48, 52-56, 64, 66, 72, 74, 92

2. What is a Solution? A solution is a homogeneous mixture comprised of one or more solutes dispersed at an atomic, ionic or molecular level uniformly throughout a medium called the solvent Solvent: Is the most abundant substance in a solution Solute: Are all of the other components that comprise the solution –Notice I did not say dissolved in the solvent

3. Importance of Solutions Most medicines are given as solutions Most chemistry occurs in solution, rather than in a pure state Focus of this chapter –Solution concentrations –Properties of solutions

4. Describing Solutes Solubility: The maximum amount of solute than can be dissolved in a specific amount of solvent under specific conditions of temperature and pressure Soluble Substance: is a substance that dissolves to a significant extent in the solvent Insoluble Substance: A substance that does not dissolve to a significant extent in a solvent Immiscible: A term used to describe liquids that are insoluble in each other

5. Describing Solutions Saturated: A solution that has the maximum amount of solute dissolved in a given amount of solvent Super Saturated: A solution that has a solute dissolved at a greater amount than the solubility of that solute

6. Process of Solution Formation Ionic Solutes: Need Polar solvent IMF’s between solute/solvent > solute/solute

7. Process of Solution Formation Molecular Solutes: Need proper solvent Polar if Polar soluteNon-polar if Non-polar solute Dissolved gases: O 2, N 2

8. Solution Concentrations: Percent Definitions

10. Beware of question wording –If solute is added to enough solvent to make a solution of a certain volume This volume is the volume of solution –If problem states a volume of solute is added to a volume of solvent Then you need to add the two volumes to get volume of solution

11. Remember that percentages are best used if based out of a total of 100 –This is true whether it be mass or volume For example a 5 % (w/v) solution –This is the same as saying:

12. Percent Example What is the percent (w/v) concentration of a solution prepared by dissolving 45 grams of glucose in enough water to give 300.0 mL of solution?

13. Percent Example Normal saline is 0.89% (w/v) NaCl in water. What volume of normal saline is required to deliver 45 grams of NaCl?

14. Percent Example D-5-W is 5.0% (w/v) dextrose in water. How many grams of dextrose are contained in 1500.0 mL D-5-W?

15. Solution Concentrations: Molarity Useful unit in dealing with chemicals in solution

16. Molarity Example What is the molarity of a solution prepared by dissolving 58.5 grams of Cu(NO 3 ) 2 in enough water to give a total volume of 500.0 mL?

17. Molarity Example How many moles of HCl are contained in 750.0 mL of a 2.5 M solution?

18. Titration A titration is a chemical analysis that uses volume and molarity In simple acid-base titrations, you can use this equation*: M acid V acid = M base V base *must be a 1:1 stoichiometric reaction or else this equation does not work

19. Titration Example A 25 mL sample of vinegar (which contains acetic acid) is titrated with 0.100 M NaOH. If 6.75 mL of NaOH are required, what is the molarity of the acetic acid in vinegar? 25 mL of vinegar 0.100 M NaOH

20. Dilutions Many reagents and medicines are available as “stock” solutions that must be diluted prior to use In any dilution, you can always use this equation: C 1 V 1 =C 2 V 2 C = concentration V = volume

21. Example If 8.33 mL of 12 M HCl are diluted with water to give a new volume of 1000.0 mL, what is the molarity of the resulting solution?

22. Example How many mL of 5.0% NaCl solution are needed to prepare 5.0 Liters of normal saline?

23. Electrolytes Strong electrolytes dissolve 100% in water to afford solutions that conduct electricity –Soluble ionic compounds –Strong acids (HCl, H 2 SO 4, HNO 3 )

24. Weak Electrolytes Weak electrolytes dissociate less than 100% into ions when dissolved in water and produce solutions with varying ability to conduct electricity –Weak Acids (H 3 PO 4, HF, H 2 S)

25. Non-Electrolytes When molecular compounds (covalently bonded compounds) dissolve in water, no ions are produced, so the solution does not conduct electricity

26. Colligative Properties of Solutions Colligative properties are those properties that depend on the concentration of the solute, not the identity of the solute Examples: –Electrical Conductivity –Vapor Pressure –Boiling Point –Freezing Point

27. Freezing Point Depression The freezing point of a solution goes down as the concentration of solute increase Should use molality

28. Freezing Point Depression Example Calculate the freezing point of a solution comprised of 171 g of C 12 H 22 O 11 dissolved in enough water to have a final volume of 1.00 L.

29. Boiling Point Elevation The boiling point of a solution increases as the concentration of solute increases Should use molality

30. Boiling Point Elevation Example If 13.4 g of NH 4 Cl is dissolved in water to form a 500.0 mL solution, what is the new boiling point of this solution, assuming that water boils at 100 o C?

31. Osmotic Pressure The osmotic pressure of a solution increases as the concentration of solute increases

32. Diffusion Diffusion is the movement of a substance from an area of high concentration to an area of low concentration

33. Osmosis Osmosis is diffusion of water through a semipermeable membrane Solute particles are too big (or too polar) to make it across the membrane This is how water gets moved around cells

34. Hydrostatic Pressure –As the water level rises so does the hydrostatic pressure against the membrane, until a pressure is reached that causes the net movement of water to equilibrate and the volume levels of the two sides become constant

35. Osmotic Pressure Osmotic Pressure (  ) is the hydrostatic pressure required to stop the flow of a solvent from low concentration to high concentration  =nMRT n = moles of particles obtained when one mole of solute dissolves M= molarity of the solution R = is the ideal gas constant T = the temperature in Kelvin nM = Osmolarity, a term used in biology and medicine

36. Tonicity Isotonic solutions have equal concentrations of solute particles A hypertonic solution has a greater concentration of solute A hypotonic solution is a lower concentration of solute

37. Example Na + H2OH2OH2OH2O H2OH2OH2OH2O Cl - Hypertonic solution Less water Na + H2OH2OH2OH2O H2OH2OH2OH2O Cl - Hypotonic solution More water Direction of osmosis SPM Which direction will the water diffuse?

38. Question What will happen to a red blood cell when it is placed into pure water? Cells are isotonic with normal saline (0.89% NaCl). Hint: think about the flow of H 2 O. Hemolysis

39. Question What will happen to a red blood cell when it is placed into 10% aqueous sodium chloride? Cells are isotonic with normal saline (0.89% NaCl)