1. SOLUTIONS Chapters 15 and 16

2. NOT a solution Oil and Water DON’T mix SUSPENSION

3. Heterogenous Mixtures Suspensions have much larger particles than solutions- therefore they do not stay suspended indefinitely >1,000 nm particle size Colloids: particles spread evenly throughout the dispersion medium 1 nm-1,000 nm particle size

4. The Tyndall Effect The scattering of visible light by colloidal particles

5. Emulsions A colloidal dispersion of a liquid in a liquid Soaps/detergents Egg yolk

6. Homogenous Mixtures Smallest particle size Uniform composition Solute- dissolved particles Solvent- dissolving medium

7. Homogenous Aqueous Systems Water- “Universal Solvent” Aqueous Solution- water that contains dissolved substances COMPOUNDS THAT DISSOLVE MOST READILY IN WATER INCLUDE: IONIC COMPOUNDS POLAR COVALENT MOLECULES

8. Why do these dissolve in water?? ION MOLECULE ATTRACTION!!!!

9. The Solution Process

10. SOLVATION Positive and negative ions of an ionic solid become surrounded by solvent molecules Some ionic compounds have attractions that are too strong to be overcome by solvation insoluble BaSO 4 CaCO 3

11. TABLE F SOLUBILITY GUIDELINES

12. Reactions in Aqueous Solutions AgNO 3(aq) + NaCl (aq)  AgCl (s) + NaNO 3(aq) Most ionic compounds dissociate into cations and anions when dissolved in water We can write a complete ionic equation to show the dissolved ionic compounds as dissociated free ions

13. Complete Ionic Equation Ag + (aq) + NO 3 - (aq) + Na + (aq) + Cl - (aq)  AgCl (s) + Na + (aq) + NO 3 - (aq) Na + (aq) and NO 3 - (aq) appear unchanged on either side of the equations; they did not technically participate in the reaction.

14. Spectator Ion An ion that appears on both sides of an equation and is not directly involved in the reaction

15. Net Ionic Equation An equation for a reaction in solution that shows only those particles directly involved in the chemical change Ag + (aq) + Cl - (aq) --> AgCl (s) **You must make sure that the charges on either side are balanced **You must make sure that the charges on either side are balanced

16. Try this one KBr (aq) + AgNO 3(aq) 

17. ELECTROLYTES All ionic compounds are electrolytes because they dissociate into: Mobile ions able to conduct electricity Molecular compounds= nonelectrolytes not composed of ions BUT….some polar molecular compounds become electrolytes in aqueous solutions

18. STRONG WEAK Soluble salts Inorganic acids Inorganic bases NH 3 Organic acids Organic bases Mercury (II) chloride

19. Properties of Water Many other important and unique properties of water result from hydrogen bonding Low vapor pressure High surface tension

20. Surface Tension Water molecules at the surface of a drop tend to be drawn inward Due to high IMFs!! The inward force, or pull, that tends to minimize the surface area is called SURFACE TENSION

21. SURFACTANT A surfactant is any substance that interferes with the H-bonding between water molecules and thereby reduces surface tension Soaps and detergents

22. Cooling Water Typical liquid- contracts when cooled, density increases Density of water is at maximum at 4°C then density starts to decrease ICE FLOATS

23. What does it look like? The structure of ice is a regular open framework of water molecules arranged like a honeycomb

24. HYDRATES CuSO 4. 5H 2 O Water contained in a crystal is called the water of hydration or water of crystallization

25. Properties of Solutions Several things determine whether or not and how quickly a substance will dissolve: Composition of solute and solvent Stirring (agitation) Surface area of solute Temperature

26. Stirring Affects only the RATE Does not influence amount of solute that will dissolve

27. Temperature As temp , KE   frequency and force of collisions between solvent and solute particles

28. Particle Size The more surface of the solute that is exposed, the faster the rate of dissolving Smaller particle size = greater surface area!!!!!!! greater surface area!!!!!!!

29. Solubility The amount of solute that dissolves in a given amount of a solvent at a certain temp and pressure to produce a saturated solution. Is often expressed in grams of solute per 100g of solvent

30. Table G- Solubility Curves

31. Saturated Solution Contains the MAXIMUM amount of solute for a given quantity of solvent at a constant temp and pressure.

32. Unsaturated Solution A solution that contains less solute than a saturated solution at a given temp and pressure

33. Supersaturated Solution Contains more solute than it can theoretically hold at a given temp Crystallization can occur under certain conditions Addition of a seed crystal Scratching inside of container

34. Two liquids are MISCIBLE If they dissolve in each other in all proportions Liquid present in larger amount usually considered the solvent Ethanol and Water “LIKE DISSOLVES LIKE” Oil and water don’t mix- they are IMMISCIBLE

35. Temperature and GASES Effect on solubility is opposite that of solids Solubilities of most gases are GREATER in cold water than hot Lakes, aquatic animal and plant life Soda

36. Pressure Has little affect on solubility of solids and liquids, but strongly influences solubility of gases. Gas solubility increases as the partial pressure of the gas above the solution increases It’s like gas is “forced” into solution by increased pressure solution by increased pressure Carbonated beverages

37. Concentrations of Solutions Is a measure of the amount of solute that is dissolved in a given quantity of solvent Dilute/concentrated

38. MOLARITY (M) Is the number of moles of solute dissolved in one liter of solution “moles per liter”

39. To calculate the molarity of a solution: Divide the moles of solute by the volume of the solution (in liters) Molarity (M)= moles of solute liters of solution liters of solution The volume involved is the TOTAL volume of the resulting solution, not the volume of the solvent alone

40. EXAMPLE IV saline solutions are often administered to patients in the hospital. One saline solution contains 0.90 g NaCl in exactly 100 mL of solution. What is the molarity of the solution?

41. You can also do the reverse How many moles are in 2.00 L of 2.5M LiCl? Known: Molarity (M)= moles of solute liters of solution liters of solution So: moles of solute= molarity (M) x liters of solution (V)

42. Example Household laundry bleach is a dilute aqueous solution of sodium hypochlorite (NaClO). How many moles of solute are present in 1.5 L of 0.70 M NaClO?

43. Making Dilutions Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles of solute in solution does not change Moles of solute= M 1 V 1 =M 2 V 2

44. Example How many milliliters of aqueous 2.00 M MgSO 4 solution must be diluted with water to prepare 100.0 mL of aqueous 0.400 MgSO 4 ?

45. Percent Solutions The concentration of a solution in percent can be expressed in two ways: As the ratio of volume of the solute to the volume of the solution As the ratio of mass of the solute to the mass of the solution

46. Volume/Volume Percent by volume (% (v/v) ) = Volume of solute Volume of solute volume of solution volume of solution X 100

47. Example What is the percent by volume of ethanol (C 2 H 6 O) in the final solution when 85 mL of ethanol is diluted to a volume of 250 mL with water?

48. Mass/Mass Percent by mass (% (m/m) )= Mass of solute Mass of solute mass of solution mass of solution X 100

49. Example You want 2,000 g of a solution of glucose in water that has a 2.8% (m/m) concentration of glucose. How much glucose do you need?

50. parts per million (ppm) A part per million is equal to: *one penny in $10,000 *one minute in two years

51. ppm example Suppose 17 grams of sucrose is dissolved in 183 grams of water. What is the concentration of sucrose in ppm?

52. Colligative Property A property that depends only on the number of solute particles, and not upon their identity Vapor-pressure lowering Boiling-point elevation Freezing-point depression

53. Vapor Pressure Lowering Formation of “shells of water of solvation” reduces the number of solvent molecules with enough KE to escape as a vapor The decrease in a solution’s vapor pressure is proportional to the number of particles the solute makes in solution NaCl- 2 particles MgCl 2 - 3 particles

54. Freezing Point Depression Freezing point of solution vs. freezing point of pure solvent The magnitude of f.p. depression is proportional to the # of particles and not the identity of those particles 1 mol of solute particles to 1,000 g water  f.p. by 1.86°C

55. Boiling Point Elevation Because of the  in v.p., additional KE must be added to  the v.p. of the liquid phase to initiate boiling. B.P. of water  0.512°C/ mol of solute in 1,000 g water