1. Solutions Ions in Solution Colligative Properties

2. Review Types of mixtures: Heterogeneous mixtures: do not have a uniform composition Homogeneous mixtures: have a uniform composition, solute particles are too small to be seen.  A homogeneous mixture is a solution.

3. Terms Soluble: capable of being dissolved Solution: a homogeneous mixture of two or more substances in a single phase Solute: the substance that is dissolved, usually the lesser quantity Solvent: the dissolving medium, usually the greater quantitiy Water is the universal solvent

4. Types of Solutions Solid in liquid: sugar in water Solid in solid: metal alloys; 14-karat gold is a mixture of pure gold with silver and copper to make it more durable Gas in liquid: CO 2 in water = carbonation, NH 3 in water = cleaning solution Liquid in liquid: alcohol in water

5. Types of Mixtures: THINK PARTICLE SIZE!!! Solutions: solute particles too small to be seen (<1nm) Colloids: solute particles intermediate in size – they remain suspended throughout the solvent. (1-1000nm)  Examples: smoke, fog, foams Suspensions: solute particles are so large they settle out upon standing. (>1000nm ) The Tyndall Effect: Is it a true solution or a colloid???  The particles in a colloid will scatter light  A true solution will transmit light

6. Electrolytes & Nonelectrolytes Substances that dissolve in water are classified according to whether they yield neutral molecules (a nonelectrolyte) or charged ions (an electrolyte) in solution! If the solution conducts electricity, the solute is an electrolyte. Electrolyte: a substance that dissolves in water to give a solution that conducts an electric current.

7. The solution process When the solute is an ionic solid and the solvent is water, solute particles are attracted to the charged ends of the POLAR water molecules. The water molecules pull the ions away from the crystal surface and into solution.

8. The Solution Process: Hydration of Solute Particles The polar ends of the water molecules are attracted to the charged ions of the solute particles: Na +1 & Cl -1

9. The solution process The ions are said to be hydrated. If the solvent is not water, the solute particle is said to be solvated. The process is called hydration or solvation.

10. The solution process & solids To increase the rate of dissolution of the SOLID solute: crush to increase Surface Area stir to disperse heat to increase movement  All bring solute & solvent in contact with each other

11. The solution process & gases To increase the rate of dissolution of a solute gas, increase the pressure & decrease the temperature.  Just think soda!!!  Cold = low temperature  Lid on tightly = high pressure Henry’s Law: The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of a liquid.

12. Solubility For every combination of solute and solvent, there is a limit to the amount of solute that can be dissolved. Factors: Nature of solute and solvent: are they ionic, polar covalent or nonpolar covalent?! The temperature The pressure if a gas is the solute

13. Solubility & Solution Equilibrium Eventually, solution equilibrium is reached:  solute particles dissolve & return to the crystal at equal rates.  Ex: CaF 2 (s) ⟷ Ca +2 (aq) + 2 F -1 (aq)

14. Solution Equilibrium Defined:  The physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates.

15. Solubility Defined The amount of substance required to form a saturated solution with a specific amount of solvent at a specified temperature.

16. Solubility & Solution Equilibrium Solutions can be: Unsaturated: contains less than max. amt. of solute possible at that temp. Saturated: contains max. amt. of solute possible at that temp. Supersaturated: contains more than max. amt. of solute possible at that temp.

17. Supersaturated Solutions If solution is saturated, additional solute will settle to the bottom Heat and stir and more solute is forced to enter the solution Solute remains dissolved even after solution cools down but will re-crystalize easily

18. Solubility Solubility Values: Given in grams of solute per 100.g of water at 20.  C. Determined experimentally and reported in reference tables. Temperature must be specified. For gases, pressure must also be specified.

19. Solubility Curve

20. Practice Using the Solubility Curve What is the solubility of NH3 at 50°C? What is the solubility of KCl at 50°C? What is the solubility of KNO3 at 50°C? Which substances have lower solubility at higher temps? Why?

21. ANSWERS 30g 42g 88g The gases! HCl, NH3, and SO2

22. Solubility Rules

23. Practice Using the Solubility Rules Determine if the following are soluble… 1. NaNO3 2. CaCO3 3. AgCl 4. Fe(OH)3 5. BaCl2 6. PbSO4

24. ANSWERS Determine if the following are soluble… 1. NaNO3 = YES = (aq) 2. CaCO3 = NO = (s) 3. AgCl = NO 4. Fe(OH)3 = NO 5. BaCl2 = YES 6. PbSO4 = NO

25. The Solubility Rule: “Like Dissolves Like” Refers to LIKE or UNLIKE in POLARITY Consider the following: type of bonding: ionic, polar covalent or nonpolar covalent polarity of molecules: polar molecules have partial charges! type of intermolecular forces present 1. Dispersion: between nonpolar molecules 2. Dipole-Dipole: between polar molecules 3. Hydrogen Bonds: between H & F, O, N

26. The Solubility Rule: “Like Dissolves Like” Polar dissolves polar and ionic. Nonpolar dissolves nonpolar.

27. “Like Dissolves Like” Liquids that are not soluble in each other are immiscible. Ex: oil (non-polar) & water (polar) Liquids that dissolve freely in each other are miscible. Ex: gasoline & grease (both non-polar) Some solvents are slightly polar: ethanol

28. Enthalpy of Solution The amount of energy absorbed as heat when a specific amount of solute dissolves in a solvent. EX: The dissolving process KI (s) + energy → K + (aq) + I - (aq)  THIS PROCESS IS ENDOTHERMIC NaOH (s) → Na + (aq) + OH - (aq) + energy  THIS PROCESS IS EXOTHERMIC

29. Concentration of Solutions Molarity: the number of moles of solute in one liter of solution. Molarity (M) = amount of solute (mol) volume of solution (L)

30. Concentration of Solutions

31. Preparing Solutions Note: a 1 M solution is NOT made by adding 1 mole of solute to 1 Liter of solvent because the final volume may be > 1 Liter! Instead, dissolve 1 mole of solute in less than 1 Liter of solvent first, then add enough solvent to bring the total volume up to 1 Liter.

32. Types of Solution Problems 1. Find concentration of a solution given solute and solvent amounts 2. Prepare a solution with a specific concentration 3. Find how much of a solution to use to get a certain amount of solute (in grams or moles) when concentration is given 4. Diluting a given solution to a desired concentration

33. Molarity Problems What is the molarity of a solution that contains 1.724 moles of H 2 SO 4 in 2.50 L of solution? What is the molarity of a solution prepared by dissolving 25.0 g of HCl (g) in enough water to make 150.0 mL of solution?water

34. Molarity Problems Given: 90.0 g NaCl, 3.50L of solution, find Molarity Given: 5.85g of KI, 0.125L of solution, find Molarity

35. Molarity Problems Given: 0.8L of 0.5M HCl, find moles of HCl How many grams of sulfuric acid are in 0.500L of 0.150M solution?

36. Molarity Problems If a reaction requires 146.3g of NaCl, what volume of 3.00M NaCl should be used? How many grams of NaCl would you need to prepare 500. mL of a 2.00 M solution?

37. Molarity Problems A reaction requires 23.4g of K2CrO4. I have a 6.0M stock solution. How much of it should I use for the reaction? How many mL of 0.54 M AgNO3 would contain 0.34g of the solute?

38. Dilution Problems: V c M c = V d M d c = starting concentrated solution and d = desired diluted solution What volume of concentrated sulfuric acid, 18.0 M, is required to prepare 5.00 L of 0.150 M solution by dilution with water? A chemist adds water to 120 mL of a 6.0 M solution of NaOH until the final volume is 2.0 L. What is the molarity of the resulting solution?

39. Additional Practice Problems Antifreeze is a solution of ethylene glycol, C 2 H 6 O 2 in water. If 4.50 L of antifreeze contains 27.5 g of ethylene glycol, what is the concentration of the solution? answer: [C 2 H 6 O 2 ] = 0.098 M What mass of sodium carbonate, Na 2 CO 3 is present in 50.00 mL of a 0.750 M solution? Answer: 3.98g

40. Additional Practice Problems How many mL of 1.50 M HCl solution contains 10.0 g of hydrogen chloride? Answer: 183mL An experiment requires 2.00 L of 0.200 M hydrochloric acid (HCl) solution. What volume of concentrated hydrochloric acid, containing 11.9 M hydrogen chloride, is needed? Answer: 33.6 mL

41. Review 1. As temperature increases, the solubility of gases in liquids __________________ 2. The substance dissolved is called the ____________ 3. A mixture whose particles separate is a __________ 4. A mixture with particles too small to see is a_______ 5. A mixture that scatters light is a________________ and exhibits the _______________ effect. 6. A substance that d0es not dissolve in a polar solvent is probably __________________ 7. To carry an electric current a solution must contain __________________

42. Review 8. Liquid solutes and solvents that are not soluble in each other are __________________ and examples include…. 9. A __________________ is a solution whose solute and solvent are both solid metals. 10. The solubility of an ionic compound such as CuCl2 would __________________ with increasing temp. 11. A solution that contains the max. amount of dissolved solute is __________________ 12. A solute molecule that is surrounded by solvent molecules is __________________ 13. Name three alloys:

43. Concentration of Solutions Molality: the number of moles of solute per kilogram of solvent. molality (m) = amount of solute (mol) mass of solvent (kg)

44. Molality Problems Given: 17.1g sugar, C 12 H 22 O 11 dissolved in 125g water, find the molality

45. Molality Problems Given: 225g acetone, (CH 3 ) 2 CO, dissolved in 200.g water, find the molality

46. Molality Problems Given: 0.480 m solution of iodine, I 2, dissolved in 100.0g of carbon tetrachloride Find mass of solute

47. Molality Problems How many grams of the solute methanol, CH3OH, are required to prepare a 0.244 m solution in 400.g of water?

48. Molality Problems How many grams of the solute HNO3, nitric acid, are required to prepare a 1.00 m solution in 2.00 kg of water?

49. Ch13 Dissociation The separation (dissolution) of ions that occurs when an ionic compound dissolves. EXAMPLES: Dissociation Equations CaCl 2 (s) → Ca +2 (aq) + 2Cl -1 (aq) Al 2 (SO 4 ) 3 (s) → 2Al +3 (aq) + 3 (SO 4 ) -2 (aq) AlPO 4 (s) → Al +3 (aq) + PO 4 -3 (aq)

50. You Try: Dissociation of Ionic Compounds Na 2 SO 4 (s) → 2Na +1 (aq) +1SO 4 -2 (aq) AlCl 3 (s) → 1Al +3 (aq) + 3 Cl -1 (aq)

51. Precipitation Reactions (from Ch 8) Double Replacement: C + C → C + C Reactants are in solution: (aq) The ions trade partners There is no change in the charge on the ions Often form a precipitate: use solubility rules

52. Net Ionic Equations Include only the compounds and ions that change.

53. Precipitation Reactions & Net Ionic Equations EX: Reactants are aqueous solutions of zinc nitrate and ammonium sulfide: Net Ionic Equation: includes only those compounds and ions that change

54. Precipitation Reactions & Net Ionic Equations EX: Reactants are aqueous solutions of potassium sulfate and barium nitrate. Net ionic equation:

55. Ionization Some molecular compounds can form ions (where there were none) in solutions if the solvent is polar. EX: HCl (g) → H +1 (aq) + Cl -1 (aq) OR HCl (g) + H 2 O (l) → H 3 O +1 (aq) + Cl -1 (aq) H 3 O +1 = the hydronium ion = hydrated H +1

56. Strong & Weak Electrolytes ……differ in the degree of ionization/dissociation of solute Strong electrolytes include: strong acids, strong bases & ionic salts ionize completely & yield only ions when dissolved EX: NaCl.  Weak Electrolytes: include weak acids & bases ionize only slightly & yield only a few ions when dissolved EX: vinegar, CH 3 COOH. Nonelectrolytes: do not yield any ions in aqueous solution, EX: sugar molecules remain whole in water.

57. Strong Electrolytes – ionize completely 1. EX: hydrochloric acid, a strong acid HCl (aq) + H 2 O (l) ⟶ H +1 (aq) + Cl -1 (aq) 2. EX: sodium hydroxide, a strong base NaOH (aq) + H 2 O (l) ⟶ Na +1 (aq) + OH -1 (aq) 3. EX: NaCl, a salt NaCl (s) + H 2 O (l) ⟶ Na +1 (aq) + Cl -1 (aq)

58. Weak Electrolytes yield only small amounts of ions b/c most of the dissolved molecules remain whole & only a small percentage of the molecules ionize. EX: hydrofluoric acid HF (aq) + H 2 O (l) ↔ H 3 O +1 (aq) + F -1 (aq)  The reversible arrow indicates incomplete ionization. EX: acetic acid (vinegar) CH 3 COOH (aq) + H 2 O (l) ↔ H 3 O +1 (aq) + CH 3 COO -1 (aq)

59. REVIEW QUESTIONS 1. Distinguish b/w ionization and dissociation: 2. Distinguish b/w electrolyte and nonelctrolyte: 3. Distinguish b/w strong and weak electrolytes: 4. Write the formula for aluminum chloride: 5. Write equation that shows the dissociation of aluminum chloride (a salt) in water: 6. How many moles of ions are released in solution when aluminum chloride dissolves? 7. Is aluminum chloride soluble?

60. Answers 1. Distinguish b/w ionization and dissociation: use ionization for covalent compounds, dissociation for ionic compounds 2. Distinguish b/w electrolyte and nonelctrolyte: electrolytes yield ions in solution, non-electrolytes do not. 3. Distinguish b/w strong and weak electrolytes: strong electrolytes ionize completely, weak electrolytes do not 4. Write the formula for aluminum chloride: AlCl3 5. Write eqn that shows the dissociation of aluminum chloride (a salt) in water: AlCl3 (s) → Al +3 (aq) + 3Cl -1 (aq) 6. How many moles of ions are released in solution when aluminum chloride dissolves? 4 7. Is aluminum chloride soluble? yes

61. Colligative Properties of Solutions Properties that depend on the concentration and presence of solutes but not on their identity. Colligative properties are proportional to the number of moles of particles the solute makes in solution. The vapor pressure of a solvent containing a nonvolatile solute is LOWER than the vapor pressure of a pure solvent. The greater the concentration of a solution, the greater its osmotic pressure.

62. Colligative Properties of Solutions

64. Why is the vapor pressure of a solution lower than the vapor pressure of pure water? Dissolved solute particles are solvated. It takes more E for solvated particles to escape at the surface (evaporate).

65. Why is the boiling point of a solution higher than the BPt of pure water? Attractive forces exist b/w the solvent and solute particles. It takes more E for solvent particles to overcome these forces and change state. For example, the BPt of water ↑ 0.51 ˚C for every mole of solute particles.

66. Why is the freezing point of a solution lower than the FPt of pure water? Attractive forces exist b/w the solvent and solute particles. more E must be taken from the solution in order to change state and form a solid. the FPt of water ↓ 1.86 ˚C for every mole of solute particles.

67. Why would sugar (a nonelectrolyte) have less of an effect than an ionic salt like MgCl 2 ? A solute that dissociates into several particles has a greater colligative effect than a solute that does not dissociate.

68. Why would sugar have less of an effect than an ionic salt like MgCl 2 ? When sugar dissolves, the molecule does not dissociate. When 1 mole of MgCl 2 dissolves, 3 moles of ions are produced: MgCl 2 (s) → Mg +2 (aq) + 2Cl -1 (aq)

69. Write dissociation equations… How many moles of ions are produced when K 3 N dissolves? K 3 N (s) → 3K +1 (aq) + N -3 (aq) NaCl? NaCl (s) → Na +1 (aq) + Cl -1 (aq)

70. Colligative Properties of Solutions EX: Calculate the expected freezing point depression of a 0.200 m solution of potassium nitrate ∆t f = K f x m x i

71. Colligative Properties of Solutions EX: Calculate the expected boiling point elevation of a solution that contains 150g NaCl dissolved in 1.0kg of water. ∆t b =K b x m x i

72. Strong Electrolytes STRONG ACIDS INCLUDE STRONG BASES INCLUDE HCl HBr HI HNO3 HClO3 HClO4 H2SO4 NaOH KOH LiOH Ba(OH)2 Ca(OH)2

73. Weak Electrolytes WEAK ACIDS INCLUDE WEAK BASES INCLUDE HF CH3COOH H3PO4 H2CO3 NH3