Chapter 12 Solutions Types of Mixtures: - PowerPoint Presentation

1. Chapter 12Solutions

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

3. The Tyndall Effect: Is it a true solution or a colloid???

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6. Solutionsare homogeneous mixtures of two or more substances. contain a solute, usually in smaller quantity, and uniformly dispersed in another substance called the solvent, usually present in greater quantity.

7. Solutes in a true solutionSolutes are not visible andcannot be separated by filtration. can be separated by evaporation. can give color to a solution.

8. Types of Solutions – some examplesSolid in liquid: sugar in waterSolid in solid: metal alloys; 14-karat gold is a mixture of pure gold with silver and copper to make it more durableGas in liquid: CO2 in water = carbonation, NH3 in water = cleaning solutionLiquid in liquid: alcohol in water

9. Types of Solutes and Solventssolutes and solvents can be solids, liquids, or gases.Alloy: a solid solution of two or more metals

10. Solute–Solvent AttractionsTHE SOLUBILITY RULE: “like dissolves like”The expression “like dissolves like” describes the polarities of the solute and solvent particles needed to form a solution. NONPOLAR DISSOLVES NONPLARPOLAR DISSOLVE POLAR AND IONICAttractive forces only occur when they are similar in polarity.

11. Water as a SolventWater, the most common solvent,is a polar molecule partial charges on H and O.forms hydrogen bonds between molecules.

12. Solutions: Ionic solutesNa+ & Cl− ions on the surface of a NaCl crystal are attracted to partial charges in polar water molecules.oxygen atoms attract Na+ ions.hydrogen atoms attract Cl− ionsIons are hydrated by surrounding H2O molecules.

13. Solutions: Polar SolutesPolar molecules such as CH3—OH are soluble because of the polar –OH group that forms hydrogen bonds with the polar solvent water. Some polar solvents include water, H2O, acetic acid (vinegar), CH3COOH, and alcohols.

14. Solutions: Nonpolar SolutesSolutes that are nonpolar, such as iodine (I2), oil, or grease, do not dissolve in the polar solvent water.There are no attractions between the nonpolar solute particles and the polar solvent. Oil and water don’t mix!Nonpolar molecules will only form a solution with other nonpolar solvents.Nonpolar solvents include hydrocarbons like grease, oil, gasoline.

15. Learning CheckWill the following solutes dissolve in water? A. Na2SO4B. gasoline (nonpolar)C. I2D. HCl

16. SolutionWill the following solutes dissolve in water? Na2SO4 Yes, the solute is ionic. gasoline (nonpolar) No, the solute is nonpolar. I2 No, the solute is nonpolar. HCl Yes, the solute is polar.Most polar and ionic solutes dissolve in water because water is a polar solvent.

17. The solution process & solidsTo increase the rate of dissolution of the SOLID solute:crush solute to increase Surface Area stir to disperseheat to increase movement

18. The solution process & gasesTo 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 pressureHenry’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.

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20. Solutes: Strong ElectrolytesIn water, strong electrolytescompletely dissociate. produce ions.conduct an electric current. Examples: DISSOCIATION EQNs100% ionsNaCl(s) Na+(aq) + Cl− (aq) CaBr2(s) Ca2+(aq) + 2Br−(aq)H2OH2OA strong electrolyte in an aqueous solution will completely dissociate into ions.

21. Dissociation of ionic solutesThe separation (dissolution) of ions that occurs when an ionic compound dissolves. EXAMPLES: Dissociation Equations CaCl2 (s) → Ca+2 (aq) + 2Cl-1 (aq)Al2(SO4)3 (s) → 2Al+3(aq) + 3 SO4-2 (aq)AlPO4 (s) → Al+3(aq) + PO4 -3 (aq)

22. You Try: Dissociation of Ionic CompoundsNa2SO4 (s) → 2Na+1(aq) +1SO4-2 (aq)AlCl3 (s) → 1Al+3(aq) + 3 Cl-1 (aq)

23. How many moles of ions formed?EXAMPLES: Dissociation Equations CaCl2 (s) → 1Ca+2 (aq) + 2Cl-1 (aq) Al2(SO4)3 (s) → 2Al+3(aq) + 3SO4-2 (aq)AlPO4 (s) → 1Al+3(aq) + 1PO4 -3 (aq)Na2SO4 (s) → 2Na+1(aq) +1SO4-2 (aq)AlCl3 (s) → 1Al+3(aq) + 3 Cl-1 (aq)

24. Ionization of molecular acidsSome molecular compounds can form ions (where there were none) in solutions if the solvent is polar. These are also strong electrolytes.EX: HCl (g) → H+1 (aq) + Cl-1 (aq)ORHCl (g) + H2O (l) → H3O+1 (aq) + Cl-1 (aq)H3O+1 = the hydronium ion = hydrated H+1

25. Solutes, Weak ElectrolytesIn water, weak electrolytesdissolve mostly as molecules.produce only a few ions.conduct a weak current.Examples: HF(g) + H2O H3O+(aq) + F−(aq) NH3(g) NH4+(aq) + OH−(aq)A weak electrolyte forms mostly molecules and a few ions in an aqueous solution.

26. Solutes, NonelectrolytesIn water, nonelectrolytesdissolve as molecules.do not produce ions.do not conduct a current.Example:C12H22O11(s) C12H22O11(aq) A nonelectrolyte dissolves in water only as molecules,which do not ionize.H2O

27. Classifying Solutes

28. Check for understanding1. Write the equation for the formation of a solution for each of the following.2. Indicate whether solutions of each of the following contain only ions, only molecules, ormostly molecules and a few ions. a. Na2SO4(s), a strong electrolyteb. sucrose, C12H22O11(s), a nonelectrolytec. acetic acid, CH3COOH(l), a weak electrolyted. Hydrochloric acid, H2SO4 (l), a strong electrolyte

29. Solutions of Electrolytes & NonelectrolytesC12H22O11(s) C12H22O11(aq) H2ONa2SO4(s) 2Na+ (aq) + SO42–(aq)H2OCH3COOH(l) H+(aq) + CH3COO–(aq) H2Oa. An aqueous solution of Na2SO4(s) contains only the ions Na+ and SO42−.b. A nonelectrolyte such as sucrose, C12H22O11(s), produces only molecules when it dissolves in water.c. A weak electrolyte such as CH3COOH (l) produces mostly molecules and a few ions when it dissolves in water.

30. SolubilityFor every combination of solute and solvent, there is a limit to the amount of solute that can dissolve.Factors:Nature of solute and solvent: polarity!Nature of solvent: polarity!The temperatureThe pressure if a gasDefined: The amount of substance required to form a saturated solution with a specific amount of solvent at a specified temperature.

31. Solubility & Solution EquilibriumEventually, solution equilibrium is reached: The solute particles dissolve and return to the crystal at equal rates. Defined:The physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates.

32. Solubility & Solution EquilibriumSolutions 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.

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34. Supersaturated SolutionsIf solution is saturated, additional solute will settle to the bottom Heat and stir and more solute is forced to enter the solutionSolute remains dissolved even after solution cools down but will re-crystalize easily – it is unstable

35. Solubility CurveSOLUBILITY: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

36. Practice Using the Solubility CurveWhat 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?

37. ANSWERS30g42g88gThe gases! HCl, NH3, and SO2 WHY? The solubility of gases ↓ as temp ↑

38. Solubility Rules

39. Practice Using the Solubility RulesDetermine if the following are soluble…NaNO3CaCO3AgClFe(OH)3BaCl2PbSO4

40. ANSWERSDetermine if the following are soluble…NaNO3 = YES = (aq)CaCO3 = NO = (s)AgCl = NOFe(OH)3 = NOBaCl2 = YESPbSO4 = NO

41. Review As temperature increases, the solubility of gases in liquids __________________The substance dissolved is called the ____________A mixture whose particles separate is a __________A mixture with particles too small to see is a_______A mixture that scatters light is a________________ and exhibits the _______________ effect.A substance that d0es not dissolve in a polar solvent is probably __________________To carry an electric current a solution must contain __________________

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

43. ANSWERSDecreaseSoluteSuspensionsolutionColloid, TyndallnonpolarionsimmisciblealloyIncreaseSaturatedHydrated/solvated

44. Enthalpy of SolutionThe 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 ENDOTHERMICNaOH (s) → Na+ (aq) + OH- (aq) + energy THIS PROCESS IS EXOTHERMIC

45. Precipitation Reactions (from Ch 8) & Net Ionic EquationsPrecipitation Reactions Review:Double Replacement: C + C → C + CReactants are in solution: (aq)The ions trade partnersThere is no change in the charge on the ions Often form a precipitate: use solubility rulesNet Ionic Equations:Include only the compounds and ions that change.

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

47. Precipitation Reactions & Net Ionic EquationsEX: Reactants are aqueous solutions of potassium sulfate and barium nitrate.Net ionic equation:

48. Concentration of SolutionsMolarity: the number of moles of solute in one liter of solution.Molarity (M)= 

49. Concentration of SolutionsFor example, a 0.25 M NaOH solution (this is read as 0.25 molar) contains 0.25 moles of the solute NaOH in every liter of solution = = Anytime you see the abbreviation M immediately think of it as  

50. Preparing SolutionsNote: 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.

51. Molarity Problems – Finding MolarityGiven: 90.0 g NaCl, 3.50L of solution, find MolarityGiven: 5.85g of KI, 0.125L of solution, find MolarityAntifreeze is a solution of ethylene glycol in water. If 4.50L of antifreeze contains 27.5 grams of ethylene glycol, C2H6O2, what is the concentration of the solution?

52. Molarity Problems – Finding MolarityWhat is the molarity of a solution that contains 1.724 moles of H2SO4 in 2.50 L of solution?What is the molarity of a solution prepared by dissolving 25.0 g of HCl (g) in in enough water to make 150.0 mL of solution?

53. Molarity Problems – Molarity GivenIf 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?

54. Molarity Problems – Molarity GivenA 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?

55. Dilutions: Changing VolumeIn a dilution, the amount of solute does not change; only the volume of the solution changes. C1V1 = C2V2 where C is the concentration of the solution (it can be molarity or percent concentration), and V is the volume of the solution.Grams or molesof solute in concentrated solution=Grams or moles of solute in diluted solution

56. Dilutions: Changing Volume When water is added to a concentrated solution, there is no change in the number of particles. The solute particles spread out as the volume of the diluted solution increases.

57. Molarity of a Diluted SolutionWhat is the molarity of a solution when 75.0 mL of a 4.00 M KCl solution is diluted to a volume of 500. mL?STEP 1 Prepare a table of the concentrations and volumes of the solutions.

58. Molarity of a Diluted SolutionWhat is the molarity of a solution when 75.0 mL of a 4.00 M KCl solution is diluted to a volume of 500. mL?STEP 2 Rearrange the dilution expression to solve for the unknown quantity.

59. Molarity of a Diluted SolutionWhat is the molarity of a solution when 75.0 mL of a 4.00 M KCl solution is diluted to a volume of 500. mL?STEP 3 Substitute the known quantities into the dilution expression and calculate.

60. Strong ElectrolytesSTRONG ACIDS INCLUDESTRONG BASES INCLUDEHClHBrHIHNO3HClO3HClO4H2SO4NaOHKOHLiOHBa(OH)2Ca(OH)2

61. Weak ElectrolytesWEAK ACIDS INCLUDEWEAK BASES INCLUDEHFCH3COOHH3PO4H2CO3NH3

62. REVIEW QUESTIONSDistinguish b/w ionization and dissociation:Distinguish b/w electrolyte and nonelctrolyte:Distinguish b/w strong and weak electrolytes:Write the formula for aluminum chloride:Write equation that shows the dissociation of aluminum chloride (a salt) in water:How many moles of ions are released in solution when aluminum chloride dissolves?Is aluminum chloride soluble?

63. AnswersDistinguish b/w ionization and dissociation: use ionization for covalent compounds, dissociation for ionic compoundsDistinguish b/w electrolyte and nonelctrolyte: electrolytes yield ions in solution, non-electrolytes do not.Distinguish b/w strong and weak electrolytes: strong electrolytes ionize completely, weak electrolytes do notWrite the formula for aluminum chloride: AlCl3Write eqn that shows the dissociation of aluminum chloride (a salt) in water: AlCl3 (s) → Al+3 (aq) + 3Cl-1 (aq)How many moles of ions are released in solution when aluminum chloride dissolves? 4Is aluminum chloride soluble? yes

64. Put 160 grams of sodium acetate in a flask and add 30 mL of water.Put the flask on a hot plate, heat it gently and stir until the crystals of sodium acetate dissolve. Use a small amount of water to rinse down the inside of the flask.Remove the flask from the heat and let it cool slowly without disturbing it.Add one or two crystals (that’s right, it only takes a single crystal) to the liquid in the flask. Don’t take your eyes off of the liquid as beautiful crystals begin to form inside the flask.Feel the flask… it’s warm!  - See more at: http://www.stevespanglerscience.com/lab/experiments/instant-hot-ice#sthash.wOjlrPFp.dpufIf you attempt to dissolve sugar in water, you reach a point where you cannot dissolve any more sugar. This is called a saturated solution. However, if you heat this solution, more sugar will dissolve. When the solution is cooled, the sugar will remain in solution. This is called a supersaturated solution, which is very unstable and will crystallize easily. If you had really wanted to fool your mom when you added more sugar to the Kool-Aid, you should have heated the liquid to dissolve the extra sugar and then allowed it to cool. Your supersaturated Kool-Aid would have been "super sweet!" The process of crystallization gives off heat. It’s said to be exothermic. That’s why the solution is used in hand warmers (the old-style liquid-type of hand warmers).How do Hand Warmers Work?  Commercially available hand warmers use a supersaturated solution of sodium acetate.These products consist of a concentrated aqueous salt solution together with a flexible metallic activator strip (usually stainless steel) in a sealed, flexible container. Sodium acetate and calcium nitrate are examples of suitable salts. These salts are much more soluble in hot water than in cold water.The flexible metal strip is bent back and forth a few times, whereupon a white cloud of crystals begins to precipitate. Within seconds, the entire pack is filled up with solid crystalline needles of sodium acetate without any solution left, and the temperature rises to 130°F for about 30 minutes. Because heat is released upon this precipitation, it is called an exothermic reaction (the opposite is called an endothermic reaction).Supercooled liquids can be cooled below their normal freezing point without turning solid. Then, at the flick of button, the supercooled liquid is triggered to solidify (crystallize) and at the same time release large amounts of heat. Salt solutions that have been processed in such a way that their temperature can be lowered well below their solidification (or melting) temperature and still remain in liquid are defined as supercooled or metastable liquids.The triggering device initiates the rapid solidification of the solution. In the case of salt solutions that release or absorb large amounts of energy during phase changes (common table salt sodium chloride does not do this), the solidification process is a rapid crystallization that releases a large amount of heat at the salt solution's normal melting temperature.The activator is a thin metal piece with ridges and a specially roughened surface. The flexing causes metal-to-metal contact that releases one or more very tiny particles of metal from the roughened surface. This acts as a nesting site for one crystal deposited from the solution and (voila!) all of the crystals fall out instantly. These heat packs are reusable because, by reheating the pack in boiling water for a few minutes, the salt re-dissolves and the pack again contains a clear solution. Best of all, the activator strip can be reused dozens of times!- See more at: http://www.stevespanglerscience.com/lab/experiments/instant-hot-ice#sthash.wOjlrPFp.dpuf

65. Colligative Properties of SolutionsProperties 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. (evaporates more slowly)The greater the concentration of a solution, the greater its osmotic pressure.A nonvolatile solute will elevate the Boiling PointA nonvolatile solute will depress the Freezing Point

66. 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.

67. 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.

68. Why would sugar (a nonelectrolyte) have less of an effect than an ionic salt like MgCl2? A solute that dissociates into several particles has a greater colligative effect than a solute that does not dissociate.

69. Why would sugar have less of an effect than an ionic salt like MgCl2?When sugar dissolves, the molecule does not dissociate.When 1 mole of MgCl2 dissolves, 3 moles of ions are produced: MgCl2 (s) → Mg+2 (aq) + 2Cl-1 (aq)

70. dissociation equations…How many moles of ions are produced when K3N dissolves? K3N (s) → 3K+1 (aq) + N-3 (aq)NaCl?NaCl (s) → Na+1 (aq) + Cl-1 (aq)