1. Solutions Mechanisms and Phenomena, Separations, and Concentration Problems

2. Solutions How they form, What they do, Separations, and Concentration Problems

3. Standards 6. Solutions are homogeneous mixtures of two or more substances. As a basis for understanding this concept: a. Students know the definitions of solute and solvent. 6. b. Students know how to describe the dissolving process at the molecular level by using the concept of random molecular motion. 6. c. Students know temperature, pressure, and surface area affect the dissolving process. 6. d. Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, parts per million, and percent composition. 6. e.* Students know the relationship between the molality of a solute in a solution and the solution’s depressed freezing point or elevated boiling point. 6. f.* Students know how molecules in a solution are separated or purified by the methods of chromatography and distillation.

6. Examples of Chemical Change vs. Physical Change BurningBoiling RustingFreezing Bread RisingMelting Photosynthesis Mixing Salt dissolving in H 2 O Salt precipitating from H 2 O

7. Chemical Change Chemical changes occur when the atoms in a substance change their electron configurations. Chemical changes are often noticeable due to the appearance of a new substance or the release or absorption of energy (light, heat, electricity).

8. Reaction Symbols SymbolMeaning (s), (l), (g) Substance is a solid, liquid, or gas (aq)Aqueous, substance is dissolved in H 2 O “Produces” or “makes” “Produces” through reversible reaction heat or Δ Heat is added to the reactants Pt A catalyst is used to speed up the reaction

9. Definitions Heterogeneous – a mixture with large particles (clumps of molecules or ions). Homogeneous – a mixture with very small particles (individual molecules or ions). Solution – a homogeneous mixture of two or more substances. (ex. salt in water)  Solvent – the main ingredient of a solution. (ex. water)  Solute – the other ingredients dissolved into the solvent. (ex. salt)

10. More Definitions Solution – a homogeneous mixture of two or more substances. (ex. salt in water)  Solvent – the main ingredient of a solution. (ex. water)  Solute – the other ingredients dissolved into the solvent. (ex. salt) Colloid – a heterogeneous mixture of two or more substances with medium-sized particles. Usually stable. (ex. whipping cream, mayonnaise, Jell-O) Suspension – a heterogeneous mixture of two or more substances with larger-sized particles. Usually unstable. (ex. clay in water, smoke in air)

11. Diffusion of Gases

12. Ionic compounds

15. Polar molecules O H H + + – O H H + + – O H H + + –

16. Ionic compounds Na + Cl – Na + Cl – Na + Cl – Na + Cl – – Na + + Cl –

17. NaCl Dissolved in Water O H H + + – O H H + + – O H H + + – Cl – O H H + + –

18. NaCl Dissolved in Water O H H + + – O H H + + – O H H + + – Na + O H H + + –

19. NaCl Dissolved in Water

21. Sucrose Dissolved in Water

22. Precipitate Precipitate – A solid that comes out of the solution. Iron (II) hydroxide benzoic acid

23. Precipitate lead (II) nitrate

24. Concentrations Concentration – how much solute is dissolved within a certain amount of solution. g solute/L solution ppm – parts per million (mass) ppb – parts per billion Molarity (M) – mol solute/L solution Molality – mol solute/kg solvent % composition = mass solute/mass total

25. Concentrations Examples ppm – parts per million (mass) Molarity (M) = g solute L solution = 3.7 g NaCl 1 L solution = mol solute L solution = 3.0 mol MgCl 2 1 L solution = 3.0 M MgCl 2 solution 25 g LiF 1,000,000 g solution = 25 ppm (mass)

26. Concentrations Examples Molality – mol solute/kg solvent % composition = mass solute/mass total

27. Concentration Example #1 If 12 moles of KCl are dissolved in a 3 L solution with water, what is the molarity of the KCl solution? 12 mol KCl 3 L solution = 4 M KCl solution

28. Concentration Example #2 How many moles of sodium chloride (NaCl) are dissolved in 5 L of NaCl solution with a concentration of 3M? 5 L solution 1 x 3 mol NaCl 1 L solution = 15 mol NaCl OR 3 mol NaCl 1 L solution = x mol NaCl 5 L solution

29. Solubility soluble – something that can dissolve into a solution. insoluble – something that cannot dissolve into a solution. saturated – no more solute can dissolve into the solution. unsaturated – more solute can still dissolve into the solution.

30. Solubility supersaturated – more than the normal amount of solute is dissolved in the solution. A slight change may force the excess solute to precipitate out of solution.

31. Solubility Graph

34. Electrical Conductivity Distilled water does not conduct electricity Electrolytes – dissolved salts or acids that allow water to conduct electricity because of positive or negative ions.

35. Diluting Solutions While the molarity (M) and the volume (V) may change, the number of moles (M × V) will not change. M 1 × V 1 = M 2 × V 2 before after

36. Diluting Example #1 5.0 liters of a 3.0 M NaCl solution is diluted so the volume of the solution is now 30 liters. What is the molarity of the diluted solution? M 1 × V 1 = M 2 × V 2 (3.0 M) × (5.0 L) = M 2 × (30 L) 15 = 30 M 2 0.5 M = M 2 30

37. Like Dissolves Like Polar molecules dissolve polar molecules.  Water, alcohols, vinegar Nonpolar molecules dissolve nonpolar molecules.  Fats, oils, gasoline Usefulness of soap in washing off greasy hands comes from soap molecules having both polar and nonpolar ends.

38. Factors that Affect Solubility Surface Area – Smaller particles have more surface area than larger particles. Surface area allows the solute to dissolve faster.

39. Factors that Affect Solubility Surface Area – Smaller particles have more surface area than larger particles. Surface area allows the solute to dissolve faster.

40. Factors that Affect Solubility Stirring – increases solute’s contact with low concentration solvent. The solute dissolves faster. Temperature – Higher temperatures usually allow more solids to dissolve in liquids but less gases. Pressure – Higher pressures usually allow more gases to dissolve in liquids.

41. Gas Dissolved in Water

42. Concentration Effects (aka Colligative Properties) Depressed Freezing Point (anti-freeze, salting the roads and sidewalks in winter) – freezes at a lower temperature because of the solute. Elevated Boiling Point (anti-boil radiator fluid) – boils at a higher temperature because of the solute.

43. Separations Decanting – carefully pouring the solution from a container while leaving the precipitate. Centrifugation – spinning a suspension very fast so the precipitate settles on the bottom. Filtration – using a filter to trap the precipitate while the solution passes through. Evaporation – heating and evaporating out the solvent so only the solute remains. Chromatography – Utilizing different substances’ varying attraction to certain materials so one substance travels faster than the other. Distillation – Separating 2 liquids heating them both and having them boil out at their different boiling points.

44. Decanting Decanting – carefully pouring the solution from a container while leaving the precipitate.

45. Centrifugation Centrifugation – spinning a suspension very fast so the precipitate settles on the bottom.

46. Filtration Filtration – using a filter to trap the precipitate while the solution passes through.

47. Evaporation Evaporation – heating and evaporating out the solvent so only the solute remains.

48. Chromatography Chromatography – Utilizing different substances’ varying attraction to certain materials so one substance travels faster than the other.

49. Distillation Distillation – Separating 2 liquids heating them both and having them boil out at their different boiling points.

50. Concentration Example #3 Pure gold nuggets are very rare. Instead most mining companies settle for rocks that contain only small amount of gold. If a 1,000 g rock contains 200 mg of gold, then what is the concentration in parts per million of gold in the rock? 200 mg Au 1,000 g rock = 0.200 g Au 1,000 g rock x = 200 ppm Au (mass) 200 g Au 1,000,000 g rock 1,000 =

51. Concentration Example #3 Pure gold nuggets are very rare. Instead most mining companies settle for rocks that contain only small amount of gold. If a 1,000 g rock contains 200 mg of gold, then what is the concentration in parts per million of gold in the rock? 200 mg Au 1,000 g rock x 1 g 1,000 mg x = 10 6 1,000 10 6 1,000 = 200 ppm Au (mass) 200 g Au 1,000,000 g rock

52. Concentration Example #4 11.1 g of CaCl 2 are dissolved within a 500 mL solution with water. What is the molarity of the CaCl2 solution? 11.1 g CaCl 2 500 mL solution x 1 mol CaCl 2 111 g CaCl 2 x = 0.2 M CaCl 2 solution 1,000 mL 1 L =

54. Carbonated Soda Under High pressureUnder Normal Pressure Save for Equilibrium Shifts Unit since technically there is an unstable acid compound that CO2 forms in solution.

55. Ne F ONC B Be He Li H KrAr Cl Br Xe ISPSi Mg Al Ca Na K

56. Ne F ONC B Be He Li H KrAr Cl Br Xe ISPSi Mg Al Ca Na K

57. Bad Example #X Carbon dioxide (CO2) is present in a mixture of gases at STP with a concentration of 500 ppm. If there are a 44.8 L of the gas mixture, how many moles of carbon dioxide? 44.8 L mixture 1 x = 0.001 mol CO 2 500 mol CO 2 10 6 mol mixture 1 mol mixture 22.4 L mixture x

58. 4 e – in valence shell

59. Solubility Graph