Agenda:

1. Homework: Read from Chapter 15 to complete tables 3,4,7 & 8 Agenda: • Warm-up: Explain the solvation process • Review – terms, importance, “likes dissolve likes” • Solubility Curves • What can they tell us about solutions? • Measuring concentration of solutions • Peer review of lab reports

2. Warm-up: Solvation Process • Explain what is happening when an ionic compound is dissolved in water (called solvation or hydration) • View the video - what are key steps that need? • How does the water molecules interact with the ionic compound? • http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/solutionSalt.html

3. Solution process

4. Homework:Solutions: Chapter 15 • Read pp 453-457, 476-479 • Complete tables in notes 3. Examples of solutions 4. Size of solute particles 7. Making solutions Questions: • States of Matter Summary – Due on Thursday

5. Why are solutions important?

6. 6. Making Solutions: Molecules (Covalent compounds) • General Rule: “Likes dissolve likes”

7. Likes dissolve likes Polar solvents will dissolve polar solutes Non-electrolytes – do not separate into ions Sugar Ethanol

8. Water cannot dissolve non-polar solutes Insoluble • Examples:

9. Organic solvents • Non-polar solvent dissolving non-polar solutes • Examples: • To remove oily stains in dry-cleaning • Lipids will dissolve in hydrocarbon • To clean oil based paints • To manufacture plastics, man-made fibers, adhesives

10. 7. Making Solutions: Factors that impact the solubility of solids in liquids • Energy is involved – 2 steps • Endothermic to separate solute & solvent particles • Exothermics – attraction between solvent & solute particles

11. 9. Measuring Concentration • Solubility: number of grams of solute in 100 grams of water at 20℃ • Solubility Curves • Saturated solutions • Unsaturated • Supersaturated • http://www.youtube.com/watch?v=XSGvy2FPfCw • http://www.youtube.com/watch?v=1y3bKIOkcmk&feature=related

12. Solubility & Temperature • Reading curves Line shows the amount of solute in a saturated solution Super saturated Solute (g) per 100 g H₂O Unsaturated Temperature • http://www.youtube.com/watch?v=XSGvy2FPfCw

13. http://www.youtube.com/watch?v=XSGvy2FPfCw • The video begins with a few crystals of sodium acetate placed on the lab bench. A supersaturated solution of sodium acetate is poured over the crystals providing a seed or crystallization. The salt begins to crystallize, forming a large sodium acetate structure from the precipitation of the ions out of solution. When the sodium acetate crystallizes, the oppositely charged ions are brought closer together by the crystal structure. Since formation of a crystal lattice lowers potential energy by placing like charges close together, the system releases the excess energy in the crystallization process. Thus, the structure ends up being warm to the touch from this excess energy

14. Examples of supersaturated solutions • A good example of supersaturation is provided by Na2S2O3, sodium thiosulfate, whose solubility at 25°C is 50 g Na2S2O3 per 100 g H2O. If 70 g Na2S2O3 crystals is dissolved in 100 g hot H2O and the solution cooled to room temperature, the extra 20 g Na2S2O3 usually does not precipitate. The resulting solution is supersaturated; consequently it is also unstable. It can be “seeded” by adding a crystal of Na2S2O3, whereupon the excess salt suddenly crystallizes and heat is given off. After the crystals have settled and the temperature has returned to 25°C, the solution above the crystals is a saturated solution—it contains 50 g Na2S2O3.

15. Interpreting solubility curves Y axis X axis Lines If the amount needed is more or less than 100 g of H₂O 1 g H₂0 = 1 mL H₂0

16. Determine the amount of soluterequired to make a saturated solution

17. Determine the amount of soluterequired to make a saturated solution

18. Gases What additional information is in this curve? Explain how gases are different from the other compounds? Type: Size: Temperature:

19. 8. Making solutions: Factors that affect the solubility of gases in liquids Think about soda (carbonated drinks)

20. Practice: Interpreting Solubility Curve • Activity 5-5 • Define: solubility (quantitative ) • Saturated • Precipitate

21. Solubility Rules determined under specified concentration (often 0.1% molarity)

22. 9f. Measuring Concentrations • Molarity (M) by definition = • Molarity = Moles of solute • 1 Liter of solution • Therefore: 2 molar solution = __________________ • Discovery Education video • Standard Deviants School Chemistry: solutions & dilutions

23. Molarity: moles of solute liters of solution

24. Molarity problems • What I s the molarity of a solution in which 58 gram of NaCl are dissolved in 1.0 L of solution? • What is the molarity of a solution in which 10.0 grama of silver I nitrate is dissolved in 500 mL of solution? • How many grams of potassium nitrate should be used to prepare a 2.0 L of a 0.5 molar solution?

25. Steps needed in molarity calculations • Moles For grams: • Liters of solution • If less than 1L ? mL = 1L • Comparison __________ = moles of solute 1 liter of solution

26. Molarity practice • To what volume should 5.0 g of KCl be diluted in order to prepare a 0.25M solution? • How many grams of copper II sulfate – penta hydrate are needed to prepare 100 mL of a 0.10M solution?

27. 9g. Dilution of concentrated solutions: V₁M₁= V₂M₂ • Molarity by dilution practice problems • Most reagents are sold & sorted in concentrated solutions • How much concentrated 18M sulfuric acide is needed to prepare 250mL of a 6.0M solution? • How much concentrated 12M hydrochloric acid is needed to prepare 100 mL of a 2.0 M solution?

28. To what volume should 25 mL of 15 M nitric actid be diluted to prepare a 3.0 M solution? • To how much water should 50 mL of 12 M hydrochloric acid be added to produce a 4.0 M solution? • To how much water should 100 mL of 18M sulfuric acid be added to prepare 1.5 M solution?

29. Colligative Properties • The properties of the solution that depend on the number of particles in solution, not the identity of the solute. • The solvent properties will be changed. • NaCl • CaCl₂ • AlCl₃ • Melting point depression; boiling point elevation; • Vapor pressure lowering

30. Resources • http://www.karentimberlake.com/solution.htm • http://www.afn.org/~afn02809/powerpoint-list.htm • http://www.chemistrygeek.com/chemistrypowerpoint/Student%20Ch%2015%20Solutions.ppt • http://college.cengage.com/chemistry/general/zumdahl/world_of_chem/1e/instructors/ppt/figures/viewindex.html

31. Solution process