Solubility

1. Solubility • A solution is a homogeneous mixture that may be a solid, liquid, or gas. • What factors affect the rate of dissolving for a solution? • Stirring (agitation) • Temperature • Surface area of dissolving particles

2. Three types of solutions: • Saturated solution-solution containing the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure. • Unsaturated solution-a solution that contains less solute than a saturated solution at a given temperature and pressure. • Supersaturated solution-solution containing more solute than it can theoretically hold at a given temperature.

3. The crystallization of a supersaturated solution can be initiated if a very small crystal, a seed crystal of the solute is added. Crystallization can also occur if the inside of the container is scratched.

4. UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form Solubility increasing concentration

5. gases solids Solubility Table Solubility vs. Temperature for Solids 140 KI 130 120 NaNO3 110 100 KNO3 90 80 HCl NH4Cl • shows the dependence • of solubility on temperature 70 Solubility (grams of solute/100 g H2O) 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

6. Solubility • Solubility • maximum grams of solute that will dissolve in 100 g of solvent at a given temperature • varies with temp • based on a saturated solution

7. Solubility • Solids are more soluble at... • high temperatures. • Gases are more soluble at... • low temperatures & • high pressures (Henry’s Law). • EX: nitrogen narcosis, the “bends,” soda

8. Sol. Sol. To To Solubility Solids dissolved in liquids Gases dissolved in liquids As To , solubility As To , solubility

9. KNO3 (s) KCl (s) Solubility (g/100 g H2O) HCl (g) Temp. (oC) Solubilityhow much solute dissolves in a given amt. of solvent at a given temp. SOLUBILITY CURVE unsaturated: solution could hold more solute; below line saturated: solution has “just right” amt. of solute; on line supersaturated: solution has “too much” solute dissolved in it; above the line

10. Two types of liquids: • Miscible liquids-two liquids that dissolve in each other in all proportions. Examples-water and ethanol, water and ethylene glycol. • Immiscible liquids-liquids that are insoluble in one another. Examples-oil and vinegar; oil and water.

11. Factors Affecting Solubility: • Temperature-for solids, liquids and gases. • Pressure-gases only. • For some substances, solubility decreases with temperature.

12. Pressure and the gas laws: • Changes in pressure strongly influence the solubility of gases, however, have little affect on the solubility of solids and liquids. Gas solubility increases as the partial pressure of the gas above the solution increases. Ex. Carbonated beverages produce a fizz. • Henry’s law-states that at a given temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. • Equation for Henry’s Law: S1/P1 = S2/P2

13. Example 1: • The solubility of a gas in water is 0.16g/L at 104kPa. What is the solubility when the pressure of the gas is increased to 288kPa? Assume the temperature remains constant. • S2 =?

14. Molarity • Concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent. • Dilute solution- a solution containing a small amount of solute. • Concentrated solution- solution containing a large amount of solute. • How do chemists express concentration quantitatively? By utilizing molarity. • Molarity (M)-the number of moles of solute dissolved in one liter of solution. Molarity=moles of solute/liter of solution.

15. 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. • Molarity by dilution: M1V1=M2V2 • The first M and V are initial Molarity and Volume of solution, The second M and V are the molarity and volume of the diluted solution. • See sample Problem 16.4

16. Percent Solutions • The concentration of a solution in percent can be expressed in two ways: as the ratio of the volume of the solute to the volume of the solution, or as the ratio of the mass of solute to the mass of the solution. • % by volume (%v of V)=solute volume/solution volume x 100 • % by mass (%m of m)=solute mass/solution mass x 100

17. Colligative Properties: • Colligative property- a property that depends only upon the number of solute particles in the solution, and not their identity. • There are three important colligative properties of solutions: • Vapor-pressure lowering • Boiling point elevation • Freezing point depression

18. Colligative Properties… • The decrease in a solution’s vapor pressure is proportional to the number of particles the solute makes in solution. • The magnitude of the freezing-point depression is proportional to the number of solute particles dissolved in the solvent and does not depend upon their identity. • The magnitude of the boiling-point elevation is proportional to the number of solute particles dissolved in the solvent.

19. Colligative Properties… • Vapor pressure=the pressure exerted by a vapor that is in dynamic equilibrium with its liquid in a closed system. • Freezing-point depression=the difference in temperature between the freezing point of a solution and the freezing point of the pure solvent. • Boiling-point elevation=the difference in temperature between the boiling-point of a solution and the boiling point of the pure solvent.

20. Molality and Mole Fraction: • Chemists may express the concentration of a solution utilizing molality and mole fraction. • Molality=moles of solute/kg of solvent • 1kg=1000g See sample problem 16.6 • Mole fraction-the ratio of the moles of solute to the total number of moles of solvent and solute. • nA=moles of solute A nB=moles of solvent B • XA=mole fraction of solute A, XB=mole fraction of solvent B. • The magnitude of the freezing point depression ∆Tf and boiling point elevation ∆Tb of a solution are directly proportional to the molal concentration m, when the solute is molecular, not ionic.

21. Solubility Classify as unsaturated, saturated, or supersaturated. per 100 g H2O 80 g NaNO3 @ 30oC unsaturated 45 g KCl @ 60oC saturated 50 g NH3 @ 10oC unsaturated 70 g NH4Cl @ 70oC supersaturated Per 500 g H2O, 120 g KNO3 @ 40oC saturation point @ 40oC for 100 g H2O = 66 g KNO3 So sat. pt. @ 40oC for 500 g H2O = 5 x 66 g = 330 g 120 g < 330 g unsaturated

22. Describe each situation below. (A) Per 100 g H2O, 100 g Unsaturated; all solute NaNO3 @ 50oC. dissolves; clear solution. (B) Cool solution (A) very Supersaturated; extra slowly to 10oC. solute remains in solution; still clear. (C) Quench solution (A) in Saturated; extra solute an ice bath to 10oC. (20 g) can’t remain in solution, becomes visible.

23. Hotpack / Coldpack

24. Hot and Cold Packs Article Article "Hot and Cold Packs" ChemMatters Feb. 1987 Questions Article "Hot and Cold Packs" ChemMatters Feb. 1987 Questions Keys http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

25. Solubility of Sodium Acetate 150 Saturated Supersaturated solution Video Clip 100 Solubility(g/100 g H2O) Unsaturated solution 50 0 The small crystal causes extensive crystallization, and eventually A single crystal of sodium acetate, NaC2H3O2, is dropped into a supersatureated solution 25 50 75 100 the solute forms a solid mass of NaC2H3O2. Temperature (oC) Charles H.Corwin, Introductory Chemistry 2005, page 378

26. Solubility Equilibrium

27. Vitamins • Multi Vitamin • Provides many essential vitamins • “Expensive urine” • Water Soluble • Vitamin C • Must be replenished regularly • Fat Soluble • Can overdose • Vitamin A • Can be ingested periodically, stored in body fat

28. Steroids Bob Hazelton Article - Steroids Bob Hazelton Article - Steroids Keys http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

29. Reverse Osmosis

30. Reverse Osmosis Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 267

31. semipermeable membrane Net Solvent Flow Dilute solution Net flow of solvent Net flow of solvent Concentrated solution Solute particle Solvent particle Ralph A. Burns, Fundamentals of Chemistry 1999, page 430

32. Gas, Liquid, and Solid Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 441

33. Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions Acid-Base Reactions Combustion Reactions Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 240

34. Summary of Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions Acid-Base Reactions Combustion Reactions Synthesis reactions (Reactants are elements.) Decomposition reactions (Products are elements.) Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 242

35. Dissociate in Water

36. Hydrogen Bonding • Intermolecular forces of attraction between molecules • Bonds exist within molecules Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 442

37. K+ NO3- K+ K+ NO3- NO3- K+ NO3- NO3- K+ NO3- K+ AgCl precipitate AgCl precipitate

38. Dissolving of NaCl Timberlake, Chemistry 7th Edition, page 287

39. Solutions Unit 10

40. Liquid Nitrogen Demonstrations         Liquid Nitrogen Liquid Nitrogen Keys http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

41. Titration of Vitamin C with Iodine Titration of Vitamin C with Iodine Titration of Vitamin C with Iodine Keys http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

42. Definitions Solute - KMnO4 Solvent - H2O

43. Resources - Solutions Objectives Objectives - kinetics / equilibrium Worksheet - vocabulary Worksheet - review colligative properties Demonstration - tyndall effect Worksheet - molarity and stoichiometry Worksheet - textbook problems Article - soap (questions) Activity - serial dilution activity Lab - soap Worksheet - dilution of solutions Article - lava lamp Worksheet - molarity of solutions Article - hot / cold pack Article - don't sweat the small stuff Lab - salol (freezing point depression) Worksheet - colligative properties Lab - titration of vit C with I2 Article - steroids (Bob Hazelton) Worksheet - electrolytes and colligative properties Outline(general)

44. Resources - Solutions Objectives Objectives - kinetics / equilibrium Worksheet - vocabulary Worksheet - review colligative properties Demonstration - tyndall effect Worksheet - molarity and stoichiometry Worksheet - textbook problems Article - soap (questions) Activity - serial dilution activity Lab - soap Worksheet - dilution of solutions Article - lava lamp Worksheet - molarity of solutions Article - hot / cold pack Article - don't sweat the small stuff Lab - salol (freezing point depression) Worksheet - colligative properties Lab - titration of vit C with I2 Article - steroids (Bob Hazelton) Worksheet - electrolytes and colligative properties Lab - ions in solution Outline(general)