Solubility A solution is a homogeneous mixture that

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

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.

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.

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

Solubility vs. Temperature for Solids 140 KI 130 Solubility Table shows the dependence of solubility on temperature Solubility (grams of solute/100 g H 2 O) 120 Na. NO 3 110 gases solids 100 KNO 3 90 80 HCl NH 4 Cl 70 60 NH 3 KCl 50 40 30 Na. Cl 20 10 KCl. O 3 SO 2 0 10 20 30 40 50 60 70 80 90 100 Le. May Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

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

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

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

Solubility how much solute dissolves in a given amt. of solvent at a given temp. SOLUBILITY CURVE KNO 3 (s) KCl (s) Solubility (g/100 g H 2 O) HCl (g) Temp. (o. C) unsaturated: supersaturated: above the line solution could hold more solute; below line below solution has “just right” amt. of solute; on line on solution has “too much” solute dissolved in it;

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.

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

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: S 1/P 1 = S 2/P 2

Example 1: • The solubility of a gas in water is 0. 16 g/L at 104 k. Pa. What is the solubility when the pressure of the gas is increased to 288 k. Pa? Assume the temperature remains constant. • S 2 =?

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.

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: M 1 V 1=M 2 V 2 • 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

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

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

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.

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.

Molality and Mole Fraction: • Chemists may express the concentration of a solution utilizing molality and mole fraction. • Molality=moles of solute/kg of solvent • 1 kg=1000 g See sample problem 16. 6 • Mole fraction-the ratio of the moles of solute to the total number of moles of solvent and solute. • n. A=moles of solute A n. B=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.

Solubility Classify as unsaturated, or supersaturated. per 100 g H 2 O 80 g Na. NO 3 @ 30 o. C unsaturated 45 g KCl @ 60 o. C saturated 50 g NH 3 @ 10 o. C unsaturated 70 g NH 4 Cl @ 70 o. C supersaturated Per 500 g H 2 O, 120 g KNO 3 @ 40 o. C saturation point @ 40 o. C for 100 g H 2 O = 66 g KNO 3 So sat. pt. @ 40 o. C for 500 g H 2 O = 5 x 66 g = 330 g 120 g < 330 g unsaturated

Describe each situation below. (A) Per 100 g H 2 O, 100 g Na. NO 3 @ 50 o. C. Unsaturated; all solute dissolves; clear solution. (B) Cool solution (A) very Supersaturated; extra slowly to 10 o. C. solute remains in solution; still clear. (C) Quench solution (A) in an ice bath to 10 o. C. Saturated; extra solute (20 g) can’t remain in solution, becomes visible.

Hotpack / Coldpack

Hot and Cold Packs Article "Hot and Cold Packs" Chem. Matters Feb. 1987 Questions Keys http: //www. unit 5. org/christjs/temp. T 27 d. Fi elds-Jeff/Solutions 1. htm

Solubility of Sodium Acetate Solubility(g/100 g H 2 O) 150 Saturated Supersaturated solution 100 Unsaturated solution 50 0 25 50 75 Temperature (o. C) Charles H. Corwin, Introductory Chemistry 2005, page 378 Video Clip 100 The small crystal causes extensive A single crystal of sodium acetate, crystallization, and eventually Na. C 2 H 3 O 2, is dropped into a supersatureated solution the solute forms a solid mass of Na. C 2 H 3 O 2.

Solubility Equilibrium

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

Steroids Bob Hazelton Article - Steroids Keys http: //www. unit 5. org/christjs/temp. T 27 d. Fi elds-Jeff/Solutions 1. htm

Reverse Osmosis

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

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

Gas, Liquid, and Solid Zumdahl, De. Coste, World of Chemistry 2002, page 441

Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions Combustion Reactions Zumdahl, De. Coste, World of Chemistry 2002, page 240 Acid-Base Reactions

Summary of Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions Combustion Reactions Synthesis reactions (Reactants are elements. ) Zumdahl, De. Coste, World of Chemistry 2002, page 242 Acid-Base Reactions Decomposition reactions (Products are elements. )

Dissociate in Water

Hydrogen Bonding • Intermolecular forces of attraction between molecules • Bonds exist within molecules Zumdahl, De. Coste, World of Chemistry 2002, page 442

K+ K+ NO 3 - NO 3 - K+ K+ Ag. Cl precipitate

Dissolving of Na. Cl Timberlake, Chemistry 7 th Edition, page 287

Solutions Unit 10

Liquid Nitrogen Demonstrations Liquid Nitrogen Keys http: //www. unit 5. org/christjs/temp. T 27 d. Fi elds-Jeff/Solutions 1. htm

Titration of Vitamin C with Iodine Keys http: //www. unit 5. org/christjs/temp. T 27 d. Fi elds-Jeff/Solutions 1. htm

Definitions Solute - KMn. O 4 Solvent - H 2 O

Resources - Solutions 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 I 2 Worksheet - electrolytes and colligative properties Article - steroids (Bob Hazelton) Outline (general)

Resources - Solutions 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 I 2 Worksheet - electrolytes and colligative properties Article - steroids (Bob Hazelton) Lab - ions in solution Outline (general)