Solubility.

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Solubility

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

of solubility on temperature
Solubility vs. Temperature for Solids 140 KI 130 120 gases solids NaNO3 110 Solubility Table 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 “Solubility Curves for Selected Solutes” Description: This slide is a graph of solubility curves for 10 solutes. It shows the number of grams of solute that will dissolve in 100 grams of water over a temperature range of 0cC to 10 cC. Basic Concepts The maximum amount of solute that will dissolve at a given temperature in 100 grams of water is given by the solubility curve for that substance. When the temperature of a saturated solution decreases, a precipitate forms. Most solids become more soluble in water as temperature increases, whereas gases become less soluble as temperature increases. Teaching Suggestions Use this slide to teach students how to use solubility curves to determine the solubilities of various substances at different temperatures. Direct their attention to the dashed lines; these can be used to find the solubility of KClO3 at 50 cC (about 21 g per 100 g of H2O). Make sure students understand that a point on a solubility curve represents the maximum quantity of a particular solute that can be dissolved in a specified quantity of solvent or solution at a particular temperature. Point out that the solubility curve for a particular solute does not depend on whether other solutes also are present in the solution (unless there is a common-ion effect; this subject usually is covered at a later stage in a chemistry course). Questions Determine the solubilities (in water) of the following substance at the indicated temperatures: NH3 at 50 oC; KCl at 90 oC; and NaNO3 at 0 oC. Which of the substances shown on the graph is most soluble in water at 20 oC? Which is lease soluble at that temperature? For which substance is the solubility lease affected by changes in temperature? Why do you think solubilities are only shown between 0 oC and 100 oC? In a flask, you heat a mixture of 120 grams of KClO3 and 300 grams of water until all of the KClO3 has just been dissolved. At what temperature does this occur? You then allow the flask to cool. When you examine it later, the temperature is 64 oC and you notice a white powder in the solution. What has happened? What is the mass of the white powder? Compare the solubility curves for the gases HCl, NH3, and SO2) with the solubility curves for the solid solutes. What generalizations(s) can you make about the relationship between solubility and temperature? According to an article in an engineering journal, there is a salt whose solubility in water increases as the water temperature increases from 0 oC to 65 oC. The salt’s solubility then decreases at temperatures above 65 oC, the article states. In your opinion, is such a salt likely to exist? Explain your answer. What could you do to verify the claims of the article? 40 30 NaCl KClO3 20 10 SO2 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

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

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

Solubility  how much solute dissolves in a given amt.
of solvent at a given temp. SOLUBILITY CURVE Temp. (oC) Solubility (g/100 g H2O) KNO3 (s) KCl (s) HCl (g) 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

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

Classify as unsaturated, saturated, or supersaturated.
100 g H2O 80 g 30oC unsaturated 45 g 60oC saturated 50 g 10oC unsaturated 70 g 70oC supersaturated Per 500 g H2O, 120 g 40oC saturation 40oC for 100 g H2O = 66 g KNO3 So sat. 40oC for 500 g H2O = 5 x 66 g = 330 g 120 g < 330 g unsaturated

Describe each situation below.
(A) Per 100 g H2O, 100 g Unsaturated; all solute 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.

Hotpack / Coldpack

Hot and Cold Packs Article
Article "Hot and Cold Packs"  ChemMatters Feb Questions Article "Hot and Cold Packs" ChemMatters Feb Questions Keys

Solubility of Sodium Acetate
150 Supersaturated solution Saturated 100 Solubility(g/100 g H2O) Unsaturated solution video clip Add 100 g sodium acetate into 100 g of water at 55oC. Allow to cool to 20oC. Only 82 g of sodium acetate should remain in solution at this temperature. Place a seed crystal in the supersaturated solution and ~18 g of sodium acetate will precipitate out of solution. The resulting solution will be saturated. Include a table of data for students to graph. 50 A single crystal of sodium acetate, NaC2H3O2, is dropped into a supersaturated solution The small crystal causes extensive crystallization, and eventually 25 50 75 100 the solute forms a solid mass of NaC2H3O2. Temperature (oC) Charles H.Corwin, Introductory Chemistry 2005, page 378

Solubility Equilibrium

Vitamins Multi Vitamin Water Soluble Fat Soluble
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

Reverse Osmosis

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

Net Solvent Flow semipermeable membrane Dilute solution
Net flow of solvent Net flow of solvent Concentrated solution Net solvent flow through a semipermeable membrane occurs spontaneously in only one direction, from the compartment containing dilute solution (or pure solvent) into the compartment of concentrated solution. Remember –ordinarily the terms dilute and concentrated are used to describe the concentration of solute. The net flow of solvent is from where the solvent is more concentrated to where the solvent is less concentrated. Solute particle Solvent particle Ralph A. Burns, Fundamentals of Chemistry 1999, page 430

Gas, Liquid, and Solid Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441

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

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 Chemistry 2002, page 242

Dissociate in Water

Hydrogen Bonding Intermolecular forces of attraction between molecules
Bonds exist within Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 442

K+ NO3- K+ K+ NO3- NO3- K+ NO3- NO3- K+ NO3- K+ AgCl precipitate AgCl precipitate

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

Solutions

Liquid Nitrogen Demonstrations
Keys

Titration of Vitamin C with Iodine
Keys

Definitions Solute - KMnO4 Solvent - H2O

NaCl(s)  Na+(aq) + Cl–(aq)
Solvation Dissociation separation of an ionic solid into aqueous ions NaCl(s)  Na+(aq) + Cl–(aq)

HNO3(aq) + H2O(l)  H3O+(aq) + NO3–(aq)
Solvation Ionization breaking apart of some polar molecules into aqueous ions HNO3(aq) + H2O(l)  H3O+(aq) + NO3–(aq)

Solvation C6H12O6(s)  C6H12O6(aq) Molecular Solvation
molecules stay intact C6H12O6(s)  C6H12O6(aq)

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