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

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute

dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

increasing concentration

Solubility Table

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

0 10 20 30 40 50 60 70 80 90 100

Solubility vs. Temperature for Solids

Sol

ubili

ty (

gram

s of

sol

ute/

100

g H

2O)

KI

KCl

20

10

30

40

50

60

70

80

90

110

120

130

140

100

NaNO3

KNO3

HCl NH4Cl

NH3

NaCl KClO3

SO2

shows the dependence

of solubility on temperature

gases

solids

Solubility

SolubilitySolubility

maximum grams of solute that will dissolve in 100 g of solvent at a given temperature

varies with temp

based on a saturated solution

SolubilitySolubility

Solids are more soluble at...Solids are more soluble at...• high temperatures.

Gases are more soluble at...Gases are more soluble at...• low temperatures &• high pressures

(Henry’s Law).• EX: nitrogen narcosis,

the “bends,” soda

Solubility

To

Sol.

To

Sol.

Solids dissolved in liquids Gases dissolved in liquids

As To , solubility As To , solubility

Temp. (oC)

Solubility(g/100 g H2O)

KNO3 (s)

KCl (s)

HCl (g)

SOLUBILITYCURVE

Solubility how much solute dissolves in a given amt.

of solvent at a given temp.

unsaturated: solution could hold more solute; belowbelow line

saturated: solution has “just right” amt. of solute; onon line

supersaturated: solution has “too much” solute dissolved in it;

above the line

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: S1/P1 = S2/P2

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 =?

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: 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

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• 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.

Solubility

per100 gH2O

Classify as unsaturated, saturated, or supersaturated.

80 g NaNO3 @ 30oC unsaturated

45 g KCl @ 60oC saturated

50 g NH3 @ 10oC unsaturated

70 g NH4Cl @ 70oC supersaturated

So sat. pt. @ 40oC for 500 g H2O = 5 x 66 g = 330 g

120 g < 330 g unsaturated

saturation point @ 40oC for 100 g H2O = 66 g KNO3

Per 500 g H2O, 120 g KNO3 @ 40oC

(A) Per 100 g H2O, 100 g Unsaturated; all

soluteNaNO3 @ 50oC. dissolves; clear

solution.

(B) Cool solution (A) very Supersaturated; extraslowly to 10oC. solute remains in solution;

still clear.

Describe each situation below.

(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

http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

KeysKeysKeysKeys

Article "Hot and Cold Packs" 

ChemMatters Feb. 1987 Questions

Article "Hot and Cold Packs"

ChemMatters Feb. 1987 Questions

Solubility of Sodium Acetate

Temperature (oC)

025 50 75 100

Sol

ubili

ty(g

/100

g H

2O)

50

100

150Supersaturated

solution

Unsaturated solution

Saturated

Video Clip

Charles H.Corwin, Introductory Chemistry 2005, page 378

A single crystal of sodium acetate, NaC2H3O2, is dropped into a

supersatureated solution

The small crystal causes extensivecrystallization, and eventually

the solute forms a solid mass of NaC2H3O2.

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

http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

KeysKeysKeysKeys

Bob Hazelton Article - Steroids

Bob Hazelton Article - Steroids

Reverse Osmosis

Reverse Osmosis

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

Net flow of solvent

Net Solvent Flow

Dilutesolution Concentrated

solution

Solute particle Solvent particle

Ralph A. Burns, Fundamentals of Chemistry 1999, page 430

semipermeable membrane

Net flow of solvent

Gas, Liquid, and Solid

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441

Classes of Reactions

Chemical reactionsChemical reactions

Precipitation reactions

Precipitation reactions

Acid-BaseReactionsAcid-BaseReactions

Oxidation-ReductionReactions

Oxidation-ReductionReactions

Combustion Reactions

Combustion Reactions

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 240

Summary of Classes of Reactions

Chemical reactionsChemical reactions

Precipitation reactions

Precipitation reactions

Acid-BaseReactionsAcid-BaseReactions

Oxidation-ReductionReactions

Oxidation-ReductionReactions

Combustion Reactions

Combustion Reactions

Decomposition reactions

(Products are elements.)

Decomposition reactions

(Products are elements.)

Synthesis reactions

(Reactants are elements.)

Synthesis reactions

(Reactants are elements.)

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 242

Dissociate in Water

Hydrogen Bonding

• Intermolecular forcesof attraction between

molecules

• Bonds exist withinmolecules

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 442

K+

K+

K+NO3-

NO3-

NO3-

AgCl precipitate

K+

K+

K+NO3-

NO3-

NO3-

AgCl precipitate

Dissolving of NaCl

Timberlake, Chemistry 7th Edition, page 287

Solutions

Unit 10

Liquid Nitrogen Demonstrations

http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

KeysKeysKeysKeys

        Liquid Nitrogen

        Liquid Nitrogen

Titration of Vitamin C with Iodine

http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

KeysKeysKeysKeys

Titration of Vitamin C with Iodine

Titration of Vitamin C with Iodine

DefinitionsDefinitions

Solute Solute - KMnO4 Solvent Solvent - H2O

Resources - Solutions

ObjectivesObjectives - kinetics / equilibrium - kinetics / equilibrium

WorksheeWorksheet - vocabulary - vocabulary

Demonstration - tyndall effectDemonstration - tyndall effect

Worksheet - textbook problemsWorksheet - textbook problems

Activity - serial dilution activityActivity - serial dilution activity

Worksheet - dilution of solutionsWorksheet - dilution of solutions

Worksheet - molarity of solutionsWorksheet - molarity of solutions

Article - don't sweat the small stuffArticle - don't sweat the small stuff

Worksheet - colligative propertiesWorksheet - colligative properties

Outline (general)(general)

Worksheet - review colligative propertiesWorksheet - review colligative properties

Worksheet - molarity and stoichiometryWorksheet - molarity and stoichiometry

Article - soap (questions) Article - soap (questions)

Lab - soapLab - soap

Article - lava lampArticle - lava lamp

Article - hot / cold packArticle - hot / cold pack

Lab - salol (freezing point depression)Lab - salol (freezing point depression)

Lab - titration of vit C with ILab - titration of vit C with I22

Worksheet - electrolytes and colligative properties Worksheet - electrolytes and colligative properties Article - steroids (Bob Hazelton)Article - steroids (Bob Hazelton)

Resources - Solutions

ObjectivesObjectives - kinetics / equilibrium - kinetics / equilibrium

Worksheet - vocabulary - vocabulary

Demonstration - tyndall effectDemonstration - tyndall effect

Worksheet - textbook problemsWorksheet - textbook problems

Activity - serial dilution activityActivity - serial dilution activity

Worksheet - dilution of solutions - dilution of solutions

Worksheet - molarity of solutions - molarity of solutions

Article - don't sweat the small stuff - don't sweat the small stuff

Worksheet - colligative properties- colligative properties

Outline (general)(general)

Worksheet - review colligative propertiesWorksheet - review colligative properties

Worksheet - molarity and stoichiometryWorksheet - molarity and stoichiometry

Article - soap (questions) Article - soap (questions)

Lab - soapLab - soap

Article - lava lampArticle - lava lamp

Article - hot / cold packArticle - hot / cold pack

Lab - salol (freezing point depression)Lab - salol (freezing point depression)

Lab - titration of vit C with ILab - titration of vit C with I22

Worksheet - electrolytes and colligative properties Worksheet - electrolytes and colligative properties Article - steroids (Bob Hazelton)Article - steroids (Bob Hazelton)

Lab - ions in solutionLab - ions in solution