Properties of SolutionsProperties of Solutions

SoluteSoluteA solute is the dissolved substance in a solution.

A solvent is the dissolving medium in a solution.

SolvenSolventt

Salt in salt water Sugar in soda drinks

Carbon dioxide in soda drinks

Water in salt water Water in soda

Calculations of Solution Calculations of Solution ConcentrationConcentration

Mass percent - the ratio of mass units of solute to mass units of solution, expressed as a percent

100xsolutionofmass

soluteofmasspercentMass

Calculations of Solution Calculations of Solution ConcentrationConcentration

Mole fraction – the ratio of moles of solute to total moles of solution

BA

AA nn

nAoffractionMole

Calculations of Solution Calculations of Solution ConcentrationConcentration

Molality – moles of solute per kilogram of solvent

solventramloki

solutemolesmMolality

g

Calculations of Solution Calculations of Solution ConcentrationConcentration

Molarity - the ratio of moles of solute to liters of solution

solutionofLiter

soluteofmolesMMolarity

““Like Dissolves Like”Like Dissolves Like”

Fats BenzeneBenzene

SteroidsSteroids HexaneHexane

WaxesWaxes TolueneToluene

Polar and ionic solutes dissolve best in polar solvents

Nonpolar solutes dissolve best in nonpolar solvents

Inorganic Salts WaterWater

SugarsSugars Small alcoholsSmall alcohols

Acetic acidAcetic acid

Solubility TrendsSolubility Trends The solubility of MOST solids The solubility of MOST solids

increases with temperature.increases with temperature. The rate at which solids dissolve The rate at which solids dissolve

increases with increasing surface increases with increasing surface area of the solid.area of the solid.

The solubility of gases decreases The solubility of gases decreases with increases in temperature.with increases in temperature.

The solubility of gases increases The solubility of gases increases with the pressure above the with the pressure above the solution.solution.

Therefore…Therefore…Solids tend to dissolve best when:

o Heatedo Stirredo Ground into small particles

Gases tend to dissolve best when:o The solution is cold

o Pressure is high

Saturation of SolutionsSaturation of Solutions A solution that contains the maximum A solution that contains the maximum

amount of solute that may be dissolved amount of solute that may be dissolved under existing conditions is under existing conditions is saturatedsaturated..

A solution that contains less solute than A solution that contains less solute than a saturated solution under existing a saturated solution under existing conditions is conditions is unsaturatedunsaturated..

A solution that contains more dissolved A solution that contains more dissolved solute than a saturated solution under solute than a saturated solution under the same conditions is the same conditions is supersaturatedsupersaturated..

Solubility ChartSolubility Chart

Henry’s LawHenry’s Law

The concentration of a dissolved gas in a solution is directly proportional to the pressure of the gas above the solution

Applies most accurately for dilute solutions of gases that do not dissociate or react with the solvent

Yes CO2, N2, O2No HCl, HI

S1/P1 = S2/P2

S = solubility in g/L

P = pressure

An electrolyte is:

A substance whose aqueous solution conducts an electric current.

A nonelectrolyte is:

A substance whose aqueous solution does not conduct an electric current.

Definition of Electrolytes and Definition of Electrolytes and NonelectrolytesNonelectrolytes

1.Pure water2.Tap water3.Sugar solution4.Sodium chloride solution5.Hydrochloric acid solution6.Lactic acid solution7.Ethyl alcohol solution8.Pure sodium chloride

Electrolytes?Electrolytes?

ELECTROLYTES: NONELECTROLYTES:

Tap water (weak)

NaCl solution

HCl solution

Lactate solution (weak)

Pure water

Sugar solution

Ethanol solution

Pure NaCl

Answers to Answers to ElectrolytesElectrolytes

Colligative PropertiesColligative Properties

Colligative properties are those that depend on the concentration of particles in a solution, not upon the identity of those properties.

Boiling Point Elevation Freezing Point Depression Osmotic Pressure Vapor Pressure Lowering

Freezing Point DepressionFreezing Point Depression

Each mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 degrees Celsius.

Kf = 1.86 C kilogram/mol

solutef mKiT

m = molality of the solution

i = van’t Hoffvan’t Hoff factor

Boiling Point ElevationBoiling Point Elevation

Each mole of solute particles raises the boiling point of 1 kilogram of water by 0.51 degrees Celsius.

Kb = 0.51 C kilogram/mol

soluteb mKiT

m = molality of the solution

i = van’t Hoffvan’t Hoff factor

Freezing Point Depression and Boiling Point Elevation Constants,

C/m

Solvent Kf Kb

Acetic acid 3.90 3.07

Benzene 5.12 2.53

Nitrobenzene 8.1 5.24

Phenol 7.27 3.56

Water 1.86 0.512

The van’t Hoff Factor, The van’t Hoff Factor, ii

Electrolytes may have two, three or more times the effect on boiling point, freezing point, and osmotic pressure, depending on its dissociation.

Dissociation Equations and Dissociation Equations and the Determination of the Determination of ii

NaCl(s)

AgNO3(s) MgCl2(s)

Na2SO4(s)

AlCl3(s)

Na+(aq) + Cl-(aq)

Ag+(aq) + NO3-(aq)

Mg2+(aq) + 2 Cl-(aq)

2 Na+(aq) + SO42-

(aq)Al3+(aq) + 3 Cl-(aq)

i = 2

i = 2

i = 3

i = 3

i = 4

Suspensions and Suspensions and ColloidsColloids

Suspensions and colloids are NOT solutions. Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred.

Colloids: The particles intermediate in size between those of a suspension and those of a solution.

Types of ColloidsTypes of Colloids

ExamplesExamples DispersinDispersing g

MediumMedium

Dispersed Dispersed

SubstancSubstancee

Colloid TypeColloid Type

Fog, aerosol spraysFog, aerosol sprays GasGas LiquidLiquid AerosolAerosol

Smoke, airborn germsSmoke, airborn germs GasGas SolidSolid AerosolAerosol

Whipped cream, soap Whipped cream, soap sudssuds

LiquidLiquid GasGas FoamFoam

Milk, mayonnaiseMilk, mayonnaise LiquidLiquid LiquidLiquid EmulsionEmulsion

Paint, clays, gelatinPaint, clays, gelatin LiquidLiquid SolidSolid SolSol

Marshmallow, Marshmallow, StyrofoamStyrofoam

SolidSolid GasGas Solid FoamSolid Foam

Butter, cheeseButter, cheese SolidSolid LiquidLiquid Solid Solid EmulsionEmulsion

Ruby glassRuby glass SolidSolid SolidSolid Solid solSolid sol

The Tyndall EffectThe Tyndall Effect

Colloids scatter light, making a beam visible. Solutions do not scatter light.

Which glass contains a colloid?

solutioncolloid