Is there a LIMIT Is there a LIMIT to how much to how much

solutesolute can can dissolve into the dissolve into the

solvent?solvent?

SolutionsSolutionsHomogeneous Homogeneous

MixturesMixtures

Solution :Solution :Solvent:Solvent: substance present in a substance present in a Greater (Larger) amount Greater (Larger) amount

Solute:Solute: substance that is substance that is present in a lesser (Smaller) present in a lesser (Smaller) amount amount

““Likes dissolve Likes dissolve likes”likes”

Polar dissolves in polarSugar and water

Nonpolar dissolves in non polar

crayons and oil

CONCENTRATIOCONCENTRATIONN

Molarity (M or mol/L) Mole fraction ( or mol/

mol total)Molality (m or mol/Kg solvent)Mass percent (% or g/ g total)

6

Solutions can be classified as

saturated or unsaturated.

Definitions

A saturated solution contains the maximum quantity of solute

that dissolves at that temperature.

SolvatioSolvation n

Process Process D6 c20Solvation: The attaching of

solvent particles to solute particles..

SATURATED SOLUTIONSSolubility: Maximum amount of solute

per 100 g solvent

Dissolving Effects: c34Dissolving Effects: c34 Saturated SolutionSaturated Solution- maximum amount - maximum amount

of solute in solutionof solute in solution Any extra solute added just sits on bottom.Any extra solute added just sits on bottom.

UnsaturatedUnsaturated- less than max. solute than - less than max. solute than then can be dissolve.then can be dissolve.

SupersaturatedSupersaturated- A solution containing - A solution containing more solute than normal for a given more solute than normal for a given temperature.temperature. Must heat a saturated solution up. Must heat a saturated solution up.

Then return it to room temperature.Then return it to room temperature.

For a Supersaturated solution, when more solute is

added, the extra solute will settle to the bottom

12

SupersaturatedSupersaturatedSodium AcetateSodium Acetate

• One application of a supersaturated solution is the sodium acetate “heat pack.”

• Sodium acetate has an ENDOthermic heat of solution.

Temperature effects the solubility of a substance

Solubility Curves

How much LiCl will dissolve into 100 ml of water at a temperature of 20 C?

How much KCl will dissolve into 500 ml of water at a temperature of 80 C?

How much RbCl will fall out of solution if 200 ml of solution is cooled from a temperature of 80 C to 20 C?

Dissolving EffectsDissolving Effects SolubilitySolubility- the quantity of solute - the quantity of solute

that will dissolve in 100 g of that will dissolve in 100 g of solvent at a set temperaturesolvent at a set temperature

If solution is holding the MAX. If solution is holding the MAX. Amount of solute called Amount of solute called saturatedsaturated

SolidSolid ionic compounds:ionic compounds: more in more in with higher temperaturewith higher temperature

GasesGases:: More in at lower More in at lower temperaturestemperatures

GAS

SOLIDS

Dissolving Gases & Dissolving Gases & PressurePressure

Gas solubility can be Gas solubility can be changed by both the changed by both the

temperature and temperature and PRESSUREPRESSURE..

When the can of soda is When the can of soda is opened the pressure (opened the pressure (PPgasgas) )

drops and causes the drops and causes the solubility to decrease. solubility to decrease.

19

Henry’s LawGas solubility (mol/L) = Sg

Sg = kH • Pgas

kH = Henry’s law constants

for O2 = 1.66 x 10-6 M/mmHg

When Pgas increases, solubility

increases.

Henry’s LawHenry’s LawWhat is the concentration of oxygen in fresh water

when the air pressure is 1 atm?

Sg = kH • Pgas

kH for O2 = 1.66 x 10-6 M/mmHg

O2 = 21% so 0.21(760 torr) = Pgas

Sg = 1.66 x 10-6 M/mmHg • 160 torr = 2.66 x 10-4 M

What is the concentration of oxygen in milligrams/ liter? O2 = 8.5 mg/L