Solutions

Solution Saturation

Compares the amount of dissolved solute in a solution with the maximum amount of dissolved solute possible under the given conditions.

SolubilitySATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute

dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

increasing concentration

Solubility

• A solution that contains the maximum possible amount of solute is saturated.

• If a solution contains less than the maximum amount of solute, it is unsaturated.

Solubility• When a solution is saturated and excess

solute is present, the rate of dissolution is equal to the rate of crystallization.

• Solubility increases with increasing temperature — a saturated solution that was prepared at a higher temperature contains more dissolved solute than it would contain at a lower temperature, when the solution is cooled, it can become supersaturated.

Hotpack / Coldpack

Solubility vs. Temperature

Timberlake, Chemistry 7th Edition, page 297

KI

NaNO 3

KN

O 3

Na 3PO 4

NaCl

Temperature (oC)

Sol

ubili

ty (

g so

lute

/ 10

0 g

H2O

)200

180

160

140

120

100

80

60

40

20

020 40 60 80 100

Gas SolubilityCH4

O2

CO

He

Temperature (oC)

Sol

ubili

ty (

mM

)

2.0

1.0

0 10 20 30 40 50

Higher Temperature

…Gas is LESS Soluble

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

– Solubility is expressed as (g/L) or (g/g) or (mol/L).

varies with temperature

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

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 linesaturated: solution has “just right” amt. of solute; onon linesupersaturated: solution has “too much” solute dissolved in it; above the line

To

Sol.

To

Sol.

Solids dissolved in liquids Gases dissolved in liquids

As To , solubility As To , solubility

per100 gH2O

Classify as unsaturated, saturated, or supersaturated.

80 g NaNO3 @ 30oC

45 g KCl @ 60oC

50 g NH3 @ 10oC

70 g NH4Cl @ 70oC

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

unsaturated

saturated

unsaturated

supersaturated

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.