### Solubility - Westmount High School

```Solubility
Today’s class:
Solubility
Saturation
Separation of
mixtures
unsaturated solution
saturated solution
remaining
undissolved solute
precipitate
Practice solubility / saturated solution
Solubility:
Maximum concentration
amount of solute
of athat
solute
canthat
be can
be
dissolved
attained
in in
a given
given amount
solvent. of solvent.
Saturated
Solution:
Contains maximum amount of solute that can
be dissolved.
Unsaturated More solute can be dissolved in the solution.
Solution:
Supersaturated
Solution:
An extra amount of solute was
dissolved; solution “wants” to
precipitate some solute
2.65 g of a solute is dissolved in 70.0 mL of
water to produce a saturated solution at 20 oC.
Calculate the solubility in units of g/100 mL; g/L.
1.) in g/100ml = % m/v
m = 2.65 g
v = 70 ml
g/100ml = ?
100 mL
100 mL
The solubility is 3.79 g /100 mL
=
msolute
vsolution
=
2.65 g
70 ml
=
2.65 g 100 mL
70 ml
=
3.79 g
2.65 g of a solute is dissolved in 70.0 mL of
water to produce a saturated solution at 20 oC.
Calculate the solubility in units of g/100 mL; g/L.
2.) in g/L
m = 2.65 g
v = 70 mL
= 0.07 L
c = ? g/L
The solubility is 37.9 g /L
c =
msolute
vsolution
c =
2.65 g = 37.9 g/L
0.07 L
Example 2
4.5 g is the maximum amount of a solute that
can be dissolved in 200 mL of water at 20 oC.
Calculate the solubility in units of g/100 mL; g/L.
Effect of temperature on solubility
• How to make a supersaturated solution
For most
:
The warmer the water the
salt dissolves
1.) make a saturated solution at high temperature
2.) let hot, saturated solution cool
 supersaturated
3.) eventually excess solute will
PRECIPATE (form new
crystals)
solubility
(g/100 ml of water)
 For most solids
solubility increases
with temperature
Temperature °C
Solubility of gases and temperature
Air bubbles
forming, before
the water starts
to boil
The warmer the water the
can be dissolved
Oxygen / CO2
Solubility of most gases
decreases with temperature
 When oceans warm up,
less CO2 can be dissolved –
CO2 is released
Solubility and solvent
?
salt
• salt is soluble in water
• salt is not soluble in oil
Solubility of a substance depends on the nature of the solvent
• Substances that are soluble in water are called
hydrophilic
• Substances that are soluble in oil are called
lipophilic
• Soap has a hydrophilic and a lipophilic part
and can help oily substances dissolve in water.
Solubility
Saturation
Separation of
mixtures
Separating mixtures
their pure form in nature but need to
be isolated from a mixture.
Separating solid and liquid
- a difference in state of matter
• Filtration
A difference in density I
Example:
• Decantation
Pouring water off rice /
pasta (without using a
strainer).
oil
water
A difference in density II
• Centrifugation
Accelerates and improves
sorting by density
 dense material collects
at the bottom
Example:
Centrifugation of blood
samples
A difference in speed of travel
• Chromatography
• Mixture is separated into
its components using
paper and a solvent.
• The different components
of the mixture are
transported by the solvent
along the paper, but with
different speeds.
Isolating a solute - evaporation
The liquid solvent is
evaporated, leaving
behind the solid solvent
Example:
Harvesting of sea
salt form the ocean.
A difference in boiling point
• Distillation
Example:
Distilling wine to
make brandy.
Notes on separating mixtures
Homework
• Solubility: work book p. 8 # 4, 5
p. 10 # 9
• Separating mixtures p. 12
```