Transcript 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
Most substances are not found in
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