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Solutions Goals
a. Describe solutions in terms of
• solute/solvent
• conductivity
• concentration
b. Explain factors affecting the rate a
solute dissolves in a specific solvent.
c. Explain that solubility is related to
temperature by constructing and reading a
solubility curve.
A solution is made up of two
parts—a solute and a solvent.
A solute is the substance being
dissolved, while a solvent is the
substance doing the dissolving.
For example, in a saltwater
solution, salt is the solute and water
is the solvent.
The ability of a substance to
dissolve in another substance is
called solubility.
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Effects of Adding a Solute to a Solvent
Freezing point
depression
Adding a solute
interferes with the
formation of the solid
making it harder for the
solvent to freeze.
Ex: Antifreeze
(ethylene glycol).
Raising of the boiling
point
Solute particles
interfere with the
evaporation process and
more energy is needed
for the molecules to
escape into the gas
phase.
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Solutions and Conductivity
•Solutions can only conduct
electricity if the atoms ionize
(break apart into ions)
•Solutions that conduct
electricity are called
electrolytes.
•Solutions that do not
conduct electricity are called
nonelectrolytes.
•They do not produce ions
in solution.
Strong vs.
Weak
Electrolytes
Strong: Ionize
completely.
NaCl
Weak:
Produce few
ions in
solution.
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Factors affecting the rate a solute dissolves in a
specific solvent.
What Affects the rate at which a solute will dissolve in a
solvent?
1.Crystal Size
2.Temperature
3.For Gases:
Pressure
above the
solvent
Increased surface area increases
the rate of dissolving. Remember:
dissolving occurs at the surface.
Increases the speed of the
molecules in the solvent.
More atmospheric pressure
pushing down on the solvent
makes it harder for the gas
molecules to escape the solvent.
Dissolving Website
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Factors affecting the rate a solute dissolves in a
specific solvent.
Polar
Molecular
Structure
Polar
solutes
dissolve
in Polar
solvents
EX: Water
and HCl
Nonpolar
Nonpolar
solutes
dissolve in
Nonpolar
solvents
“Like
dissolves
like”
EX: Gas
and Oil
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Concentration
Concentrated
Dilute
A lot of solute in
a little solvent
A little solute in a
lot of solvent
NOT VERY Precise!
To be more precise we need to express the concentration by
volume. Usually as a percentage by volume.
In order to compare concentrations, we express the amount
dissolved in 100g of water.
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Solubility Curves
•As the temperature
increases...
•The amount of oxygen
that is able to dissolve in
water…
•decreases.
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Unsaturated
Can dissolve
more solute
at a given
temperature
Saturated
Contains all
of the
solute it can
hold/
dissolve at
a certain
temperature
Supersaturated
Contains more
solute that a
saturated
solution at a
given
temperature.
Can be created
by cooling a
saturated
solution without
disturbing itno solute come
out of solution.
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Solubility Curves
1.30g of KNO3 @
120˚C?
2.50g of NaCl @
20˚C?
3.56g of NaCl @
20˚C?
4.120g of KNO3 @
20˚C?
5.How would you
make a saturated
sol. of KNO3 at
80˚C?
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