SOLUTIONS
TYPES OF MIXTURES
•
Heterogeneous mixtures-mixtures that do not
blend smoothly-not uniform throughout-individual
substances remain distinct.
•
Two Types of Heterogeneous Mixtures are:
Suspensions
Colloids
SUSPENSIONS

Suspensions-heterogeneous mixture that settles upon
standing. Can be separated by filter paper.
COLLOIDS

Colloids-heterogeneous mixtures that appear cloudy,
cannot be separated by filtration, and demonstrate the
Tyndall effect.
TYNDALL EFFECT
TYPES OF MIXTURES (CONTINUED)
•
Homogeneous mixtures-mixtures that do blend
smoothly-uniform throughout-one set of properties.
•
Homogeneous mixtures are called solutions.
SOLUTIONS
•
Solutions consist of:
– Solute-part of the solution that gets
dissolved
– Solvent-part of the solutions that does the
dissolving
– Water is called the universal solvent.
TYPES OF SOLUTIONS
State of Solute
0%
Gas
1.
State of Solvent
Enter answer
Gas text...
Example
Air
Gas
Liquid
Soft drink
Liquid
Liquid
Antifreeze, vinegar
Liquid
Gas
Humidity
Liquid
Solid
Dental filling
Solid
Liquid
Ocean water
Solid
Solid
Bronze. Brass (alloys)
MUDDY WATER IS AN EXAMPLE OF A
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colloid
solution
suspension
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FOG IS AN EXAMPLE OF A
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0%
colloid
solution
suspension
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ITALIAN SALAD DRESSING IS AN
EXAMPLE OF A
0%
colloid
solution
suspension
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KOOL-AID IS AN EXAMPLE OF A
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colloid
solution
suspension
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PURE AIR IS AN EXAMPLE OF A
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colloid
solution
suspension
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SALT IS DISSOLVED IN WATER.
SALT IS THE
solute
solvent
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SUGAR IS DISSOLVED IN SWEET TEA.
THE TEA IS THE
solute
solvent
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OXYGEN GAS DISSOLVED IN LAKE
WATER IS AN EXAMPLE OF A
Liquid dissolved in a gas
Gas dissolved in a liquid
Gas dissolved in a solid
Solid dissolved in a gas
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CARBON DISSOLVED IN IRON TO
MAKE STEEL IS AN EXAMPLE OF A
Solid dissolved in a solid
Solid dissolved in a liquid
Solid dissolved in a gas
Liquid dissolved in a solid
Gas dissolved in a solid
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PROPERTIES OF SOLUTIONS
 A substance that dissolves
in a solvent is said to
be soluble.
 Two liquids that are soluble in each other are
said to be miscible.
 A substance that does not dissolve in a solvent
is said to be insoluble.
 Two liquids that are not soluble in each other
are said to be immiscible.
Insoluble Solids
Immiscible Liquids
“LIKE DISSOLVES LIKE”

Water is polar (due to
asymmetrical
arrangement of the
molecule).
 Polar substances
dissolve other polar
substances (or ionic
compounds).
WHICH OF THE FOLLOWING WILL
DISSOLVE IN WATER?
This one because it
is polar!
“LIKE DISSOLVES LIKE” (CONTINUED)
Nonpolar substances dissolve nonpolar substances.
 Polar substances cannot dissolve nonpolar substances.

Nonpolar iodine dissolves
in nonpolar hexane
Nonpolar iodine does NOT
dissolve in polar water
Nonpolar hexane and polar water
do not mix.
CORN OIL DOES NOT DISSOLVE IN
WATER. CORN OIL IS
Polar
nonpolar
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WHICH OF THE FOLLOWING IS
IMMISCIBLE IN WATER?
Food coloring
Vinegar
Gasoline
Lemon-aid
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WILL CALCIUM CHLORIDE (CACL2)
DISSOLVE IN WATER?
0%
Yes
No
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2.
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WHY? Calcium chloride is an ionic compound. In your notes it
states that water (polar) will dissolve other polar compounds OR
ionic compounds (which are extremely polar because of the large
electronegativity difference).
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REMEMBER HOW TO DRAW LEWIS STRUCTURES?
SYMMETRICAL STRUCTURES=NONPOLAR
ASYMMETRICAL STRUCTURE= POLAR
http://www.youtube.com/watch?v=aWNf9YTzaaA
Only watch this video clip from the beginning until the
4:00 minute mark. This should remind you how to use the
N-A=S method for drawing lewis structures.
DETERMINE WHICH COMPOUND WILL DISSOLVE BEST
IN WATER? DRAW A LEWIS STRUCTURE TO
DETERMINE POLARITY.
0%
1.
0%
2.
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Nitrogen trichloride
Methane (CH4)
WHY? Nitrogen trichloride (NCl3) is a polar compound. The lone
pair at the top of Nitrogen causes the structure to be asymmetrical.
Methane is a nonpolar compound. Nitrogen trichloride will dissolve
because water is also polar.
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DETERMINE WHICH COMPOUND WILL DISSOLVE BEST
IN METHANOL (CH3OH)? DRAW A LEWIS
STRUCTURE TO DETERMINE POLARITY.
0%
HCN
Carbon Dioxide
1.
2.
0%
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WHY? HCN is a polar compound. Carbon Dioxide is a nonpolar
compound. HCN will dissolve because methanol is also polar.
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FACTORS AFFECTING THE RATE OF
DISSOLVING
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Agitation-(stirring)-stirring or shaking increases
the rate at which solutes dissolve.
•
Surface area-breaking up a solid increases the
surface area and increases the rate at which
solids dissolve
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Temperature-as temperature increases, the rate
of dissolving of solid solutes increases.
SOLUBILITY
•
Solubility is defined as the amount
of solute that will dissolve in a given
amount of solvent at a particular
temperature
SOLUBILITY (CONT.)
•
Solutions that contain the maximum amount of
dissolved solute at a given temperature are said to
be saturated.
•
Solutions that contain less than the maximum
amount of solute are said to be unsaturated.
•
Solutions that contain more than the expected
maximum amount of solute are said to be
supersaturated (can be accomplished only through
heating and careful cooling of the solvent).
TEMPERATURE AND SOLUBILITY
 In warmer water, more solid will dissolve.

This is because a high temperature means
water molecules are moving faster which
keeps more solid molecules suspended.
 Conversely a gas will be less soluble at a higher
temperature.
 This is because when a gas molecules are
moving faster they are able to escape from
the liquid surface.
SOLUBILITY CURVES
 A solubility curve is a graph of the solubilities of
various substances as a function of
temperature.
 When
graphing the data for solubility,
temperature is the manipulated variable, and
mass of solute dissolved is the responding
variable.
INTERPRETING SOLUBILITY
CURVES

1. What is the maximum amount of NaNO3 that will
dissolve in 100 g of water at 10oC?

2. At what temperature will 70 g of NH4Cl dissolve in
100g of water?

3. Which substance has the greatest solubility at 0oC?

4. Which substance is the least soluble at 100oC?

5. 15 g of KClO3 is dissolved in 100 g of water at 50oC. Is
the solution saturated, unsaturated, or supersaturated?
CONCENTRATION OF SOLUTIONS
 Qualitative descriptions:


Concentrated solutions-large amount of solute
and small amount of solvent.
Dilute solutions-large amount of solvent and
small amount of solute.
 Quantitative descriptions:



Solubility-grams of solute/ml of solution
Molarity-moles of solute/L of solution
Molality-moles of solute/kg of solvent
MOLARITY
 A solution of NaCl has a molarity of 1 (1M). What does
this mean?
• 1 mole of NaCl is dissolved in enough water to make 1
L.
• 1 mole = 58 g NaCl
 A 1M solution of NaCl contains 58 g of NaCl dissolved in 1
liter of water.
• How much salt is dissolved in a 2M solution?
• 116 g
• How much salt is dissolved in a 6 M solution?
• 348 g
• Which is more concentrated?
MOLALITY
A solution of NaCl contains 58 g of NaCl dissolved in 1
liter of water. The density of water is 1.00g/mL. What is
the molality of the solution?
 1 liter = 1000 mL = 1000 g = 1 kg
 58 g = 1 mole
 Molality = 1 mole/1 kg = 1 m
 How much salt must be dissolved in 100 g of water in
order to make a 2.0 molal (m) solution?
 100 g = .1 kg
 2.0 = x/.1
 X = .2 moles x 58 g = 11.6 g
 Will molarity and molality for the same solution always
be equal? Explain.

COLLIGATIVE PROPERTIES
 Colligative properties are properties that
depend on the number (not the type) of solute
particles present in solution.
 Colligative properties include:
1) freezing point
2) boiling point
3) vapor pressure
FREEZING POINT DEPRESSION
 The freezing point of a solution is
lower than the
freezing point of the pure solvent.

Example: Saltwater freezes at a lower temperature
than pure water (below zero degrees Celsius).
 The greater the number of ions in the solution, the
lower the freezing point.

Example:
NaCl consists of two ions; Na+ and Cl-
CaCl2 consists of three ions; Ca2+ , Cl- , and ClWhich has the lower freezing point?
CaCl2
BOILING POINT ELEVATION
 The boiling point of a solution is
higher than the
boiling point of the pure solvent.
 Example: Saltwater boils at a higher
temperature than pure water (at a temperature
above 100 degrees Celsius).
 The greater the number of ions in the solution, the
higher the boiling point.
 Which boils at a higher temperature; a solution
of NaCl or a solution of CaCl2

CaCl2
VAPOR PRESSURE LOWERING
 Vapor pressure is the pressure exerted by the
vapor particles on the surface of a liquid.
 The vapor pressure of a solution is lower than the
vapor pressure of the pure solvent.
 Due to the presence of solute particles, fewer
solvent particles are able to escape from the
surface of the liquid resulting in a lower
pressure.
 If the vapor pressure is lower, the boiling point
will be higher.
WHICH OF THE FOLLOWING IS NOT
A COLLIGATIVE PROPERTY?
10
Boiling point
2. Density
3.
Freezing point
4.
Vapor pressure
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THE FREEZING POINT OF A SOLVENT WILL
____ WHEN A SOLUTE IS ADDED.
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go up
go down
remain the same
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THE BOILING POINT OF A SOLVENT
WILL ____ WHEN A SOLUTE IS ADDED.
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go up
go down
remain the same
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WHICH
OF THE FOLLOWING SOLUTES WILL RESULT
IN A SOLUTION HAVING THE HIGHEST BOILING
POINT?
10
NaCl
CaCl2
AlCl3
C12H22O11
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IF
COST WAS NOT AN ISSUE, WHICH OF THE
FOLLOWING SALTS WOULD BE THE MOST
EFFECTIVE ROAD DEICER?
NaCl
CaCl2
AlCl3
All would be equally effective
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WHICH SOLUTION WOULD HAVE THE
LOWEST FREEZING POINT?
1 M AlCl3
2 M NaCl
3 M CaCl2
4 M C6H12O6
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PROBLEMS INVOLVING COLLIGATIVE PROPERTIES

The equation used to determine the Freezing Point
Depression and Boiling Point Elevation is:
∆T =i Kfm
where:
∆T represents temperature change
Kf is the freezing point depression constant (this value is specific to
each solvent)
m represents molality
i represents the number of ions making up the solute.

Note:
molality = moles of solute/kg of solvent
The same equation is used to determine the boiling point
elevation however, Kb is substituted for Kf.
PRACTICE PROBLEM

Sodium chloride is often used to prevent icy roads and
to freeze ice cream. What is the freezing point of a
0.029 m aqueous solution of sodium chloride?
Molality = 0.029
 Kf for water = 1.86
 i=2
 ∆T =i Kfm
 ∆T = 2 (1.86) 0.029
 ∆T = .11
 0 -.11 = -.11oC

PRACTICE PROBLEM #2

A lab technician determines that the boiling point of an
aqueous solution of a calcium chloride solution (CaCl2)
is 101.12oC. What is the solution’s molality?
∆T = 101.12 – 100 = 1.12
 Kb for water = .512
 i = 3 for CaCl2
 ∆T =i Kbm
 1.12 = 3 (0.512) x
 X=0.729 moles/kg of solvent

DILUTING MOLAR SOLUTIONS
You can prepare a less concentrated solution from a
more concentrated solution by diluting the solution
(increase the solvent particles)
 The following equation can be used:
 M1V1 = M2V2 where:
 M1 and V1 represent the molarity and volume of the
concentrated solutions
 M2 and V2 represent the molarity and volume of the
diluted solutions.

PRACTICE PROBLEM
How many milliliters of a 5.0 M H2SO4 solution would
you need to prepare 100 mL of a 0.25 M H2SO4
solution?
 M1V1 = M2V2
 M1 = 5.0 M
 V1 = x
 M2 = 0.25 M
 V2=100 mL
 M1V1 = M2V2
 5(x) = 0.25 (100)
 X = 5 mL
