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Concentration of Solutions
Qualitatively: dilute vs. concentrated.
Qualitatively: dilute vs. concentrated.
Quantitatively:
1. Mass percent and parts per million:
mass of component
Mass % of component  x 100
total mass of solution
mass of component
parts per million  ppm  x 106
total mass of solution
Qualitatively: dilute vs. concentrated.
Quantitatively:
1. Mass percent and parts per million:
mass of component
Mass % of component  x 100
total mass of solution
mass of component
parts per million  ppm  x 106
total mass of solution
Example: 1g glucose per 100 kg solution
1g
[C6H12O6 ]  x 100  0.001 %
100,000 g
1g
[C 6H12O 6 ]  x 10 6  10 ppm
100,000 g
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Qualitatively: dilute vs. concentrated.
Quantitatively:
1. Mass percent and parts per million:
mass of component
Mass % of component  x 100
total mass of solution
mass of component
parts per million  ppm  x 10 6
total mass of solution
mass of component
parts per billion  ppb  x 10 9
total mass of solution
Example: EPA standard for arsenic (As) in drinking water = 0.010 ppm = 10 ppb
Concentration of Solutions
Qualitatively: dilute vs. concentrated.
Quantitatively:
2. Mole fraction:
moles of component
Mole fraction of component   
total moles of all components
Example: 1 mole glucose dissolved in 10 moles water
1 mol
 C6H12O6   0.09
1 mol  10 mol
Concentration of Solutions
Qualitatively: dilute vs. concentrated.
Quantitatively:
3. Molarity:
moles of solute
Molarity 
volume of solution (in liters)
Example: 2.0 moles glucose dissolved in enough water to make 15 liters of solution
2.0 mol
[C6H12O6 ]   0.13 M
15 L
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Concentration of Solutions
Qualitatively: dilute vs. concentrated.
Quantitatively:
4. Molality: moles of solute
Molality 
mass of solvent (in kg)
Example: 3.0 moles glucose dissolved in 12 kg of water
3.0 mol
[C6H12O6 ]   0.25 m
12 kg
Solubility Fig. 13.9
Dynamic equilibrium:
Dissolve
solute + solvent solution
Crystallize
Saturated solution: contains maximum amount of solute
that will dissolve in solution.
Solubility: conc. of solute in a saturated solution.
NaCl(s) Na+(aq) + Cl-(aq)
Unsaturated solution: contains less than
maximum amount of solute that will dissolve in
the solvent.
Types of Solutions
• Supersaturated
– In supersaturated solutions, the solvent holds
more solute than is normally possible at that
temperature.
– These solutions are unstable; crystallization can
usually be stimulated by adding a “seed crystal” or
scratching the side of the flask.
© 2009, Prentice-Hall, Inc.
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Factors Affecting Solubility
1. Structural Factors: Like Dissolves Like
Hexanol
Butanol
Ethanol
Factors Affecting Solubility
1. Structural Factors: Like Dissolves Like
hexane
H H H H H H
Are hexane and water
miscible? H C C C
C C C H
H H H H H H
water
-
- O -
H H
Factors Affecting Solubility
1. Structural Factors: Like Dissolves Like
immiscible hexane
H H H H H H
H C C C
C C C H
H H H H H H
hexane water
-
water
- O -
H H
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Factors Affecting Solubility
1. Structural Factors: Like Dissolves Like
C N O F Ne
Ar
Kr
Glucose (which has
hydrogen bonding)
is very soluble in
water, while
cyclohexane (which
only has dispersion
forces) is not.
© 2009, Prentice-Hall, Inc.
Factors Affecting Solubility
1. Structural Factors: Like Dissolves Like
Strong intermolecular
interactions between High solubility
solute and solvent
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Factors Affecting Solubility
2. Pressure Effects:
A) Does external pressure influence solubility of gas in liquid?
Factors Affecting Solubility
2. Pressure Effects:
A) Does external pressure influence solubility of gas in liquid?
Carbonated drinks:
k(CO2) = 3 x 10-2 mol L-1 atm-1
P(CO2) during bottling = 3-5 atm
S(CO2) = 0.1 – 0.2 M equal rates
Dynamic
equilibrium
P(CO2) ambient = 3 x 10-4 atm
S(CO2) ambient = 1 x 10-5 M
Henry’s Law:
Sg = kPg
Sg = solubility of gas in solution
k = Henry’s Law Constant
Pg = partial pressure of gas above solution Fig. 13.14
Factors Affecting Solubility
2. Pressure Effects:
A) Does external pressure influence solubility of gas in liquid?
B) Does external pressure influence
solubility of solid in liquid?
C) Does external pressure influence
solubility of liquid in liquid?
Fig. 13.14
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Factors Affecting Solubility
3. Temperature Effects: Solubility of gases in water
Hsoln < 0
Fig. 13.18
Factors Affecting Solubility
3. Temperature Effects: Solubility of salts in water
Hsoln varies
Fig. 13.17
Colligative properties: depend on the number of solute particles, not the nature of the
particles.
Among colligative properties are
Vapor pressure lowering
Boiling point elevation
Melting point depression
Osmotic pressure
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Colligative Properties: Vapor Pressure
Vapor pressure: pressure exerted by a liquid’s vapor when the liquid and vapor are in
dynamic equilbrium.
Fig. 11.22
Colligative Properties: Vapor Pressure
Which is greater?
A B
Vapor pressure A or Vapor pressure B?
Raoult’s Law:
Psoln = solventP°solvent
Pure liquid Solution with
Psoln = vapor pressure of solution nonvolatile solute
solvent = mole fraction of solvent
P°solvent = vapor pressure of pure solvent
Colligative Properties: Vapor Pressure
-
+ O +
Solution with two volatile liquids H H
- O
Raoult’s Law: Acetone
+C
Ptotal = PA + PB = AP°A + BP°B H 3C CH3
Hsolution < 0
Ideal solution Nonideal solution Ideal or non-ideal?
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Colligative Properties: Vapor Pressure
Benzene Toluene
H
Solution with two volatile liquids H
H
C
H
H C H H C H
Raoult’s Law: C C C C
C C C C
Ptotal = PA + PB = AP°A + BP°B
H C H H C H
H H
Hsolution ~ 0
Ideal solution Nonideal solution Ideal or non-ideal?
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