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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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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
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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