Chapter 11
Properties of Solutions
AP*
AP Learning Objectives
LO 1.16 The student can design and/or interpret the results of an experiment regarding the absorption of light to determine the concentration of an absorbing species in a solution. (Sec 11.1)
LO 2.8 The student can draw and/or interpret representations of solutions that show the interactions between the solute and solvent. (Sec 11.1)
LO 2.9 The student is able to create or interpret representations that link the concept of molarity with particle views of solutions. (Sec 11.2)
LO 2.14 The student is able to apply Coulomb’s Law qualitatively (including using representations) to describe the interactions of ions, and the attractions between ions and solvents to explain the factors that contribute to the solubility of ionic compounds. (Sec 11.2)
LO 2.15 The student is able to explain observations regarding the solubility of ionic solids and molecules in water and other solvents on the basis of particle views that include intermolecular interactions and entropic effects. (Sec 11.2-11.3)
AP Learning Objectives
LO 5.10 The student can support the claim about whether a process is a chemical or physical change (or may be classified as both) based on whether the process involves changes in intramolecular versus intermolecular interactions. (Sec 11.2)
LO 6.24 The student can analyze the enthalpic and entropic changes associated with the dissolution of a salt, using particulate level interactions and representations. (Sec 11.2)
Section 11.1Solution Composition
AP Learning Objectives, Margin Notes and References Learning Objectives LO 1.16 The student can design and/or interpret the results of an experiment regarding the absorption of light to
determine the concentration of an absorbing species in a solution. LO 2.8 The student can draw and/or interpret representations of solutions that show the interactions between the
solute and solvent.
AP Margin Notes Spectral analysis is a common method for analyzing the composition of a solution. See Appendix 3 “Spectral
Analysis” for a discussion of the Beer-Lambert law.
Additional AP References LO 1.16 (see APEC #2, “The Percentage of Copper in Brass”)
Section 11.1Solution Composition
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Various Types of Solutions
Section 11.1Solution Composition
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Solution Composition
AA
moles of soluteMolarity ( ) =
liters of solution
mass of soluteMass (weight) percent = 100%
mass of solution
molesMole fraction ( ) =
total moles of solution
moles of soluteMolality ( ) =
kilogram of s
M
molvent
Section 11.1Solution Composition
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Molarity
moles of soluteMolarity ( ) =
liters of solution M
Section 11.1Solution Composition
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You have 1.00 mol of sugar in 125.0 mL of solution. Calculate the concentration in units of molarity.
8.00 M
EXERCISE!EXERCISE!
Section 11.1Solution Composition
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You have a 10.0 M sugar solution. What volume of this solution do you need to have 2.00 mol of sugar?
0.200 L
EXERCISE!EXERCISE!
Section 11.1Solution Composition
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Consider separate solutions of NaOH and KCl made by dissolving 100.0 g of each solute in 250.0 mL of solution. Calculate the concentration of each solution in units of molarity.
10.0 M NaOH 5.37 M KCl
EXERCISE!EXERCISE!
Section 11.1Solution Composition
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Mass Percent
mass of soluteMass (weight) percent = 100%
mass of solution
Section 11.1Solution Composition
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What is the percent-by-mass concentration of glucose in a solution made my dissolving 5.5 g of glucose in 78.2 g of water?
6.6%
EXERCISE!EXERCISE!
Section 11.1Solution Composition
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Mole Fraction
AA
molesMole fraction ( ) =
total moles of solution
Section 11.1Solution Composition
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A solution of phosphoric acid was made by dissolving 8.00 g of H3PO4 in 100.0 mL of water. Calculate the mole fraction of H3PO4. (Assume water has a density of 1.00 g/mL.)
0.0145
EXERCISE!EXERCISE!
Section 11.1Solution Composition
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Molality
moles of soluteMolality ( ) =
kilogram of solvent m
Section 11.1Solution Composition
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A solution of phosphoric acid was made by dissolving 8.00 g of H3PO4 in 100.0 mL of water. Calculate the molality of the solution. (Assume water has a density of 1.00 g/mL.)
0.816 m
EXERCISE!EXERCISE!
Section 11.2The Energies of Solution Formation
AP Learning Objectives, Margin Notes and References Learning Objectives LO 2.9 The student is able to create or interpret representations that link the concept of molarity with particle
views of solutions. LO 2.14 The student is able to apply Coulomb’s Law qualitatively (including using representations) to describe the
interactions of ions, and the attractions between ions and solvents to explain the factors that contribute to the solubility of ionic compounds.
LO 2.15 The student is able to explain observations regarding the solubility of ionic solids and molecules in water and other solvents on the basis of particle views that include intermolecular interactions and entropic effects.
LO 5.10 The student can support the claim about whether a process is a chemical or physical change (or may be classified as both) based on whether the process involves changes in intramolecular versus intermolecular interactions.
LO 6.24 The student can analyze the enthalpic and entropic changes associated with the dissolution of a salt, using particulate level interactions and representations.
Additional AP References LO 5.10 (see Appendix 7.6, “Distinguishing between Chemical and Physical Changes at the Molecular Level”) LO 6.24 (see Appendix 7.7, “Intermolecular Forces and Thermodynamics: Why Aren’t All Ionic Solids Soluble in
Water?”)
Section 11.2The Energies of Solution Formation
Formation of a Liquid Solution
1. Separating the solute into its individual components (expanding the solute).
2. Overcoming intermolecular forces in the solvent to make room for the solute (expanding the solvent).
3. Allowing the solute and solvent to interact to form the solution.
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Section 11.2The Energies of Solution Formation
Steps in the Dissolving Process
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Section 11.2The Energies of Solution Formation
Steps in the Dissolving Process
Steps 1 and 2 require energy, since forces must be overcome to expand the solute and solvent.
Step 3 usually releases energy. Steps 1 and 2 are endothermic, and step 3 is often
exothermic.
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Section 11.2The Energies of Solution Formation
Enthalpy (Heat) of Solution
Enthalpy change associated with the formation of the solution is the sum of the ΔH values for the steps:
ΔHsoln = ΔH1 + ΔH2 + ΔH3
ΔHsoln may have a positive sign (energy absorbed) or a negative sign (energy released).
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Section 11.2The Energies of Solution Formation
Enthalpy (Heat) of Solution
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Section 11.2The Energies of Solution Formation
Explain why water and oil (a long chain hydrocarbon) do not mix. In your explanation, be sure to address how ΔH plays a role.
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CONCEPT CHECK!CONCEPT CHECK!
Section 11.2The Energies of Solution Formation
The Energy Terms for Various Types of Solutes and Solvents
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ΔH1 ΔH2 ΔH3 ΔHsoln Outcome
Polar solute, polar solvent Large Large Large, negative Small Solution forms
Nonpolar solute, polar solvent Small Large Small Large, positive No solution forms
Nonpolar solute, nonpolar solvent
Small Small Small Small Solution forms
Polar solute, nonpolar solvent Large Small Small Large, positive No solution forms
Section 11.2The Energies of Solution Formation
In General
One factor that favors a process is an increase in probability of the state when the solute and solvent are mixed.
Processes that require large amounts of energy tend not to occur.
Overall, remember that “like dissolves like”.
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Section 11.3Factors Affecting Solubility
AP Learning Objectives, Margin Notes and References Learning Objectives LO 2.15 The student is able to explain observations regarding the solubility of ionic solids and molecules in water
and other solvents on the basis of particle views that include intermolecular interactions and entropic effects.
Section 11.3Factors Affecting Solubility
Structure Effects: Polarity
Pressure Effects: Henry’s law
Temperature Effects: Affecting aqueous solutions
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Section 11.3Factors Affecting Solubility
Structure Effects
Hydrophobic (water fearing) Non-polar substances
Hydrophilic (water loving) Polar substances
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Section 11.3Factors Affecting Solubility
Pressure Effects
Little effect on solubility of solids or liquids Henry’s law: C = kP
C = concentration of dissolved gask = constantP = partial pressure of gas solute
above the solution Amount of gas dissolved in a solution is directly proportional to
the pressure of the gas above the solution.
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Section 11.3Factors Affecting Solubility
A Gaseous Solute
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Section 11.3Factors Affecting Solubility
Temperature Effects (for Aqueous Solutions)
Although the solubility of most solids in water increases with temperature, the solubilities of some substances decrease with increasing temperature.
Predicting temperature dependence of solubility is very difficult.
Solubility of a gas in solvent typically decreases with increasing temperature.
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Section 11.3Factors Affecting Solubility
The Solubilities of Several Solids as a Function of Temperature
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Section 11.3Factors Affecting Solubility
The Solubilities of Several Gases in Water
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