chapter 11 properties of solutions ap*. ap learning objectives lo 1.16 the student can design...

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”)


Copyright © Cengage Learning. All rights reserved 5

Various Types of Solutions



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



Molarity

moles of soluteMolarity ( ) =

liters of solution M



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!



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!



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!



Mass Percent

mass of soluteMass (weight) percent = 100%

mass of solution



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!



Mole Fraction

AA

molesMole fraction ( ) =

total moles of solution



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!



Molality

moles of soluteMolality ( ) =

kilogram of solvent m



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?”)


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.



Steps in the Dissolving Process



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.



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).



Enthalpy (Heat) of Solution



Explain why water and oil (a long chain hydrocarbon) do not mix. In your explanation, be sure to address how ΔH plays a role.


CONCEPT CHECK!CONCEPT CHECK!


The Energy Terms for Various Types of Solutes and Solvents


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


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”.


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.


Structure Effects: Polarity

Pressure Effects: Henry’s law

Temperature Effects: Affecting aqueous solutions



Structure Effects

Hydrophobic (water fearing) Non-polar substances

Hydrophilic (water loving) Polar substances



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.



A Gaseous Solute



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.



The Solubilities of Several Solids as a Function of Temperature



The Solubilities of Several Gases in Water


chapter 11 properties of solutions ap*. ap learning objectives lo 1.16 the student can design...

Documents

solution composition

sugar solution

molarity slide

representations of solutions

brass slide

properties of solutions

intermolecular interactions

interactions of ions