AP Chemistry
Unit 10 – Aqueous Solutions: Properties & Reactions
This unit focuses on aqueous solutions: properties and reactions. It addresses Topic II (States of
Matter) in the College Board's Advanced Placement Chemistry Topic Outline. In particular it
focuses on Solutions.
Lesson 1 – Behavior of Solutions
This lesson will explore the various kinds of solutions, the solution process, and the meaning of
solubility.
Objectives
Define the term "solution."
Identify a mixture as a gaseous, liquid, or solid solution.
Describe the steps in the formation of a solution.
Explain the molecular basis for the heat of solution as a solute is added to water.
Define the term "solubility."
Describe several factors that influence solubility.
Define the term "saturated solution."
Lesson 2 – Chemical and Physical Properties of Solutions
This lesson starts by exploring a number of colligative properties: the properties of a solution
that depend on the number, but not the identity, of the solute particles. We'll look at four
colligative properties in detail: vapor pressure lowering, boiling point elevation, freezing point
depression, and osmotic pressure. Once we understand the molecular basis of each of these
properties, we'll be able to determine the properties of the solute, such as its molar mass and the
number of particles into which it dissociates in solution.
Objectives
Define the term "colligative property."
Explain the molecular basis for vapor pressure lowering.
State Raoult's law and identify the terms it contains.
Calculate the vapor pressure of a solution using Raoult's law.
Determine the van't Hoff factor for any solute.
Explain the molecular basis of boiling point elevation.
Calculate the change in boiling point of a solution.
Explain the molecular basis of freezing point depression.
Calculate the change in freezing point of a solution.
Define the term "osmosis."
Describe the function of a semipermeable membrane.
Explain the molecular basis of osmotic pressure.
Use boiling point elevation, freezing point depression, or osmotic pressure to calculate the molar
mass of a solute.
Identify an unknown solute from its empirical formula and its molar mass as determined from its
colligative properties.
Define the term "colligative properties".
Lesson 1 – Tutorial: Formation of Solutions
Question 1
Liquid methyl alcohol, which has polar molecules, will dissolve:
A. only solutes that are other polar liquids.
B. only solutes that are other liquids.
C. polar solutes.
D. only solutes that are other alcohols.
E. nonpolar solutes.
Question 2
The reason that nonpolar oil will not dissolve in polar water is that the attractive forces
between:
A. the oil molecules and the water molecules are weaker than the attractive forces between the
oil molecules alone.
B. the oil molecules are stronger than those between the water molecules.
C. the water molecules are weaker than the attractive forces between the water molecules and
the oil molecules.
D. the oil molecules and the water molecules are weaker than those between the water
molecules alone.
E. the oil molecules are ionic and the attractive forces between the water molecules are covalent.
Question 3
Solutions are classified by:
A. the phases of the solute and solvent.
B. whether they are colored or transparent.
C. whether they are exothermic or endothermic.
D. whether there is more solvent or more solute.
E. the rate of at which the solute dissolves.
Question 4
Which of the following lists the molecular steps of the formation of a solution?
A.
1. pour
2. mix
3.let stand
B.
1. expand the solute
2. overcome the intermolecular forces of the solvent
3. interaction of the solute and the solvent
C.
1. heat the solute
2. heat the solvent
3. mix
4. let cool
D.
1. overcome the forces of attraction between the solute and solvent
2. adjust the temperature to the proper level
3.add crystals
E.
1. compact the solute
2. condense the solvent
3. separate the particles by type
Question 5
Separating the solute particles from each other is always endothermic because:
A. it is a very slow process.
B. the solute particles are at a higher energy than the solvent particles.
C. it only occurs at high temperatures.
D. solutes are endothermic while solvents are exothermic.
E. it requires an input of energy to overcome the attractive forces that hold the solute particles
together.
Question 6
When water molecules surround solute particles, it is called___________. In order for a
solute to dissolve, this process must be ________.
A. heat of solution; endothermic
B. heat of hydration; exothermic
C. hydrogenation; highly energetic
D. heat of hydrogenation; exothermic
E. solution formation; endothermic
Question 7
The heat of solution, or DHsolution, affects solution formation in which of the following
ways?
A. If the heat of solution is positive, the reaction is enothermic and the solution gets warmer.
B. If the heat of solution is negative, the reaction is endothermic and the solution gets cooler.
C. If the heat of solution is positive, the reaction is endothermic and the solution gets cooler.
D. If the heat of solution is negative, the reaction is exothermic and the solution gets cooler.
E. If the heat of solution is positive, the reaction is exothermic and the solution gets warmer.
Question 8
Saturation refers to the amount of solute dissolved in a solvent. Which of the following
properly indicates the degree of saturation?
A. When there is more solute than solvent, it is a saturated solution.
B. If there is excess solute at the bottom of he beaker, then the solution is unsaturated.
C. If there is excess solute at the bottom of the beaker, then the solution is supersaturated.
D. A solution becomes more saturated the more it is mixed.
E. When the maximum amount of solute has been dissolved, the solution is saturated.
Question 9
The vast majority of solutions encountered in the chemistry laboratory use liquid solvents.
What is the effect of temperature on the solubility of liquid solutions?
A. All liquid solutions increase in solubility with increased temperature.
B. A solution with an endothermic heat of solution will increase in solubility with increased
temperature.
C. A solution with an exothermic heat of solution will increase in solubility with increased
temperature.
D. The change in solubility due to temperature depends solely on the phase of the solute.
E. All liquid solutions decrease in solubility with increased temperature.
Question 10
Which of the following best describes Henry's law, Sgas = kH • Pgas?
A. The solubility of solid and liquid solutes will decrease with an increase in pressure.
B. An increase in pressure will increase the temperature of the solution.
C. Henry's law constant is directly proportional to the partial pressure of the gas.
D. The solubility of a gaseous solute is directly proportional to the partial pressure of the gas.
E. All gases are more soluble at lower temperatures.
Lesson 2 – Tutorial: Colligative Properties
Question 1
Vapor pressure lowering, boiling point elevation, and freezing point depression are colligative
properties, which means they:
A. are unique to solutions.
B. are impossible to calculate.
C. are determined by the type of particle dissolved.
D. are dependent on the number of particles dissolved.
E. only refer to ionic solids dissolved in polar solvents.
Question 2
How is the vapor pressure of a solution affected by an increase in the amount of dissolved
solute?
A. The extent of evaporation will increase.
B. The pressure of the liquid will increase.
C. It depends on the type of crystals in solution.
D. The vapor pressure will increase.
E. The vapor pressure will decrease.
Question 3
When a solute is dissolved in a solvent, the vapor pressure of the solution is lower than the
vapor pressure of the pure solvent because of which of the following?
I. The solute particles have more pressure than the solvent.
II. The solute particles interfere with the ability of the solvent particles to escape to the vapor
state.
III. The solvent particles move more slowly when solute is added.
IV. The solute particles take up some of the area on the surface of the liquid.
A. I only
B. I and III only
C. II and IV only
D. I, II, and IV only
E. II, III, and IV only
Question 4
In the lab, you make a solution containing 0.1 moles of glucose and 1.9 moles of water. The
vapor pressure of pure water is 100.0 torr. What is the vapor pressure of this glucose solution?
A. 5.0 torr
B. 5.3 torr
C. 95.0 torr
D. 105.3 torr
E. 190.0 torr
Question 5
How is the boiling point of a liquid related to its vapor pressure?
A. The boiling point is the temperature at which the vapor pressure of the liquid is equal to the
atmospheric pressure.
B. The boiling point is the temperature at which the solution's vapor pressure is equal to the
vapor pressure of the pure solvent.
C. The boiling point is the temperature at which vapor bubbles first appear in the liquid.
D. The boiling point is the temperature at which vapor bubbles are moving rapidly to the
surface.
E. The boiling point is the temperature at which the vapor pressure of the liquid is equal to the
temperature of the room.
Question 6
When a solute is added to a solvent, which of the following statements is (are) true?
I. The boiling point increases.
II. The freezing point increases.
III. The vapor pressure decreases.
IV. Osmosis occurs.
A. I only
B. I and II only
C. I and III only
D. I, II, and III only
E. I, III, and IV only
Question 7
Why is the van't Hoff factor included in the equations for boiling point elevation, freezing
point depression, and osmotic pressure?
A. Ionic solutes, such as salts, dissociate into individual ions.
B. Ionic solutes, such as salts, are composed of metals and nonmetals in the same compound.
C. The van't Hoff factor is used to determine the direction of the temperature or pressure change.
D. Only certain compounds have values for the van't Hoff factor.
E. The van't Hoff factor is used for converting Kelvin to Celsius.
Question 8
Sulfuric acid, H2SO4, dissociates into three particles in solution. The molal boiling point
constant for water is 0.51°C/m. What is the boiling point of a 0.67 molal solution of sulfuric
acid?
A. 98.97°C
B. 99.66°C
C. 100.34°C
D. 101.03°C
E. 103.94°C
Question 9
Osmotic pressure is a particularly useful colligative property for characterizing solutions and
determining molar masses because:
A. it depends only on the number of particles dissolved in a solution.
B. a small amount of dissolved solute produces a large change in osmotic pressure.
C. it can be calculated in the laboratory.
D. there is a direct relationship between the amount of dissolved solute and the change in
osmotic pressure.
E. the other colligative properties cannot be used to determine the molar mass of a compound.
Question 10
Which of the following applies to osmotic pressure?
I.  = iMRT
II. It is the amount of applied pressure needed to prevent a flow of solvent between two
solutions.
III. It's the difference in solute concentrations across a semipermeable membrane.
IV. Only the number of particles in the solution is important.
A. I and IV only
B. II and III only
C. I, III, and IV only
D. II, III, and IV only
E. I, II, III, and IV