Princeton 2012/Barron 4th ed.
AP Practice Problems
Unit 9 – Solutions
Multiple Choice (no calculator)
For questions 1-3, one or more of the
following responses will apply; each
response may be used more than once or not
at all in these questions.
A.
B.
C.
D.
E.
a.
b.
c.
d.
e.
Molarity (M)
Molality (m)
Density
pH
pOH
1. Has the units moles/kg. (P9.1)
2. Can have the units grams/liter. (P9.3)
3. Has the units moles per liter (P9.4)
4. Which of the following is (are)
colligative properties? (P9.5)
I.
II.
III.
a.
b.
c.
d.
e.
5. Which of the following aqueous
solutions has the highest boiling
point? (P9.6)
Freezing-point
depression
Vapor pressure
lowering
Boiling-point
elevation
I only
I and II only
I and III only
II and III only
I, II, and III
0.5m NaCl
0.5m KBr
0.5m CaCl2
0.5m C6H12O6
0.5m NaNO3
6. When sodium chloride is added to a
saturated solution of silver chloride,
which of the following precipitates
would be expected to appear? (P9.7)
a.
b.
c.
d.
e.
Sodium
Silver
Chlorine
Sodium chloride
Silver chloride
7. A substance is dissolved in water,
forming a 0.50-molar solution. If 4.0
liters of solution contains 240 grams
of the substance, what is the
molecular mass of the substance?
(P9.8)
a.
b.
c.
d.
e.
60 grams/mole
120 grams/mole
240 grams/mole
480 grams/mole
640 grams/mole
Princeton 2012/Barron 4th ed.
8. When 31.0 grams of a nonionic
substance is dissolved in 2.00 kg of
water, the observed freezing-point
depression of the solution is 0.93°C.
If kf for water is 1.86°C/m, which of
the following expressions is equal to
the molar mass of the substance?
(P9.11)
a.
g/mol
b.
g/mol
c.
g/mol
d.
g/mol
e. (31.0)(0.93)(1.86)(2.00)
g/mol
9. What is the boiling point of a 2 m
solution of NaCl in water? (The
boiling point elevation constant, kb,
for water is 0.5°C/m.) (P9.12)
a.
b.
c.
d.
e.
100°C
101°C
102°C
103°C
104°C
10. When an aqueous solution of
potassium chloride is compared with
water, the salt solution will have
(P9.13)
a.
b.
c.
d.
e.
a higher boiling point, a lower
freezing point, and a lower vapor
pressure
a higher boiling point, a higher
freezing point, and a lower vapor
pressure
a higher boiling point, a higher
freezing point, and a higher vapor
pressure
a lower boiling point, a lower
freezing point, and a lower vapor
pressure
a lower boiling point, a higher
freezing point, and a higher vapor
pressure
11. If 46 grams of MgBr2 (molar mass
184 grams) are dissolved in water to
form 0.50 liters of solution, what is
the concentration of bromine ions in
the solution? (P9.14)
a.
b.
c.
d.
e.
0.25-molar
0.50-molar
1.0-molar
2.0-molar
4.0-molar
12. A solution contains equal masses of
glucose (molecular mass 180) and
toluene (molecular mass 90). What
is the mole fraction of glucose in the
solution? (P9.15)
a.
b.
c.
d.
e.
¼
1/3
½
2/3
¾
13. When benzene and toluene are
mixed together, they form an ideal
solution. If benzene has a higher
vapor pressure than toluene, then the
vapor pressure of a solution that
contains an equal number of moles
of benzene and toluene will be
(P9.16)
a. higher than the vapor
pressure of benzene
b. equal to the vapor pressure of
benzene
c. lower than the vapor pressure
of benzene and higher than
the vapor pressure of toluene
d. equal to the vapor pressure of
toluene
e. lower than the vapor pressure
of toluene
Princeton 2012/Barron 4th ed.
14. How many moles of Na2SO4 must be
added to 500 milliliters of water to
create a solution that has a 2-molar
concentration of the Na+ ion?
(Assume the volume of the solution
does not change). (P9.17)
a.
b.
c.
d.
e.
0.5 moles
1 mole
2 moles
4 moles
5 moles
15. Given that a solution of NaCl (molar
mass 58.5 g/mole) in water (molar
mass 18 g/mole) has a molality of
0.5m, which of the following can be
determined? (P9.18)
I.
II.
III.
a.
b.
c.
d.
e.
The mass of the NaCl
in the solution
The total mass of the
solution
The mole fraction of
the NaCl in the
solution
I only
III only
I and II only
II and III only
I, II, and III
16. How many liters of water must be
added to 4 liters of a 6-molar HNO3
solution to create a solution that is 2molar? (P9.19)
a.
b.
c.
d.
e.
2 liters
4 liters
6 liters
8 liters
12 liters
17. Which of the following expressions
is equal to the Ksp of Ag2CO3?
(P9.20)
a.
b.
c.
d.
e.
Ksp = [Ag+][CO3-2]
Ksp = [Ag+][CO3-2]2
Ksp = [Ag+]2[CO3-2]
Ksp = [Ag+]2 [CO3-2] 2
Ksp = [Ag+]2 [CO3-2] 3
18. If the solubility of BaF2 is equal to x,
which of the following expressions is
equal to the solubility product, Ksp,
for BaF2? (P9.21)
a.
b.
c.
d.
e.
x2
2x2
x3
2x3
4x3
19. A beaker contains 50.0 mL of a 0.20
M Na2SO4 solution. If 50.0 mL of a
0.10 M solution of Ba(NO3)2 is
added to the beaker, what will be the
final concentration of sulfate ions in
the solution? (P9.22)
a.
b.
c.
d.
e.
0.20 M
0.10 M
0.050 M
0.025 M
0.012 M
Princeton 2012/Barron 4th ed.
20. The bottler of a carbonated beverage
dissolves carbon dioxide in water by
placing carbon dioxide in contact
with water at a pressure of 1 atm at
room temperature. The best way to
increase the amount of dissolved
CO2 would be to (P9.24)
a. increase the temperature and
increase the pressure of CO2
b. decrease the temperature and
decrease the pressure of CO2
c. decrease the temperature and
increase the pressure of CO2
d. increase the temperature
without changing the
pressure of CO2
e. increase the pressure of CO2
without changing the
temperature
21. Copper II chloride will be LEAST
soluble in a 0.02-molar solution of
which of the following compounds?
(P9.27)
a.
b.
c.
d.
e.
NaCl
CuNO3
CaCl2
NaCO3
KI
For questions 22-25, one or more of the
following responses will apply. Each
response may be used more than once or not
at all in these questions.
I.
II.
III.
IV.
V.
Osmotic Pressure
Freezing-point Depression
Vapor Pressure
Raoult’s Law
Henry’s Law
22. Which of these best explains why a
soda bottle fizzes when opened?
(B9.1)
a.
b.
c.
d.
e.
I
II
III
IV
V
23. Which of these is the method of
choice to determine the molecular
mass of large biomolecules? (B9.2)
a.
b.
c.
d.
e.
I
II
III
IV
V
24. Which two items are most closely
related to each other? (B9.3)
a.
b.
c.
d.
e.
I and III
II and V
III and IV
IV and V
V and I
25. The extent of ion pairing in a
solution of an electrolyte can be best
estimated by using which of these?
(B9.4)
a.
b.
c.
d.
e.
I and III
II
III and V
IV
V
Princeton 2012/Barron 4th ed.
26. All of the following physical
properties change as solute is added
to the solution. Which is NOT a
colligative property? (B9.7)
a.
b.
c.
d.
e.
Boiling point
Surface tension
Vapor pressure
Melting point
Osmotic pressure
27. Which of the following is expected
to be the most soluble in hexane,
C6H14? (B9.8)
a.
b.
c.
d.
e.
KCl
C2H5OH
C6H6
H2O
HC2H3O2
28. Molarity units are most appropriate
in calculating which of the
following? (B9.9)
a.
b.
c.
d.
e.
Freezing-point depression
Vapor pressure
Boiling-point elevation
Surface tension
Osmotic pressure
29. All of the following may be used to
determine molar masses. Which one
requires an ideal solution for
accurate results? (B9.10)
a.
b.
c.
d.
e.
Freezing-point depression
Boiling-point elevation
Osmotic pressure
Vapor pressure
Gas density
30. To make a solution, 3.45 mol of
C6H13Cl and 1.26 mol of C5H12 are
mixed. Which of the following is
needed, but not readily available, to
calculate the molarity of this
solution? (B9.11)
a. The density of the solution
b. The densities of C6H13Cl and
C5H12
c. The temperature
d. The molar masses of C6H13Cl
and C5H12
e. The volumes of C6H13Cl and
C5H12
31. Ethyl alcohol, C2H5OH, and water
become noticeable warmer when
mixed. This is due to (B9.13)
a. The decrease in volume when
they are mixed
b. Smaller attractive forces in
the mixture than in the pure
liquids
c. The hydrogen bonding of the
two liquids
d. The change in vapor pressure
observed
e. Stronger attractive forces in
the mixture than in the pure
liquids
32. Which is the most appropriate
method for determining the molar
mass of a newly discovered enzyme?
(B9.14)
a.
b.
c.
d.
e.
Freezing-point depression
Osmotic pressure
Boiling-point depression
Gas density
Vapor pressure
Princeton 2012/Barron 4th ed.
33. When algae decay in a pond, the
process uses up the available oxygen.
Which of the following factors will
also contribute to a decrease in
oxygen in a pond? (B9.16)
a. Decreasing salinity (salt
concentration)
b. Increasing acidity due to acid
rain
c. Increasing temperature
d. Increasing surface tension of
the water
e. Increasing atmospheric
pressure
34. Which of the following compounds
is incorrectly classified? (B9.19)
a.
b.
c.
d.
NaF electrolyte
CH3OH weak electrolyte
Mg(C2H3O2)2 electrolyte
CH3CH2COOH weak
electrolyte
e. Glucose nonelectrolyte
35. If equal numbers of moles of each of
the following are dissolved in 1 kg of
distilled water, the one with the
lowest boiling point will be (B9.21)
a.
b.
c.
d.
e.
NaF
AlCl3
Mg(C2H3O2)2
CH3CH2COOH
Glucose
36. Which of the following changes as
temperature changes? (B6.2)
a.
b.
c.
d.
e.
Molarity
Mass percentage
Molar mass
Empirical formula
Molecular formula
Princeton 2012/Barron 4th ed.
Additional Multiple Choice – Calculator my be used
37. The solubility of cadmium chloride,
CdCl2 is 140 g per 100 mL of
solution. What is the molar
solubility (molarity) of a saturated
solution of CdCl2? (B9.5)
a.
b.
c.
d.
e.
0.765 M
1.31 M
7.65 M
12.61 M
0.131 M
38. The vapor pressure of an ideal
solution is 456 mmHg. If the vapor
pressure of the pure solvent is 832
mmHg, what is the mole fraction of
the nonvolatile solute? (B9.6)
f.
g.
h.
i.
j.
0.548
0.345
0.645
1.82
0.452
39. Which of the following, when added
to 1.00 kg H2O, is expected to give
the greatest increase in the boiling
point of water? (kb = 0.052°Cm-1)
(B9.12)
k.
l.
m.
n.
o.
1.25 mol sucrose
0.25 mol iron (III) nitrate
0.50 mol ammonium chloride
0.60 mol calcium sulfate
1.00 mol acetic acid
40. A polluted pond contains 25 ppb of
lead ions. What is the concentration
of lead ions in molarity units?
(B9.15)
a.
b.
c.
d.
e.
1.2×108 M
1.2×10-7 M
2.5×10-8 M
0.121 M
1.2×10-10 M
41. Liquid A has a vapor pressure of 437
mmHg, and liquid B has a vapor
pressure of 0.880 atm at 85°C.
Which of the following represents a
possible solution of the two liquids?
(B9.17)
a. A mixture with a vapor
pressure of 345 mmHg
b. A mixture with a vapor
pressure of 0.750 atm
c. A mixture with a boiling
point of 165°C
d. A mixture with a vapor
pressure of 1106 mmHg
e. A mixture with a boiling
point of 85°C
42. The freezing-point depression
constant for water is 1.86°Cm-1.
When 100 g of a compound is
dissolved in 500 g H2O, the freezing
point is -10°C. Of the five
possibilities below, which is the
identity of the compound? (B9.18)
a.
b.
c.
d.
e.
Mg(NO3)2
KCl
Na2SO4
HCOOH
HF
Princeton 2012/Barron 4th ed.
43. The kf and kb values for water are
1.86 and 0.52°Cm-1, respectively. A
solution boils at 107.5°C. At what
temperature does this solution
freeze? (B9.20)
a.
b.
c.
d.
e.
7.5°C
-7.5°C
0.0°C
-26.8°C
-284.5°C
44. The solubility of acetylene, CHCH,
in water at 30°C is 0.975gL-1 when
the pressure of acetylene is 1.00 atm.
What is the solubility, at the same
temperature, when the pressure of
acetylene above the water is reduced
to 0.212 atm? (B9.22)
a.
b.
c.
d.
e.
4.60 gL-1
0.207 gL-1
0.975 gL-1
0.212 gL-1
The answer cannot be
determined from the data
45. If 20.0g of ethanol (molar mass =
46) and 30.0g of water (molar mass
= 18) are mixed together, the mole
fraction of ethanol in this mixture is
(B9.24)
a.
b.
c.
d.
e.
0.207
0.261
0.739
0.793
4.83
46. What weight of KClO3 (molar mass
= 122.5) is needed to make 200 mL
of a 0.150 M solution of this salt?
(B6.5)
a.
b.
c.
d.
e.
2.73 g
3.68 g
27.3 g
164 g
3.69 g
47. How many milligrams of Na2SO4
(molar mass = 142) are needed to
prepare 100 mL of a solution that is
0.00100 M in Na+ ions? (B6.10)
a.
b.
c.
d.
e.
28.4
14,200
1.00
7.1
14.2
Princeton 2012/Barron 4th ed.
Essays
1. The molecular weight and formula of a hydrocarbon are to be determined through the use
of the freezing-point depression method. The hydrocarbon is known to be 86 percent
carbon and 14 percent hydrogen by mass. In the experiment, 3.72 grams of the unknown
hydrocarbon were placed into 50.0 grams of liquid benzene, C6H6. The freezing point of
the solution was measured to be 0.06°C. The normal freezing point of benzene is 5.50°C,
and the freezing-point depression constant for benzene is 5.12°C/m. (P9.1)
a. What is the molecular weight of the compound?
b. What is the molecular formula of the hydrocarbon?
c. What is the mole fraction of benzene in the solution?
d. If the density of the solution is 875 grams per liter, what is the molarity of the
solution?
2. Explain the following statements in terms of the chemical properties of the substances
involved. (P9.3)
a. A 1-molal aqueous solution of sodium chloride has a lower freezing point than a
1-molal aqueous solution of ethanol.
b. NaCl is a strong electrolyte, whereas PbCl2 is a weak electrolyte.
c. Propanol is soluble in water, but propane is not.
d. In a dilute aqueous solution, molarity and molality have the same value.
Princeton 2012/Barron 4th ed.
3. Answer the following questions according to the equation below. (P5.4)
2 Mg(s) + 2 CuSO4(aq) + H2O(l)  2 MgSO4(aq) + Cu2O(s) + H2(g)
a. If 1.46 grams of Mg(s) are added to 500mL of a 0.200 M solution of CuSO4, what
is the maximum molar yield of H2(g)?
b. When all of the limiting reagent has been consumed in (a), how many moles of
the other reactant (not water) remain?
c. What is the mass of the Cu2O produced in (a)?
d. What is the value of [Mg+2] in the solution at the end of the experiment? (Assume
that the volume of the solution remains unchanged.)
4. Consider solutions and their behaviors. (B9.1)
a. Explain the concept “like dissolves like”.
b. Explain how a nonvolatile, non-dissociating solute affects the boiling point of a
solvent.
c. The freezing-point depression constant of cyclohexane is 20.2°C per molal. The
melting point of cyclohexane is 6.50°C. What is the freezing point of a hexane
solution prepared by dissolving 20.0 g of C18H38 in 100 g of cyclohexane?
d. Solutes in aqueous systems are usually classified based on how electricity is
conducted. Name these classifications and give an example of each.
e. A solution is prepared by dissolving 15.2 milligrams of CrCl3 in 2.50 liters of
water. What is the concentration of cesium in parts per million?
Princeton 2012/Barron 4th ed.
Answer Key – Unit 9 Solutions
Multiple Choice
1. B
2. C
3. A
4. E
5. C
6. E
7. B
8. B
9. C
10. A
11. C
12. B
13. C
14. A
15. B
16. D
17. C
18. E
Additional Multiple Choice
37. C
40. B
38. E
41. B
39. A
42. B
19. C
20. C
21. C
22. E
23. A
24. C
25. B
26. B
27. C
28. E
29. D
30. A
43. D
44. B
45. A
31. E
32. B
33. C
34. B
35. E
36. A
46. B
47. D
Essays
1. For the problem
a. Freezing point depression ∆T = 5.50°C – 0.06°C = 5.44°C
∆T = kfm
5.44°C = (5.12°C/m)m
m = 1.06
m = moles solute/kg solvent
Rearrange to
moles solute = (molality)(kg solvent)
moles solute = (1.06m)(0.050 kg) = 0.053 moles
Molecular weight = grams/mole = 3.72 g/0.053 moles = 70.2 grams
b. Use percent by mass and molecular weight
For carbon  (86%)(70g/mol) = 60 g/mol
Molar mass of carbon = 12 g/mol so 60/12 = 5 moles C
For hydrogen  (14%)(70g/mol) = 10 g/mol
Molar mass of hydrogen = 1 g/mol so 10/1 = 10 moles H
Molecular Formula = C5H10
c. There are 0.053 moles of hydrocarbon. Find moles of benzene.
Total moles = 0.64 mol + 0.53 mol = 0.69 mol
Mole fraction = 0.64/0.69 = 0.93
Princeton 2012/Barron 4th ed.
d. M = mol/L
Mass of solution = 50.00 g + 3.72 g = 53.72 g
D = m/V
875 g/L = (53.72g)/(V)
V = 0.0614 L
M = (0.053 mol)/(0.0614 L) = 0.863 M
2. For the problem
a. Freezing-point depression is a colligative property which means that it depends on
the number of particles in solution, not their identity. Sodium chloride dissociates
into Na+ and Cl- so every unit of sodium chloride produces 2 particles in solution.
Ethanol does not dissociate, so sodium chloride will put twice as many particles in
solution as ethanol.
b. An electrolyte ionizes in solution causing the solution to conduct electricity. Both
salts dissociate into ions, but PbCl2 is almost insoluble, so it will produce very
few ions in solution, which NaCl is extremely soluble and produces many ions.
c. Water is best at dissolving polar solvents according to “like dissolves like”.
Propanol (C3H7OH) has a hydroxide group, which makes it polar, and thus
soluble in water. Propane (C3H8) is nonpolar and is best dissolved in nonpolar
solvents.
d. Molarity = moles solute/liter of solution
Molality = moles of solute/kilograms of solvent
For water, 1 liter weighs 1 kilogram, so for a dilute solution, this distinction
disappears. If there is very little solute, the mass and volume of the solution will
be indistinguishable from the mass and volume of the solvent.
3. For the problem
a.
M
X = 0.100 mol CuSO4
Mg and CuSO4 react in a 1:1 ratio so Mg is the limiting reagent
= 0.030 moles H2
Princeton 2012/Barron 4th ed.
b. Moles of CuSO4 remaining = 0.100 mol – 0.060 mol = 0.040 mol
c.
= 0.030 moles Cu2O
d. All of the Mg consumed ends up a Mg+2 ions in the solution.
4. Behaviors of solutions
a. Polar substances tend to dissolve polar solutes better than nonpolar solutes and
nonpolar solutes dissolve nonpolar solutes better than polar solutes.
b. The nonvolatile solute decreases the fraction of the solute with enough kinetic
energy to vaporize. Because the vapor pressure is decreased, it therefore requires
a higher temperature to achieve a vapor pressure of 1.0 atm than is required for
boiling.
c. m = =
Tf = -(0.787m)(20.2°Cm-1) = -15.91°C
T = 6.50 – 15.91 = -9.41°C
d. Strong electrolytes completely dissociate in water and conduct electricity well.
Weak electrolytes dissociate but not completely. They conduct electricity, but
poorly. Nonelectrolytes do not dissociate and do not conduct electricity.
e. 15.2×10-3 g CrCl3 ×