Chapter 11: Properties of Solutions
1. In a 0.1 molar solution of NaCl in water, which one of the following will be closest to 0.1?
A)
The mole fraction of NaCl.
B)
The mass fraction of NaCl.
C)
The mass percent of NaCl.
D)
The molality of NaCl.
E)
All of these are about 0.1.
2. Which of the following concentration measures will change in value as the temperature of a
solution changes?
A)
mass percent
B)
mole fraction
C)
molality
D)
molarity
E)
all of these
3. For an acid-base reaction, 1 M Al(OH)3 has a normality of 3 N. This is best explained
because:
A)
The equivalent mass is three times the molar mass.
B)
Each mole contains 3 moles of hydroxide ions that can react with 3 moles of
hydrated protons.
C)
The mole fraction is equal to 3 when aluminum hydroxide is mixed with water.
D)
The normality is always three times stronger than the concentration of a solution.
E)
At least two of the above statements are correct.
4. How many milliliters of 15.7 M H2SO4 are needed to prepare 600.0 mL of 0.10 M H2SO4?
A)
0.26 mL
B)
94 mL
C)
3.8 mL
D)
1.9 mL
E)
4.8 mL
5. 1.68 L of an aqueous solution containing 25.00 g of KCl dissolved in pure water is prepared.
The molarity of the solution is:
A)
0.200 M
B)
14.9 M
C)
5.01 M
D)
0.399 M
E)
0.0998 M
6. What volume of a 0.771 M solution of CaCl2 contains 1.28 g of solute?
A)
66.8 mL
B)
15.0 mL
C)
1.66 mL
D)
8.89 mL
E)
85.0 mL
7. Determine the molarity of a solution containing 6.76 g BaCl2 in 750.0 mL of solution.
A)
3.25 10–2 M
B)
2.44 10–2 M
C)
9.01 10–3 M
D)
4.33 10–2 M
E)
9.01 M
8. A solution containing 306.5 g of Mg(NO3)2 per liter has a density of 1.114 g/mL. The
molarity of the solution is:
A)
2.066 M
B)
1.855 M
C)
6.199 M
D)
2.302 M
E)
none of these
9. Calculate the molality of C2H5OH in a water solution that is prepared by mixing 50.0 mL of
C2H5OH with 112.7 mL of H2O at 20°C. The density of the C2H5OH is 0.789 g/mL at 20°C.
(Assume the density of water at this temperature is 1.00 g/mL.)
A)
0.00963 m
B)
0.155 m
C)
0.132 m
D)
7.60 m
E)
9.63 m
10. What is the molality of a solution of 30.1 g of propanol (CH3CH2CH2OH) in 152 mL water,
if the density of water is 1.00 g/mL?
A)
3.29 m
B)
0.00330 m
C)
0.303 m
D)
0.501 m
E)
5.01 m
11. A solution containing 292 g of Mg(NO3)2 per liter has a density of 1.108 g/mL. The molality
of the solution is:
A)
2.00 m
B)
2.41 m
C)
1.77 m
D)
6.39 m
E)
none of these
12. A 3.140 molal solution of NaCl is prepared. How many grams of NaCl are present in a
sample containing 2.314 kg of water?
A)
726.6 g
B)
124.3 g
C)
257.6 g
D)
424.6 g
E)
none of these
13. How many molecules of sucrose (table sugar), C12H22O11, dissolved in 450.0 g of water are
needed to make a 1.81 m solution?
A)
4.90 1023 molecules
B)
8.15 1023 molecules
C)
2.42 1024 molecules
D)
2.72 1025 molecules
E)
1.50 1023 molecules
14. A 20.0-g sample of methyl alcohol (CH3OH, molar mass = 32.04 g/mol) was dissolved in
43.3 g of water. The mole fraction of CH3OH is:
A)
0.260
B)
0.624
C)
0.316
D)
4.85
E)
0.206
15. What is the mole percent of ethanol (C2H5OH), which consists of 71.0 g of ethanol for every
16.7 g of water present?
A)
62.4%
B)
1.66%
C)
9.23%
D)
81.0%
E)
37.6%
16. If 2.00 g of helium gas and 3.82 g of oxygen gas are mixed together, what is the mole
fraction of helium in the solution?
A)
0.344
B)
0.193
C)
0.807
D)
0.119
E)
1.24
17. Calculate the mole fraction of NaCl in a solution prepared by dissolving 117 g NaCl in
1.15 kg H2O.
A)
9.90 10–1
B)
1.11 10–2
C)
6.08 10–2
D)
1.52 10–2
E)
3.04 10–2
18. Find the mass percent of CuSO4 in a solution whose density is 1.30 g/mL and whose
molarity is 1.36 M.
A)
83.3%
B)
1.77%
C)
16.7%
D)
2.66%
E)
none of these
19. Find the mass percent of CaCl2 in a solution whose molarity is 2.20 M and whose density is
1.18 g/mL.
A)
20.7%
B)
26.1%
C)
79.3%
D)
24.4%
E)
none of these
20. A solution of hydrogen peroxide is 23.6% H2O2 by mass and has a density of 1.11 g/cm3.
The molarity of the solution is:
A)
7.23 M
B)
0.262 M
C)
7.70 M
D)
8.03 M
E)
none of these
21. The term “proof” is defined as twice the percent by volume of pure ethanol in solution.
Thus, a solution that is 95% (by volume) ethanol is 190 proof. What is the molarity of
ethanol in a 92 proof ethanol/water solution?
density of ethanol
= 0.80 g/cm3
density of water
= 1.0 g/cm3
mol. wt. of ethanol
= 46 g/mol
A)
0.46 M
B)
0.80 M
C)
0.92 M
D)
8.0 M
E)
17 M
22. Calculate the molarity of a solution of magnesium chloride with a concentration of
26.8 mg/mL.
A)
0.563 M
B)
0.281 M
C)
0.141 M
D)
3.55 M
E)
0.448 M
23. What is the molarity of a HNO3 solution prepared by adding 255.4 mL of water to 350.0 mL
of 12.3 M HNO3?
A)
16.9 M
B)
7.45 M
C)
7.11 M
D)
2.61 M
E)
3.14 M
24. When 0.811 g of NH4NO3 was added to 150.0 g of water in a Styrofoam cup, the
temperature dropped by 0.413°C. The heat capacity of H2O is 4.18 J/g°C. Assume the
specific heat of the solution equals that of pure H2O and that the calorimeter neither absorbs
nor leaks heat. The molar heat of solution of solid NH4NO3 is:
A)
+257 J/mol
B)
+25.7 kJ/mol
C)
+2.57 kJ/mol
D)
–2.57 kJ/mol
E)
–257 J/mol
25. Which of the following chemical or physical changes is an endothermic process?
A)
the evaporation of water
B)
the combustion of gasoline
C)
the mixing of sulfuric acid and water
D)
the freezing of water
E)
none of these
26. How many of the following help determine whether or not a solution forms?
I.
the polarities of the solute and solvent
II.
the densities of the solute and solvent
III.
the probability of the mixed state (of the solution)
IV.
the energies needed for the solution formation to occur
V.
the state of matter of the solute (solid, liquid, gas)
A)
1
B)
2
C)
3
D)
4
E)
5
27. Rank the following compounds according to increasing solubility in water.
CH3–CH2–CH2–CH3
CH3–CH2–O–CH2–CH3
CH3–CH2–OH
CH3–OH
A)
I < III < IV < II
B)
I < II < IV < III
C)
III < IV < II < I
D)
I < II < III < IV
E)
None of these (A-D) is correct.
28. Which statement about hydrogen bonding is true?
A)
Hydrogen bonding is the intermolecular attractive forces between two hydrogen
atoms in solution.
B)
The hydrogen bonding capabilities of water molecules cause CH3CH2CH2CH3 to
be more soluble in water than CH3OH.
C)
Hydrogen bonding of solvent molecules with a solute will not affect the solubility
of the solute.
D)
Hydrogen bonding interactions between molecules are stronger than the covalent
bonds within the molecule.
E)
Hydrogen bonding arises from the dipole moment created by the unequal sharing
of electrons within certain covalent bonds within a molecule.
29. Which of the following favors the solubility of an ionic solid in a liquid solvent?
A)
a large magnitude of the solvation energy of the ions
B)
a small magnitude of the lattice energy of the solute
C)
a large polarity of the solvent
D)
all of the above
E)
none of the above
30. Solid KF has a lattice energy of 804 kJ/mol and a heat of solution (in water) of –15 kJ/mol.
RbF has a lattice energy of 768 kJ/mol and a heat of solution (in water) of –24 kJ/mol.
Which salt forms stronger attractions with water?
A)
KF, since it has a larger lattice energy.
B)
RbF, since it has a smaller lattice energy.
C)
KF, since it has a more negative heat of hydration.
D)
RbF, since it has a more negative heat of hydration
E)
They form equally strong attractions with water, since they both have negative
heats of mixing.
31. The lattice energy of KF is 808 kJ/mol and its heat of solution is –17.7 kJ/mol. Calculate the
hydration of energy of KF(s).
A)
–35.4 kJ/mol
B)
–790.3 kJ/mol
C)
–825.7 kJ/mol
D)
790.3 kJ/mol
E)
825.7 kJ/mol
32. When a substance dissolves in water, heat energy is released if:
A)
The lattice energy is positive.
B)
The hydration energy is positive.
C)
The hydration energy is more negative than the lattice energy is positive.
D)
The hydration energy is negative.
E)
None of these (A-D).
33. We can predict the solubility of a compound by looking at the sign of the enthalpy of
solution.
34. Use the following drawing of a gaseous solute in equilibrium with a solution to help answer
the question below.
Which of the following statements are true when the piston is pushed in (downward)?
A)
This will cause the pressure of the gas to increase and the concentration of the
dissolved gas to go down.
B)
This will cause the pressure of the gas to decrease and the concentration of the
dissolved gas to go down.
C)
This will cause the pressure of the gas to increase and the concentration of the
dissolved gas to go up.
D)
This will cause the volume of the gas to decrease and the concentration of the
dissolved gas to go down.
E)
This will cause the volume of the gas to increase and the concentration of the
dissolved gas to go up.
35. Which of the following correctly states the relationship between temperature and the
solubility of a substance in water?
A)
The solubility of a substance in water increases as the temperature rises, especially
for gases.
B)
The solubility of a substance in water decreases as the temperature rises, especially
for ionic solids.
C)
The solubility of a substance in water with temperature cannot be accurately
predicted, especially for ionic solids.
D)
The solubility of a substance in water decreases as the temperature lowers,
especially for gases.
E)
Both A and D are correct.
36. When solid Ca(CH3COO)2 is dissolved in a nearly saturated solution of Ca(CH3COO)2, the
solution becomes warmer. This information indicates that if the temperature of a solution is
decreased:
A)
H will become negative.
B)
H will become zero.
C)
The solubility of Ca(CH3COO)2 will decrease.
D)
The solubility of Ca(CH3COO)2 will increase.
E)
The solubility of Ca(CH3COO)2 will not change.
37. A correct statement of Henry’s law is:
A)
The concentration of a gas in solution is inversely proportional to temperature.
B)
The concentration of a gas in solution is directly proportional to the mole fraction
of solvent.
C)
The concentration of a gas in solution is independent of pressure.
D)
The concentration of a gas in a solution is inversely proportional to pressure.
E)
None of these.
38. The solubility of O2 in water is 0.590 g/L at an oxygen pressure of around 14.5 atm. What is
the Henry’s law constant for O2 (in units of mol/L·atm)?
A)
4.07 10–2
B)
1.27 10–3
C)
7.86 102
D)
2.67 10–1
E)
None of the above are within 5% of the correct answer.
39. What partial pressure of nitrogen gas is required in order for 0.00134 g of the gas to dissolve
in 13.1 mL of pure water? The Henry’s law constant for nitrogen gas is 6.1 10–4 M atm–1.
A)
6.2 10–8 atm
B)
1.7 10–1 atm
C)
6.0 100 atm
D)
2.9 10–8 atm
E)
1.7 10–2 atm
40. The solubility of a gas usually increases with increasing temperature.
41. The vapor pressure of water at 25.0°C is 23.8 torr. Determine the mass of glucose (molar
mass = 180 g/mol) needed to add to 500.0 g of water to change the vapor pressure to
22.8 torr.
A)
21.9 g
B)
219 g
C)
180 g
D)
6.21 kg
E)
188 g
42. A solution is prepared from 53.8 g of a nonvolatile, nondissociating solute and 85.0 g of
water. The vapor pressure of the solution at 60°C is 132 torr. The vapor pressure of water at
60°C is 150. torr. What is the molar mass of the solute?
A)
61.1 g/mol
B)
11.4 g/mol
C)
34.6 g/mol
D)
186 g/mol
E)
83.6 g/mol
43. An ideal solution is formed from a mixture of the nonvolatile solute urea, CO(NH2)2, and
methanol, CH3OH. The vapor pressure of pure methanol at 20°C is 89 mmHg. If 4.4 g of
urea is mixed with 39.9 g of methanol, calculate the vapor pressure of the methanol solution.
A)
4.9 mmHg
B)
80 mmHg
C)
74 mmHg
D)
15 mmHg
E)
84 mmHg
44. A salt solution sits in an open beaker. Assuming constant temperature and pressure, the
vapor pressure of the solution
A)
increases over time
B)
decreases over time
C)
stays the same over time
D)
need to know which salt is in the solution to answer this
E)
need to know the temperature and pressure to answer this
For each of the following solutions, describe the deviation with respect to Raoult’s Law.
45. hexane (C6H14) and chloroform (CHCl3)
A)
relatively ideal
B)
positive deviation
C)
negative deviation
D)
more information needed
E)
none of these
46. acetone (C3H6O) and water
A)
relatively ideal
B)
positive deviation
C)
negative deviation
D)
more information needed
E)
none of these
47. hexane (C6H14) and octane (C8H18)
A)
relatively ideal
B)
positive deviation
C)
negative deviation
D)
more information needed
E)
none of these
48. At a given temperature, you have a mixture of benzene (vapor pressure of pure benzene =
745 torr) and toluene (vapor pressure of pure toluene = 290. torr). The mole fraction of
benzene in the solution is 0.590. Assuming ideal behavior, calculate the mole fraction of
toluene in the vapor above the solution.
A)
0.213
B)
0.778
C)
0.641
D)
0.359
E)
0.590
49. At a given temperature, you have a mixture of benzene (vapor pressure of pure benzene =
745 torr) and toluene (vapor pressure of pure toluene = 290 torr). The mole fraction of
benzene in the vapor above the solution is 0.590. Assuming ideal behavior, calculate the
mole fraction of toluene in the solution.
A)
0.213
B)
0.778
C)
0.641
D)
0.359
E)
0.590
50. At 40°C, heptane has a vapor pressure of about 92.2 torr and octane has a vapor pressure of
about 31.2 torr. Assuming ideal behavior, what is the vapor pressure of a solution that
contains twice as many moles of heptane as octane?
A)
61.5 torr
B)
51.5 torr
C)
71.9 torr
D)
82.3 torr
E)
none of these
51. A solution contains 1 mole of liquid A and 3 moles of liquid B. This solution has a vapor
pressure of 314 torr at 25°C. At 25°C, liquid A has a vapor pressure of 265 torr and liquid B
has a vapor pressure of 355 torr. Which of the following is true?
A)
This solution exhibits a positive deviation from Raoult’s Law.
B)
This solution exhibits a negative deviation from Raoult’s Law.
C)
This solution is ideal.
D)
More information is needed to answer this question.
E)
None of these (A-D).
52.
Vapor pressure at 25°C
benzene (C6H6)
94.4 torr
chloroform (CHCl3)
172.0 torr
Using the above data, calculate the vapor pressure of chloroform over a chloroform-benzene
solution at 25°C, which contains 43.3 g CHCl3 and 43.3 g C6H6. Assume the solution
behaves ideally.
A)
68.0 torr
B)
37.3 torr
C)
104 torr
D)
86.0 torr
E)
none of these
Solutions of benzene and toluene obey Raoult’s law. The vapor pressures at 20°C are:
benzene, 76 torr; toluene, 21 torr.
53. What is the mole fraction of benzene in a benzene-toluene solution whose vapor pressure is
51 torr at 20°C?
A)
0.26
B)
0.45
C)
0.55
D)
0.67
E)
0.74
54. If the mole fraction of benzene in a particular benzene-toluene solution is 0.64, what is the
mole fraction of benzene in the vapor phase in equilibrium with that solution?
A)
0.24
B)
0.50
C)
0.64
D)
0.78
E)
0.87
55. A benzene-toluene solution is allowed to come to equilibrium with its vapor. The vapor is
then condensed and found to contain 50.0 mole percent of each component. Calculate the
composition (mole percent) of the original solution. The vapor pressures of pure benzene
and toluene at this temperature are: 750. torr and 300. torr, respectively.
A)
50.2% benzene
B)
28.6% benzene
C)
71.0% benzene
D)
40.0% benzene
E)
none of these
56. A solution is made by adding 0.100 mole of ethyl ether to 0.491 mole of ethyl alcohol. If the
vapor pressure of ethyl ether and ethyl alcohol at 20°C are 375 torr and 20.0 torr,
respectively, the vapor pressure of the solution at 20°C (assuming ideal behavior) is:
A)
80.1 torr
B)
315 torr
C)
46.8 torr
D)
395 torr
E)
none of these
57. A solution of two liquids, A and B, shows negative deviation from Raoult’s law. This means
that:
A)
The molecules of A interact strongly with other A-type molecules.
B)
The two liquids have a positive heat of solution.
C)
Molecules of A interact weakly, if at all, with B molecules.
D)
The molecules of A hinder the strong interaction between B molecules.
E)
Molecules of A interact more strongly with B than A with A, or B with B.
58. Benzene and toluene form an ideal solution. At 298 K, what is the mole fraction of benzene
in the liquid that is in equilibrium with a vapor that has equal partial pressures of benzene
and toluene? At 298 K, the vapor pressures of pure benzene and pure toluene are 95 and 28
torr, respectively.
A)
0.50
B)
0.77
C)
0.23
D)
0.30
E)
none of these
59. A solution of CH3OH in H2O would most likely
A)
be ideal
B)
show positive deviations from Raoult’s law
C)
show negative deviations from Raoult’s law
D)
not be ideal, but the deviations cannot be predicted
E)
obey Raoult’s law