130) Assume that you start with a mixture containing 0.80 mol of decane and 0.20 mol of octane, what
region of the diagram corresponds to vapor?
A) region a
B) region b
C) region c
D) regions a and c
A phase diagram of temperature versus composition for a mixture of the two volatile liquids octane (bp
= 69°C) and decane (bp = 126°C) is shown.
131) Assume that you start with a mixture containing 0.80 mol of decane and 0.20 mol of octane, at
what approximate temperature will the mixture begin to boil?
A) temperature at point a
B) temperature at point b
C) temperature at point d
D) temperature at point f
132) Assume that you start with a mixture containing 0.80 mol of decane and 0.20 mol of octane, what
is the liquid composition at the boiling point?
A) 100% decane
B) composition at point b
C) composition at point c
D) composition at point e
133) Assume that you start with a mixture containing 0.80 mol of decane and 0.20 mol of octane, what
is the vapor composition at the boiling point?
A) 100% decane
B) composition at point b
C) composition at point c
D) composition at point e
134) Assume that the vapor at point c is condensed and reboiled. What is the liquid composition of the
condensed vapor prior to reboiling?
A) 100% decane
B) composition at point b
C) composition at point d
D) composition at point e
135) Assume that the vapor at point c is condensed and reboiled. What is the vapor composition during
reboiling?
A) 100% decane
B) composition at point b
C) composition at point c
D) composition at point e
136) Assume that the vapor at point c is condensed and reboiled. What is the boiling point?
A) temperature at point b
B) temperature at point c
C) temperature at point d
D) temperature at point f
137) What is the approximate boiling temperature of a mixture that is 0.70 XA and 0.30 XB?
A) 50°C
B) 75°C
C) 95°C
D) 100°C
138) What is the approximate vapor composition above a boiling solution that is 0.70 XA and 0.30 XB?
A) 0.70 XA, 0.30 XB
B) 0.50 XA, 0.50 XB
C) 0.30 XA, 0.70 XB
D) 0 XA, 1.00 XB
139) What is the approximate boiling temperature of the liquid formed from the condensation of the
vapor above a boiling solution that is 0.70 XA and 0.30 XB?
A) 50°C
B) 55°C
C) 90°C
D) 100°C
140) At 80°C, pure liquid A has a vapor pressure of 700 mm Hg and pure liquid B has a vapor pressure
of 940 mm Hg. What is XA for a solution of A and B with a normal boiling point of
A) 0.25
B) 0.50
C) 0.75
D) A solution of A and B cannot boil at 80°C.
11.2 Algorithmic Questions
1) Which cation in each set is expected to have the larger (more negative) hydration energy?
I. Be2+ or Ca2+
II. Rb+ or Zn2+
A) Be2+ in set I and Rb+ in set II
B) Be2+ in set I and Zn2+ in set II
C) Ca2+ in set I and Rb+ in set II
D) Ca2+ in set I and Zn2+ in set II
2) What is the mole fraction of ethanol in a solution made by dissolving 29.2 g of ethanol, C2H5OH, in
53.6 g of water?
A) 0. 176
B) 0. 213
C) 0. 352
D) 0. 545
3) What is the mole fraction of I2 in a solution made by dissolving 55.6 g of I2 in 245 g of hexane,
C6H14?
A) 0. 0715
B) 0. 0770
C) 0. 133
D) 0. 154
4) What is the mole fraction of oxygen in a gas mixture that is 37% oxygen and 63% nitrogen by
volume?
A) 0. 34
B) 0. 37
C) 0. 25
D) 0. 52
5) What is the weight percent of vitamin C in a solution made by dissolving 6.50 g of vitamin C,
C6H8O6, in 55.0 g of water?
A) 0. 547%
B) 1.21%
C) 10.6%
D) 11.8%
6) What is the weight percent of a caffeine solution made by dissolving 8.35 g of caffeine,
C8H10N4O2, in 75 g of benzene, C6H6?
A) 0.0 10%
B) 0.0 11%
C) 10%
D) 11%
7) What volume of a 0.716 M KBr solution is needed to provide 30.5 g of KBr?
A) 21.8 mL
B) 42.7 mL
C) 184 mL
D) 357 mL
8) What volume of 3.00 M CH3OH solution is needed to provide 0. 220 mol of CH3OH?
A) 1.52 mL
B) 13.6 mL
C) 73.3 mL
D) 660 mL
9) How much water must be added to 40.0 g of CaCl2 to produce a solution that is 35.0 wt% CaCl2?
A) 54.0 g
B) 74.2 g
C) 87.5 g
D) 114 g
10) To make a 0.500 M solution, one could take 0.500 moles of solute and add
A) 1.00 L of solvent.
B) 1.00 kg of solvent.
C) enough solvent to make 1.00 L of solution.
D) enough solvent to make 1.00 kg of solution.
11) To make a 2.00 m solution, one could take 2.00 moles of solute and add
A) 1.00 L of solvent.
B) 1.00 kg of solvent.
C) enough solvent to make 1.00 L of solution.
D) enough solvent to make 1.00 kg of solution.
12) What molality of pentane is obtained by dissolving 15 g pentane, C5H12, in 245.0 g hexane,
C6H14?
A) 0.0 58 m
B) 0. 068 m
C) 0.85 m
D) 61 m
13) A solution is 2.25% by weight NaHCO3. How many grams of NaHCO3 are in 150.0 g of solution?
A) 1.50 g
B) 3.38 g
C) 66.7 g
D) 225 g
14) How many grams of KBr are required to make 350. mL of a 0.115 M KBr solution?
A) 0. 338 g
B) 3.04 g
C) 4.79 g
D) 40.3 g
15) What is the molality of a glucose solution prepared by dissolving 18.0 g of glucose, C6H12O6, in
125.9 g of water?
A) 7.94 × 10– 4 m
B) 0. 143 m
C) 0.695 m
D) 0.794 m
16) A solution of LiCl in water has XLiCl = 0.0 900. What is the molality?
A) 4.46 m LiCl
B) 5.00 m LiCl
C) 5.49 m LiCl
D) 9.89 m LiCl
17) A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl?
A) 0. 0960
B) 0. 106
C) 0. 472
D) 4. 44
18) In which case should CO2(g) be more soluble in water?
A) The total pressure is 5 atm and the partial pressure of CO2 is 0.5 atm.
B) The total pressure is 3 atm and the partial pressure of CO2 is 1 atm.
C) The total pressure is 1 atm and the partial pressure of CO2 is 0. 03 atm.
D) The total pressure is 1 atm and the partial pressure of CO2 is 0. 4 atm.
19) The Henry’s Law constant of methyl bromide, CH3Br, is k = 0.159 mol/(L ∙ atm) at 25°C. What is
the solubility of methyl bromide in water at 25°C and at a partial pressure of 270. mm Hg?
A) 0.0 565 mol/L
B) 0.3 55 mol/L
C) 0.4 48 mol/L
D) 42.9 mol/L
20) A solution is prepared by dissolving 40.0 g of sucrose, C12H22O11, in 250. g of water at 25°C.
What is the vapor pressure of the solution if the vapor pressure of water at 25°C is 23.76 mm Hg?
A) 0. 198 mm Hg
B) 20.5 mm Hg
C) 23.6 mm Hg
D) 24. 0 mm Hg
21) A KCl solution is prepared by dissolving 20.0 g KCl in 250.0 g of water at 25°C. What is the vapor
pressure of the solution if the vapor pressure of water at 25°C is 23.76 mm Hg?
A) 22.0 mm Hg
B) 22.9 mm Hg
C) 23.3 mm Hg
D) 24.6 mm Hg
22) At a given temperature the vapor pressures of benzene and toluene are 183 mm Hg and 59.2 mm Hg,
respectively. Calculate the total vapor pressure over a solution of benzene and toluene with Xbenzene =
0. 580.
A) 106 mm Hg
B) 121 mm Hg
C) 131 mm Hg
D) 242 mm Hg
23) Which of the following solutions will have the lowest freezing point?
A) 0.010 m K Br
B) 0.010 m Na2CO3
C) 0.035 m CH3CH2OH
D) 0.015 m BaCl2
24) What is the expected freezing point of a 0.50 m solution of Li2SO4 in water? Kf for water is
1.86°C/m.
A) -0.93°C
B) -1.9°C
C) -2.8°C
D) -6.5°C
25) Calculate the freezing point of a solution of 40.0 g methyl salicylate, C7H6O2, dissolved in 800. g
of benzene, C6H6. Kf for benzene is 5.10°C /m and the freezing point is 5.50°C for benzene.
A) – 2.09°C
B) 2.09°C
C) 3.41°C
D) 7.59°C
26) What is the freezing point of a solution of 7.15 g MgCl2 in 100 g of water? Kf for water is
A) -0. 140°C
B) – 1.40°C
C) – 2.80°C
D) – 4.18°C
27) An aqueous solution has a normal boiling point of 10 3.0°C. What is the freezing point of this
solution? For water Kb = 0.51°C /m and Kf = 1.86°C /m.
A) -0. 82°C
B) – 3.0°C
C) -3.6°C
D) – 11°C
11.3 Short Answer Questions
1) In a solution that is 55% ethyl alcohol and 45% water, the solute is ________ and the solvent is
________.
2) According to the rule of thumb “like dissolves like.” ionic solids like NaCl or polar substances like
glucose are more soluble in ________ solvents, whereas nonpolar substances like I2 are more soluble in
________ solvents.
3) When KI is dissolved in water, the major forces overcome are ________ forces in the solute and
________ forces in the solvent, and the major forces created between solute and solvent particles are
________ forces.
42
4) A person is considered legally intoxicated with a blood alcohol level of 80 mg/dL. Assuming that
blood plasma has a density of 1.025 g/mL, what is this concentration expressed in parts per million?
5) Amphetamines in urine can be confirmed by mass spectroscopy at a concentration of 500 ng/mL.
Assuming a urine density of 1.025 g/mL, what is this concentration in parts per million?
6) Molarity is defined as ________, whereas molality is defined as ________.
7) The number of moles of ions in 25 mL of 2.0 M Na2SO4 is ________ moles.
8) The volume of 0.200 M H2SO4 that contains 5.00 mmol of H+ is ________ mL.
9) Cocaine, C17H21NO4, in urine can be confirmed by mass spectroscopy at a concentration of 150
ng/mL. Assuming a urine density of 1.025 g/mL, what is this concentration expressed as molality?
10) Concentrations of fluoride in drinking water greater than 4.0 mg/L can cause mottled teeth in
children. What is 4.0 mg/L expressed as molality?
11) The solubility of a gas in a liquid is greatest at ________ pressures and ________ temperatures.
12) Dinitrogen monoxide is still used as a general anesthetic. The Henry’s law constant for the solubility
of N2O in water is 2.5 × 10-2 mol/L·atm. What is the molar solubility of N2O in water if the partial
pressure of N2O is 1500 m Hg?
13) At 20°C and 0.28 atm pressure Xenon has a solubility in water of 1.4 mmol/L. What is the Henry’s
Law-constant in mol/ L·atm at 20°C?
14) Freezing point depression, boiling point elevation, vapor pressure lowering, and osmotic pressure
are examples of ________ properties, which depend on the amount but not the chemical identity of
dissolved particles.
15) At 80.0°C heptane, C7H16, has a vapor pressure of 428 mm Hg and octane, C8H18, has a vapor
pressure of 175 mm Hg. What is the vapor pressure of a solution that contains 20.0 g C7H16 and 11.4 g
C8H18?
16) At 80.0°C benzene has a vapor pressure of 96.0 mm Hg and toluene has a vapor pressure of 30.3
mm Hg. If a mixture of benzene and toluene has a vapor pressure of 54.6 mm Hg, what are the mole
fractions of benzene and toluene?
17) If dissociation of MgCl2 in water were 100%, the van’t Hoff factor would be ________; however,
for real solutions the van’t Hoff factor for MgCl2 is ________ (greater than, less than) this value.
18) The vapor pressure of water at 25°C is 23.8 mm Hg. The vapor pressure lowering, ΔP, of an
aqueous solution containing 0.500 mole fraction NaCl is ________ (equal to, greater than, less than)
11.9 mm Hg?
19) At 25°C the vapor pressures of benzene and toluene are 96.0 mm Hg and 30.5 mm Hg, respectively.
The vapor pressure of a solution that has a 0.50 mole fraction of toluene will have a vapor pressure
________ (equal to, greater than, less than) 30.5 mm Hg.
20) The boiling point of a solution containing a nonvolatile solute will be ________ than the boiling
point of the pure solvent, whereas the boiling point of a solution of two volatile liquids will be ________
than the boiling point of the more volatile liquid and ________ than the boiling point of the less volatile
liquid.
21) A 1.0 m aqueous CaCl2 solution will have a ________ vapor pressure, ________ freezing point, and
________ boiling point than a 1.0 m aqueous solution of NaCl.
22) The osmotic pressure of a 0.10 M solution of sucrose, C12H22O11 will be ________ (equal to,
greater than, less than) the osmotic pressure of a 0.10 M solution of fructose, C6H12O6.
23) The osmotic pressure of a 100-mL solution containing 1.0 g of sucrose, C12H22O11 will be
________ (equal to, greater than, less than) the osmotic pressure of a 100-mL solution containing 1.0 g
of fructose, C6H12O6.
24) At 300 K a 500.0 mL solution containing 0.4314 g of dextrose has an osmotic pressure of 89.6 mm
Hg. What is the molar mass of dextrose?
25) At 25 oC the vapor pressures of benzene and toluene are 96.0 mm Hg and 30.5 mm Hg,
respectively. When a 1:1 molar mixture of benzene and toluene is fractionally distilled, the first fraction
will have a mole fraction of benzene that is ________ (equal to, greater than, less than) 0.50.