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Chapter 13

Solutions

Educators

WM
+ 3 more educators

Problem 1

1. What is a solution? What are the solute and solvent?

David C.
Numerade Educator

Problem 2

What does it mean when we say that a substance is soluble in
another substance? Which units do we use to report solubility?

George M.
Numerade Educator

Problem 3

Why do two ideal gases thoroughly mix when combined? What
drives the mixing?

Jekaterina V.
Numerade Educator

Problem 4

What is entropy? What role does entropy play in the formation of
solutions?

George M.
Numerade Educator

Problem 5

What kinds of intermolecular forces are involved in solution
formation?

Jekaterina V.
Numerade Educator

Problem 6

Explain how the relative strengths of solute-solute interactions,
solvent-solvent interactions, and solvent-solute interactions
affect solution formation.

George M.
Numerade Educator

Problem 7

What does the statement like dissolves like mean with respect to
solution formation?

Jekaterina V.
Numerade Educator

Problem 8

List the three steps involved in evaluating the enthalpy changes
associated with solution formation.

George M.
Numerade Educator

Problem 9

What is the heat of hydration (Hhydration) ? How does the
enthalpy of solution depend on the relative magnitudes of
Hsolute and Hhydration?

A. Elizabeth H.
Numerade Educator

Problem 10

Explain dynamic equilibrium with respect to solution formation.
What is a saturated solution? An unsaturated solution? A
supersaturated solution?

George M.
Numerade Educator

Problem 11

How does temperature affect the solubility of a solid in a liquid?
How is this temperature dependence exploited to purify solids
through recrystallization?

Jekaterina V.
Numerade Educator

Problem 12

How does temperature affect the solubility of a gas in a liquid?
How does this temperature dependence affect the amount of
oxygen available for fish and other aquatic animals?

George M.
Numerade Educator

Problem 13

How does pressure affect the solubility of a gas in a liquid? How
does this pressure dependence account for the bubbling that
occurs upon opening a can of soda?

Jekaterina V.
Numerade Educator

Problem 14

What is Henry"s law? For what kinds of calculations is Henry"s
law useful?

Aadit S.
Numerade Educator

Problem 15

What are the common units for expressing solution
concentration?

Jekaterina V.
Numerade Educator

Problem 16

How are parts by mass and parts by volume used in
calculations?

Aadit S.
Numerade Educator

Problem 17

What is the effect of a nonvolatile solute on the vapor pressure of
a liquid? Why is the vapor pressure of a solution different from
the vapor pressure of the pure liquid solvent?

Jekaterina V.
Numerade Educator

Problem 18

What is Raoult"s law? For what kind of calculations is Raoult"s
law useful?

George M.
Numerade Educator

Problem 19

Explain the difference between an ideal and a nonideal solution.

Jekaterina V.
Numerade Educator

Problem 20

What is the effect on vapor pressure of a solution with
particularly strong solute-solvent interactions? With particularly
weak solute-solvent interactions?

George M.
Numerade Educator

Problem 21

Explain why the lower vapor pressure for a solution containing a
nonvolatile solute results in a higher boiling point and lower
melting point compared to the pure solvent.

Jekaterina V.
Numerade Educator

Problem 22

What are colligative properties?

George M.
Numerade Educator

Problem 23

What is osmosis? What is osmotic pressure?

Jekaterina V.
Numerade Educator

Problem 24

Explain the significance of the van"t Hoff factor (i) and its role in
determining the colligative properties of solutions containing
ionic solutes.

George M.
Numerade Educator

Problem 25

Pick an appropriate solvent from Table 13.3 to dissolve each substance.
State the kind of intermolecular forces that would occur
between the solute and solvent in each case.
a. motor oil (nonpolar)
b. ethanol (polar, contains an OH group)
c. lard (nonpolar)
d. potassium chloride (ionic)

David C.
Numerade Educator

Problem 26

Pick an appropriate solvent from Table 13.3 to dissolve each substance.
State the kind of intermolecular forces that would occur
between the solute and solvent in each case.
a. isopropyl alcohol (polar, contains an OH group)
b. sodium chloride (ionic)
c. vegetable oil (nonpolar)
d. sodium nitrate (ionic)

George M.
Numerade Educator

Problem 27

Which molecule would you expect to be more soluble in water,
CH3CH2CH2CH2OH or HOCH2CH2CH2OH?

Jekaterina V.
Numerade Educator

Problem 28

Which molecule would you expect to be more soluble in water,
CCl4 or CH2Cl2?

George M.
Numerade Educator

Problem 29

For each compound, would you expect greater solubility in water
or in hexane? Indicate the kinds of intermolecular forces that
occur between the solute and the solvent in which the molecule
is most soluble.

Jekaterina V.
Numerade Educator

Problem 30

For each compound, would you expect greater solubility in water
or in hexane? Indicate the kinds of intermolecular forces that
would occur between the solute and the solvent in which the
molecule is most soluble.

George M.
Numerade Educator

Problem 31

When ammonium chloride (NH4Cl) is dissolved in water, the
solution becomes colder.
a. Is the dissolution of ammonium chloride endothermic or
exothermic?
b. What can you conclude about the relative magnitudes of the
lattice energy of ammonium chloride and its heat of
hydration?
c. Sketch a qualitative energy diagram similar to Figure 13.6 for
the dissolution of NH4Cl.
d. Why does the solution form? What drives the process?

David C.
Numerade Educator

Problem 32

When lithium iodide (LiI) is dissolved in water, the solution becomes hotter.
a. Is the dissolution of lithium iodide endothermic or exothermic?
b. What can you conclude about the relative magnitudes of the lattice energy of lithium iodide and its heat of hydration?
c. Sketch a qualitative energy diagram similar to Figure 13.6 for the dissolution of LiI.
d. Why does the solution form? What drives the process?

David C.
Numerade Educator

Problem 33

Silver nitrate has a lattice energy of -820 kJ>mol and a heat of
solution of -22.6 kJ>mol. Calculate the heat of hydration for
silver nitrate.

A. Elizabeth H.
Numerade Educator

Problem 34

Use the given data to calculate the heats of hydration of lithium
chloride and sodium chloride. Which of the two cations, lithium
or sodium, has stronger ion-dipole interactions with water? Why?

George M.
Numerade Educator

Problem 35

Lithium iodide has a lattice energy of -7.3 * 102 kJ>mol and a
heat of hydration of -793 kJ>mol. Find the heat of solution for
lithium iodide and determine how much heat is evolved or
absorbed when 15.0 g of lithium iodide completely dissolves in
water.

Jekaterina V.
Numerade Educator

Problem 36

Potassium nitrate has a lattice energy of -163.8 kcal>mol and a
heat of hydration of -155.5 kcal>mol. How much potassium
nitrate has to dissolve in water to absorb 1.00 * 102 kJ of heat?

George M.
Numerade Educator

Problem 37

A solution contains 25 g of NaCl per 100.0 g of water at 25 C.
Is the solution unsaturated, saturated, or supersaturated? (Refer
to Figure 13.10.)

Jekaterina V.
Numerade Educator

Problem 38

A solution contains 32 g of KNO3 per 100.0 g of water at 25 C.
Is the solution unsaturated, saturated, or supersaturated? (Refer
to Figure 13.10.)

George M.
Numerade Educator

Problem 39

A KNO3 solution containing 45 g of KNO3 per 100.0 g of water is
cooled from 40 C to 0 C. What happens during cooling? (Refer
to Figure 13.10.)

Jekaterina V.
Numerade Educator

Problem 40

A KCl solution containing 42 g of KCl per 100.0 g of water is
cooled from 60 C to 0 C. What happens during cooling? (Refer
to Figure 13.10.)

George M.
Numerade Educator

Problem 41

Some laboratory procedures involving oxygen-sensitive reactants
or products call for using water that has been boiled (and then
cooled). Explain.

Jekaterina V.
Numerade Educator

Problem 42

A person preparing a fish tank fills the tank with water that has
been boiled (and then cooled). When the person puts fish into
the tank, they die. Explain.

George M.
Numerade Educator

Problem 43

Scuba divers breathing air at increased pressure can suffer from
nitrogen narcosis-a condition resembling drunkenness-when
the partial pressure of nitrogen exceeds about 4 atm. What
property of gas/water solutions causes this to happen? How can a
diver reverse this effect?

A. Elizabeth H.
Numerade Educator

Problem 44

Scuba divers breathing air at increased pressure can suffer from
oxygen toxicity-too much oxygen in their bloodstream-when
the partial pressure of oxygen exceeds about 1.4 atm. What
happens to the amount of oxygen in a diver"s bloodstream when
he or she breathes oxygen at elevated pressures? How can this be
reversed?

George M.
Numerade Educator

Problem 45

Calculate the mass of nitrogen dissolved at room temperature in
an 80.0-L home aquarium. Assume a total pressure of 1.0 atm
and a mole fraction for nitrogen of 0.78.

A. Elizabeth H.
Numerade Educator

Problem 46

Use Henry"s law to determine the molar solubility of helium at a
pressure of 1.0 atm and 25 C.

George M.
Numerade Educator

Problem 47

An aqueous NaCl solution is made using 112 g of NaCl diluted to a
total solution volume of 1.00 L. Calculate the molarity, molality,
and mass percent of the solution. (Assume a density of 1.08 g>mL
for the solution.)

Jekaterina V.
Numerade Educator

Problem 48

An aqueous KNO3 solution is made using 72.5 g of KNO3 diluted to
a total solution volume of 2.00 L. Calculate the molarity, molality,
and mass percent of the solution. (Assume a density of 1.05 g>mL
for the solution.)

George M.
Numerade Educator

Problem 49

To what volume should you dilute 50.0 mL of a 5.00-M KI solution
so that 25.0 mL of the diluted solution contains 3.05 g of KI?

Jekaterina V.
Numerade Educator

Problem 50

To what volume should you dilute 125 mL of an 8.00-M CuCl2
solution so that 50.0 mL of the diluted solution contains 4.67 g
CuCl2?

George M.
Numerade Educator

Problem 51

Silver nitrate solutions are used to plate silver onto other
metals. What is the maximum amount of silver (in grams) that
can be plated out of 4.8 L of an AgNO3 solution containing
3.4% Ag by mass? Assume that the density of the solution is
1.01 g >mL.

Jekaterina V.
Numerade Educator

Problem 52

A dioxin-contaminated water source contains 0.085% dioxin by
mass. How much dioxin is present in 2.5 L of this water? Assume
a density of 1.00 g>mL.

George M.
Numerade Educator

Problem 53

A hard-water sample contains 0.0085% Ca by mass (in the form
of Ca2+ ions). How much water (in grams) contains 1.2 g of Ca?
(1.2 g of Ca is the recommended daily allowance of calcium for
adults between 19 and 24 years old.)

JM
Jamonica M.
Numerade Educator

Problem 54

Lead is a toxic metal that affects the central nervous system. A
Pb-contaminated water sample contains 0.0011% Pb by mass.
How much of the water (in mL) contains 150 mg of Pb? (Assume
a density of 1.0 g>mL.)

George M.
Numerade Educator

Problem 55

You can purchase nitric acid in a concentrated form that is 70.3%
HNO3 by mass and has a density of 1.41 g>mL. How can you prepare
1.15 L of 0.100 M HNO3 from the concentrated solution?

Jekaterina V.
Numerade Educator

Problem 56

You can purchase hydrochloric acid in a concentrated form that
is 37.0% HCl by mass and that has a density of 1.20 g>mL. How
can you prepare 2.85 L of 0.500 M HCl from the concentrated
solution?

George M.
Numerade Educator

Problem 57

Describe how to prepare each solution from the dry solute and
the solvent.
a. 1.00 * 102 mL of 0.500 M KCl
b. 1.00 * 102 g of 0.500 m KCl
c. 1.00 * 102 g of 5.0% KCl solution by mass

A. Elizabeth H.
Numerade Educator

Problem 58

Describe how to prepare each solution from the dry solute and
the solvent.
a. 125 mL of 0.100 M NaNO3
b. 125 g of 0.100 m NaNO3
c. 125 g of 1.0% NaNO3 solution by mass

George M.
Numerade Educator

Problem 59

A solution is prepared by dissolving 28.4 g of glucose (C6H12O6)
in 355 g of water. The final volume of the solution is 378 mL. For
this solution, calculate the concentration in each unit.
a. molarity
b. molality
c. percent by mass
d. mole fraction
e. mole percent

Jekaterina V.
Numerade Educator

Problem 60

A solution is prepared by dissolving 20.2 mL of methanol
(CH3OH) in 100.0 mL of water at 25 C. The final volume of the
solution is 118 mL. The densities of methanol and water at this
temperature are 0.782 g>mL and 1.00 g>mL, respectively. For this
solution, calculate the concentration in each unit.
a. molarity
b. molality
c. percent by mass
d. mole fraction
e. mole percent

George M.
Numerade Educator

Problem 61

Household hydrogen peroxide is an aqueous solution containing
3.0% hydrogen peroxide by mass. What is the molarity of this
solution? (Assume a density of 1.01 g>mL.)

Jekaterina V.
Numerade Educator

Problem 62

One brand of laundry bleach is an aqueous solution containing
4.55% sodium hypochlorite (NaOCl) by mass. What is the
molarity of this solution? (Assume a density of 1.02 g>mL.)

George M.
Numerade Educator

Problem 63

An aqueous solution contains 36% HCl by mass. Calculate the
molality and mole fraction of the solution.

Jekaterina V.
Numerade Educator

Problem 64

An aqueous solution contains 5.0% NaCl by mass. Calculate the
molality and mole fraction of the solution.

George M.
Numerade Educator

Problem 65

A beaker contains 100.0 mL of pure water. A second beaker
contains 100.0 mL of seawater. The two beakers are left side by
side on a lab bench for one week. At the end of the week, the
liquid level in both beakers has decreased. However, the level has
decreased more in one of the beakers than in the other. Which
one and why?

Jekaterina V.
Numerade Educator

Problem 66

Which solution has the highest vapor pressure?
a. 20.0 g of glucose(C6H12O6) in 100.0 mL of water
b. 20.0 g of sucrose(C12H22O11) in 100.0 mL of water
c. 10.0 g of potassium acetate KC2H3O2 in 100.0 mL of water

George M.
Numerade Educator

Problem 67

Calculate the vapor pressure of a solution containing 24.5 g of
glycerin(C3H8O3) in 135 mL of water at 30.0 C. The vapor
pressure of pure water at this temperature is 31.8 torr. Assume
that glycerin is not volatile and dissolves molecularly (that is, it
is not ionic), and use a density of 1.00 g>mL for the water.

Jekaterina V.
Numerade Educator

Problem 68

A solution contains naphthalene(C10H8) dissolved in hexane
(C6H14) at a concentration of 12.35% naphthalene by mass.
Calculate the vapor pressure at 25 C of hexane above the
solution. The vapor pressure of pure hexane at 25 C is 151 torr.

George M.
Numerade Educator

Problem 69

A solution contains 50.0 g of heptane(C7H16) and 50.0 g of
octane(C8H18) at 25 C. The vapor pressures of pure heptane and
pure octane at 25 C are 45.8 torr and 10.9 torr, respectively.
Assuming ideal behavior, answer each question.
a. What is the vapor pressure of each solution component in the
mixture?
b. What is the total pressure above the solution?
c. What is the composition of the vapor in mass percent?
d. Why is the composition of the vapor different from the
composition of the solution?

A. Elizabeth H.
Numerade Educator

Problem 70

A solution contains a mixture of pentane and hexane at room
temperature. The solution has a vapor pressure of 258 torr. Pure
pentane and hexane have vapor pressures of 425 torr and
151 torr, respectively, at room temperature. What is the mole
fraction composition of the mixture? (Assume ideal behavior.)

George M.
Numerade Educator

Problem 71

A solution contains 4.08 g of chloroform(CHCl3) and 9.29 g of
acetone(CH3COCH3). The vapor pressures at 35 C of pure
chloroform and pure acetone are 295 torr and 332 torr, respectively.
Assuming ideal behavior, calculate the vapor pressures of
each component and the total vapor pressure above the solution.
The experimentally measured total vapor pressure of the solution
at 35 C is 312 torr. Is the solution ideal? If not, what can you say
about the relative strength of chloroform-acetone interactions
compared to the acetone-
acetone and chloroform-chloroform
interactions?

Jekaterina V.
Numerade Educator

Problem 72

A solution of methanol and water has a mole fraction of water of
0.312 and a total vapor pressure of 211 torr at 39.9 C. The vapor
pressures of pure methanol and pure water at this temperature are
256 torr and 55.3 torr, respectively. Is the solution ideal? If not,
what can you say about the relative strengths of the solute-solvent
interactions compared to the solute-solute and solvent-solvent
interactions?

George M.
Numerade Educator

Problem 73

A glucose solution contains 55.8 g of glucose(C6H12O6) in 455 g
of water. Determine the freezing point and boiling point of the
solution. (Assume a density of 1.00 g>mL for water.)

Jekaterina V.
Numerade Educator

Problem 74

An ethylene glycol solution contains 21.2 g of ethylene glycol
(C2H6O2) in 85.4 mL of water. Determine the freezing point and
boiling point of the solution. (Assume a density of 1.00 g>mL for
water.)

George M.
Numerade Educator

Problem 75

Calculate the freezing point and melting point of a solution
containing 10.0 g of naphthalene (C10H8) in 100.0 mL of
benzene. Benzene has a density of 0.877 g>cm3.

Jekaterina V.
Numerade Educator

Problem 76

Calculate the freezing point and melting point of a solution
containing 7.55 g of ethylene glycol (C2H6O2) in 85.7 mL of
ethanol. Ethanol has a density of 0.789 g>cm3.

George M.
Numerade Educator

Problem 77

An aqueous solution containing 17.5 g of an unknown molecular
(nonelectrolyte) compound in 100.0 g of water has a freezing
point of -1.8 C. Calculate the molar mass of the unknown
compound.

Jekaterina V.
Numerade Educator

Problem 78

An aqueous solution containing 35.9 g of an unknown molecular
(nonelectrolyte) compound in 150.0 g of water has a freezing
point of -1.3 C. Calculate the molar mass of the unknown
compound.

George M.
Numerade Educator

Problem 79

Calculate the osmotic pressure of a solution containing 24.6 g of
glycerin(C3H8O3) in 250.0 mL of solution at 298 K.

A. Elizabeth H.
Numerade Educator

Problem 80

What mass of sucrose (C12H22O11) would you combine with
5.00 * 102 g of water to make a solution with an osmotic
pressure of 8.55 atm at 298 K? (Assume a density of 1.0 g>mL for
the solution.)

George M.
Numerade Educator

Problem 81

A solution containing 27.55 mg of an unknown protein per
25.0mL solution was found to have an osmotic pressure of
3.22torr at 25 C. What is the molar mass of the protein?

Jekaterina V.
Numerade Educator

Problem 82

Calculate the osmotic pressure of a solution containing 18.75 mg
of hemoglobin in 15.0 mL of solution at 25 C. The molar mass of
hemoglobin is 6.5 * 104 g>mol.

George M.
Numerade Educator

Problem 83

Calculate the freezing point and boiling point of each aqueous
solution, assuming complete dissociation of the solute.
a. 0.100 m K2S
b. 21.5 g of CuCl2 in 4.50 * 102 g water
c. 5.5% NaNO3 by mass (in water)

A. Elizabeth H.
Numerade Educator

Problem 84

Calculate the freezing point and boiling point in each solution,
assuming complete dissociation of the solute.
a. 10.5 g FeCl3 in 1.50 * 102 g water
b. 3.5% KCl by mass (in water)
c. 0.150 m MgF2

George M.
Numerade Educator

Problem 85

What mass of salt (NaCl) should you add to 1.00 L of water in an
ice-cream maker to make a solution that freezes at -10.0 C?
Assume complete dissociation of the NaCl and a density of
1.00 g>mL for water.

A. Elizabeth H.
Numerade Educator

Problem 86

Determine the required concentration (in percent by mass) for an
aqueous ethylene glycol(C2H6O2) solution to have a boiling point
of 104.0 C.

George M.
Numerade Educator

Problem 87

Referring to the van"t Hoff factors in Table 13.7, calculate the
mass of solute required to make each aqueous solution.
a. a sodium chloride solution containing 1.50 * 102 g of water
that has a melting point of -1.0 C
b. 2.50 * 102 mL of a magnesium sulfate solution that has an
osmotic pressure of 3.82 atm at 298 K
c. an iron(III) chloride solution containing 2.50 * 102 g of water
that has a boiling point of 102 C

Aadit S.
Numerade Educator

Problem 88

Referring to the van"t Hoff factors in Table 13.7, calculate the
mass of solute required to make each aqueous solution.
a. a sodium chloride solution containing 1.50 * 102 g of water
that has a melting point of -1.0 C
b. 2.50 * 102 mL of a magnesium sulfate solution that has an
osmotic pressure of 3.82 atm at 298 K

George M.
Numerade Educator

Problem 89

A 1.2-m aqueous solution of an ionic compound with the formula
MX2 has a boiling point of 101.4 C. Calculate the van"t Hoff
factor (i) for MX2 at this concentration.

A. Elizabeth H.
Numerade Educator

Problem 90

A 0.95-m aqueous solution of an ionic compound with the
formula MX has a freezing point of -3.0 C. Calculate the van"
t
Hoff factor (i) for MX at this concentration.

George M.
Numerade Educator

Problem 91

A 0.100-M ionic solution has an osmotic pressure of 8.3 atm at
25 C. Calculate the van"t Hoff factor (i) for this solution.

A. Elizabeth H.
Numerade Educator

Problem 92

A solution contains 8.92 g of KBr in 500.0 mL of solution and has
an osmotic pressure of 6.97 atm at 25 C. Calculate the van"t Hoff
factor (i) for KBr at this concentration.

George M.
Numerade Educator

Problem 93

Calculate the vapor pressure at 25 C of an aqueous solution that
is 5.50% NaCl by mass. (Assume complete dissociation of the
solute.)

A. Elizabeth H.
Numerade Educator

Problem 94

An aqueous CaCl2 solution has a vapor pressure of 81.6 mmHg at
50 C. The vapor pressure of pure water at this temperature is
92.6 mmHg. What is the concentration of CaCl2 in mass percent?
(Assume complete dissociation of the solute.)

George M.
Numerade Educator

Problem 95

The solubility of carbon tetrachloride(CCl4) in water at 25 C is
1.2 g>L. The solubility of chloroform(CHCl3) at the same temperature
is 10.1 g>L. Why is chloroform almost ten times more
soluble in water than carbon tetrachloride?

A. Elizabeth H.
Numerade Educator

Problem 96

The solubility of phenol in water at 25 C is 8.7 g>L. The solubility
of naphthol at the same temperature is only 0.074 g>L. Examine
the structures of phenol and naphthol shown here and explain
why phenol is so much more soluble than naphthol.

George M.
Numerade Educator

Problem 97

Potassium perchlorate (KClO4) has a lattice energy of -599 kJ>mol
and a heat of hydration of -548 kJ>mol. Find the heat of solution
for potassium perchlorate and determine the temperature change
that occurs when 10.0 g of potassium perchlorate is dissolved with
enough water to make 100.0 mL of solution. (Assume a heat capacity
of 4.05 J>g # C for the solution and a density of 1.05 g>mL.)

A. Elizabeth H.
Numerade Educator

Problem 98

Sodium hydroxide (NaOH) has a lattice energy of -887 kJ>mol
and a heat of hydration of -932 kJ>mol. How much solution
could be heated to boiling by the heat evolved by the dissolution
of 25.0 g of NaOH? (For the solution, assume a heat capacity of
4.0 J>g # C, an initial temperature of 25.0 C, a boiling point of
100.0 C, and a density of 1.05 g>mL.)

George M.
Numerade Educator

Problem 99

A saturated solution forms when 0.0537 L of argon, at a pressure
of 1.0 atm and temperature of 25 C, is dissolved in 1.0 L of water.
Calculate the Henry"
s law constant for argon.

A. Elizabeth H.
Numerade Educator

Problem 100

A gas has a Henry"s law constant of 0.112 M>atm. What total
volume of solution is needed to completely dissolve 1.65 L of the
gas at a pressure of 725 torr and a temperature of 25 C?

George M.
Numerade Educator

Problem 101

The Safe Drinking Water Act (SDWA) sets a limit for mercury-a
toxin to the central nervous system-at 0.0020 ppm by mass.
Water suppliers must periodically test their water to ensure that
mercury levels do not exceed this limit. Suppose water becomes
contaminated with mercury at twice the legal limit (0.0040 ppm).
How much of this water would a person have to consume to
ingest 50.0 mg of mercury?

Jekaterina V.
Numerade Educator

Problem 102

Water softeners often replace calcium ions in hard water with
sodium ions. Because sodium compounds are soluble, the
presence of sodium ions in water does not cause the white,
scaly residues caused by calcium ions. However, calcium is
more beneficial to human health than sodium because calcium
is a necessary part of the human diet, while high levels of
sodium intake are linked to increases in blood pressure. The
U.S. Food and Drug Administration (FDA) recommends that
adults ingest less than 2.4 g of sodium per day. How many
liters of softened water, containing a sodium concentration of
0.050% sodium by mass, does a person have to consume to
exceed the FDA recommendation? (Assume a water density of
1.0 g >mL.)

George M.
Numerade Educator

Problem 103

An aqueous solution contains 12.5% NaCl by mass. What mass of
water (in grams) is contained in 2.5 L of the vapor above this
solution at 55 C? The vapor pressure of pure water at 55 C is
118 torr. (Assume complete dissociation of NaCl.)

A. Elizabeth H.
Numerade Educator

Problem 104

The vapor above an aqueous solution contains 19.5 mg water per
liter at 25 C. Assuming ideal behavior, what is the concentration
of the solute within the solution in mole percent?

George M.
Numerade Educator

Problem 105

What is the freezing point of an aqueous solution that boils at
106.5 C?

A. Elizabeth H.
Numerade Educator

Problem 106

What is the boiling point of an aqueous solution that has a vapor
pressure of 20.5 torr at 25 C? (Assume a nonvolatile solute.)

George M.
Numerade Educator

Problem 107

An isotonic solution contains 0.90% NaCl mass to volume.
Calculate the percent mass to volume for isotonic solutions containing
each solute at 25 C. Assume a van"t Hoff factor of 1.9 for
all ionic solutes.
a. KCl
b. NaBr
c. glucose(C6H12O6)

A. Elizabeth H.
Numerade Educator

Problem 108

Magnesium citrate, Mg3(C6H5O7)2, belongs to a class of laxatives
called hyperosmotics, which cause rapid emptying of the bowel.
When a person consumes a concentrated solution of magnesium citrate,
it passes through the intestines, drawing water and promoting
diarrhea, usually within 6 hours. Calculate the osmotic pressure of
a magnesium citrate laxative solution containing 28.5 g of magnesium
citrate in 235 mL of solution at 37 C (approximate body temperature).
Assume complete dissociation of the ionic compound.

George M.
Numerade Educator

Problem 109

A solution is prepared from 4.5701 g of magnesium chloride and
43.238 g of water. The vapor pressure of water above this solution
is 0.3624 atm at 348.0 K. The vapor pressure of pure water at this
temperature is 0.3804 atm. Find the value of the van"
t Hoff factor
(i) for magnesium chloride in this solution.

A. Elizabeth H.
Numerade Educator

Problem 110

When HNO2 dissolves in water, it partially dissociates according
to the equation HNO2(aq)H+(aq) + NO2
-(aq). A
solution contains 7.050 g of HNO2 in 1.000 kg of water. Its
freezing point is -0.2929 C. Calculate the fraction of HNO2
that has dissociated.

George M.
Numerade Educator

Problem 111

A solution of a nonvolatile solute in water has a boiling point of
375.3 K. Calculate the vapor pressure of water above this solution
at 338 K. The vapor pressure of pure water at this temperature is
0.2467 atm.

A. Elizabeth H.
Numerade Educator

Problem 112

The density of a 0.438-M solution of potassium chromate (K2CrO4)
at 298 K is 1.063 g>mL. Calculate the vapor pressure of water
above the solution. The vapor pressure of pure water at this
temperature is 0.0313 atm. (Assume complete dissociation of the
solute.)

George M.
Numerade Educator

Problem 113

The vapor pressure of carbon tetrachloride, CCl4, is 0.354 atm,
and the vapor pressure of chloroform, CHCl3, is 0.526 atm at
316 K. A solution is prepared from equal masses of these two
compounds at this temperature. Calculate the mole fraction of
the chloroform in the vapor above the solution. If the vapor
above the original solution is condensed and isolated into a
separate flask, what would the vapor pressure of chloroform be
above this new solution?

A. Elizabeth H.
Numerade Educator

Problem 114

Distillation is a method of purification based on successive
separations and recondensations of vapor above a solution. Use
the result of the previous problem to calculate the mole fraction
of chloroform in the vapor above a solution obtained by three
successive separations and condensations of the vapors above
the original solution of carbon tetrachloride and chloroform.
Show how this result supports the use of distillation as a
separation method.

Aadit S.
Numerade Educator

Problem 115

A solution of 49.0% H2SO4 by mass has a density of 1.39 g>cm3 at
293 K. A 25.0 cm3 sample of this solution is mixed with enough
water to increase the volume of the solution to 99.8 cm3. Find the
molarity of sulfuric acid in this solution.

A. Elizabeth H.
Numerade Educator

Problem 116

Find the mass of urea (CH4N2O) needed to prepare 50.0 g of a
solution in water in which the mole fraction of urea is 0.0770.

George M.
Numerade Educator

Problem 117

A solution contains 10.05 g of unknown compound dissolved in
50.0 mL of water. (Assume a density of 1.00 g>mL for water.) The
freezing point of the solution is -3.16 C. The mass percent
composition of the compound is 60.97% C, 11.94% H, and the
rest is O. What is the molecular formula of the compound?

A. Elizabeth H.
Numerade Educator

Problem 118

The osmotic pressure of a solution containing 2.10 g of an
unknown compound dissolved in 175.0 mL of solution at 25 C is
1.93 atm. The combustion of 24.02 g of the unknown compound
produced 28.16 g CO2 and 8.64 g H2O. What is the molecular
formula of the compound (which contains only carbon, hydrogen,
and oxygen)?

George M.
Numerade Educator

Problem 119

A 100.0-mL aqueous sodium chloride solution is 13.5% NaCl by
mass and has a density of 1.12 g>mL. What would you add
(solute or solvent) and what mass of it to make the boiling point
of the solution 104.4 C? (Use i = 1.8 for NaCl.)

A. Elizabeth H.
Numerade Educator

Problem 120

A 50.0-mL solution is initially 1.55% MgCl2 by mass and has a
density of 1.05 g>mL. What is the freezing point of the solution
after you add an additional 1.35 g MgCl2? (Use i = 2.5 for
MgCl2.)

George M.
Numerade Educator

Problem 122

The vapor above a mixture of pentane and hexane at room
temperature contains 35.5% pentane by mass. What is the mass
percent composition of the solution? Pure pentane and hexane
have vapor pressures of 425 torr and 151 torr, respectively, at
room temperature.

George M.
Numerade Educator

Problem 123

A 1.10-g sample contains only glucose (C6H12O6) and sucrose
(C12H22O11). When the sample is dissolved in water to a total
solution volume of 25.0 mL, the osmotic pressure of the solution
is 3.78 atm at 298 K. What is the mass percent composition of
glucose and sucrose in the sample?

Aadit S.
Numerade Educator

Problem 124

A solution is prepared by mixing 631 mL of methanol with
501mL of water. The molarity of methanol in the resulting
solution is 14.29 M. The density of methanol at this temperature
is 0.792 g>mL. Calculate the difference in volume between this
solution and the total volume of water and methanol that were
mixed to prepare the solution.

George M.
Numerade Educator

Problem 125

Two alcohols, isopropyl alcohol and propyl alcohol, have the
same molecular formula, C3H8O. A solution of the two that is
two-thirds by mass isopropyl alcohol has a vapor pressure of
0.110 atm at 313 K. A solution that is one-third by mass
isopropyl alcohol has a vapor pressure of 0.089 atm at 313 K.
Calculate the vapor pressure of each pure alcohol at this temperature.
Explain the difference given that the formula of
propyl alcohol is CH3CH2CH2OH and that of isopropyl alcohol
is (CH3)2CHOH.

A. Elizabeth H.
Numerade Educator

Problem 126

A metal, M, of atomic mass 96 amu reacts with fluorine to form a
salt that can be represented as MFx. In order to determine x and
therefore the formula of the salt, a boiling point elevation
experiment is performed. A 9.18-g sample of the salt is dissolved
in 100.0 g of water, and the boiling point of the solution is found
to be 374.38 K. Find the formula of the salt. (Assume complete
dissociation of the salt in solution.)

George M.
Numerade Educator

Problem 127

Sulfuric acid in water dissociates completely into H+ and HSO4
-
ions. The HSO4
- ion dissociates to a limited extent into H+ and
SO4
-. The freezing point of a 0.1000-m solution of sulfuric acid in
water is 272.76 K. Calculate the molality of SO4
- in the solution,
assuming ideal solution behavior.

Aadit S.
Numerade Educator

Problem 128

A solution of 75.0 g of benzene (C6H6) and 75.0 g of toluene
(C7H8) has a total vapor pressure of 80.9 mmHg at 303 K.
Another solution of 100.0-g benzene and 50.0-g toluene has a
total vapor pressure of 93.9 mmHg at this temperature. Find the
vapor pressure of pure benzene and pure toluene at 303 K.
(Assume ideal solutions.)

George M.
Numerade Educator

Problem 129

A solution is prepared by dissolving 11.60 g of a mixture of
sodium carbonate and sodium bicarbonate in 1.00 L of water. A
300.0 cm3 sample of the solution is treated with excess HNO3
and boiled to remove all the dissolved gas. A total of 0.940 L of
dry CO2 is collected at 298 K and 0.972 atm. Find the molarity of
the carbonate and bicarbonate in the solution.

Aadit S.
Numerade Educator

Problem 130

Substance A is a nonpolar liquid and has only dispersion forces
among its constituent particles. Substance B is also a nonpolar
liquid and has about the same magnitude of dispersion forces
among its constituent particles as substance A. When substance
A and B are combined, they spontaneously mix.
a. Why do the two substances mix?
b. Predict the sign and magnitude of Hsoln.
c. Determine the signs and relative magnitudes of Hsolute,
Hsolvent, and Hmix.

George M.
Numerade Educator

Problem 131

A power plant built on a river uses river water as a coolant. The
water is warmed as it is used in heat exchangers within the plant.
Should the warm water be immediately cycled back into the
river? Why or why not?

A. Elizabeth H.
Numerade Educator

Problem 132

The vapor pressure of a 1-M ionic solution is different from the
vapor pressure of a 1-M nonelectrolyte solution. In both cases,
the solute is nonvolatile. Which set of diagrams best represents
the differences between the two solutions and their vapors?

Aadit S.
Numerade Educator

Problem 133

If each substance listed here costs the same amount per kilogram,
which would be most cost-effective as a way to lower the
freezing point of water? (Assume complete dissociation for all
ionic compounds.) Explain.
a. HOCH2CH2OH
b. NaCl
c. KCl
d. MgCl2
e. SrCl2

A. Elizabeth H.
Numerade Educator

Problem 134

A helium balloon inflated on one day falls to the ground the next
day. The volume of the balloon decreases somewhat overnight
but not by enough to explain why it no longer floats. (If you
inflate a new balloon with helium to the same size as the balloon
that fell to the ground, the newly inflated balloon floats.)
Explain.

George M.
Numerade Educator

Problem 135

Explain why 1-propanol (CH3CH2CH2OH) is miscible in both
water (H2O) and hexane (C6H6) when hexane and water are
barely soluble in each other.

A. Elizabeth H.
Numerade Educator

Problem 136

Have each group member make a flashcard with one of the following
on the front: Hsoln, Hlattice, Hsolvent, Hmix, and
Hhydration. On the back of the card, each group member should
describe (in words) the H process his or her card lists and how
that H relates to other H values mathematically. Each member
then presents his or her H to the group. After everyone has
presented, members should trade cards and quiz each other.

George M.
Numerade Educator

Problem 137

Complete the table by adding increases, decreases, or no effect:

A. Elizabeth H.
Numerade Educator

Problem 138

138. When 13.62 g (about one tablespoon) of table sugar (sucrose,
C12H22O11) is dissolved in 241.5 mL of water (density 0.997 g>mL),
the final volume is 250.0 mL (about one cup). Have each group
member calculate one of the following for the solution, and present
his or her answer to the group:
a. mass percent
b. molarity
c. molality

George M.
Numerade Educator

Problem 139

Calculate the expected boiling and freezing points for the solution
in the previous problem. If you had to bring this syrup to the
boiling point for a recipe, would you expect it to take much more
time than it takes to boil the same amount of pure water? Why or
why not? Would the syrup freeze in a typical freezer (-18 C)?
Why or why not?

A. Elizabeth H.
Numerade Educator

Problem 140

The salinity of seawater can vary in the world"s oceans as shown
in the map, which indicates salinity in units of percent by mass
NaCl. Examine the image and answer the questions.
a. Which regions of the globe generally have higher salinity?
Lower salinity? State your answer as a general trend in the
salinity of seawater.
b. Speculate on possible reasons for the trend you observed in
part a.
c. Calculate the freezing point of a sample of seawater taken
from the middle of the Atlantic Ocean. Use a van"t Hoff factor
of 1.9 for your calculation.
d. Make a graph of the freezing point of the seawater versus salinity
for the range of salinities in the world"s oceans.

George M.
Numerade Educator