Chemistry A Molecular Approach

Nivaldo J. Tro

Chapter 14

Solutions - all with Video Answers

Educators

Chapter Questions

Problem 1

Explain why drinking seawater results in dehydration.

Amy Jiang

Amy Jiang

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Problem 2

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

Qiao Ruan

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Problem 3

What does it mean to say that a substance is soluble in another substance? Which units are used in reporting solubility?

Amy Jiang

Numerade Educator

Problem 4

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

Qiao Ruan

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Problem 5

What is entropy? Why is entropy important in discussing the formation of solutions?

Amy Jiang

Numerade Educator

Problem 6

What kinds of intermolecular forces are involved in solution formation?

Jekaterina Viktorova

Jekaterina Viktorova

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Problem 7

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

George Mckeown

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Problem 8

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

Qiao Ruan

Numerade Educator

Problem 9

What are the three steps involved in evaluating the enthalp: changes associated with solution formation?

Shahina -

Numerade Educator

Problem 10

What is the heat of hydration $\left(\Delta H_{\text {hydration }}\right) ?$ How does the enthalpy of solution depend on the relative magnitudes of $\Delta H_{\text {solute }}$ and $\Delta H_{\text {hydration }} ?$

Jacqueline Winston

Jacqueline Winston

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Problem 11

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

George Mckeown

Numerade Educator

Problem 12

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

Adriano Chikande

Adriano Chikande

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Problem 13

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

Amy Jiang

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Problem 14

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

Qiao Ruan

Numerade Educator

Problem 15

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

Amy Jiang

Numerade Educator

Problem 16

What are the common units for expressing solution concentration?

Qiao Ruan

Numerade Educator

Problem 17

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

Aadit Sharma

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Problem 18

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?

Qiao Ruan

Numerade Educator

Problem 19

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

George Mckeown

Numerade Educator

Problem 20

Explain the difference between an ideal and a nonideal solution.

Jekaterina Viktorova

Jekaterina Viktorova

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Problem 21

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

George Mckeown

Numerade Educator

Problem 22

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 Viktorova

Jekaterina Viktorova

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Problem 23

What are colligative nronerties?

Jennifer Hudspeth

Jennifer Hudspeth

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Problem 24

What is osmosis? What is osmotic pressure?

Jekaterina Viktorova

Jekaterina Viktorova

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Problem 25

Explain the meaning of the van't Hoff factor and its role in determining the colligative properties of solutions containing ionic solutes.

Amy Jiang

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Problem 26

Describe a colloidal dispersion. What is the difference between a colloidal dispersion and a true solution?

Qiao Ruan

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Problem 27

What is the Tyndall effect, and how can it be used to help identify colloidal dispersions?

Amy Jiang

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Problem 28

What keeps the particles in a colloidal dispersion from coalescing?

Qiao Ruan

Numerade Educator

Problem 29

Pick an appropriate solvent from Table 14.3 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)

Amy Jiang

Numerade Educator

Problem 30

Pick an appropriate solvent from table 14.3 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)

Qiao Ruan

Numerade Educator

Problem 31

Which molecule would you expect to be more soluble in water:

Ronald Prasad

Numerade Educator

Problem 32

Which molecule would you expect to be more soluble in water: $\mathrm{CCl}_{4}$ or $\mathrm{CH}_{2} \mathrm{Cl}_{2} ?$

Ma Ednelyn Lim

Numerade Educator

Problem 33

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.
a. glucose
b. naphthalene
c. dimethyl ether

Shalini Tyagi

Numerade Educator

Problem 34

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.
a. toluene
b. sucrose (table sugar)
c. isobutene
d. ethylene glycol

Qiao Ruan

Numerade Educator

Problem 35

When ammonium chloride $\left(\mathrm{NH}_{4} \mathrm{Cl}\right)$ 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 14.7 for the dissolution of $\mathrm{NH}_{4} \mathrm{Cl}$.
d. Why does the solution form? What drives the process?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 36

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 14.7 for the dissolution of Lil.

David Collins

Numerade Educator

Problem 37

Silver nitrate has a lattice energy of $-820 \mathrm{~kJ} / \mathrm{mol}$ and a heat of solution of $22.6 \mathrm{~kJ} / \mathrm{mol}$. Calculate the heat of hydration for silver nitrate.

Amy Jiang

Numerade Educator

Problem 38

Use the 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?
$$
\begin{array}{lcc}
\text { Compound } & \text { Lattice Energy (kJ/mol) } & \Delta H_{\text {soln }}(\mathrm{kJ} / \mathrm{mol}) \\
\hline \mathrm{LiCl} & -834 & -37.0 \\
\hline \mathrm{NaCl} & -769 & +3.88 \\
\hline
\end{array}
$$

Shahina -

Numerade Educator

Problem 39

Lithium iodide has a lattice energy of $-7.3 \times 10^{2} \mathrm{~kJ} / \mathrm{mol}$ and a heat of hydration of $-793 \mathrm{~kJ} / \mathrm{mol}$. Find the heat of solution for lithium iodide and determine how much heat is evolved or absorbed when $15.0 \mathrm{~g}$ of lithium iodide completely dissolves in water.

Amy Jiang

Numerade Educator

Problem 40

Potassium nitrate has a lattice energy of $-163.8 \mathrm{kcal} / \mathrm{mol}$ and a heat of hydration of -155.5 kcal/mol. How much potassium nitrate has to dissolve in water to absorb $1.00 \times 10^{2} \mathrm{~kJ}$ of heat?

Qiao Ruan

Numerade Educator

Problem 41

A solution contains $25 \mathrm{~g}$ of $\mathrm{NaCl}$ per $100.0 \mathrm{~g}$ of water at $25^{\circ} \mathrm{C}$. Is the solution unsaturated, saturated, or supersaturated? (Use Figure 14.11 .)

Amy Jiang

Numerade Educator

Problem 42

A solution contains 32 g of $\mathrm{KNO}_{3}$ per $100.0 \mathrm{~g}$ of water at $25^{\circ} \mathrm{C}$. Is the solution unsaturated, saturated, or supersaturated? (Use Figure $14.11 .)$

Qiao Ruan

Numerade Educator

Problem 43

A KNO $_{3}$ solution containing 45 g of $\mathrm{KNO}_{3}$ per $100.0 \mathrm{~g}$ of water is cooled from $40^{\circ} \mathrm{C}$ to $0^{\circ} \mathrm{C}$. What happens during cooling? (Use Figure 14.11.)

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 44

A KCl solution containing 42 g of KCl per 100.0 g of water is cooled from $60^{\circ} \mathrm{C}$ to $0{ }^{\circ} \mathrm{C}$. What happens during cooling? (Use Figure $14.11 .)$

Qiao Ruan

Numerade Educator

Problem 45

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

Amy Jiang

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Problem 46

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 Mckeown

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Problem 47

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?

Amy Jiang

Numerade Educator

Problem 48

Scuba divers breathing air at increased pressure can suffer from oxygen toxicity-too much oxygen in their bloodstreamwhen 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?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 49

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

Amy Jiang

Numerade Educator

Problem 50

Use Henry's law to determine the molar solubility of helium at a pressure of 1.0 atm and $25^{\circ} \mathrm{C}$.

Qiao Ruan

Numerade Educator

Problem 51

eAn aqueous NaCl solution is made using $112 \mathrm{~g}$ of $\mathrm{NaCl}$ diluted to a total solution volume of $1.00 \mathrm{~L}$. Calculate the molarity, molality, and mass percent of the solution. (Assume a density of $1.08 \mathrm{~g} / \mathrm{mL}$ for the solution. $)$

Amy Jiang

Numerade Educator

Problem 52

An aqueous KNO $_{3}$ solution is made using $72.5 \mathrm{~g}$ of $\mathrm{KNO}_{3}$ diluted to a total solution volume of $2.00 \mathrm{~L}$. Calculate the molarity, molality, and mass percent of the solution. (Assume a density of $1.05 \mathrm{~g} / \mathrm{mL}$ for the solution.

Jacqueline Winston

Jacqueline Winston

Numerade Educator

Problem 53

To what volume should you dilute $50.0 \mathrm{~mL}$ of a $5.00 \mathrm{M}$ KI solution so that $25.0 \mathrm{~mL}$ of the diluted solution contains $3.05 \mathrm{~g}$ of KI?

Amy Jiang

Numerade Educator

Problem 54

To what volume should you dilute $125 \mathrm{~mL}$ of an $8.00 \mathrm{M} \mathrm{CuCl}_{2}$ solution so that $50.0 \mathrm{~mL}$ of the diluted solution contains $4.67 \mathrm{~g}$ $\mathrm{CuCl}_{2} ?$

Qiao Ruan

Numerade Educator

Problem 55

Silver nitrate solutions are often used to plate silver onto other metals. What is the maximum amount of silver (in grams) that can be plated out of $4.8 \mathrm{~L}$ of an $\mathrm{AgNO}_{3}$ solution containing $3.4 \%$ Ag by mass? Assume that the density of the solution is $1.01 \mathrm{~g} / \mathrm{mL}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 56

A dioxin-contaminated water source contains $0.085 \%$ dioxin by mass. How much dioxin is present in $2.5 \mathrm{~L}$ of this water? Assume a density of $1.00 \mathrm{~g} / \mathrm{mL}$

Jacqueline Winston

Jacqueline Winston

Numerade Educator

Problem 57

A hard water sample contains $0.0085 \%$ Ca by mass (in the form of $\mathrm{Ca}^{2+}$ ions). How much water (in grams) contains $1.2 \mathrm{~g}$ of Ca? (1.2 g of Ca is the recommended daily allowance of calcium for adults between 19 and 24 years old. $)$

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 58

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

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 59

You can purchase nitric acid in a concentrated form that is $70.3 \% \mathrm{HNO}_{3}$ by mass and has a density of $1.41 \mathrm{~g} / \mathrm{mL}$. Describe exactly how you would prepare $1.15 \mathrm{~L}$ of $0.100 \mathrm{M} \mathrm{HNO}_{3}$ from the concentrated solution.

Amy Jiang

Numerade Educator

Problem 60

You can purchase hydrochloric acid in a concentrated form that is $37.0 \% \mathrm{HCl}$ by mass and that has a density of $1.20 \mathrm{~g} / \mathrm{mL} .$ Describe exactly how to prepare $2.85 \mathrm{~L}$ of $0.500 \mathrm{M} \mathrm{HCl}$ from the concentrated solution.

Qiao Ruan

Numerade Educator

Problem 61

Describe how to prepare each solution from the dry solute and the solvent.
a. $1.00 \times 10^{2} \mathrm{~mL}$ of $0.500 \mathrm{M} \mathrm{KCl}$
b. $1.00 \times 10^{2} \mathrm{~g}$ of $0.500 \mathrm{~m} \mathrm{KCl}$
c. $1.00 \times 10^{2} \mathrm{~g}$ of $5.0 \% \mathrm{KCl}$ solution by mass

Amy Jiang

Numerade Educator

Problem 62

Describe how to prepare each solution from the dry solute and the solvent.
a. $125 \mathrm{~mL}$ of $0.100 \mathrm{M} \mathrm{NaNO}_{3}$
b. $125 \mathrm{~g}$ of $0.100 \mathrm{~m} \mathrm{NaNO}_{3}$
c. $125 \mathrm{~g}$ of $1.0 \% \mathrm{NaNO}_{3}$ solution by mass

Qiao Ruan

Numerade Educator

Problem 63

A solution is prepared by dissolving $28.4 \mathrm{~g}$ of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ 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

Pahk Thepchatri

Pahk Thepchatri

Numerade Educator

Problem 64

A solution is prepared by dissolving $20.2 \mathrm{~mL}$ of methanol $\left(\mathrm{CH}_{3} \mathrm{OH}\right)$ in $100.0 \mathrm{~mL}$ of water at $25^{\circ} \mathrm{C} .$ The final volume of the solution is $118 \mathrm{~mL}$. The densities of methanol and water at this temperature are $0.782 \mathrm{~g} / \mathrm{mL}$ and $1.00 \mathrm{~g} / \mathrm{mL}$, respectively. For this solution, calculate the concentration in each unit.
a. molarity
b. molality
c. percent by mass
d. mole fraction
e. mole percent

Qiao Ruan

Numerade Educator

Problem 65

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 $1.01 \mathrm{~g} / \mathrm{mL}$.)

Amy Jiang

Numerade Educator

Problem 66

One brand of laundry bleach is an aqueous solution containing $4.55 \%$ sodium hypochlorite $(\mathrm{NaOCl})$ by mass. What is the molarity of this solution? (Assume a density of $1.02 \mathrm{~g} / \mathrm{mL} .)$

Qiao Ruan

Numerade Educator

Problem 67

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

NG

Natasha Gunawan

Numerade Educator

Problem 68

An aqueous solution contains $5.0 \% \mathrm{NaCl}$ by mass. Calculate the molality and mole fraction of the solution.

Qiao Ruan

Numerade Educator

Problem 69

A beaker contains $100.0 \mathrm{~mL}$ of pure water. A second beaker contains $100.0 \mathrm{~mL}$ of seawater. The two beakers are left side by side on a lab bench for 1 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?

Amy Jiang

Numerade Educator

Problem 70

Which solution has the highest vapor pressure?
a. $20.0 \mathrm{~g}$ of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ in $100.0 \mathrm{~mL}$ of water
b. $20.0 \mathrm{~g}$ of sucrose $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)$ in $100.0 \mathrm{~mL}$ of water
c. $10.0 \mathrm{~g}$ of potassium acetate $\mathrm{KC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ in $100.0 \mathrm{~mL}$ of water

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 71

Calculate the vapor pressure of a solution containing $24.5 \mathrm{~g}$ of glycerin $\left(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}\right)$ in $135 \mathrm{~mL}$ of water at $30.0^{\circ} \mathrm{C}$. The vapor pressure of pure water at this temperature is 31.8 torr. Assume that glycerin is not volatile and dissolves molecularly (i.e., it is not ionic), and use a density of $1.00 \mathrm{~g} / \mathrm{mL}$ for the water.

Shahina -

Numerade Educator

Problem 72

A solution contains naphthalene $\left(\mathrm{C}_{10} \mathrm{H}_{8}\right)$ dissolved in hexane $\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)$ at a concentration of $12.35 \%$ naphthalene by mass. Calculate the vapor pressure at $25^{\circ} \mathrm{C}$ of hexane above the solution. The vapor pressure of pure hexane at $25^{\circ} \mathrm{C}$ is 151 torr.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 73

A solution contains $50.0 \mathrm{~g}$ of heptane $\left(\mathrm{C}_{7} \mathrm{H}_{16}\right)$ and $50.0 \mathrm{~g}$ of octane $\left(\mathrm{C}_{8} \mathrm{H}_{18}\right)$ at $25^{\circ} \mathrm{C}$. The vapor pressures of pure heptane and pure octane at $25^{\circ} \mathrm{C}$ are 45.8 torr and 10.9 torr, respectively. Assuming ideal behavior, answer the following:
a. What is the vapor pressure of each of the solution components 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?

David Collins

Numerade Educator

Problem 74

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 Mckeown

Numerade Educator

Problem 75

A solution contains $4.08 \mathrm{~g}$ of chloroform $\left(\mathrm{CHCl}_{3}\right)$ and $9.29 \mathrm{~g}$ of acetone $\left(\mathrm{CH}_{3} \mathrm{COCH}_{3}\right) .$ The vapor pressures at $35^{\circ} \mathrm{C}$ of pure chloroform and pure acetone are 295 torr and 332 torr, respectively. Assuming ideal behavior, calculate the vapor pressures of each of the components and the total vapor pressure above the solution. The experimentally measured total vapor pressure of the solution at $35^{\circ} \mathrm{C}$ 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?

Pahk Thepchatri

Pahk Thepchatri

Numerade Educator

Problem 76

A solution of methanol and water has a mole fraction of water of 0.312 and a total vapor pressure of 211 torr at $39.9{ }^{\circ} \mathrm{C}$. 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?

Qiao Ruan

Numerade Educator

Problem 77

A glucose solution contains $55.8 \mathrm{~g}$ of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ in $455 \mathrm{~g}$ of water. Determine the freezing point and boiling point of the solution.

Pahk Thepchatri

Pahk Thepchatri

Numerade Educator

Problem 78

An ethylene glycol solution contains $21.2 \mathrm{~g}$ of ethylene glycol $\left(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}\right)$ in $85.4 \mathrm{~mL}$ of water. Determine the freezing point and boiling point of the solution. (Assume a density of $1.00 \mathrm{~g} / \mathrm{mL}$ for water.)

Qiao Ruan

Numerade Educator

Problem 79

Calculate the freezing point and boiling point of a solution containing $10.0 \mathrm{~g}$ of naphthalene $\left(\mathrm{C}_{10} \mathrm{H}_{8}\right)$ in $100.0 \mathrm{~mL}$ of benzene. Benzene has a density of $0.877 \mathrm{~g} / \mathrm{cm}^{3}$.

David Collins

Numerade Educator

Problem 80

Calculate the freezing point and boiling point of a solution containing $7.55 \mathrm{~g}$ of ethylene glycol $\left(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}\right)$ in $85.7 \mathrm{~mL}$ of ethanol. Ethanol has a density of $0.789 \mathrm{~g} / \mathrm{cm}^{3} .$

Qiao Ruan

Numerade Educator

Problem 81

An aqueous solution containing $17.5 \mathrm{~g}$ of an unknown molecular (nonelectrolyte) compound in $100.0 \mathrm{~g}$ of water has a freezing point of $-1.8^{\circ} \mathrm{C}$. Calculate the molar mass of the unknown compound.

Amy Jiang

Numerade Educator

Problem 82

An aqueous solution containing $35.9 \mathrm{~g}$ of an unknown molecular (nonelectrolyte) compound in $150.0 \mathrm{~g}$ of water has a freezing point of $-1.3^{\circ} \mathrm{C}$. Calculate the molar mass of the unknown compound.

Qiao Ruan

Numerade Educator

Problem 83

Calculate the osmotic pressure of a solution containing $24.6 \mathrm{~g}$ of glycerin $\left(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}\right)$ in $250.0 \mathrm{~mL}$ of solution at $298 \mathrm{~K}$.

DT

David Tompkins

Numerade Educator

Problem 84

What mass of sucrose $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)$ would you combine with $5.00 \times 10^{2} \mathrm{~g}$ of water to make a solution with an osmotic pressure of 8.55 atm at 298 K? (Assume a density of $1.0 \mathrm{~g} / \mathrm{mL}$ for the solution.)

Jacqueline Winston

Jacqueline Winston

Numerade Educator

Problem 85

A solution containing $27.55 \mathrm{mg}$ of an unknown protein per $25.0 \mathrm{~mL}$ solution was found to have an osmotic pressure of 3.22 torr at $25^{\circ} \mathrm{C} .$ What is the molar mass of the protein?

DT

David Tompkins

Numerade Educator

Problem 86

Calculate the osmotic pressure of a solution containing $18.75 \mathrm{mg}$ of hemoglobin in $15.0 \mathrm{~mL}$ of solution at $25^{\circ} \mathrm{C}$. The molar mass of hemoglobin is $6.5 \times 10^{4} \mathrm{~g} / \mathrm{mol}$.

Qiao Ruan

Numerade Educator

Problem 87

Calculate the freezing point and boiling point of each aqueous solution, assuming complete dissociation of the solute.
a. $0.100 \mathrm{~m} \mathrm{~K}_{2} \mathrm{~S}$
b. $21.5 \mathrm{~g}$ of $\mathrm{CuCl}_{2}$ in $4.50 \times 10^{2} \mathrm{~g}$ water
c. $5.5 \% \mathrm{NaNO}_{3}$ by mass (in water)

David Collins

Numerade Educator

Problem 88

Calculate the freezing point and boiling point in each solution, assuming complete dissociation of the solute.
a. $10.5 \mathrm{~g} \mathrm{FeCl}_{3}$ in $1.50 \times 10^{2} \mathrm{~g}$ water
b. $3.5 \%$ KCl by mass (in water)
c. $0.150 \mathrm{~m} \mathrm{MgF}_{2}$

Qiao Ruan

Numerade Educator

Problem 89

What mass of salt (NaCl) should you add to $1.00 \mathrm{~L}$ of water in an ice-cream maker to make a solution that freezes at $-10.0^{\circ} \mathrm{C} ?$ Assume complete dissociation of the $\mathrm{NaCl}$ and density of $1.00 \mathrm{~g} / \mathrm{mL}$ for water.

Pahk Thepchatri

Pahk Thepchatri

Numerade Educator

Problem 90

Determine the required concentration (in percent by mass) for an aqueous ethylene glycol ( $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}$ ) solution to have a boiling point of $104.0^{\circ} \mathrm{C}$

Qiao Ruan

Numerade Educator

Problem 91

Use the van't Hoff factors in Table 14.9 to calculate each colligative property:
a. the melting point of a $0.100 \mathrm{~m}$ iron(III) chloride solution
b. the osmotic pressure of a $0.085 \mathrm{M}$ potassium sulfate solution at $298 \mathrm{~K}$
c. the boiling point of a $1.22 \%$ by mass magnesium chloride solution

David Collins

Numerade Educator

Problem 92

Using the van't Hoff factors in Table $14.9,$ calculate the mass of solute required to make each aqueous solution:
a. a sodium chloride solution containing $1.50 \times 10^{2} \mathrm{~g}$ of water that has a melting point of $-1.0^{\circ} \mathrm{C}$
b. $2.50 \times 10^{2} \mathrm{~mL}$ of a magnesium sulfate solution that has an osmotic pressure of 3.82 atm at $298 \mathrm{~K}$
c. an iron(III) chloride solution containing $2.50 \times 10^{2} \mathrm{~g}$ of water that has a boiling point of $102^{\circ} \mathrm{C}$

David Collins

Numerade Educator

Problem 93

A $1.2 \mathrm{~m}$ aqueous solution of an ionic compound with the formula $\mathrm{MX}_{2}$ has a boiling point of $101.4^{\circ} \mathrm{C}$. Calculate the van't Hoff factor ( $i$ ) for $\mathrm{MX}_{2}$ at this concentration.

Pahk Thepchatri

Pahk Thepchatri

Numerade Educator

Problem 94

A $0.95 \mathrm{~m}$ aqueous solution of an ionic compound with the formula MX has a freezing point of $-3.0^{\circ} \mathrm{C}$. Calculate the van't Hoff factor (i) for MX at this concentration.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 95

A $0.100 \mathrm{M}$ ionic solution has an osmotic pressure of 8.3 atm at $25^{\circ} \mathrm{C} .$ Calculate the van't Hoff factor (i) for this solution.

Pahk Thepchatri

Pahk Thepchatri

Numerade Educator

Problem 96

A solution contains $8.92 \mathrm{~g}$ of $\mathrm{KBr}$ in $500.0 \mathrm{~mL}$ of solution and has an osmotic pressure of 6.97 atm at $25^{\circ} \mathrm{C}$. Calculate the van't Hoff factor ( $i$ ) for $\mathrm{KBr}$ at this concentration.

Qiao Ruan

Numerade Educator

Problem 97

Calculate the vapor pressure at $25^{\circ} \mathrm{C}$ of an aqueous solution that is $5.50 \%$ NaCl by mass. (Assume complete dissociation of the solute.)

Jacqueline Winston

Jacqueline Winston

Numerade Educator

Problem 98

An aqueous $\mathrm{CaCl}_{2}$ solution has a vapor pressure of $81.6 \mathrm{mmHg}$ at $50^{\circ} \mathrm{C}$. The vapor pressure of pure water at this temperature is $92.6 \mathrm{mmHg} .$ What is the concentration of $\mathrm{CaCl}_{2}$ in mass percent? (Assume complete dissociation of the solute.)

Jacqueline Winston

Jacqueline Winston

Numerade Educator

Problem 99

The solubility of carbon tetrachloride $\left(\mathrm{CCl}_{4}\right)$ in water at $25^{\circ} \mathrm{C}$ is $1.2 \mathrm{~g} / \mathrm{L} .$ The solubility of chloroform $\left(\mathrm{CHCl}_{3}\right)$ at the same temperature is $10.1 \mathrm{~g} / \mathrm{L}$. Why is chloroform almost ten times more soluble in water than carbon tetrachloride?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 100

The solubility of phenol in water at $25^{\circ} \mathrm{C}$ is $87 \mathrm{~g} / \mathrm{L}$. The solubility of naphthol at the same temperature is only $0.74 \mathrm{~g} / \mathrm{L} .$ Examine the structures of phenol and naphthol shown here and explain why phenol is so much more soluble than naphthol.

Qiao Ruan

Numerade Educator

Problem 101

Potassium perchlorate $\left(\mathrm{KClO}_{4}\right)$ has a lattice energy of $-599 \mathrm{~kJ} / \mathrm{mol}$ and a heat of hydration of $-548 \mathrm{~kJ} / \mathrm{mol}$. Find the heat of solution for potassium perchlorate and determine the temperature change that occurs when $10.0 \mathrm{~g}$ of potassium perchlorate is dissolved with enough water to make $100.0 \mathrm{~mL}$ of solution. (Assume a heat capacity of $4.05 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}$ for the solution and a density of $1.05 \mathrm{~g} / \mathrm{mL}$.)

David Collins

Numerade Educator

Problem 102

Sodium hydroxide (NaOH) has a lattice energy of -887 kJ/mol and a heat of hydration of $-932 \mathrm{~kJ} / \mathrm{mol}$. How much solution could be heated to boiling by the heat evolved by the dissolution of $25.0 \mathrm{~g}$ of $\mathrm{NaOH} ?$ (For the solution, assume a heat capacity of $4.0 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C},$ an initial temperature of $25.0{ }^{\circ} \mathrm{C},$ a boiling point of $100.0^{\circ} \mathrm{C},$ and a density of $\left.1.05 \mathrm{~g} / \mathrm{mL} .\right)$

Qiao Ruan

Numerade Educator

Problem 103

A saturated solution forms when $0.0537 \mathrm{~L}$ of argon, at a pressure of 1.0 atm and a temperature of $25^{\circ} \mathrm{C},$ is dissolved in $1.0 \mathrm{~L}$ of water. Calculate the Henry's law constant for argon.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 104

A gas has a Henry's law constant of 0.112 M/atm. What total volume of solution is needed to completely dissolve $1.65 \mathrm{~L}$ of the gas at a pressure of 725 torr and a temperature of $25^{\circ} \mathrm{C} ?$

Qiao Ruan

Numerade Educator

Problem 105

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 $(0.0040 \mathrm{ppm})$. How much of this water would a person have to consume to ingest $50.0 \mathrm{mg}$ of mercury?

Jekaterina Viktorova

Jekaterina Viktorova

Numerade Educator

Problem 106

Water softeners often replace calcium ions in hard water with sodium ions. since 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 $2.4 \mathrm{~g}$ of sodium per day. How many liters of softened water, containing a sodium concentration of $0.050 \%$ sodium by mass, would a person have to consume to exceed the FDA recommendation? (Assume a water density of $1.0 \mathrm{~g} / \mathrm{mL}$.)

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 107

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

David Collins

Numerade Educator

Problem 108

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

Qiao Ruan

Numerade Educator

Problem 109

What is the freezing point of an aqueous solution that boils at $106.5^{\circ} \mathrm{C} ?$

Amy Jiang

Numerade Educator

Problem 110

What is the boiling point of an aqueous solution that has a vapor pressure of 20.5 torr at $25^{\circ} \mathrm{C} ?$ (Assume a nonvolatile solute.)

Qiao Ruan

Numerade Educator

Problem 111

An isotonic solution contains $0.90 \%$ NaCl mass to volume. Cal-
culate the percent mass to volume for isotonic solutions containing each solute at $25^{\circ} \mathrm{C}$. Assume a van't Hoff factor of 1.9 for
all ionic solutes.
a. KCl
b. $\mathrm{NaBr}$
c. glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$

David Collins

Numerade Educator

Problem 112

Magnesium citrate, $\mathrm{Mg}_{3}\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}\right)_{2}$, belongs to a class of laxatives called hyperosmotics, which cause rapid emptying of the bowel. When a concentrated solution of magnesium citrate is consumed, 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 $28.5 \mathrm{~g}$ of magnesium citrate in $235 \mathrm{~mL}$ of solution at $37^{\circ} \mathrm{C}$ (approximate body temperature). Assume complete dissociation of the ionic compound.

David Collins

Numerade Educator

Problem 113

A solution is prepared from 4.5701 g of magnesium chloride and $43.238 \mathrm{~g}$ 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.

Vinnu M

Numerade Educator

Problem 114

When HNO $_{2}$ is dissolved in water, it partially dissociates according to the equation $\mathrm{HNO}_{2} \rightleftharpoons \mathrm{H}^{+}+\mathrm{NO}_{2}^{-}$. A solution is prepared that contains $7.050 \mathrm{~g}$ of $\mathrm{HNO}_{2}$ in $1.000 \mathrm{~kg}$ of water. Its freezing point is $-0.2929^{\circ} \mathrm{C}$. Calculate the fraction of $\mathrm{HNO}_{2}$ that has dissociated.

David Collins

Numerade Educator

Problem 115

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

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 116

The density of a $0.438 \mathrm{M}$ solution of potassium chromate $\left(\mathrm{K}_{2} \mathrm{CrO}_{4}\right)$ at $298 \mathrm{~K}$ is $1.063 \mathrm{~g} / \mathrm{mL} .$ 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. $.$

Qiao Ruan

Numerade Educator

Problem 117

The vapor pressure of carbon tetrachloride, $\mathrm{CCl}_{4}$, is $0.354 \mathrm{~atm}$, and the vapor pressure of chloroform, $\mathrm{CHCl}_{3}$, is 0.526 atm at $316 \mathrm{~K}$. 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 will the vapor pressure of chloroform be above this new solution?

David Collins

Numerade Educator

Problem 118

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

David Collins

Numerade Educator

Problem 118

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 explains the use of distillation as a separation method.

Qiao Ruan

Numerade Educator

Problem 119

A solution of $49.0 \% \mathrm{H}_{2} \mathrm{SO}_{4}$ by mass has a density of $1.39 \mathrm{~g} / \mathrm{cm}^{3}$ at 293 K. $A 25.0-\mathrm{cm}^{3}$ sample of this solution is mixed with enough water to increase the volume of the solution to $99.8 \mathrm{~cm}^{3}$. Find the molarity of sulfuric acid in this solution.

Vinnu M

Numerade Educator

Problem 120

Find the mass of urea $\left(\mathrm{CH}_{4} \mathrm{~N}_{2} \mathrm{O}\right)$ needed to prepare $50.0 \mathrm{~g}$ of a solution in water in which the mole fraction of urea is 0.0770 .

Qiao Ruan

Numerade Educator

Problem 121

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

Vinnu M

Numerade Educator

Problem 122

The osmotic pressure of a solution containing $2.10 \mathrm{~g}$ of an unknown compound dissolved in $175.0 \mathrm{~mL}$ of solution at $25^{\circ} \mathrm{C}$ is 1.93 atm. The combustion of $24.02 \mathrm{~g}$ of the unknown compound produced $28.16 \mathrm{~g} \mathrm{CO}_{2}$ and $8.64 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}$. What is the molecular formula of the compound (which contains only carbon, hydrogen, and oxygen)?

Qiao Ruan

Numerade Educator

Problem 123

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

Vinnu M

Numerade Educator

Problem 124

A 50.0-mL solution is initially $1.55 \% \mathrm{MgCl}_{2}$ by mass and has a density of $1.05 \mathrm{~g} / \mathrm{mL}$. What is the freezing point of the solution after you add an additional $1.35 \mathrm{~g} \mathrm{MgCl}_{2}$ ? (Use $i=2.5$ for $\mathrm{MgCl}_{2}$.)

David Collins

Numerade Educator

Problem 125

The small bubbles that form on the bottom of a water pot that is being heated (before boiling) are due to dissolved air coming out of solution. Use Henry's law and the solubilities given to calculate the total volume of nitrogen and oxygen gas that should bubble out of $1.5 \mathrm{~L}$ of water upon warming from $25^{\circ} \mathrm{C}$ to $50^{\circ} \mathrm{C}$. Assume that the water is initially saturated with nitrogen and oxygen gas at $25^{\circ} \mathrm{C}$ and a total pressure of $1.0 \mathrm{~atm} .$ Assume that the gas bubbles out at a temperature of $50^{\circ} \mathrm{C}$. The solubility of oxygen gas at $50^{\circ} \mathrm{C}$ is $27.8 \mathrm{mg} / \mathrm{L}$ at an oxygen pressure of $1.00 \mathrm{~atm} .$ The solubility of nitrogen gas at $50^{\circ} \mathrm{C}$ is $14.6 \mathrm{mg} / \mathrm{L}$ at a nitrogen pressure of 1.00 atm. Assume that the air above the water contains an oxygen partial pressure of 0.21 atm and a nitrogen partial pressure of 0.78 atm.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 126

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.

Qiao Ruan

Numerade Educator

Problem 127

A 1.10-g sample contains only glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ and sucrose $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right) .$ When the sample is dissolved in water to a total solution volume of $25.0 \mathrm{~mL}$, the osmotic pressure of the solution is 3.78 atm at $298 \mathrm{~K}$. What is the mass percent composition of glucose and sucrose in the sample?

David Collins

Numerade Educator

Problem 128

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

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 129

Two alcohols, isopropyl alcohol and propyl alcohol, have the same molecular formula, $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}$. 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 $313 \mathrm{~K}$. Calculate the vapor pressure of each pure alcohol at this temperature. Explain the difference given that the formula of propyl alcohol is $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}$ and that of isopropyl alcohol is $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHOH}$

David Collins

Numerade Educator

Problem 130

A metal, $\mathrm{M},$ of atomic mass 96 amu reacts with fluorine to form a salt that can be represented as $\mathrm{MF}_{x}$. 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 $100.0 \mathrm{~g}$ 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.)

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 131

Sulfuric acid in water dissociates completely into $\mathrm{H}^{+}$ and $\mathrm{HSO}_{4}^{-}$ ions. The $\mathrm{HSO}_{4}^{-}$ ion dissociates to a limited extent into $\mathrm{H}^{+}$ and $\mathrm{SO}_{4}^{2-}$. The freezing point of a $0.1000 \mathrm{~m}$ solution of sulfuric acid in water is $272.76 \mathrm{~K}$. Calculate the molality of $\mathrm{SO}_{4}^{2-}$ in the solu-

David Collins

Numerade Educator

Problem 132

A solution of $75.0 \mathrm{~g}$ of benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$ and $75.0 \mathrm{~g}$ of toluene $\left(\mathrm{C}_{7} \mathrm{H}_{8}\right)$ has a total vapor pressure of $80.9 \mathrm{mmHg}$ at $303 \mathrm{~K}$ Another solution of $100.0 \mathrm{~g}$ benzene and $50.0 \mathrm{~g}$ toluene has a total vapor pressure of $93.9 \mathrm{mmHg}$ at this temperature. Find the vapor pressure of pure benzene and pure toluene at $303 \mathrm{~K}$

David Collins

Numerade Educator

Problem 133

A solution is prepared by dissolving $11.60 \mathrm{~g}$ of a mixture of sodium carbonate and sodium bicarbonate in $1.00 \mathrm{~L}$ of water. $\mathrm{A} 300.0 \mathrm{~cm}^{3}$ sample of the solution is treated with excess $\mathrm{HNO}_{3}$ and boiled to remove all the dissolved gas. A total of $0.940 \mathrm{~L}$ of dry $\mathrm{CO}_{2}$ is collected at $298 \mathrm{~K}$ and 0.972 atm. Find the molarity of the carbonate and bicarbonate in the solution.

David Collins

Numerade Educator

Problem 134

Substance A is a nonpolar liquid and has only dispersion forces among its constituent particles. Substance $\mathrm{B}$ 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 substance $\mathrm{B}$ are combined, they spontaneously $\mathrm{mix}$.
a. Why do the two substances mix?
b. Predict the sign and magnitude of $\Delta H_{\text {soln. }}$
c. Determine the signs and relative magnitudes of $\Delta H_{\text {solute }}$ $\Delta H_{\text {solvent }},$ and $\Delta H_{\text {mix }}$

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 135

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 Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 136

The vapor pressure of a $1 \mathrm{M}$ ionic solution is different from the vapor pressure of a $1 \mathrm{M}$ 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 Sharma

Numerade Educator

Problem 137

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. $\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}$
b. $\mathrm{NaCl}$
c. KCl
d. $\mathrm{MgCl}_{2}$
e. $\mathrm{SrCl}_{2}$

Jacqueline Winston

Jacqueline Winston

Numerade Educator

Problem 138

A helium balloon inflated on one day will fall to the ground by 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.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 139

Explain why 1 -propanol $\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right)$ is miscible in both water $\left(\mathrm{H}_{2} \mathrm{O}\right)$ and hexane $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$ when hexane and water are barely soluble in each other.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 140

Have each group member make a flashcard with one of the following on the front: $\Delta H_{\text {soln }}, \Delta H_{\text {lattice, }} \Delta H_{\text {solvent, }} \Delta H_{\text {mix }},$ and $\Delta H_{\text {hydration. }}$ On the back of the card, each group member should describe (in words) the $\Delta H$ process his or her card lists and how that $\Delta H$ relates to other $\Delta H$ values mathematically. Each member presents his or her $\Delta H$ to the group. After everyone has presented, members should trade cards and quiz each other.

Qiao Ruan

Numerade Educator

Problem 141

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

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 142

When $13.62 \mathrm{~g}$ (about one tablespoon) of table sugar (sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$ ) is dissolved in $241.5 \mathrm{~mL}$ of water (density $\left.0.997 \mathrm{~g} / \mathrm{mL}\right)$
the final volume is $250.0 \mathrm{~mL}$ (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

Qiao Ruan

Numerade Educator

Problem 143

Calculate the expected boiling and freezing point 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 $\left(-18^{\circ} \mathrm{C}\right) ?$ Why or why not?

David Collins

Numerade Educator