Chapter 14

Explain why drinking seawater results in dehydration.

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

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

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

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

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

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

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?

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?

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

What are the common units for expressing solution concentration?

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?

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

Explain the difference between an ideal and a nonideal solution.

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

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.

What is osmosis? What is osmotic pressure?

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

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

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

What keeps the particles in a colloidal dispersion from coalescing?

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

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

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.

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

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.

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?

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. \()\)

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 \(4.67 \mathrm{~g}\) \(\mathrm{CuCl}_{2} ?\)

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

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 \(1.00 \mathrm{~g} / \mathrm{mL}\)

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. \()\)

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 \(1.0 \mathrm{~g} / \mathrm{mL} .)\)

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.

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

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

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

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 \(1.02 \mathrm{~g} / \mathrm{mL} .)\)

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?

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.)

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?

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?

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.

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?

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.

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.

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 \(1.05 \mathrm{~g} / \mathrm{mL}\).)

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 \(1.0 \mathrm{~g} / \mathrm{mL}\).)

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.

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.