Chapter 10

A solution is prepared by dissolving \(12.15 \mathrm{~g}\) of nickel(II) nitrate in \(175 \mathrm{~mL}\) of water \((d=1.00 \mathrm{~g} / \mathrm{mL})\). Calculate (a) the mass percent of nickel(II) nitrate in the solution. (b) the mole fraction of nickel(II) ions in the solution.

Acetone, \(\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}\), is the main ingredient of nail polish remover. A solution is made up by adding \(35.0 \mathrm{~mL}\) of acetone \((d=0.790 \mathrm{~g} / \mathrm{mL})\) to \(50.0 \mathrm{~mL}\) of ethyl alcohol, \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}(d=0.789 \mathrm{~g} / \mathrm{mL})\). Assuming volumes are additive, calculate (a) the mass percent of acetone in the solution. (b) the volume percent of ethyl alcohol in the solution. (c) the mole fraction of acetone in the solution.

For a solution of acetic acid (CH \(_{3} \mathrm{COOH}\) ) to be called "vinegar," it must contain \(5.00 \%\) acetic acid by mass. If a vinegar is made up only of acetic acid and water, what is the molarity of acetic acid in the vinegar? The density of vinegar is \(1.006 \mathrm{~g} / \mathrm{mL}\).

Solutions introduced directly into the bloodstream have to be "isotonic" with blood; that is, they must have the same osmotic pressure as blood. An aqueous \(\mathrm{NaCl}\) solution has to be \(0.90 \%\) by mass to be isotonic with blood. What is the molarity of sodium ions in solution? Take the density of the solution to be \(1.00 \mathrm{~g} / \mathrm{mL}\).

Silver ions can be found in some of the city water piped into homes. The average concentration of silver ions in city water is \(0.028\) ppm. (a) How many milligrams of silver ions would you ingest daily if you drank eight glasses (eight oz/glass) of city water daily? (b) How many liters of city water are required to recover \(1.00 \mathrm{~g}\) of silver chemically?

Lead is a poisonous metal that especially affects children because they retain a larger fraction of lead than adults do. Lead levels of \(0.250 \mathrm{ppm}\) in a child cause delayed cognitive development. How many moles of lead present in \(1.00 \mathrm{~g}\) of a child's blood would \(0.250 \mathrm{ppm}\) represent?

Describe how you would prepare \(465 \mathrm{~mL}\) of \(0.3550 \mathrm{M}\) potassium dichromate solution starting with (a) solid potassium dichromate. (b) \(0.750 M\) potassium dichromate solution.

Describe how you would prepare \(1.00 \mathrm{~L}\) of \(0.750 \mathrm{M}\) barium hydroxide solution starting with (a) solid barium hydroxide. (b) \(6.00 \mathrm{M}\) barium hydroxide solution.

A solution is prepared by diluting \(225 \mathrm{~mL}\) of \(0.1885 \mathrm{M}\) aluminum sulfate solution with water to a final volume of \(1.450 \mathrm{~L}\). Calculate (a) the number of moles of aluminum sulfate before dilution. (b) the molarities of the aluminum sulfate, aluminum ions, and sulfate ions in the diluted solution.

A solution is prepared by diluting \(0.7850 \mathrm{~L}\) of \(1.262 \mathrm{M}\) potassium sulfide solution with water to a final volume of \(2.000 \mathrm{~L}\). (a) How many grams of potassium sulfide were dissolved to give the original solution? (b) What are the molarities of the potassium sulfide, potassium ions, and sulfide ions in the diluted solution?

A bottle of commercial concentrated aqueous ammonia is labeled "29.89\% \(\mathrm{NH}_{3}\) by mass; density \(=0.8960 \mathrm{~g} / \mathrm{mL}\)." (a) What is the molarity of the ammonia solution? (b) If \(250.0 \mathrm{~mL}\) of the commercial ammonia is diluted with water to make \(3.00 \mathrm{~L}\) of solution, what is the molarity of the diluted solution?

In a sugar mill, sugar cane is shredded, mixed with water and crushed between rollers. The resulting juice contains \(7-11 \%\) sucrose, \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\). Assume that \(25 \mathrm{~L}\) of collected juice (of density \(1.0 \mathrm{~g} / \mathrm{mL}\) ) yields \(11 \%\) (by mass) sucrose. What is the molality of the sucrose solution after \(33 \%\) (by mass) of the water content of the juice has been removed?

Which of the following is more likely to be soluble in benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)\) ? In each case, explain your answer. (a) \(\mathrm{CCl}_{4}\) or \(\mathrm{NaCl}\) (b) hexane \(\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)\) or glycerol \(\left(\mathrm{CH}_{2} \mathrm{OHCHOHCH}_{2} \mathrm{OH}\right)\) (c) acetic acid \(\left(\mathrm{CH}_{3} \mathrm{COOH}\right)\) or heptanoic acid \(\left(\mathrm{C}_{6} \mathrm{H}_{13} \mathrm{COOH}\right)\) (d) \(\mathrm{HCl}\) or propylchloride \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Cl}\right)\)

Which of the following is more soluble in \(\mathrm{CCl}_{4} ?\) In each case, explain your answer. (a) hexane \(\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)\) or \(\mathrm{CaCl}_{2}\) (b) \(\mathrm{CBr}_{4}\) or \(\mathrm{HBr}\) (c) benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)\) or ethyl alcohol \(\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\right)\) (d) \(\mathrm{I}_{2}\) or \(\mathrm{NaI}\)

Choose the member of each set that you would expect to be more soluble in water. Explain your answer. (a) naphthalene, \(\mathrm{C}_{10} \mathrm{H}_{8}\), or hydrogen peroxide, \(\mathrm{H}-\mathrm{O}-\mathrm{O}-\mathrm{H}\) (b) silicon dioxide or sodium hydroxide (c) chloroform, \(\mathrm{CHCl}_{3}\), or hydrogen chloride (d) methyl alcohol, \(\mathrm{CH}_{3} \mathrm{OH}\), or methyl ether, \(\mathrm{H}_{3} \mathrm{C}-\mathrm{O}-\mathrm{CH}_{3}\)

Choose the member of each set that you would expect to be more soluble in water. Explain your answer. (a) chloromethane, \(\mathrm{CH}_{3} \mathrm{Cl}\), or methanol, \(\mathrm{CH}_{3} \mathrm{OH}\) (b) nitrogen triiodide or potassium iodide (c) lithium chloride or ethyl chloride, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}\) (d) ammonia or methane

Consider the process by which lead chloride dissolves in water: $$ \mathrm{PbCl}_{2}(s) \longrightarrow \mathrm{Pb}^{2+}(a q)+2 \mathrm{Cl}^{-}(a q) $$ (a) Using data from tables in Chapter 8, calculate \(\Delta H\) for this reaction. (b) Based only on thermodynamic data, would you expect the solubility of \(\mathrm{PbCl}_{2}\) to increase if the temperature is increased?

The Henry's law constant for the solubility of helium gas in water is\(3.8 \times 10^{-4} \mathrm{M} / \mathrm{atm}\) at \(25^{\circ} \mathrm{C}\). (a) Express the constant for the solubility of helium gas in \(M / \mathrm{mm} \mathrm{Hg}\). (b) If the partial pressure of \(\mathrm{He}\) at \(25^{\circ} \mathrm{C}\) is \(293 \mathrm{~mm} \mathrm{Hg}\), what is the concentration of dissolved He in \(\mathrm{mol} / \mathrm{L}\) at \(25^{\circ} \mathrm{C} ?\) (c) What volume of helium gas can be dissolved in \(10.00 \mathrm{~L}\) of water at \(293 \mathrm{~mm} \mathrm{Hg}\) and \(25^{\circ} \mathrm{C}\) ? (Ignore the partial pressure of water.)

The Henry's law constant for the solubility of argon gas in water is \(1.0 \times 10^{-3} \mathrm{M} / \mathrm{atm}\) at \(30^{\circ} \mathrm{C}\). (a) Express the constant for the solubility of argon gas in \(M / \mathrm{mm} \mathrm{Hg}\). (b) If the partial pressure of argon gas at \(30^{\circ} \mathrm{C}\) is \(693 \mathrm{~mm} \mathrm{Hg}\), what is the concentration of dissolved argon in \(M\) at \(30^{\circ} \mathrm{C} ?\) (c) How many grams of argon gas can be dissolved in \(25 \mathrm{~L}\) of water at \(693 \mathrm{~mm} \mathrm{Hg}\) and \(30^{\circ} \mathrm{C} ?\) (Ignore the partial pressure of water.)

A carbonated beverage is made by saturating water with carbon dioxide at \(0^{\circ} \mathrm{C}\) and a pressure of \(3.0 \mathrm{~atm}\). The bottle is then opened at room temperature \(\left(25^{\circ} \mathrm{C}\right)\), and comes to equilibrium with air in the room containing \(\mathrm{CO}_{2}\left(P_{\mathrm{CO}_{2}}=3.4 \times 10^{-4} \mathrm{~atm}\right)\). The Henry's law constant for the solubility of \(\mathrm{CO}_{2}\) in water is \(0.0769\) M/atm at \(0^{\circ} \mathrm{C}\) and \(0.0313 \mathrm{M} / \mathrm{atm}\) at \(25^{\circ} \mathrm{C}\). (a) What is the concentration of carbon dioxide in the bottle before it is opened? (b) What is the concentration of carbon dioxide in the bottle after it has been opened and come to equilibrium with the air?

The Henry's law constant for the solubility of oxygen in water is \(3.30 \times 10^{-4} \mathrm{M} / \mathrm{atm}\) at \(12^{\circ} \mathrm{C}\) and \(2.85 \times 10^{-4} \mathrm{M} / \mathrm{atm}\) at \(22^{\circ} \mathrm{C}\). Air is \(21 \mathrm{~mol} \%\) oxygen. (a) How many grams of axygen can be dissolved in one liter of a trout stream at \(12^{\circ} \mathrm{C}\left(54^{\circ} \mathrm{F}\right)\) at an air pressure of \(1.00 \mathrm{~atm} ?\) (b) How many grams of oxygen can be dissolved per liter in the same trout stream at \(22^{\circ} \mathrm{C}\left(72^{\circ} \mathrm{F}\right)\) at the same pressure as in (a)? (c) A nuclear power plant is responsible for the stream's increase in temperature. What percentage of dissolved oxygen is lost by this increase in the stream's temperature?

What is the freezing point of maple syrup (66\% sucrose)? Sucrose is \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\)

The vapor pressure of pure \(\mathrm{CCl}_{4}\) at \(65^{\circ} \mathrm{C}\) is \(504 \mathrm{~mm} \mathrm{Hg}\). How many grams of naphthalene \(\left(\mathrm{C}_{10} \mathrm{H}_{8}\right)\) must be added to \(25.00 \mathrm{~g}\) of \(\mathrm{CCl}_{4}\) so that the vapor pressure of \(\mathrm{CCl}_{4}\) over the solution is \(483 \mathrm{~mm} \mathrm{Hg}\) ? Assume the vapor pressure of naphthalene at \(65^{\circ} \mathrm{C}\) is negligible.

Calculate the osmotic pressure of the following solutions of urea, \(\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\), at \(22^{\circ} \mathrm{C} .\) (a) \(0.217 \mathrm{M}\) urea (b) \(25.0 \mathrm{~g}\) urea dissolved in enough water to make \(685 \mathrm{~mL}\) of solution. (c) \(15.0 \%\) urea by mass (density of the solution \(=1.12 \mathrm{~g} / \mathrm{mL}\) )

Pepsin is an enzyme involved in the process of digestion. Its molar mass is about \(3.50 \times 10^{4} \mathrm{~g} / \mathrm{mol}\). What is the osmotic pressure in \(\mathrm{mm} \mathrm{Hg}\) at \(30^{\circ} \mathrm{C}\) of a \(0.250\) -g sample of pepsin in \(55.0 \mathrm{~mL}\) of an aqueous solution? 39\. Calculate the freezing point and normal boiling point of each of the following solutions: (a) \(25.0 \%\) by mass glycerine, \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}\) in water (b) \(28.0 \mathrm{~g}\) of propylene glycol, \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{2}\), in \(325 \mathrm{~mL}\) of water \(\left(d=1.00 \mathrm{~g} / \mathrm{cm}^{3}\right)\) (c) \(25.0 \mathrm{~mL}\) of ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(d=0.780 \mathrm{~g} / \mathrm{mL})\), in \(735 \mathrm{~g}\) of water \(\left(d=1.00 \mathrm{~g} / \mathrm{cm}^{3}\right)\)

A solution consisting of \(4.50 \mathrm{~g}\) of propylene glycol, \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{2}\), in \(40.5 \mathrm{~mL}\) of t-butyl alcohol \((d=0.780 \mathrm{~g} / \mathrm{mL})\) freezes at \(8.5^{\circ} \mathrm{C}\). The freezing point of \(\mathrm{t}\) -butyl alcohol is \(25.5^{\circ} \mathrm{C}\). What is its freezing-point constant?

nsulin is a hormone responsible for the regulation of glucose levels in the blood. An aqueous solution of insulin has an osmotic pressure of \(2.5 \mathrm{~mm} \mathrm{Hg}\) at \(25^{\circ} \mathrm{C}\). It is prepared by dissolving \(0.100 \mathrm{~g}\) of insulin in enough water to make \(125 \mathrm{~mL}\) of solution. What is the molar mass of insulin?

Lysozyme, extracted from egg whites, is an enzyme that cleaves bacterial cell walls. A 20.0-mg sample of this enzyme is dissolved in enough water to make \(225 \mathrm{~mL}\) of solution. At \(23^{\circ} \mathrm{C}\) the solution has an osmotic pressure of \(0.118 \mathrm{~mm} \mathrm{Hg}\). Estimate the molar mass of lysozyme.

The Rast method uses camphor \(\left(\mathrm{C}_{10} \mathrm{H}_{16} \mathrm{O}\right)\) as a solvent for determining the molar mass of a compound. When \(2.50 \mathrm{~g}\) of cortisone acetate is dissolved in \(50.00 \mathrm{~g}\) of camphor \(\left(k_{\mathrm{f}}=40.0^{\circ} \mathrm{C} / \mathrm{m}\right)\), the freezing point of the mixture is determined to be \(173.44^{\circ} \mathrm{C}\); that of pure camphor is \(178.40^{\circ} \mathrm{C}\). What is the molar mass of cortisone acetate?

A biochemist isolates a new protein and determines its molar mass by osmotic pressure measurements. A 50.0-mL solution is prepared by dissolving \(225 \mathrm{mg}\) of the protein in water. The solution has an osmotic pressure of \(4.18 \mathrm{~mm} \mathrm{Hg}\) at \(25^{\circ} \mathrm{C}\). What is the molar mass of the new protein?

Arrange \(0.30 \mathrm{~m}\) solutions of the following solutes in order of increasing freezing point and boiling point. (a) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}\) (b) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (c) \(\mathrm{Ba}(\mathrm{OH})_{2}\) (d) \(\mathrm{CaCr}_{2} \mathrm{O}_{7}\)

What is the osmotic pressure of a \(0.250 \mathrm{M}\) solution of \(\mathrm{K}_{2} \mathrm{CO}_{3}\) at \(25^{\circ} \mathrm{C}\) ? (Assume complete dissociation.)

The freezing point of a \(0.20 \mathrm{~m}\) solution of aqueous \(\mathrm{HF}\) is \(-0.38^{\circ} \mathrm{C}\). (a) What is \(i\) for the solution? (b) Is the solution made of (i) HF molecules only? (ii) \(\mathrm{H}^{+}\) and \(\mathrm{F}^{-}\) ions only? (iii) Primarily HF molecules with some \(\mathrm{H}^{+}\) and \(\mathrm{F}^{-}\) ions? (iv) primarily \(\mathrm{H}^{+}\) and \(\mathrm{F}^{-}\) ions with some HF molecules?

The freezing point of a \(0.21 m\) aqueous solution of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is \(-0.796^{\circ} \mathrm{C}\) (a) What is \(i\) ? (b) Is the solution made up primarily of (i) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) molecules only? (ii) \(\mathrm{H}^{+}\) and \(\mathrm{HSO}_{4}^{-}\) ions? (iii) \(2 \mathrm{H}^{+}\) and \(1 \mathrm{SO}_{4}^{2-}\) ions?

An aqueous solution of \(L \mathrm{iX}\) is prepared by dissolving \(3.58 \mathrm{~g}\) of the electrolyte in \(283 \mathrm{~mL}\) of \(\mathrm{H}_{2} \mathrm{O}(d=1.00 \mathrm{~g} / \mathrm{mL})\). The solution freezes at \(-1.81^{\circ} \mathrm{C}\). What is \(\mathrm{X}^{-}\) ? (Assume complete dissociation of \(\mathrm{LiX}\) to \(\mathrm{Li}^{+}\) and \(\mathrm{X}^{-}\).)

A sucrose \(\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)\) solution that is \(45.0 \%\) sucrose by mass has a density of \(1.203 \mathrm{~g} / \mathrm{mL}\) at \(25^{\circ} \mathrm{C}\). Calculate its (a) molarity. (b) molality. (c) vapor pressure \(\left(\mathrm{vp} \mathrm{H}_{2} \mathrm{O}\right.\) at \(25^{\circ} \mathrm{C}=23.76 \mathrm{~mm} \mathrm{Hg}\) ). (d) normal boiling point.

An aqueous solution made up of \(32.47 \mathrm{~g}\) of iron(III) chloride in \(100.0 \mathrm{~mL}\) of solution has a density of \(1.249 \mathrm{~g} / \mathrm{mL}\) at \(25^{\circ} \mathrm{C}\). Calculate its (a) molarity. (b) molality. (c) osmotic pressure at \(25^{\circ} \mathrm{C}\) (assume \(\left.i=4\right)\). (d) freezing point.

Potassium permanganate can be used as a disinfectant. How would you prepare \(25.0 \mathrm{~L}\) of a solution that is \(15.0 \% \mathrm{KMnO}_{4}\) by mass if the resulting solution has a density of \(1.08 \mathrm{~g} / \mathrm{mL}\) ? What is the molarity of the resulting solution?

Chloroform \(\left(\mathrm{CH} \mathrm{Cl}_{3}\right)\) boils at \(61.7^{\circ} \mathrm{C}\) and has a density of \(1.49 \mathrm{~g} / \mathrm{mL}\). (a) A solution prepared by dissolving \(0.146 \mathrm{~mol}\) of a nonelectrolyte in \(132 \mathrm{~mL}\) of chloroform boils at \(64.4^{\circ} \mathrm{C}\). What is the boiling point constant \(\left(k_{\mathrm{b}}\right)\) for chloroform? (b) Another solution is prepared by dissolving \(45.2 \mathrm{~g}\) of an unknown electrolyte (MM = \(154 \mathrm{~g} / \mathrm{mol}\) ) in \(427.5 \mathrm{~mL}\) of chloroform. The resulting solution boils at \(66.7^{\circ} \mathrm{C}\). What is \(i\) for the electrolyte?

Twenty-five milliliters of a solution \((d=1.107 \mathrm{~g} / \mathrm{mL})\) containing \(15.25 \%\) by mass of sulfuric acid is added to \(50.0 \mathrm{~mL}\) of \(2.45 \mathrm{M}\) barium chloride. (a) What is the expected precipitate? (b) How many grams of precipitate are obtained? (c) What is the chloride concentration after precipitation is complete?

The Henry's law constant for the solubility of radon in water at \(30^{\circ} \mathrm{C}\) is \(9.57 \times 10^{-6} \mathrm{M} / \mathrm{mm} \mathrm{Hg} .\) Radon is present with other gases in a sample taken from an aquifer at \(30^{\circ} \mathrm{C}\). Radon has a mole fraction of \(2.7 \times 10^{-6}\) in the gaseous mixture. The gaseous mixture is shaken with water at a total pressure of 28 atm. Calculate the concentration of radon in the water. Express your answers using the following concentration units. (a) molarity (b) \(\mathrm{ppm}\) (Assume that the water sample has a density of \(1.00 \mathrm{~g} / \mathrm{mL} .\) )

Pure benzene boils at \(80.10^{\circ} \mathrm{C}\) and has a boiling point constant, \(k_{\mathrm{b}}\), of \(2.53^{\circ} \mathrm{C} / \mathrm{m} .\) A sample of benzene is contaminated by naphthalene, \(\mathrm{C}_{10} \mathrm{H}_{8}\). The boiling point of the contaminated sample is \(81.20^{\circ} \mathrm{C}\). How pure is the sample? (Express your answer as mass percent of benzene.)

A single-celled animal lives in a fresh-water lake. The cell is transferred into ocean water. Does it stay the same, shrink, or burst? Explain why.

Show how 1 ppb (part per billion) is equivalent to 1 microgram \(/ \mathrm{kg}\). One microgram \(=10^{-6} \mathrm{~g}\).

The freezing point of \(0.20 \mathrm{~m}\) HF is \(-0.38^{\circ} \mathrm{C}\). Is HF primarily nonionized in this solution (HF molecules), or is it dissociated to \(\mathrm{H}^{+}\) and \(\mathrm{F}^{-}\) ions?

A certain gaseous solute dissolves in water, evolving \(12.0 \mathrm{~kJ}\) of heat. Its solubility at \(25^{\circ} \mathrm{C}\) and \(4.00\) atm is \(0.0200 M .\) Would you expect the solubility to be greater or less than \(0.0200 M\) at (a) \(5^{\circ} \mathrm{C}\) and 6 atm? (b) \(50^{\circ} \mathrm{C}\) and 2 atm? (c) \(20^{\circ} \mathrm{C}\) and 4 atm? (d) \(25^{\circ} \mathrm{C}\) and \(1 \mathrm{~atm} ?\)

The freezing point of \(0.10 \mathrm{M} \mathrm{KHSO}_{3}\) is \(-0.38^{\circ} \mathrm{C}\). Which of the following equations best represents what happens when \(\mathrm{KHSO}_{3}\) dissolves in water? (a) \(\mathrm{KHSO}_{3}(s) \longrightarrow \mathrm{KHSO}_{3}(a q)\) (b) \(\mathrm{KHSO}_{3}(s) \longrightarrow \mathrm{K}^{+}(a q)+\mathrm{HSO}^{3-}(a q)\) (c) \(\mathrm{KHSO}_{3}(s) \longrightarrow \mathrm{K}^{+}(a q)+\mathrm{SO}_{3}{\underline{\phantom{xx}}}^{2-}(a q)+\mathrm{H}^{+}(a q)\)

Explain why (a) the freezing point of \(0.10 \mathrm{~m} \mathrm{CaCl}_{2}\) is lower than the freezing point of \(0.10 \mathrm{~m} \mathrm{CaSO}_{4}\) (b) the solubility of solids in water usually increases as the temperature increases. (c) pressure must be applied to cause reverse osmosis to occur. (d) \(0.10 \mathrm{M} \mathrm{BaCl}_{2}\) has a higher osmotic pressure than \(0.10 \mathrm{M}\) glucose. (e) molarity and molality are nearly the same in dilute solutions.

In your own words, explain (a) why seawater has a lower freezing point than fresh water. (b) why one often obtains a "grainy" product when making fudge (a supersaturated sugar solution). (c) why the concentrations of solutions used for intravenous feeding must be controlled carefully. (d) why fish in a lake (and fishermen) seek deep, shaded places during summer afternoons. (e) why champagne "fizzes" in a glass.

Explain, in your own words, (a) how to determine experimentally whether a pure substance is an electrolyte or a nonelectrolyte. (b) why a cold glass of beer goes "flat" upon warming. (c) why the molality of a solute is ordinarily larger than its mole fraction. (d) why the boiling point is raised by the presence of a solute.