Chapter 8

Interpret the following verse from Coleridge's The Rime of the Ancient Mariner: Water, water, every where, And all the boards did shrink; Water, water, every where, Nor any drop to drink.

Describe the procedure of reverse osmosis for the purification of salt water for drinking water.

Diethyl ether, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OC}_{2} \mathrm{H}_{5}\), and ethyl methyl ether, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OCH}_{3}\), form an ideal solution. The vapor pressure of diethyl ether is 185 Torr and that of ethyl methyl ether is 554 Torr at \(0.0^{\circ} \mathrm{C}\). Calculate the vapor pressure of each of the following solutions and the mole fraction of each substance in the vapor phase above those solutions at \(0.0^{\circ} \mathrm{C}\) : (a) \(0.75 \mathrm{~mol}\) of diethyl ether mixed with \(0.50 \mathrm{~mol}\) of ethyl methyl ether; (b) \(25.0 \mathrm{~g}\) of diethyl ether mixed with \(35.0 \mathrm{~g}\) of ethyl methyl ether.

Bromomethane, \(\mathrm{CH}_{3} \mathrm{Br}\), and iodomethane, \(\mathrm{CH}_{3} \mathrm{I}\), form an ideal solution. The vapor pressure of bromomethane is 661 Torr and that of iodomethane is 140 Torr at \(0.0^{\circ} \mathrm{C}\). Calculate the vapor pressure of each of the following solutions and the mole fraction of each substance in the vapor phase above those solutions at \(0.0^{\circ} \mathrm{C}:\) (a) \(0.33 \mathrm{~mol}\) of bromomethane mixed with \(0.67 \mathrm{~mol}\) of iodomethane; (b) \(35.0 \mathrm{~g}\) of bromomethane mixed with \(35.0 \mathrm{~g}\) of iodomethane.

A new substance is developed in a laboratory and has the following properties: normal melting point, \(83.7^{\circ} \mathrm{C}\); normal boiling point, \(177^{\circ} \mathrm{C}\); triple point,200 Torr and \(38.6^{\circ} \mathrm{C}\). (a) Sketch the approximate phase diagram and label the solid, liquid, and gaseous phases and the solid-liquid, liquid-gas, and solid-gas phase boundaries. (b) Sketch an approximate cooling curve for a sample at constant pressure, beginning at 500 Torr and \(25^{\circ} \mathrm{C}\) and ending at \(200^{\circ} \mathrm{C}\).

The freezing point of a \(5.00 \%\) by mass \(\mathrm{CH}_{3} \mathrm{COOH}\) (aq) solution is \(-1.576^{\circ} \mathrm{C}\). Determine the experimental van't Hoff \(i\) factor for this solution. Account for its value on the basis of your understanding of intermolecular forces.

A \(0.020 \mathrm{M} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{aq})\) solution is separated from a \(0.050 \mathrm{M} \mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2}(\mathrm{aq})\) solution by a semipermeable membrante at \(25^{\circ} \mathrm{C}\). (a) Which solution has the higher osmotic pressure? (b) Which solution becomes more dilute with the passage of \(\mathrm{H}_{2} \mathrm{O}\) molecules through the membrane? (c) To which solution should an external pressure be applied in order to maintain an equilibrium flow of \(\mathrm{H}_{2} \mathrm{O}\) molecules across the membrane? (d) What external pressure (in atm) should be applied in (c)?