Chapter 14

A 100 -gram sample of sodium chloride (NaCl) is added to \(100 .\) mL of water at \(0^{\circ} \mathrm{C} .\) After equilibrium is reached, about \(64 \mathrm{g}\) of solid remains undissolved. Describe the equilibrium that exists in this system at the particulate level.A 100 -gram sample of sodium chloride (NaCl) is added to \(100 .\) mL of water at \(0^{\circ} \mathrm{C} .\) After equilibrium is reached, about \(64 \mathrm{g}\) of solid remains undissolved. Describe the equilibrium that exists in this system at the particulate level.

Which of the following substances is/are likely to dissolve in water, and which is/are likely to dissolve in benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right) ?\) (a) \(\mathrm{NaNO}_{3}\) (b) diethyl ether, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OCH}_{2} \mathrm{CH}_{3}\) (c) naphthalene, \(\mathrm{C}_{10} \mathrm{H}_{8}\) (see page 454 for structure) (d) \(\mathrm{NH}_{4} \mathrm{Cl}\)

Starch contains \(\mathrm{C}-\mathrm{C}, \mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{O},\) and \(\mathrm{O}-\mathrm{H}\) bonds. Hydrocarbons have only \(\mathrm{C}-\mathrm{C}\) and \(\mathrm{C}-\mathrm{H}\) bonds. Both starch and hydrocarbons can form colloidal dispersions in water. Which dispersion is classified as hydrophobic? Which is hydrophilic? Explain briefly.

Which substance would have the greater influence on the vapor pressure of water when added to \(1000 .\) g of the liquid: \(10.0 \mathrm{g}\) of sucrose \(\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)\) or \(10.0 \mathrm{g}\) of ethylene glycol \(\left(\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right) ?\)

A protozoan (single-celled animal) that normally lives in the ocean is placed in freshwater. Will it shrivel or burst? Explain briefly.

It is interesting how the Fahrenheit temperature scale was established. One report, given by Fahrenheit in a paper in \(1724,\) stated that the value of \(0^{\circ} \mathrm{F}\) was established as the freezing temperature of saturated solutions of sea salt. From the literature we find that the freezing point of a \(20 \%\) by mass solution of \(\mathrm{NaCl}\) is \(-16.46^{\circ} \mathrm{C}\) (This is the lowest freezing temperature reported for solutions of NaCl.) Does this value lend credence to this story of the establishment of the Fahrenheit scale?