Chapter 12

What is the Tyndall effect?

What is a micelle, and why does it form?

For an ionic compound dissolving in water, \(\Delta H_{\text {soln }}=\) \(-56 \mathrm{k} \mathrm{J} \mathrm{mol}^{-1}\) and the hydration energy is \(-894 \mathrm{~kJ} \mathrm{~mol}^{-1}\) Estimate the lattice energy of the ionic compound.

Consider the formation of a solution of aqueous potassium chloride. Write the thermochemical equations for (a) the conversion of solid KCl into its gaseous ions and (b) the subsequent formation of the solution by hydration of the ions. The lattice energy of \(\mathrm{KCl}\) is \(-715 \mathrm{~kJ} \mathrm{~mol}^{-1}\), and the hydration energy of the ions is \(-686 \mathrm{~kJ} \mathrm{~mol}^{-1}\). Calculate the enthalpy of solution of \(\mathrm{KCl}\) in \(\mathrm{kJ} \mathrm{mol}^{-1}\)

If the solubility of a gas in water is \(0.010 \mathrm{~g} \mathrm{~L}^{-1}\) at \(25^{\circ} \mathrm{C}\) with the partial pressure of the gas 1. 0 atm, predict the solubility of the gas at the same temperature but at double the pressure.

At 740 torr and \(20.0^{\circ} \mathrm{C}\), nitrogen has a solubility in water of \(0.018 \mathrm{~g} \mathrm{~L}^{-1}\). At 620 torr and \(20.0{ }^{\circ} \mathrm{C}\), its solubility is \(0.015 \mathrm{~g} \mathrm{~L}^{-1}\). Show that nitrogen obeys Henry's law.

Hydrogen gas has a solubility in water of \(0.00157 \mathrm{~g} \mathrm{~L}^{-1}\) under 1.00 atm of \(H_{2}\) pressure at \(25^{\circ} \mathrm{C}\). At 0.85 atm and \(25^{\circ} \mathrm{C}\), its solubility is \(0.00133 \mathrm{~g} \mathrm{~L}^{-1}\). Does hydrogen gas obey Henry's law?

Helium gas can be used to displace other gases from a solvent by bubbling He through the solvent, a process called sparging, and leaving an atmosphere of helium above the solvent. At 760 torr of He, the concentration of He in water is \(0.00148 \mathrm{~g} \mathrm{~L}^{-1}\) at \(298 \mathrm{~K}\). What is Henry's law constant for \(\mathrm{He}\) at \(298 \mathrm{~K} ?\)

Muriatic acid is the commercial name for hydrochloric acid that can be purchased from hardware stores as a solution that is \(30 \%(\mathrm{w} / \mathrm{w}) \mathrm{HCl}\). What mass of this solution contains \(7.5 \mathrm{~g}\) of \(\mathrm{HCl}\) ?

Hydrofluoric acid dissolves glass and must be stored in plastic containers. What mass of a \(45 \%(\mathrm{w} / \mathrm{w})\) solution of \(\mathrm{HF}(a q)\) contains \(1.5 \mathrm{~g}\) of \(\mathrm{HF}\) ?