Problem 21
(a) Given that the enthalpy change associated with the addition of \(\mathrm{H}^{+}(\mathrm{g})\) to \(\mathrm{H}_{2} \mathrm{O}(\mathrm{g})\) is \(-690 \mathrm{kJ} \mathrm{mol}^{-1},\) and \(\Delta_{\mathrm{hyd}} H^{\circ}\left(\mathrm{H}^{+}, \mathrm{g}\right)=-1091 \mathrm{kJ} \mathrm{mol}^{-1},\) calculate the enthalpy change associated with the solvation of \(\left[\mathrm{H}_{3} \mathrm{O}\right]^{+}(\mathrm{g})\) in water. (b) Outline how the nickel-metal hydride battery works, giving equations for the reactions at each electrode during charging and discharging.
Problem 22
(a) \(\mathrm{Sr}_{2} \mathrm{RuH}_{6}\) crystallizes in a lattice that can be described in terms of the \(\mathrm{CaF}_{2}\) structure type with octahedral \(\left[\mathrm{RuH}_{6}\right]^{4-}\) ions replacing \(\mathrm{Ca}^{2+}\) ions, and \(\mathrm{Sr}^{2+}\) ions replacing \(\mathrm{F}^{-}\) ions. Sketch a unit cell of \(\mathrm{CaF}_{2} .\) Show that in \(\operatorname{Sr}_{2} \mathrm{RuH}_{6},\) each \(\left[\mathrm{RuH}_{6}\right]^{2-}\) ion is surrounded by eight \(\mathrm{Sr}^{2+}\) ions in a cubic array. (b) Suggest products for the following reactions: $$\begin{array}{l} \mathrm{SiCl}_{4}+\mathrm{LiAlH}_{4} \rightarrow \\ \mathrm{Ph}_{2} \mathrm{PH}+\mathrm{KH} \longrightarrow \\ 4 \mathrm{LiH}+\mathrm{AlCl}_{3} \stackrel{\mathrm{Et}_{2} \mathrm{O}}{\longrightarrow} \end{array}$$
Problem 23
The first list below contains the formula of a hydride. Each has a 'partner' in the second list of phrases. Match the 'partners'; there is only one match for each pair. Structural descriptions refer to the solid state. $$\begin{array}{ll} \hline \text { List 1 } & \text { List 2 } \\ \hline \mathrm{BeH}_{2} & 3 \mathrm{D} \text { lattice with octahedral metal centres } \\ {\left[\mathrm{PtH}_{4}\right]^{2-}} & \text { Non-stoichiometric hydride } \\\ \mathrm{NaH} & \mathrm{M}(0) \text { complex } \\ {\left[\mathrm{NiH}_{4}\right]^{4-}} & \text { Polymeric chain } \\ {\left[\mathrm{PtH}_{6}\right]^{2-}} & \mathrm{M}(\mathrm{IV}) \text { complex } \\ {\left[\mathrm{TcH}_{9}\right]^{2-}} & \text { Tricapped trigonal prismatic hydrido } \\ & \text { complex } \\ \mathrm{HfH}_{2.1} & \text { Square planar complex } \\ \mathrm{AlH}_{3} & \text { Saline hydride } \\ \hline \end{array}$$
