Problem 3
How does the structure of graphite account for (a) its use as a lubricant, (b) the design of graphite electrodes, and (c) the fact that diamond is the more stable allotrope at very high pressures?
Problem 7
(a) Suggest why the \(\mathrm{NSi}_{3}\) skeleton in \(\mathrm{N}\left(\mathrm{SiMe}_{3}\right)_{3}\) is planar. (b) Suggest reasons why, at \(298 \mathrm{K}, \mathrm{CO}_{2}\) and \(\mathrm{SiO}_{2}\) are not isostructural. Under what conditions can phases of \(\mathrm{CO}_{2}\) with silica-like structures be made?
Problem 8
Predict the shapes of the following molecules or ions: (a) \(\mathrm{ClCN} ;\) (b) \(\mathrm{OCS}\) (c) \(\left[\mathrm{SiH}_{3}\right]_{\text {, }}^{-} ;(\mathrm{d})\left[\mathrm{SnCl}_{5}\right]^{-}\) (e) \(\mathrm{Si}_{2} \mathrm{OCl}_{6}\) \((\mathrm{f})\left[\mathrm{Ge}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{2-} ;(\mathrm{g})\left[\mathrm{PbCl}_{6}\right]^{2-} ;(\mathrm{h})\left[\mathrm{SnS}_{4}\right]^{4-}\)
Problem 9
The observed structure of \(\left[\mathrm{Sn}_{9} \mathrm{Tl}\right]^{3-}\) is a bicapped squareantiprism. (a) Confirm that this is consistent with Wade's rules. (b) How many isomers (retaining the bicapped square-antiprism core) of \(\left[\mathrm{Sn}_{9} \mathrm{Tl}\right]^{3-}\) are possible?
Problem 10
Compare and contrast the structures and chemistries of the hydrides of the group 14 elements, and give pertinent examples to illustrate structural and chemical differences between \(\mathrm{BH}_{3}\) and \(\mathrm{CH}_{4},\) and between \(\mathrm{AlH}_{3}\) and \(\mathrm{SiH}_{4}\)
Problem 11
Write equations for: (a) the hydrolysis of GeCl_; (b) the reaction of \(\mathrm{SiCl}_{4}\) with aqueous \(\mathrm{NaOH} ;(\mathrm{c})\) the 1: 1 reaction of \(\mathrm{CsF}\) with \(\mathrm{GeF}_{2} ;(\mathrm{d})\) the hydrolysis of \(\mathrm{SiH}_{3} \mathrm{Cl}\) (e) the hydrolysis of \(\operatorname{SiF}_{4} ;\) (f) the 2: 1 reaction of \(\left[\mathrm{Bu}_{4} \mathrm{P}\right] \mathrm{Cl}\) with \(\operatorname{Sn} \mathrm{Cl}_{4}\). In each case suggest the structure of the product containing the group 14 element.
Problem 13
What would you expect to form when: (a) Sn is heated with concentrated aqueous \(\mathrm{NaOH}\) (b) \(\mathrm{SO}_{2}\) is passed over \(\mathrm{PbO}_{2}\) (c) \(\mathrm{CS}_{2}\) is shaken with aqueous \(\mathrm{NaOH}\) (d) \(\operatorname{SiH}_{2} \mathrm{Cl}_{2}\) is hydrolysed by water; (e) four molar equivalents of \(\mathrm{ClCH}_{2} \mathrm{SiCl}_{3}\) react with three equivalents of \(\mathrm{Li}\left[\mathrm{AlH}_{4}\right]\) in \(\mathrm{Et}_{2} \mathrm{O}\) solution?
Problem 14
Suggest one method for the estimation of each of the following quantities: (a) \(\Delta_{r} H^{\circ}\) for the conversion: \(\mathrm{GeO}_{2}(\mathrm{quartz}) \rightarrow \mathrm{GeO}_{2}(\text { rutile })\) (b) the Pauling electronegativity value, \(\chi^{P},\) of \(\mathrm{Si}\) (c) the purity of a sample of \(\mathrm{Pb}\left(\mathrm{MeCO}_{2}\right)_{4}\) prepared in a laboratory experiment.
Problem 18
Account for the fact that when aqueous solution of KCN is added to a solution of aluminium sulfate, a precipitate of \(\mathrm{Al}(\mathrm{OH})_{3}\) forms.
Problem 19
What would you expect to be the hydrolysis products of (a) cyanic acid, (b) isocyanic acid and (c) thiocyanic acid?
