Problem 1
(a) Describe briefly how you would synthesize the solid state compound \(\mathrm{Na}_{3} \mathrm{C}_{60}\) (b) The \({ }^{13} \mathrm{C}\) MAS NMR spectrum of \(\mathrm{C}_{\omega}\) recorded at room temperature shows a single narrow resonance, but as the temperature falls the spectrum broadens to a feature covering several \(\mathrm{kHz}\). Describe the origin of the differences in the spectra. (c) Reaction of \(\mathrm{C}_{60}\) with rubidium and caesium produces an intercalation compound with the formula, \(\mathrm{Rb}_{2} \mathrm{CsC}_{60}\). Describe, with the aid of a diagram, why you would expect this compound to be a type II superconductor. (d) Explain what is meant by the underlined terms in part (c).
Problem 2
Reaction of a mixture of yttrium oxide, barium carbonate and copper oxide in a stream of oxygen produces A. Elemental analysis of the oxide A gave \(11.9 \% \mathrm{Y}, 36.8 \%\) barium and \(34.1 \%\) copper. (a) Calculate the empirical formula of \(\mathrm{A}\), assuming the rest of the molecular \% is oxygen. (b) Determine the average oxidation state of the copper. (c) If you brought a pellet of \(\mathrm{A}\) at very low temperature towards a permanent magnet, what would you expect to happen and why? (d) Draw the graph expected for the change in resistance with temperature for A. Explain the salient features of the graph, with the aid of diagrams where necessary. What type of superconductor would you expect \(\mathrm{A}\) to be?
Problem 3
\(\mathrm{Cu}(\mathrm{OH})_{2}\) reacts with \(\mathrm{Au}(\mathrm{OH})_{3}\) in a \(3: 1\) molar ratio to form \(\mathrm{A}\). The IR spectrum of A shows a strong absorption at \(3400 \mathrm{~cm}^{-1}\). \(0.541 \mathrm{~g}(1 \mathrm{mmol})\) of A decomposes in a stream of hydrogen at 500 \({ }^{\circ} \mathrm{C}\) to produce \(\mathrm{B}\) and water \((0.162 \mathrm{~g})\). Elemental analysis of the intermetallic B revealed \(50.8 \% \mathrm{Au}\). (a) Using the information given above, identify A and \(B\). (b) Given that \(\mathrm{B}\) is a superconductor which conducts at liquid helium temperatures, predict a likely structure for \(\mathrm{B}\).
Problem 4
(a) Describe the structural features of graphite which make it suitable for intercalation reactions. (b) How does the structure of the first stage intercalate of graphite differ from that of the parent material? (c) Reaction of excess potassium with graphite produced the goldcoloured compound A which contained \(28.9 \%\) potassium. Describe the type of reaction occurring, and explain the differences in appearance and conductivity of the new material compared with graphite.
Problem 5
(a) Briefly describe the important features of zeolites which make them suitable for ion exchange. Why do siliceous zeolites make poor water softeners? (b) Describe two ways in which an H-zeolite could be prepared. (c) Describe the two sorts of acid site which form in zeolites. (d) Explain why zeolites can be used for shape-selective catalysis.
