On the grid below, sketch the pattern of melting points for the Group IV elements. The point for germanium has already been plotted.
Suggest an explanation for this trend in terms of the structure and bonding of the Group IV elements.
GeO$_2$, SnO$_2$ and PbO$_2$ are amphoteric oxides. What does the term amphoteric mean?
Construct an equation for the reaction between SnO$_2$ and NaOH.
Using information from the Data Booklet, explain why the reaction between $\text{Cr}_2\text{O}_7^{2-}(aq)$ ions and acidified $\text{Sn}^{2+}(aq)$ ions is feasible.
Construct an equation for the reaction in (c)(i) and state any relevant observations. equation observations
When germanium(II) oxide is heated, it disproportionates to give germanium(IV) oxide and germanium. Using this reaction as your example, describe what is meant by a disproportionation reaction.
Some reactions of cyanogen, NC-CN, are similar to those of chlorine, Cl-Cl. When treated with cold, aqueous sodium hydroxide, cyanogen disproportionates in a similar way to chlorine. Complete the equation for this reaction. $(\text{CN})_2 + \ldots\ldots\text{NaOH} \rightarrow \ldots\ldots + \ldots\ldots + \ldots\ldots$
Draw a ‘dot-and-cross’ diagram for NC-CN. Show only the outer electrons.
At room temperature, phosphorus atoms exist as $\text{P}_4$ molecules rather than $\text{P}_2$ molecules. The phosphorus molecule, $\text{P}_4$, has a cage-like structure made only of P-P single bonds. Every phosphorus atom in $\text{P}_4$ is trivalent. Suggest a structure for $\text{P}_4$.
At 1200 K, $\text{P}_2$ and $\text{P}_4$ are in equilibrium in the gas phase. $\text{P}_2$ molecules contain the P≡P bond. The average bond energy of P-P is 198 kJ mol$^{-1}$, while that of P≡P is 489 kJ mol$^{-1}$. Use the bond energies given to calculate the enthalpy change, $\Delta H$, for the following reaction. $2\text{P}_2(g) \rightarrow \text{P}_4(g)$
When phosphorus(V) chloride, PCl$_5$, reacts with ammonium chloride, NH$_4$Cl, hydrogen chloride gas, HCl, is given off and a product with molecular formula $\text{P}_3\text{N}_3\text{Cl}_6$ forms. Construct an equation for this reaction.
$\text{P}_3\text{N}_3\text{Cl}_6$ has a cyclic structure containing alternating phosphorus and nitrogen atoms in the ring system. All the nitrogen atoms are trivalent and all the phosphorus atoms are pentavalent. Suggest a structure for $\text{P}_3\text{N}_3\text{Cl}_6$.