Chapter 26

Identify the products and write balanced equations for the following reactions (Section 26.2): (a) adding caesium to water; (b) burning rubidium in an excess of air; (c) heating lithium nitrate.

Use a Born-Haber cycle and the data below to explain why \(\mathrm{NaCl}_{2}\) doesn't exist. Assume the ionic radius of \(\mathrm{Na}^{2+}\) is the same as that for \(\mathrm{Mg}^{2}\) '. (Section 26.2) Ionic radili: \(\mathrm{Mg}^{2+}, 72 \mathrm{pm} ; \mathrm{Cl}\), \(181 \mathrm{pm}\) \\[\begin{aligned}\Delta_{a} H^{9}(\mathrm{Na}) &=+108 \mathrm{kJmol}^{-1} & \Delta_{a} H^{\circ}(\mathrm{C}) &=+121 \mathrm{kJ} \mathrm{mol}^{-1} \\ \Delta H(1)^{0}(\mathrm{Na}) &=+496 \mathrm{kJ} \mathrm{mol}^{-1} & \Delta_{\mathrm{og}} H(1)^{\mathrm{e}}(\mathrm{C}) &=-349 \mathrm{kJ} \mathrm{mol}^{-1} \\ \Delta H(2)^{\theta}(\mathrm{Na}) &=+4562 \mathrm{kJ} \mathrm{mol}^{-1} & &\end{aligned}\\]

Predict which compound in each of the following pairs has the higher decomposition temperature: (a) \(\mathrm{NaNO}_{3}\) and \(\mathrm{KNO}_{3}\) (b) \(\mathrm{LiH}\) and \(\mathrm{KH} ;(\mathrm{c}) \mathrm{Li}_{2} \mathrm{CO}_{3}\) and \(\mathrm{SrCO}_{3}\). Give reasons for your answer. (Section 26.2).

Which of the following pairs of Group 1 compounds would you expect to be more soluble in water? (Section 26.3 ) (a) \(\mathrm{LiNO}_{3}\) or \(\mathrm{CsNO}_{3}\) (b) \(\mathrm{LOH}\) or \(\mathrm{RbOH}\) (c) \(\mathrm{NaBr}\) or \(\mathrm{CsBr}\)

Magnesium chloride is prepared by reacting sea water with \(\mathrm{Ca}(\mathrm{OH})_{2}\) to precipitate \(\mathrm{Mg}(\mathrm{OH})_{2}\), reacting this with hydrochloric acid, and then evaporating the solution slowly to give crystals of magnesium chloride. (Section 26.6) (a) Write balanced equations for these reactions, ignoring any water of crystallization. (b) A sample of \(\mathrm{MgCl}_{2}\) obtained from this process contains \(18.5 \%\) magnesium by mass. Assuming there are no impurities, how many molecules of water does the MgCla crystallize with?

Identify the products and write balanced equations for the following reactions (Section 26.7 ): (a) adding beryllium to sodium hydroxide solution; (b) heating strontium carbonate; (c) heating barium oxide in air.

When magnesium burns in air, both magnesium oxide and magnesium nitride are formed. Suggest how you could obtain a pure sample of magnesium oxide from this mixture. (Section \(26.7)\)