91Ó°ÊÓ

A metal (A) on heating in nitrogen gas gives compound B. B on treatment with \(\mathrm{H}_{2} \mathrm{O}\) gives a colourless gas which when passed through \(\mathrm{CuSO}_{4}\) solution gives a dark blue-violet coloured solution. A and \(\mathrm{B}\) respectively, are: (a) \(\mathrm{Na}\) and \(\mathrm{NaNO}_{3}\) (b) \(\mathrm{Na}\) and \(\mathrm{Na}_{3} \mathrm{~N}\) (c) \(\mathrm{Mg}\) and \(\mathrm{Mg}_{3} \mathrm{~N}_{2}\) (d) \(\mathrm{Mg}\) and \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\)

The correct order of hydration enthalpies of alkali metal ions is : (a) \(\mathrm{Li}^{+}>\mathrm{Na}^{+}>\mathrm{K}^{+}>\mathrm{Cs}^{+}>\mathrm{Rb}^{+}\) (b) \(\mathrm{Na}^{+}>\mathrm{Li}^{+}>\mathrm{K}^{+}>\mathrm{Rb}^{+}>\mathrm{Cs}^{+}\) (c) \(\mathrm{Na}^{+}>\mathrm{Li}^{+}>\mathrm{K}^{+}>\mathrm{Cs}^{+}>\mathrm{Rb}^{+}\) (d) \(\mathrm{Li}^{+}>\mathrm{Na}^{+}>\mathrm{K}^{+}>\mathrm{Rb}^{+}>\mathrm{Cs}^{+}\)

The solubility order for alkali metal fluoride in water is (a) \(\mathrm{LiF}<\mathrm{RbF}<\mathrm{KF}<\mathrm{NaF}\) (b) \(\mathrm{RbF}<\mathrm{KF}<\mathrm{NaF}<\mathrm{LiF}\) (c) \(\mathrm{LiF}>\mathrm{NaF}>\mathrm{KF}>\mathrm{RbF}\) (d) \(\mathrm{LiF}<\mathrm{NaF}<\mathrm{KF} \leq \mathrm{RbF}\)

The pair of compounds which cannot exist together in solution is: (a) \(\mathrm{NaHCO}_{3}\) and \(\mathrm{NaOH}\) (b) \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and \(\mathrm{NaHCO}_{3}\) (c) \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and \(\mathrm{NaOH}\) (d) \(\mathrm{NaHCO}_{3}\) and \(\mathrm{NaCl}\)

\(\mathrm{MgSO}_{4}\) on reaction with \(\mathrm{NH}_{4} \mathrm{OH}\) and \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) forms a white crystalline precipitate. What is its formula? \([2006-5 \mathrm{M},-1]\) (a) \(\mathrm{Mg}\left(\mathrm{NH}_{4}\right) \mathrm{PO}_{4}\) (b) \(\mathrm{Mg}_{3}\left(\mathrm{PO}_{4}\right)_{2}\) (c) \(\mathrm{MgCl}_{2} \cdot \mathrm{MgSO}_{4}\) (d) \(\mathrm{MgSO}_{4}\)