A student warms 1.605 g of ammonium chloride, NH₄Cl, with an excess of sodium hydroxide solution in…

The group scheme is: zero $\text{NH}_4^+$; I $\text{Pb}^{2+}$; II $\text{Cu}^{2+}$; III $\text{Fe}^{3+}$, $\text{Al}^{3+}$; IV $\text{Zn}^{2+}$, $\text{Ni}^{2+}$, $\text{Co}^{2+}$, $\text{Mn}^{2+}$; V $\text{Ca}^{2+}$, $\text{Ba}^{2+}$; VI $\text{Mg}^{2+}$. Zinc, aluminium and lead hydroxides dissolve in excess sodium hydroxide. Copper, nickel, zinc and cobalt hydroxides dissolve in excess ammonium hydroxide as ammines. Iron(III) and hexacyanoferrate(II) make Prussian blue: $4\ \text{Fe}^{3+} + 3\ [\text{Fe(CN)}_6]^{4-} \rightarrow \text{Fe}_4[\text{Fe(CN)}_6]_3$.