Question

Give equations for the following conversions:
(i) Ferric oxide to iron
(ii) Aluminium hydroxide to aluminium oxide
(iii) Aluminium to aluminium nitride
(iv) Aluminium to sodium aluminate

Answer 1

The equations for the following reactions are as follows:

(i) Ferric oxide to iron - Aluminium has a high affinity towards oxygen and thus, it acts as a reducing agent at high temperatures. It reduces ferric oxide to iron, forming aluminium oxide in the process.

$$\begin{gathered} {\mathrm{Fe}}_2{\mathrm{O}}_3+2\mathrm{Al}\underset{\mathrm{High}\mathrm{Temp}.}{\overset{\mathrm{Heated}}{\to }}2\mathrm{Fe}+{\mathrm{Al}}_2{\mathrm{O}}_3 \\ \mathrm{Ferric}\mathrm{oxide}\mathrm{Iron} \end{gathered}$$

(ii) When aluminium hydroxide is heated strongly at around 1100 ^oC to 1200 ^oC, it decomposes to aluminium oxide (alumina)

$$\begin{gathered} 2\mathrm{Al}(\mathrm{OH}{)}_3\underset{1100-{1200}^{\mathrm{o}}\mathrm{C}}{\overset{\mathrm{Heat}}{\to }}{\mathrm{Al}}_2{\mathrm{O}}_3+3{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Aluminium}\mathrm{hydroxide}\mathrm{Aluminium}\mathrm{oxide} \end{gathered}$$

(iii) When aluminium is heated to very high temperatures, it burns brightly in the air, forming a mixture of aluminium oxide and aluminium nitride.

$$\begin{gathered} 4\mathrm{Al}+3{\mathrm{O}}_2\stackrel{}{\to }2{\mathrm{Al}}_2{\mathrm{O}}_3 \\ \mathrm{Aluminium}\mathrm{Aluminium}\mathrm{oxide} \\ 2\mathrm{Al}+{\mathrm{N}}_2\stackrel{}{\to }2\mathrm{AlN} \\ \mathrm{Aluminium}\mathrm{Aluminium}\mathrm{nitride} \end{gathered}$$

(iv) Aluminium reacts with sodium hydroxide to form sodium aluminate and liberates hydrogen gas.

$$\begin{gathered} 2\mathrm{Al}+2\mathrm{NaOH}\stackrel{}{\to }2{\mathrm{NaAlO}}_2+{\mathrm{H}}_2 \\ \mathrm{Aluminium}\mathrm{Sodium}\mathrm{hydroxide}\mathrm{Sodium}\mathrm{aluminate}\mathrm{Hydrogen}\mathrm{gas} \end{gathered}$$