Observe the following statements regarding purification of bauxite I. During Hall's process, silica is…
Observe the following statements regarding purification of bauxite
I. During Hall's process, silica is removed as Si (vapour).
II. Bauxite ore contaminated with $\mathrm{Fe}_2 \mathrm{O}_3$ is purified in Baeyer's process.
III. During Serpeck's process, AlN is formed.
The correct answer is
I, II and III are correct
Only I and II are correct
Only I and III are correct
Only II and III are correct
Solution
Red bauxite which contains $\mathrm{Fe}_2 \mathrm{O}_3$ as the main impurity, is refined either by Baeyer's process or by Hall's process. White bauxite containing $\mathrm{SiO}_2$ impurity is refined by Serpeck's method. In Serpeck's method, following reactions take place.
$\begin{gathered}
\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}+3 \mathrm{C}+\mathrm{N}_2 \stackrel{1800^{\circ} \mathrm{C}}{\longrightarrow} 2 \mathrm{AlN}+3 \mathrm{CO}+2 \mathrm{H}_2 \mathrm{O} \\
\mathrm{AlN}+3 \mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Al}(\mathrm{OH})_3+\mathrm{NH}_3 \\
2 \mathrm{Al}(\mathrm{OH})_3 \longrightarrow \mathrm{Al}_2 \mathrm{O}_3+3 \mathrm{H}_2 \mathrm{O}
\end{gathered}$