Q. Observe the following statements regarding purification of bauxite During Hall’s process, silica is removed as Si (vapour). Bauxite ore contaminated with $Fe_{2}O_{3}$ is purified in Baeyer’s process. During Serpeck’s process, AlN is formed. The correct answer is
A) I, II and III are correct
B) Only I and II are correct
C) Only I and III are correct
D) Only II and III are correct
Explanation
(d)
Red bauxite which contains $Fe_{2}O_{3}$ as the main impurity, is refined either by Baeyer’s process or by Hall’s process. White bauxite containing $SiO_{2}$ impurity is refined by Serpeck’s method. In Serpeck’s method, following reactions take place
$Al_{2}O_{3}.2H_{2}O + 3C + N_{2}\overset{\ \ 1800℃\ \ \ }{\rightarrow}2AlN + 3CO + 2H_{2}O$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ AlN + 3H_{2}O \longrightarrow Al(OH)_{3} + NH_{3}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 2Al(OH)_{3}\overset{\ \ \ \ \mathrm{\Delta}\ \ \ }{\rightarrow}Al_{2}O_{3} + 3H_{2}O$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.