Q. Bauxite ore is made up of $Al_{2}O_{3} + SiO_{2} + TiO_{2} + Fe_{2}O_{3}$. This ore is treated with conc. $NaOH$ solution at 500K and 35 bar pressure for few hours and filtered hot. In the filtrate the species present, are
A) $NaAl(OH)_{4}$ only
B) $Na_{2}Ti(OH)_{6}$ only
C) $NaAl(OH)_{4}$ and $Na_{2}SiO_{3}$ both
D) $Na_{2}SiO_{3}$ only
Explanation
(a)
In bauxite ore, only $Al_{2}O_{3}$ reacts with conc. $NaOH$ and forms sodium meta aluminate.
This further dissolves in water.
$Al_{2}O_{3} + 2H_{2}O + 2NaOH\underset{35\ bar}{\overset{\ \ \ \ 500\ K\ \ \ }{\rightarrow}}2NaAlO_{2} + 3H_{2}O$
$NaAlO_{2} + 2H_{2}O \rightarrow NaAl(OH)_{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.