Question:
The correct statement is :
Correct Option: 1
Solution:
During metallurgy of aluminium, when bauxite (powdered ore) is treated with $\mathrm{NaOH}$ (conc), sodium aluminate $\left(\mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_{4}\right]\right)$ is formed and impurity $\left(\mathrm{SiO}_{2}\right)$ present in bauxite dissolves by forming sodium silicate $\left(\mathrm{Na}_{2} \mathrm{SiO}_{3}\right)$
$\mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{~s})+2 \mathrm{NaOH}(\mathrm{aq})+3 \mathrm{H}_{3} \mathrm{O}(\mathrm{l}) \underset{2 \mathrm{Na}}{\rightarrow}\left[\mathrm{Al}(\mathrm{OH})_{4}\right](\mathrm{aq})$
Cast iron is obtained from pig iron.
Blister of copper is due to evolution of $\mathrm{SO}_{2}$.
Hall Heroult process is used for the production of aluminium.