Chemistry - Metallurgy Question with Solution | TestHub

Here only statement 4 is correct while rest are incorrect as
Hall-Heroult process is used for production of only aluminium.
Cast iron is obtained from pig iron
$\underset{4\mathrm{\%}}{\mathrm{P}\mathrm{i}\mathrm{g }\mathrm{i}\mathrm{r}\mathrm{o}\mathrm{n}}\underset{\mathrm{a}\mathrm{i}\mathrm{r }}{\stackrel{\mathrm{b}\mathrm{l}\mathrm{a}\mathrm{s}\mathrm{t }\mathrm{o}\mathrm{f }}{\to }}\underset{3\mathrm{\%}}{\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{t}\mathrm{i}\mathrm{ro}\mathrm{n}}$
The blistered appearance of copper during the metallurgical process is due to the evoluation of$\text{S}{\text{O}}_2$.
$\mathrm{C}{\mathrm{u}}_2\mathrm{S}+2\mathrm{C}{\mathrm{u}}_2\mathrm{O}\to 6\mathrm{C}\mathrm{u}+\mathrm{S}{\mathrm{O}}_2$
During leaching when bauxite is treated with concentrated NaOH, then sodium aluminate and sodium silicate is formed in the soluble form, whereas$\text{F}{\text{e}}_2{\text{O}}_3$is precipitated.