Electrolytic reduction of alumina to aluminium by the Hall-Heroult process is carried out in the presence of:

The process of the isolation of a metal by dissolving the ore in a suitable chemical reagent followed by precipitation of the metal by a more electropositive metal is called

The process,which does not use a catalyst is

What is the role of limestone during the extraction of iron from haematite ore?

The main reactions occurring in a blast furnace during the extraction of iron from haematite are $....$.
$(i)$ $Fe_2O_3 + 3CO \to 2Fe + 3CO_2$
$(ii)$ $FeO + SiO_2 \to FeSiO_3$
$(iii)$ $Fe_2O_3 + 3C \to 2Fe + 3CO$
$(iv)$ $CaO + SiO_2 \to CaSiO_3$

Spelter is