The electrolysis of pure alumina is not feasible because

What is the process of metallurgy?

In the extraction of copper from its sulphide ore,metal is finally obtained by the oxidation of cuprous sulphide with

In the electrolytic extraction of aluminium,cryolite is used:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: In the Ellingham diagram,a sharp change in slope of the line is observed for $Mg \rightarrow MgO$ at $\sim 1120^{\circ} C$.
Reason $R$: There is a large change of entropy associated with the change of state.
In the light of the above statements,choose the correct answer from the options given below.

Which substance is used as a flux to remove acidic impurities in metallurgy?