Which of the following metals cannot be extracted by carbon reduction process?

Which of the following is not a basic flux?

Which of the following fluxes is used to remove acidic impurities during metallurgy?

In the electrolysis of alumina to obtain aluminium metal,cryolite is added mainly to

Heating a mixture of $Cu_2O$ and $Cu_2S$ gives:

Formation of metallic copper from the sulphide ore in the commercial thermo-metallurgical process essentially involves which one of the following reactions as the major reaction?