Although carbon and hydrogen are better reducing agents,they are not used to reduce metallic oxides at high temperatures. Why?

In the cyanide extraction process of silver from argentite ore,the oxidizing and reducing agents used are

Refractory materials are generally used in furnaces because

In the metallurgy of copper,metallic copper is finally formed in the furnace by the reactions:

Aluminium is produced on a large scale by electrolysis of alumina,dissolved in fused cryolite and a little fluorspar. These two electrolytes,cryolite and fluorspar are respectively

The chemical that is added to reduce the melting point of the reaction mixture during the extraction of aluminium is