In the Goldschmidt aluminothermic process,which of the following reducing agents is used?

The value of ${\Delta _r}{G^\Theta }$ for the formation of $Cr_2O_3$ is $-540 \, kJ \, mol^{-1}$ and that of $Al_2O_3$ is $-827 \, kJ \, mol^{-1}$. Is the reduction of $Cr_2O_3$ possible with $Al$?

Extraction of copper by smelting uses silica as an additive to remove

Which metal is used as a reducing agent in smelting?

The flux used to remove the $FeO$ impurity present in the mixture obtained from the roasting of copper pyrites,and its nature,is .....

Although thermodynamically feasible,in practice,magnesium metal is not used for the reduction of alumina in the metallurgy of aluminium. Why?