What chemical principle is involved in choosing a reducing agent for gettting the metal from its oxide ore? Consider the metal oxides, Al₂O₃ and Fe₂O₃ and justify the choice of reducing agent in each case. 

Highly electropositive elements are obtained by the electrolysis of their oxides, hydroxides or chlorides in fused state.

Extraction of less electropositive metals say Cr, Mn, Cu, Ca, Ni etc. can be done by heating their oxides with strong reducing agent e.g., CO + H₂, Na, Al, Mg etc. The oxides of less electropositive metals like Pb, Fe, Zn, Sb and Cu are reduced by strongly heating with coal or coke.

Al₂O₃ is mixed with Na₃AlF₆ which lowers the melting point of the mix and brings conductivity. The fused Al₂O₃ is electrolysed steel cathode and graphite anode are used.

$$\begin{gathered} \mathrm{At} \mathrm{cathode}: {\mathrm{Al}}^{3+}+ 2\mathrm{e} \to \mathrm{Al}\left(\mathrm{l}\right) \\ \mathrm{At} \mathrm{andoe} \mathrm{C}\left(\mathrm{s}\right) +{\mathrm{O}}^{2-} \to \mathrm{CO}\left(\mathrm{g}\right) +2{\mathrm{e}}^{-} \\ \mathrm{C}\left(\mathrm{s}\right) +2{\mathrm{O}}^{2-} \to {\mathrm{CO}}_2\left(\mathrm{g}\right) + 4{\mathrm{e}}^{-} \\ {\mathrm{Fe}}_2{\mathrm{O}}_3 \mathrm{can} \mathrm{be} \mathrm{reduced} \mathrm{by} \mathrm{carbon} \\ 2\mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2 \stackrel{∆}{\to } 2{\mathrm{CO}}_2\left(\mathrm{g}\right) \\ {\mathrm{CO}}_2\left(\mathrm{g}\right)+\mathrm{C}\left(\mathrm{s}\right) \stackrel{∆}{\to } 2\mathrm{CO}\left(\mathrm{g}\right) \\ {\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{g}\right)+3\mathrm{CO}\left(\mathrm{g}\right) \stackrel{∆}{\to } 2\mathrm{Fe}\left(\mathrm{l}\right)+3{\mathrm{CO}}_2\left(\mathrm{g}\right) \end{gathered}$$