Chemical reduction is used in the extraction of

Chemical reduction method can be used for the extraction of metals except highly reactive metals like Na, K, Ca, Al.

${\mathrm{Cr}}_2{\mathrm{O}}_3+2\mathrm{Al}\to 2{\mathrm{Al}}_2{\mathrm{O}}_3+2\mathrm{Cr};\mathrm{CuO}+\mathrm{C}\to \mathrm{Cu}+\mathrm{Co}$

$3{\mathrm{Mn}}_3{\mathrm{O}}_4+8\mathrm{Al}\to 4{\mathrm{Al}}_2{\mathrm{O}}_3+9 \mathrm{Mn};{\mathrm{Fe}}_2{\mathrm{O}}_3+3\mathrm{C}\to 2\mathrm{Fe}+3\mathrm{CO}$