$$\eqalign{ & {\text{Calamine}} \to ZnC{O_3} \cr & {\text{Malachite}} \to CuC{O_3}.Cu{\left( {OH} \right)_2} \cr & {\text{Magnetite}} \to F{e_3}{O_4} \cr & {\text{Cryolite}} \to N{a_3}Al{F_6} \cr} $$

Decomposition of carbonates and hydrated oxides.

$$\eqalign{ & CuS{O_4} \rightleftharpoons C{u^{2 + }} + SO_4^{2 - } \cr & {H_2}O \rightleftharpoons {H^ + } + O{H^ - } \cr & {\text{At cathode :}}\,\,C{u^{2 + }} + 2{e^ - } \to Cu \cr & {\text{At anode}}\,\,:\,\,4O{H^ - } \to 2{H_2}O + {O_2} + 4{e^ - } \cr} $$

Impurities like $$F{e_2}{O_3}$$  and $$Si{O_2}$$  are present in bauxite.

During the extraction of iron, the limestone decomposes in the hot furnace forming $$CaO.$$  This reacts with the sandy impurities $$\left( {Si{O_2}} \right)$$  to form slag.

Graphite produces impurity in pig iron. Pig iron contains 2.5 to 5.0% of carbon.

It is definition of calcination.

$$\eqalign{ & {\text{Compound }}X{\text{ is}}\,\,CaC{O_3} \cr & \mathop {CaC{O_3}}\limits_X \mathop \to \limits^\vartriangle \mathop {CaO}\limits_{{\text{Residue}}} + C{O_2} \uparrow \cr & \mathop {CaO}\limits_{{\text{Residue}}} + {H_2}O \to \mathop {Ca{{\left( {OH} \right)}_2}}\limits_Y \cr & \mathop {Ca{{\left( {OH} \right)}_2}}\limits_Y + \mathop {C{O_2}}\limits_{{\text{Excess}}} + {H_2}O \to \mathop {Ca{{\left( {HC{O_3}} \right)}_2}}\limits_Z \cr & \mathop {Ca{{\left( {HC{O_3}} \right)}_2}}\limits_Z \mathop \to \limits^\vartriangle \mathop {CaC{O_3}}\limits_X + {H_2}O + C{O_2} \uparrow \cr} $$

As zinc blende $$\left( {ZnS} \right)$$  is a sulphide ore hence concentrated by froth floatation process.

Most electropositive metals are obtained by electrolysis of their fused ionic salts.