Conversion Of Ores Into Oxides

        Oxygen is more electronegative than other elements. So it is easier for oxides to accept an electron pair and get reduced.

Calcination :

        Calcination is the process of heating a substance in a limited supply of air or oxygen. During this process the water of crystallization present in the hydrated oxide escapes as moisture. Due to the thermal energy (Heat) we can change their chemical state and turn them into oxides. The hydroxides and carbonates are usually converted to oxides through this process. 

Fe₂O₃.3H₂O  ———>  Fe₂O₃  +  3H₂O

CaCO₃  ———>  CaO  +  CO₂

PbCO₃  ———>  PbO  +  CO₂

ZnCO₃  ———>   ZnO  +  CO₂

MgCO₃.CaCO₃   ———>  MgO  +  CaO  +  2CO₂

Al₂O₃.2H₂O  ———>  Al₂O₃  +  2H₂O

Roasting :

      Roasting is the method of heating sulphide ore to a high temperature in the presence of air. In this method the concentrated ore is oxidized by heating it with excess of oxygen in a suitable furnace with in the melting point of the metal. the oxygen in the air reacts with the sulphide ores to give us oxide.

Example ;

2Zns  +  3O₂  ———>  2ZnO  +  2SO₂

2Cu₂S  +  3O₂   ———>   2Cu₂O  +  2SO₂ 

2PbS  +  3O₂  ———>  2PbO  +  2SO₂

       Roasting also removes impurities such as arsenic, sulphur, phosphorus by converting them into their volatile oxides.

Examples :

4As  +  3O₂  ———>  2As₂O₃

S₈  +  8O₂  ———>  8SO₂

P₄  +  5O₂  ———>  P₄O₁₀