Wednesday, August 26, 2020

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

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