Question

Why should the metal sulphides and carbinates be converted to metals ? Name the process involved in the conversion. Write the equation for each process.

Answer 1

Conversion of concentrated ore into metal oxide 
It is easier to obtain metals from their oxides rather than from carbonates or sulphides. So the ore is first converted into an oxide. A carbonate ore is first converted into oxide ore by calcination. A sulphide ore is converted into oxide ore by roasting. 

1. Calcination process 
It is the process of heating the concentrated ore at a temperature not sufficient to melt the ore. The water content and the volatile impurities also get expelled. Zinc carbonate in its ore calamine (ZnCO3) is calcinated to obtain zinc oxide (ZnO). 
 
 

ZnCO3------------->ZnO+CO2 calcination   

2. Roasting process 
It is the process of heating the concentrated ore in the presence of excess air. Volatile impurities also get expelled. 
Zinc sulphide in its ore zinc blende ( ZnS) is roasted to obtain zinc oxide (ZnO). 
 
 

2ZnS+3O2----->2ZnO+2SO2  (from air)    

Mercuric oxide is obtained by roasting cinnabar (HgS) in air. 
 
 

2ZnS+3O2----->2ZnO+2SO2

Answer 2

as itbis easier to obtqin metals from teir oxides than from carbonates and bicarbonates.
ZnCO3. = ZnO+ Co2
calcination