Question
Compare roasting and calcination.

Answer

RoastingCalcination
1This method is generally used for sulphide oresThis method is generally used for carbonate

ores.
2In this method, ores are heated in excess of air.In this method, ores are heated in a limited

supply of air.
3In roasting, generally sulphur dioxide gas is

evolved.
In calcination, generally carbon dioxide gas is

evolved.
4In this method, sulphide ores are oxidized to form

metal oxides.


In this method, carbonate ores decompose to

form metal oxide.


E.g.

2ZnS+3O_(2)longrightarrow2ZnO+2SO_(2)uarr
E.g.ZnCO_(3)longrightarrow ZnO+CO_(2)uarr

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