Question

Roasting of copper pyrite ores is for the following purpose

• A. to burn off sulphur, arsenic, antimony etc. as oxides and convert all the iron and copper to their oxides
• B. to burn off arsenic, antimony etc. as oxides and burn off sulphur so that enough of it remains to combine with all the copper
• C. to burn off sulphur partially, in order to leave enough of sulphur to combine with arsenic, antimony etc. and to convert all the iron and copper to oxides
• D. to melt arsenic and antimony sulphides etc. and remove them by liquation and to burn off sulphur partially to leave enough to combine with copper and iron

Answer 1

Answer: (C)

Roasting: The process in which the concentrated ore is heated in blast of air and ore gets converted into oxide and impurities like sulphur, arsenic are also oxidised to their oxides and removed is called Roasting. It requires very high temperature and specialized furnace like Bessemer or reverberatory furnace.
Rreaction:
$Cu _{2} S . Fe _{2} S _{3}+ O _{2} \rightarrow Cu _{2} S +2 F eS + SO _{2}$
$Cu _{2} S +3 O _{2} \rightarrow Cu _{2} O +2 SO _{2}$