Question

Roasting of copper pyrite ores is for which of the following purposes?
A. To burn off sulphur, anatomy etc. as oxides and convert all the iron and copper to their oxides.
B. To burn off arsenic, anatomy 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 sulphur to combine with arsenic, anatomy etc. and the to convert all the iron and copper to oxides.
D. To melt arsenic and anatomy sulphides etc. and remove them by liquation and to burn off sulphur partially to leave enough to combine with copper and iron

Answer 1

Copper pyrite ores are roasted to achieve concentration of the ore. And concentration is nothing but a process to remove impurities or unwanted substances from the ore.

Complete Step by Step answer:
The ore is partially roasted because the Sulphur takes the impurities as gases and to react with remaining ore to get Copper metal undergoing auto-reduction.

$C{{u}_{2}}S.F{{e}_{2}}{{S}_{3}}+{{O}_{2}}\xrightarrow{{}}C{{u}_{2}}S+2FeS+S{{O}_{2}}$
$C{{u}_{2}}S+3{{O}_{2}}\xrightarrow{{}}C{{u}_{2}}O+2S{{O}_{2}}$
Roasting is the process of heating sulphide ore by a heat source in the presence of air. In roasting, the ore or ore concentrate is treated with extremely popular air.In the case of sulphide ores this process is commonly applied. In the process of roasting, the sulphide present is converted to an oxide, and is released as sulphur dioxide, a gas.
The main function of roasting is removing volatile impurities and to convert the ore into oxide i.e. oxidation of the ore.
COPPER-PYRITES, or Chalcopyrite, a copper iron sulphide ($CuFe{{S}_{2}}$), a crucial ore of copper. Chalcopyrite crystallizes within the tetragonal system with inclined hemihedrism, but the shape is so nearly cubic that it has not been recognized as tetragonal.
From the above explanation option(c) i.e. (To burn off sulphur partially, in order to leave enough sulphur to combine with arsenic, anatomy etc. and then to convert all the iron and copper to oxides) is correct.

Note:
-Extraction of a metal from its oxides is easier, so we convert the copper iron sulphide first into copper sulphide and then convert it into copper oxide.
-Roasting is always done in the presence of air supply.
- Main function of roasting is removing volatile impurities and converting the ore into oxide.