Question

Explain the following:

Silica is added to the sulphide ore of copper in the reverberatory furnace.

Answer 1

Copper pyrites contain iron sulphide in addition to copper sulphide. In the reverberatory furnace copper ore is roasted to give oxides. \[\ce{FeO}\] is removed by adding silica from the matte containing \[\ce{Cu2S}\] and \[\ce{FeS}\].

 \[\ce{2FeS + 3O2 -> 2FeO + 2SO2}\]

\[\ce{Feo + SiO2 -> \underset{(Slag)}{FeSiO3}}\]