State the role of silica in the metallurgy of copper.

Explanation

During roasting , the copper pyrites are converted into a mixture of FeO and `Cu_2 O`.
`underset("Copper pyrites")(2CuFeS_2)+ O_2 overset(Delta)to Cu_2 S + 2FeS + SO_2`
`2Cu_2 S + 3O_2 overset(Delta)to 2Cu_2 O + 2SO_2`
`2FeS + 3O_2 to 2FeO + 2SO_2`
To remove FeO (basic) , the roasted ore is mixed with silica and heated . Silica acts as a flux and combines with ferrous oxide present to form fusible slag of iron silicate.
`FeO + underset("Flux")(SiO_2) to underset("Slag")(FeSiO_3)`
The slag being lighter floats and forms the upper layer and is removed through slag hole. Therefore , silica helps to remove FeO in the metallurgy of copper.