State the role of silica in the metallurgy of copper.

Explanation

In the metallurgy of copper, pyrites are converted into a mixture of `FeO` and `Cu_(2)O`, during roasting.
`2CuFeS_(2)" (copper pyrites)"+O_(2)overset(Delta)rarr Cu_(2)S+2FeS+SO_(2)`
`2Cu_(2)S+3O_(2) overset(Delta)rarr 2Cu_(2)O+2SO_(2)`
`2FeS +3O_(2) rarr 2FeS+2SO_(2)`
To remove basic `FeO,` silica is added during smelting. `FeO` then combines with `SiO_(2)` to form ferrous slicate `(FeSiO_(3))` slag. The slag floats over molten matte and so can be easily removed : `FeO +SiO_(2)("flux")rarr FeSiO_(3)("slag")`
Therefore, the role of silica in the metallurgy of copper is to remove ferrous oxide as ferrous silicate slag.