State the role of silica in the metallurgy of copper.

Explanation

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