Question

State the role of silica in the metallurgy of copper.

Answer 1

During roasting, copper pyrites give $FeO$ and $C{u}_{2}O$.
$2CuFe{S}_2+O_2\stackrel{\Delta }{\to }C{u}_{2}S+2FeS+S{O}_2$

$2C{u}_{2}S+3O_2\stackrel{\Delta }{\to }2C{u}_{2}O+2S{O}_2$

$2FeS+3O_2\to 2FeO+2S{O}_2$

Roasted ore is then mixed with silica (acidic flux) and heated to remove

$FeO$ (basic) as a slag of iron silicate.

$FeO+Si{O}_2\to FeSi{O}_3$
Lighter slag forms upper layer and is removed through slag hole.