State the role of silica in the metallurgy of copper.
During the roasting of pyrite ore, a mixture of FeO and Cu2O is obtained.
The role of silica in the metallurgy of copper is to remove the iron oxide obtained during the process of roasting as ‘slag’. If the sulphide ore of copper contains iron, then silica (SiO2) is added as flux before roasting. Then, FeO combines with silica to form iron silicate, FeSiO3 (slag).
During roasting, copper pyrites are converted into a mixture of FeO and Cu20. Thus, acidic flux silica is added during smelting to remove FeO (basic). FeO combines with SiO2to form famous silicate (FeSiO3) slag which floats over molten matte.
Cr2O3 + 2Al → Al2O3 + 2Cr
(ΔGθ = -421kJ) is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?
Is it true that under certain conditions, Mg can reduce SiO2 and Si can reduce MgO? What are those conditions?