Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?
The Gibbs free energy formation ( ΔfG) of Cu2S is less than that of H2S and CS2. Therefore, H2 and C cannot reduce Cu2S to Cu.
On the other hand, the Gibbs free energy formation of Cu2O is greater than that of CO. hence, C can reduce Cu2O to Cu.
C (s) + Cu2O (s) → 2Cu (s) + CO (g)
Hence, the extraction of copper from its pyrite ore is difficult than from its oxide ore through reduction.