Why is the extractio of Cu from pyrites more difficult than that from its oxide ore through reduction?

Explanation

The standard free energy `(Delta_(f)G^(@))` of formation of `Cu_(2)S` is more negative than those of `CS_(2)` and `H_(2)S`.
Therefore, carbon or hydrogen cannot reduce `Cu_(2)S` to `Cu`

On the other hand, `(Delta_(f)G^(@))` of `Cu_(2)O` is less `-ve` than that of `CO.` Hence, carbon can easily reduce `Cu_(2)O` to `Cu.`
`Cu_(2)O(s)+C(s) rarr 2Cu(s)+CO(g)`
Therefore, the extraction of copper from pyrites is more difficult than that from its oxide ore, through reduction.