`Delta _(f) G^(@)` of `Cu_(2)s` is more negative than `Delta _(f) G^(@)` of `Cs_(2)` and `H_(2) S` So `Cu_(2)S` can not be reduced by carbon or hydrogen `Delta_(f)G^(@)`of `Cu_(2)O so `CU_(2) O can be reduced by carbon . So pyrites is first converrted to oxide before reducation to copper
`Cu_(2) S(s) +(3)/(2) O_(2) (g) to CU_(2) O (s) +So_(2)(g) `
` Cu_92)O(s) +C(s) to 2Cu (s) +CO(s)`
