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Question
Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?
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Solution
The Gibbs free energy of 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 of formation of Cu2O is greater than that of CO. Hence, C can reduce Cu2O to Cu.
\[\ce{C_{(s)} + Cu2O_{(s)} -> 2Cu_{(s)} + CO_{(g)}}\]
Hence, the extraction of copper from its pyrite ore is more difficult than from its oxide ore through reduction.
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