Question
Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?
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Answer
In the graph of $\triangle _rG^\circ$ Vs T for the formation of oxides, the $Cu_2O$ line is almost at the top. So it is quite easier to reduce oxide ores of copper directly to the metal by heating with coke $($both the lines of $C,\ CO$ and $C,\ CO_2$ are at much lower positions in the graph particularly after $500-600K).$
However sulphide ores are roasted/smelted to give oxides.
$2Cu_2S + 3O_2 → 2Cu_2O + 2SO_2$
The oxide can then be easily reduced to metallic copper using coke.
$Cu_2O + C → 2Cu + CO$
However sulphide ores are roasted/smelted to give oxides.
$2Cu_2S + 3O_2 → 2Cu_2O + 2SO_2$
The oxide can then be easily reduced to metallic copper using coke.
$Cu_2O + C → 2Cu + CO$
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