Question
Why is the extraction of copper from pyrites difficult than from its oxide ore through reduction.
Solution
In the graph of ΔrG° Vs T for the formation of oxides, the Cu2O 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, CO2 are at much lower positions in the graph particularly after 500-600 K).
However sulphide ores are roasted/smelted to give oxides.
2Cu2S + 3O2 → 2Cu2O + 2SO2
The oxide can then be easily reduced to metallic copper using coke.
Cu2O + C → 2Cu + CO
