Ncert Exercises & Solutions

6.3 Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?

The Gibbs free energy of formation (∆fG) of

C u_{2} S

is less than that of

H_{2} S a n d C S_{2}

Therefore, $H_{2}$ and C cannot reduce $C u_{2} S$ to Cu.

On the other hand, the Gibbs free energy of formation of $C u_{2} S$ is greater than that of CO. Hence, C can reduce $C u_{2} S$ to Cu.

$C_{(s)} + C u_{2} O_{(s)} \to 2 C u_{(s)} + C O_{(g)}$

Hence, the extraction of copper from its pyrite ore is difficult than from its oxide ore through reduction.