Which iof the following reactions represents the self-reduction process?

Options

A. `{(HgS,+,O_(2)rarr,HgO,+SO_(2)),(HgO,+,HgSrarr,Hg,+SO_(2)):}`
B. `{(Cu_(2)S,+,O_(2)rarr,Cu_(2)O,+SO_(2)),(Cu_(2)S,+,Cu_(2)Orarr,Cu,+SO_(2)):}`
C. `{(PbS,+,O_(2)rarr,PbO,+SO_(2)),(PbO,+,PbSrarr,Pb,+SO_(2)):}`
D. All of these

Answer

D

Explanation

Sulphide or of `Hg,Cu,Pb` are heated in air, a part of these is changed in to oxides or sulphate that then react with the remaining part of the sulphide ore to give its metal and `SO_(2)`. This is called self-reduction, auto reduction or air reduction method.