# CuS+HCl is it a reduction or oxidation reaction

How do we identify whether a reaction is oxidation or reduction and please let me know whether the equation given above is oxidation or reduction.

• We don't. There is no such thing as oxidation reaction. Ditto for reduction. Every redox reaction is a reduction and an oxidation at once. Then again, there are quite a few reactions which are not redox at all, and yours is one of those. – Ivan Neretin Feb 17 at 9:11
• Ivan is right. Your reaction is probably : $CuS + 2 HCl -> CuCl_2 + H_2S$, which is surprising, because usually $CuS$ does not react with $HCl$. Usually it goes the other way. In qualitative analysis, $Cu^{2+}$ ions react with $H_2S$ to produce a dark precipitate of $CuS$ – Maurice Feb 17 at 10:01
• @Maurice If I remember correctly, CuS precipitates from dilute HCl; in conc. or demiconc. HCl, i think no sulfide is stable. – Karl Feb 17 at 17:20