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Why sometimes, a black coloured precipitate obtained in group IV even if nickel and cobalt ions are absent? |
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Answer» A blakc coloured precipitate is obtained the group IV due to the incomplete removal of iron in group III. Iron escapes precipitation in group III due to lack of enough `NH_(4)OH.Fe^(+3)` is reduced to `Fe^(2+)` by `H_(2)S` which finally gets precipitated as FeS (black) in group IV even when both Co and Ni are absent. `FeCl_(2)+H_(2)Sto2HCl+underset(("Black ppt"))(FeS(s))` |
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