Which of the on reacting with ferrous sulphate(FeSO4) will give a black residue? a) Zn ; b) Al ; c) Fe ; d) Cu
What an interesting question! You are asking "Which [of the listed metals] on reacting with FeSO4 will give a black residue?
My answer is None of them - but possibly from either a) Zn and b) Al under certain conditions as indicated below.
Both elemental zinc and aluminum will undergo a redox (reduction-oxidation) reaction with the Fe2+ ion (of FeSO4) to give zinc and aluminum ions (Zn2+ and Al3+), which would form the zinc and aluminum salts, ZnSO4 and Al2(SO4)3 - both of which are white solids. The other product in each of these reactions is elemental iron, which is reported to be silvery, if the iron is free of contaminants). Pure elemental iron is not black. If the freshly formed iron is oxidized, it would probably from iron oxide, Fe2O3, which is "rust," which is reddish-brown, and not black.
HOWEVER, if the above elemental iron becomes colloidal in the presence of impurities (e.g., organics), it is possible that the iron might appear to to be a black residue. And this could occur from the reaction of FeSO4 with either a) Zn or b) Al.
Elemental iron (Fe) will not react with FeSO4, because there would not be any other metallic reactant present that could either oxidize or reduce it.
Finally, elemental copper (Cu) and FeSO4 would not undergo a spontaneous redox reaction written as follows: Cu + Fe2+ => Cu2+ + Fe, no reaction. (Only the reverse reaction would occur: Cu2+ + Fe => Cu + Fe2+, but the problem does not indicate the presence of either Cu2+ or Fe in choice d.)
Jun 27, 2010 |
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