1.

When aqueous KCN is added to a solution of `CuSO_(4)`, a whitie precipitate solube in RCN is formed. But no precipate to formed when `H_(2)S` gas is bubbled through this solution. Explain.

Answer» The white precipate formed dissolves in excess of KCN to form a soluble complex. ltrbgt `CuSO_(4) + 2KCN to underset("white ppt")Cu(CN)_(2) + K_(2)SO_(4)`
`Cu(CN)_(2) + 2KCN to underset("Soluble complex")(K_(2)[Cu(CN)_(4)])`
This complex is quite stable and `H_(2)S` gas is not in a position to break this. That is why, no precipitate is formed.


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