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General Principles And Processes Of Isolation Of Elements

Question
CBSEENCH12011393
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Copper sulphates dissolves in excess of KCN to give:

  • CuCN

  • [Cu(CN)4]3-

  • [Cu(CN)4]2-

  • Cu(CN)2

Solution

B.

[Cu(CN)4]3-

Copper sulphate on reaction with KCN to give cupric cyanide precipitates firstly which reduce into Cu2CN2 and dissolve in excess of KCN to give soluble K3[Cu(CN)4] complex salt
[CuSO4 + 2KCN →Cu(CN)2 + K2SO4] x 2
2Cu(CN2) → Cu2(CN)2 + NC - CN
Cu2(CN)2 + 6KCN → 2K3[Cu(CN)4]
_______________________________________
2CuSO4 + 10 KCN → 2K3[Cu(CN)4 + 2K2SO4 + (CN)2]

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