Punjab Medical Punjab - MET Solved Paper-2007

  • question_answer
    \[CuS{{O}_{4}}\] when reacts with \[KCN\] forms \[CuCN\]. Which is insoluble in water. It is soluble in excess of \[KCN\], due to formation of the following complex

    A) \[{{K}_{2}}[Cu{{(CN)}_{4}}]\]     

    B) \[[{{K}_{2}}{{[CuCn)}_{4}}]\]

    C) \[CuC{{N}_{2}}\]                             

    D) \[Cu[K\,\,Cu{{(CN)}_{4}}]\]

    Correct Answer: B

    Solution :

    \[CuS{{O}_{4}}\]reacts with \[KCN\] gives a white precipitate of cuprous cyanide and cyanogen gas. The cuprous cyanide dissolves in excess of \[KCN\] forming\[{{K}_{3}}[Cu{{(CN)}_{4}}]\]. \[CuS{{O}_{4}}+2KCN\xrightarrow{{}}{{K}_{2}}S{{O}_{4}}+Cu{{(CN)}_{2}}\] \[2Cu{{(CN)}_{2}}\xrightarrow{{}}\underset{\text{insoluble}}{\mathop{2CuCN}}\,+\underset{\text{cyanogen}}{\mathop{CN-CN}}\,\] \[CuCN+3KCN\xrightarrow{{}}{{K}_{3}}\underset{\text{soluble}}{\mathop{[Cu{{(CN)}_{4}}]}}\,\]


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