NEET Chemistry NEET PYQ-Metallurgy

  • question_answer
    Extraction of gold and silver involves leaching with \[C{{N}^{-}}\]ion. Silver is later recovered by [NEET-2017]

    A) Displacement with Zn

    B) Liquation

    C) Distillation

    D) Zone refining

    Correct Answer: A

    Solution :

    [a] Zn being more reactive than Ag and Au, displaces them.
    From Native ore,
    \[4Ag+8NaCN+2{{H}_{2}}O+{{O}_{2}}\xrightarrow{\text{Leaching}}\]
    \[\underset{\begin{smallmatrix}  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{Souble} \\  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{Sodium}\,  \\  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{dicyanoargen}\,\text{late}\,\text{(I)} \end{smallmatrix}}{\mathop{4Na[Ag{{(CN)}_{2}}]}}\,+4NaOH\]
    \[2Na[Ag{{(CN)}_{2}}]+Zn\xrightarrow{\text{Displaceement}}\]
    \[N{{a}_{2}}[Zn{{(CN)}_{4}}]+2Ag\downarrow \]


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