Extraction of Metals - Result Question 29
####29. In the process of extraction of gold,
Roasted gold ore $+CN^{-}+H _2 O \xrightarrow{O _2}[X]+HO$
$$ [X]+Zn \longrightarrow[Y]+Au $$
Identify the complexes $[X]$ and $[Y]$.
$(2003,1 M)$
(a) $X=\left[Au(CN) _2\right]^{-}, \quad Y=\left[Zn(CN) _4\right]^{2-}$
(b) $X=\left[Au(CN) _4\right]^{3-}, Y=\left[Zn(CN) _4\right]^{2-}$
(c) $X=\left[Au(CN) _2\right]^{-}, Y=\left[Zn(CN) _6\right]^{4-}$
(d) $X=\left[Au(CN) _4\right]^{-}, Y=\left[Zn(CN) _4\right]^{2-}$
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Solution:
$$ \begin{aligned} & Au+2 CN^{-} \longrightarrow\left[Au(CN) _2\right]^{-} \ & 2 Au(CN) _2^{-}+Zn \longrightarrow\left[Zn(CN) _4\right]^{2-}+2 Au \ & Y \end{aligned} $$
