Question

In the process of extraction of gold, $Roastedgoldore+C{N}^{-}+H_{2}O\stackrel{O_2}{\to }\left[X\right]+O{H}^{-}$ $\left[X\right]+Zn\to \left[Y\right]+Au$

Identify the complexes [X] and [Y].

• A. X = $\left[Au\right(CN{)}_2^{-}]$, Y = $\left[Zn\right(CN{)}_4{]}^{2-}$
• B. X = $\left[Au\right(CN{)}_4{]}^{3-}$, Y = $\left[Zn\right(CN{)}_4{]}^{2-}$
• C. X = $\left[Zn\right(CN{)}_2{]}^{-}$ , Y = $\left[Zn\right(CN{)}_6{]}^{4-}$
• D. X = $\left[Zn\right(CN{)}_4{]}^{-}$, Y = $\left[Zn\right(CN{)}_4{]}^{2-}$

Answer 1

The correct option is A X = $\left[Au\right(CN{)}_2^{-}]$, Y = $\left[Zn\right(CN{)}_4{]}^{2-}$

The roasted gold ore reacts with cyanide ion in presence of water and oxygen to form the dicyano complex [X].
Gold is displaced from the dicyano complex [X] by treatment with zinc.
Roasted gold ore + $C{N}^{-}+H_{2}O\stackrel{O_2}{\to }\underset{\left[X\right]}{\left[Au\right(CN{)}_2^{-}]}+O{H}^{-}$
$\underset{\left[X\right]}{\left[Au\right(CN{)}_2^{-}]}+Zn\to \underset{\left[Y\right]}{\left[Zn\right(CN{)}_4{]}^{2-}}+Au$