Leaching of gold with dilute NaCN gives complex [A]... | Metallurgy | JEE Main 2022

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JEE MAIN 2022

25-06-22 S1

Question

Leaching of gold with dilute aqueous solution of NaCN in presence of oxygen gives complex [A], which on reaction with zinc forms the elemental gold and another complex [B]. [A] and [B], respectively are :-

Select the correct option:

A

$\left[\mathrm{Au}(\mathrm{CN})_4\right]^{-}$and $\left[\mathrm{Zn}(\mathrm{CN})_2(\mathrm{OH})_2\right]^{2-}$

B

$\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}$and $[\mathrm{Zn}(\mathrm{OH}) 4]^{2-}$

C

$\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}$and $\left[\mathrm{Zn}(\mathrm{CN})_4\right]^{2-}$

D

$[\mathrm{Au}(\mathrm{CN}) 4]^{2-}$ and $\left[\mathrm{Zn}(\mathrm{CN})_6\right]^{4-}$

✓ Correct! Well done.

✗ Incorrect. Try again or view the solution.

Solution

$\begin{aligned} & \mathrm{Au}+\mathrm{NaCN} \rightarrow \mathrm{Na}\left[\mathrm{Au}(\mathrm{CN})_2\right] \\ & \mathrm{Zn}+\mathrm{Na}\left[\mathrm{Au}(\mathrm{CN})_2\right] \rightarrow \mathrm{Na}_2\left[\mathrm{Zn}(\mathrm{CN})_4\right]+\mathrm{Au}\end{aligned}$

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