Q1 / 180 · COMEDK 2020 · Chemistry
During the extraction of gold the following reactions take place
$$
\begin{aligned}
&\mathrm{Au}+\mathrm{CN}^{-}+\mathrm{H}_{2} \mathrm{O} \underset{\mathrm{O}}{2}[X] \\
&{[X]+\mathrm{Zn} \longrightarrow[Y]+\mathrm{Au}}
\end{aligned}
$$
$X$ and $Y$ are respectively
- Correct answerA$\left[\mathrm{Au}(\mathrm{CN})_{2}\right]^{-}$and $\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}$
- B$\left[\mathrm{Au}(\mathrm{CN})_{4}\right]^{3-}$ and $\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}$
- C$\left[\mathrm{Au}(\mathrm{CN})_{4}\right]^{2-}$ and $\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}$
- D$\left[\mathrm{Au}(\mathrm{CN})_{2}\right]^{-}$and $\left[\mathrm{Zn}(\mathrm{CN})_{6}\right]^{4-}$
Solution
During the extraction of gold, following reactions
$2\left[\mathrm{Au}(\mathrm{CN})_{2}\right]^{-}+\mathrm{Zs}(s) \longrightarrow\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}(u q)+2 \mathrm{Au}(\mathrm{s})$
$(X)$
( $)$
Pure gold
One chlorine molecule contains 2 chlorine atoms and one HCl molecule contains l chlorine atom.
Hence, the correct answer is option: 'A'.