Q2 / 160 · WBJEE 2015 · Chemistry
"Extraction of gold $(\mathrm{Au})$ involves the formation of complex ions $X$ and $Y$
$X$ and $Y$ respectively are
$X$ and $Y$ respectively are- Correct answerA$Au(CN) ^{-}_{2}$ and $\mathrm{Zn} (\mathrm{CN)}_{4}^{2-}$
- B$Au(CN) ^{3-}_{4}$ and $\mathrm{Zn} (\mathrm{CN)}_{4}^{2-}$
- C$Au(CN) ^{-}_{3}$ and $\mathrm{Zn} (\mathrm{CN)}_{6}^{4-}$
- D$Au(CN) ^{-}_{4}$ and $\mathrm{Zn} (\mathrm{CN)}_{3}^{-}$
Solution
Extraction of gold (Au) involves the following sequence of reaction,
$\begin{array}{l}
\text { Gold ore } \frac{\text { Roasting }}{\mathrm{CN}^{-}, \mathrm{H}_{2} \mathrm{O}, \mathrm{O}_{2}} \quad \mathrm{HO}^{-}+\mathrm{Au}(\mathrm{CN})_{2}^{-}
\quad \stackrel{\mathrm{Zn}}{\longrightarrow} \mathrm{Zn}(\mathrm{CN})_{4}^{2-}+\mathrm{Au} \\
Y
\end{array}$
Hence, $X=\mathrm{Au}(\mathrm{CN})_{2}^{-}, Y=\mathrm{Zn}(\mathrm{CN})_{4}^{2-}$
Hence, the correct answer is option: 'A'.