JEE Main 2023 — Redox Reactions Question with Solution

Gold is then extracted from this complex by displacement technique by using a more electropositive zinc metal.

In this method, zinc ($\mathrm{Zn}$) acts as a reducing agent and it reduces$\mathrm{Au}{ }^{+}$ to $\mathrm{Au}$ and itself gets oxidized from $\mathrm{Zn}$ to ${\mathrm{Zn}}^{+2}$ ions which combine with ${\mathrm{CN}}^{-}$ ions and form soluble complex, sodium tetracyanozincate (II).

$2{\left[\mathrm{Au}(\mathrm{CN}{)}_2\right]}^{-} \left(\mathrm{aq}\right)+\mathrm{Zn} \left(\mathrm{s}\right)\to 2\mathrm{Au} \left(\mathrm{s}\right)+{\left[\mathrm{Zn}(\mathrm{CN}{)}_4\right]}^{2-} \left(\mathrm{aq}\right)$