Chemistry - Metallurgy Question with Solution | TestHub

Gold is extracted by making soluble cyanide complex. The cyanide complex is$\left[\mathrm{A}\mathrm{u}\right(\mathrm{C}\mathrm{N}{)}_2{]}^{-}$
$4\mathrm{A}\mathrm{u}+8\mathrm{C}{\mathrm{N}}^{-}+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2\to 4\left[\mathrm{A}\mathrm{u}\right(\mathrm{C}\mathrm{N}{)}_2{]}^{-}+4\mathrm{O}{\mathrm{H}}^{-}$
The metal is recovered by reduction with zinc.
$2\left[\mathrm{A}\mathrm{u}\right(\mathrm{C}\mathrm{N}{)}_2{]}^{-}+\mathrm{Z}\mathrm{n}\to \left[\mathrm{Z}\mathrm{n}\right(\mathrm{C}\mathrm{N}{)}_4{]}^{2-}+2\mathrm{A}\mathrm{u}$