In the process of extraction of gold, Roasted gold ore +CN^- + H2O O2 → [X] + OH^-

Question

In the process of extraction of gold,

Roasted gold ore \( + CN^- + H_2O \xrightarrow{O_2} [X] + O H ^-\)

\([X] + Zn \longrightarrow [Y] + Au\)

Identify the complexes [Y]

(a) X = [Au(CN)₂]^- , Y = [Zn(CN)₄]^2- 

(b) X = [Au(CN)₄]^3-, Y = [Zn(CN)₄]^2- 

(c) X = [Au(CN)₂]^- , Y = [Zn(CN)₆]^4-

(d) X = [Au(CN)₄]^- , Y = [Zn(CN)₄]^2-

Answer 1

Correct option is (a) X = [Au(CN)₂]^- , Y = [Zn(CN)₄]^2- 

In the presence of water and oxygen, the roasted gold ore interacts with the cyanide ion to generate the dicyano complex [X].

Treatment with zinc causes gold to be displaced from the dicyano complex. The following reaction is obtained as the result,

Roasted gold ore \(+CN^- + H_2O \xrightarrow {O_2} Au (CN)^-_2 + OH^- Au (CN)^-_2 + Zn \rightarrow Zn (CN) ^{2-} _4.\)