In the process of extraction of gold.
Roasted gold ore `+CN^(-)+H_(2)O overset(O_(2))rarr [X]+OH^(-)`
`[X]+Znrarr [Y]+Au`
Identify the complexes `[X] ` and `[Y]`.

Options

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]^(2-)`
D. `X=[Au(CN)_4]^(-) , Y=[Zn(CN)_4]^(2-)`

Answer

A

Explanation

`Au+4CN^(-) + H_2O + 1/2 O_2 to 2[Au(CN)_2]^(-) + 2OH^(-)`
`2[Au(CN)_2]^(-) + Zn to [Zn(CN)_4]^(2-) + 2Au`