Metallic gold ferquently is found is aluminosilicate rocks and it is finely dispersed among other minerals. It may be extracted by treating the crushed rock with aearated sodium cyanide solution. During this process metallic gold is slowly converted to `[Au(CN)_(2)]^(-)`, Which is soluble in water. After equilibrium has been reached, the aqueous phase is pumped off and the metallic gold is recoverd form it by reacting the gold complex with zinc, whihc is converted tio `[Zn(CN)_(4)]^(2-)`. Gold in nature is frequently alloyed with silver. which is also oxidised vy aerated sodium by aerated sodium cyanide solution.
The correct ionic reaction for the process are:
A. `4Au+8CN^(-)+2H_(2)O+O_(2)(air)`
`" " 4 [Au(CN)_(2)]^(-)("soluble")+4OH^(-)
B. `Au+2CN^(-)to Au[(CN)_(2)]^(-)`
C. `Zn+2CN^(-) to Zn[(CN)_(2)]^(-)`
D. `Zn+4CN^(-) to Zn[(CN)_(2)_(4)]^(2-)`
