In the process of extraction, gold combines with cyanide in the presence of oxygen and water to make a complex. The formula of the complex is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $[Au(CN)_2]^{-}$
Step 1: Recall the process
- Gold is extracted by cyanidation (the MacArthur–Forrest process).
- In the presence of oxygen and water, gold reacts with cyanide:
$4Au + 8CN^- + O_2 + 2H_2O → 4[Au(CN)2]^- + 4OH^-$
- Here, gold forms a linear complex with cyanide.
Step 2: Identify the complex
- The complex formed is: $[Au(CN)2]^-$
This is a monoanionic complex of gold.