Write the chemical reactions involved in the process of extraction of Gold. Explain the role of dilute NaCN and Zn in this process.

Dilute NaCN solution is used in presence of oxygen (from air) for leaching gold sample.
4Au(s)+8CN⁻(aq)+2H₂O(aq)+O₂(g)→4[Au(CN)₂]⁻(aq)+4OH⁻(aq)
Zinc displaces gold from the complex [Au(CN)₂]⁻(aq).
Zn(s)+2[Au(CN)₂]⁻(aq)→[Zn(CN)₄]²⁻(aq)+2Au(s)