General Principles And Processes of Isolation Of Elements

General Principles And Processes of Isolation Of Elements

Question

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

Answer

The roasted ore of gold is leached with a solution of sodium cyanide in the presence of oxygen for many days. The role of NaCN in this process is to dissolve the gold to form an aurocyanide complex, from which the metal is obtained by displacement.

4Au + 8NaCN + 2H2O + O2   4Na[Au(CN)2] + 4KOH2Na[Au(CN)2] + Zn   Na2[Zn(CN)4] + 2Au

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