Question

Gold is extracted by hydrometallurgical process, based on its property

• A. of being electropositive
• B. of being less reactive
• C. to form complexes which are water soluble
• D. to form salts which are water soluble

Answer 1

Answer: (C)

to form complexes which are water soluble

Answer 2

Hydrometallurgy is the process of dissolving the metal or its ore by the action of a suitable chemical reagent followed by recovery of the metal either by electrolysis or by the use of a suitable precipitating agent.

$4 Au +8 KCN +2 H _{2} O + \underset{\text{Air}}{{O _{2}}} \rightarrow 4 K \left[ Au ( CN )_{2}\right]$

Air $+4 KOH$
$2 K \left[ Au ( CN )_{2}\right]+ Zn \rightarrow 2 Au + K _{2}\left[ Zn ( CN )_{4}\right]$