Question

In the cyanide extraction process of silver from argentite ore, the oxidising and reducing agents used are

• A. $O_2$ and $CO$ respectively
• B. $O_2$ and $Zn$ dust respectively
• C. $HNO_3$ and $Zn$ dust respectively
• D. $HNO_3$ and $CO$ respectively

Answer 1

Answer: (B)

$O_2$ and $Zn$ dust respectively

Answer 2

The reactions involved in extraction of silver by cyanide process are
$Ag_2S+CN^-+O_2\rightarrow [Ag(CN)_2]^-+SO_2$...(i)
$[Ag(CN)_2]^-+Zn\rightarrow [Zn(CN)_4]^{2-}+Ag$...(ii)
In reaction (i), sulphide is oxidised to $S0_2$ by oxygen. In the reaction (ii), silver ion $(Ag^+)$ is reduced to Ag by Zn. Therefore, $O_2$ is oxidising agent and Zn is reducing agent.