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Q.
$CN ^{\ominus}$ solution used in extraction of which
Rajasthan PMTRajasthan PMT 2002General Principles and Processes of Isolation of Elements
Solution:
$CN ^{-}$ion is used in the extraction of silver (Ag) metal. Since, silver is precipitated by complex formation.
Powered argentite $\left( Ag _{2} S\right.$ ) is lixivated with dil. $NaCN$ solution in presence of air.
$Ag _{2} S +4 NaCN \xrightarrow{\text { air }}\underset{\overset{\text{Argentocyanide }}{\text{(complex salt)}}}{2 Na \left[ Ag ( CN )_{2}\right]}+ Na _{2} SO _{4}$
To, this complex salt metallic zinc is added.
$2 Na \left[ Ag ( CN )_{2}\right]+ Zn \longrightarrow Na _{2}\left[ Zn \left( CN _{4}\right)(\text { aq })\right] +\underset{\text{Black ppt}}{2Ag}$