Question

the extraction of silver by leaching with sodium cyanide (redox reaction)

Answer 1

in the extraction of gold and silver , the metal is leached with NACN or Kcn , which is an oxidation reaction , 
2- during this process Ag is oxidised to Ag + 
then the reaction with zn result in formation of free metal 
, if u want me to mention the reaction , then let me know , 

In the extraction of gold and silver, the metal is leached with NaCN or KCN, which is an oxidation reaction.During the process, Ag is oxidised to Ag+ .Here M =Ag or Au.Subsequent reaction with Zn leads to formation of free metal.
Role of NaCN in the extraction of silver (Ag) is to do the leaching of Ag ore in the presence of air from which the silver is obtained later by replacement.4Ag + 8CN- + 2H2O + O2 → 4 [Ag(CN)2-] + 4OH-
Silver and gold ores containing native metal are leached with a dilute solution of Sodium cyanide(NaCN) {or Potassium cyanide(KCN) } in the presence of air.This is an oxidation reaction. During this process Ag is oxidised to Ag + , then the reaction with Zn result in formation of free metal.Ag2S + 4NaCN --> 2Na[Ag(CN)2] + 4Na2S2Na[Ag(CN)2]+Zn --->Na2[Zn(CN)4]+4Ag(ppt.)

Answer 2

Answer:

$NaCN$ is used to extract precious metals like silver and gold by converting these metals or their ores into their soluble complexes by the process called as leaching.

In this process, the finely powdered argentite $Ag_2S$ or silver is treated with a dilute solution of sodium cyanide while a current of air is continuously passed. As a result, silver get oxidized which then combine with $CN^-$ ion forming their respective soluble complex cyanides while the impurities remain unaffected which are filtered off.

$4Ag+8NaCN+2H_2O+O_2\rightarrow 4Na[Ag(CN)_2](soluble complex)+4NaOH$