Name the important ore of silver. Write all the steps and reactions involved in the cyanide process for the extraction of silver from its ore.

Explanation

The important ore of silver are Argentite `(Ag_(2)S)` and Horn silver (AgCl)
Extraction of Silver from ore by cyanide process : In this process the finely powdered ore is concentrated by froth floatation process and then treated with dilute NaCN and a current of air is passed into the solution so that Ag present in the ore is converted into soluble sodium argento cyanide complex.
`Ag_(2)S+4NaCNrarrundersetunderset("complex")("Sodium argento cyanide")(2Na[Ag(CN)_(2)])+Na_(2)S`
The current of air passed into the solution oxidises `Na_(2)S` formed in the above reaction into `Na_(2)S_(2)O_(3), Na_(2)SO_(4) and S` and thus enables the above reversible reaction to proceed in forward direction.
`2Na_(2)S+2O_(2)+H_(2)OrarrNa_(2)S_(2)O_(3)+2NaOH`
`4Na_(2)S+5O_(2)+2H_(2)Orarr2Na_(2)SO_(4)+4NaOH+2S`
Then the solution containing `Na[Ag(CN)_(2)]` is `2Na[Ag(CN)_(2)]+Zn("dust")rarrNa_(2)[Zn(CN)_(4)]+underset("ppt.")(2Agdarr)`
Precipitated Ag is purified by electrolytic method. The cathode is pure silver, anode is block of impure silver and electrolyte is 6% `AgNO_(3)` wth 1% `HNO_(3)`. On passing current, impurities get deposited at the anode and pure silver at the cathode. Zn and Cu remain in solution while Au settles down as anode mud.