Question

# What happens when silver is leached with NaCN in the presence of air?

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Hint: Free State elements like carbon, sulfur, gold, and noble gases while others are combined forms in earth’s crust. Various principles of chemistry involve the extraction and isolation of an element. The process of isolation and metallurgy should be chemically feasible and commercially viable.

Complete step by step solution:
The minerals which are naturally occurring chemical compounds in the earth’s crust are known as ores. The extraction and isolation of metals from ores generally involve the following steps:
(i) Concentration of ore
(ii) Isolation of the metal from its concentration ore, &
(iii) Purification of the metal
-The process of isolation of the metal from its ores by using scientific and technological methods is known as metallurgy.
-Leaching: The process where ore is soluble with insoluble impurities is known as leaching, which is widely used in the metallurgy process for converting metal into soluble salts in an aqueous medium.
-During silver leaching, the Silver cyanide complex formed when silver is leached with NaCN in the presence of air.
$4Ag+8NaCN+2{{H}_{2}}O+{{O}_{2}}\to 4Na[Ag{{(CN)}_{2}}]+4NaOH$
-In the extraction of silver (Ag), the role of NaCN is to do leaching of Ag ore in the presence of air where the silver is obtained by replacement. Ag is oxidized to $A{{g}^{+}}$ which reacts with $C{{N}^{-}}$ formed during leaching.

Note: The process of extraction of metal from ore by preparing an aqueous solution of the metal salt and recovering from its solution is known as hydrometallurgy. Silver and gold are leached from their ores with a dilute solution of potassium cyanide or sodium cyanide in presence of oxygen from the air.