Question

Give the equations for the conversion of argentite ($A{g_2}S$) to metallic silver.

Answer 1

Silver Sulphide mineral is also called as argentite. It is an important ore of Silver. They exist only at high temperatures. When Acanthite is heated to high temperatures, argentite is formed. Minerals are extracted from ores.

Complete step by step answer:
Conversion of $A{g_2}S$ to Ag means that a compound is reduced to an element.
We know that reduction is the gain of electrons or an increase in the oxidation number. Let us see the oxidation number of silver in silver sulphide and elemental silver as well.
In $A{g_2}S$, the oxidation number on Ag is $+ 1$, whereas the oxidation number on Ag is Zero.
So we can say that there is a decrease in the oxidation number. This means that reduction is taking place.
For the reduction to take place, it should be heated or any reducing agents should be used.
$A{g_2}S$ on treatment with $NaCN$ forms a complex $Na[Ag{(CN)_2}]$ which on treatment with Zn that acts as a reducing agent reduces to Ag metal.
The reaction is as follows:
$A{g_2}S + 4NaCN \to 2Na[Ag{(CN)_2}] + N{a_2}S$
The complex formed reacts with Zn and replaces Ag.
$2Na[Ag{(CN)_2}] + Zn \to N{a_2}[Zn{(CN)_4}] + 2Ag$
We can see that silver metal is formed.
The $N{a_2}S$ formed in the first reaction reacts with oxygen and forms $N{a_2}S{O_4}$.

Note: Oxidation is the loss of electrons or it can also be mentioned as an increase in the oxidation state of an atom. Other reducing agents are Al, Li, Oxalic acid, etc. When a reduction and oxidation takes place in a single reaction, it is called a redox reaction. In this case, Ag is getting reduced.