Question

In the leaching of $A{g}_{2}S$ with $NaCN$, a stream of air is also passed. It is because:

• A. of the reversible nature of reaction between $A{g}_{2}S$ and $NaCN$
• B. to oxidise $N{a}_{2}S$ formed into $N{a}_{2}S{O}_4$ and sulphur
• C. both (A) and (B)
• D. None of the above

Answer 1

The correct option is C both (A) and (B)

The leaching process of argentite is given below.
$A{g}_{2}S+2NaCN\stackrel{\text{Air}}{\rightleftharpoons }2AgCN+N{a}_{2}S$
$4N{a}_{2}S+5O_2+2H_{2}O\to 2N{a}_{2}S{O}_4+4NaOH+2S$

The reaction is reversible and hence it is conducted in the presence of air. The sodium sulphide is oxidised to sodium sulphate and removed from the equilibrium.