Question

The following are the extraction process of silver but not:
(a) as a side product in electrolytic refining of copper.
(b) Parke’s process in which Zn is used to extract silver by solvent extraction from molten lead.
(c) by reaction of silver sulphide with KCN and then reaction of soluble complex with Zn.
(d) by heating Na[Ag(CN)$_2$]

Answer 1

Hint: There are several methods used for the extraction of silver. The ore-argentite is the main ore used for the extraction of silver. We can look at the options, and write down the reaction performed between the ore-argentite, and sodium cyanide.

Complete step by step answer:
- First, we will write the reaction performed between the ore-argentite (Ag$_2$S), and sodium cyanide (NaCN). The chemical reaction is
Ag$_2$S + NaCN $\rightleftharpoons$ 2Na[Ag(CN)$_2$] + Na$_2$S

- This reaction represents the cyanide process as we have used the sodium cyanide solution, here the sodium argento cyanide is formed as a product.
- Now, sodium argento cyanide (a soluble complex product) will react with the zinc dust to attain the precipitated form of silver, also known as spongy silver. The reaction is

2Na[Ag(CN)$_2$] + Zn $\rightarrow$ Na$_2$[Zn(CN)$_4$] + Ag

- If we talk about the options, first is electrolytic refining of copper, so when we attain the spongy silver, it further reacts with potassium nitrate, and the silver is purified by electrolytic process.
- The second option is the Parke’s process, used for the desilverization of PbS, and 0.01 to 1 % of Ag, as we know silver is more soluble in molten zinc, so Zn-Ag alloy can be easily removed and further distillation is used to separate the zinc.
- The third option is an example of cyanide process, as mentioned reaction with NaCN, same can be performed with KCN.
- The fourth option is the heating of sodium argento cyanide, but we have already seen that it reacts with zinc to form silver.
- In the last, we can conclude that the heating of sodium argento cyanide is not used for the extraction of silver. The correct option is (D).

Note: Don’t get confused between the numerous methods performed for the extraction of silver. In Parke's process the distribution principle is followed. The Zn-Ag can be easily removed because the alloy of Zn-Ag is lighter than Pb, and it will start floating, which will be helpful in the removal from molten Pb.