Question

In the cyanide extraction process of silver from argentite ore, the oxidizing and reducing agents used are:
(A) ${{O}_{2}}$ and CO, respectively
(B) ${{O}_{2}}$ and Zn dust, respectively
(C) $HN{{O}_{3}}$ and Zn dust, respectively
(D) $HN{{O}_{3}}$ and CO, respectively

Answer 1

Hint: -An oxidizing agent is a chemical that removes electrons from other chemicals during a redox reaction. Ex: Hydrogen peroxide, ozone, and oxygen etc.
-A reducing agent is a chemical that donates electrons to other chemicals during a redox reaction. Ex: alkali and alkaline earth metals and formic acid etc.

Complete step by step solution:
-Silver is going to be extracted from argentite ore by using the cyanide process.
-In the cyanide process other than cyanide we need the help of oxidizing and reducing agents.
-The extraction of silver from argentite ore through the cyanide process involves the following two steps.
Step-1:
$A{{g}_{2}}S+2C{{N}^{-}}+{{O}_{2}}\to 2{{[Ag{{(CN)}_{2}}]}^{-}}+S{{O}_{2}}$
-In the above reaction silver sulphide reacts with cyanide ion in presence of oxygen forms silver cyanide complex and sulphur dioxide.
-Means here sulphide is oxidized to sulphur dioxide by oxygen. Therefore here the oxidizing agent is oxygen.
Step-2:
${{[Ag{{(CN)}_{2}}]}^{-}}+Zn\to {{[Zn{{(CN)}_{4}}]}^{2-}}+Ag$
-In the above reaction the formed silver cyanide complex in step-1 reacts with zinc dust and converts into zinc cyanide complex by liberating pure form of silver as the product.
-Silver ion in ${{[Ag{{(CN)}_{2}}]}^{-}}$ has an oxidation state of +1 is converted into Ag of zero oxidation state. Means Zinc is acting as a reducing agent.
-Therefore, in the cyanide extraction process of silver from argentite ore, the oxidizing and reducing agents used are ${{O}_{2}}$ and $Zn$ dust, respectively.

So, the correct answer is option (B).

Note: Oxidizing agent gives the oxygen atoms to the other chemicals. In the cyanide process oxygen reacts with sulphide ore of silver and liberates sulphur dioxide. Reducing agent decreases the oxidation number of other chemicals. In the cyanide process, zinc dust reacts with Ag (+1) and forms Ag (0) in pure form.