Question

In the preparation of chlorine from $HCl$ , $Mn{{O}_{2}}$ ​ acts as
(A) Oxidising agent
(B) Reducing agent
(C) Catalytic agent
(D) Dehydrating agent

Answer 1

Hint: In a redox reaction, the element that gains an electron is known as an oxidising agent, and the element that loses an electron is known as a reducing agent. A catalytic agent, also known as a catalyst, is a substance that does not itself take part in the chemical reaction; it just increases the rate of the chemical reaction. A dehydrating agent is a substance that removes water from a material.

Complete Step by Step Solution:
In the preparation of chlorine from $HCl$, $Mn{{O}_{2}}$, in which $Mn$ is in a +4 oxidation state gets converted to $MnC{{l}_{2}}$ , in which it is in a +2 oxidation state. This means the oxidation number is decreased and reduction is occurring. Thus, $Mn{{O}_{2}}$ acts as an oxidising agent.

Here, manganese dioxide ($Mn{{O}_{2}}$) reacts with hydrochloric acid ($HCl$) to give manganese chloride ($MnC{{l}_{2}}$), water (${{H}_{2}}O$), and chlorine ($C{{l}_{2}}$).
Correct Option: (A) Oxidising agent.

Additional Information: Manganese dioxide ($Mn{{O}_{2}}$) is used in dry battery cells and to remove the green tint caused by iron impurities. Manganese reacts with oxygen in the atmosphere and forms manganese dioxide. This is the reason why manganese does not exist in its elemental form in nature. It is insoluble in water.

Note: Manganese dioxide ($Mn{{O}_{2}}$) can act as both an oxidising and a reducing agent. It can oxidise alcohols to aldehydes or ketones. It exists in a +4 oxidation state. $Mn{{O}_{2}}$ is black or brown in colour. It crystallises in a rutile crystal structure.