Question

Concentrated hydrochloric acid when kept in the open air sometimes produces a cloud of white fumes. The explanation for it is that:
(A) Concentrated hydrochloric acid emits strong smelling $HCl$ gas at all times
(B) Oxygen in air reacts with emitted $HCl$gas to form a cloud of chlorine gas
(C) Strong affinity of$HCl$ gas for moisture in air results in forming of droplets of liquid solution which appears like cloudy smoke
(D) Due to strong affinity for water, concentrated hydrochloric acid pulls moisture from the air towards itself. This moisture forms droplets of water and hence, the cloud.

Answer 1

Concentrated $HCl$ is highly acidic in nature and it is exposed to air for a longtime, it keeps on emitting fumes of $HCl$ gas. The released $HCl$ gas into the atmosphere reacts with oxygen which is present in the air.

Complete step by step solution:

$HCl$ is a strong acid. It reacts with the surrounding gases.
The pH of the $HCl$ is less than 7.
The concentrated $HCl$ releases $HCl$ fumes into the atmosphere after long standing.
The released fumes of $HCl$ reacts with oxygen which is present in the air and causes the formation of clouds of chlorine gas.
The chemical reaction of $HCl$ with oxygen is as follows.
$4HCl+{{O}_{2}}\to 2C{{l}_{2}}+2{{H}_{2}}O$
Therefore, the cloud is due to the formation of chlorine gas, which is released into the atmosphere by the reaction of fumes of $HCl$ with oxygen.

So, the correct option is B.

Note: Don’t be confused with the words concentrated and diluted $HCl$. Both are not the same.Concentrated$HCl$: pure form of $HCl$ is called concentrated $HCl$.
Diluted$HCl$: if we are going to mix $HCl$ in water, then it is called diluted $HCl$.