Question

Manganese dioxide reacts with $HCl$ and releases gas that turns moist blue litmus red. The gas is:
A) ${H_2}$
B) $C{l_2}$
C) ${O_2}$
D) ${H_2}S{O_4}$

Answer 1

To solve this question, we must first understand some basic concepts and reactions about Manganese dioxide. Then we need to assess the information to conclude the products of the given reaction and then only we can conclude the correct answer.

Complete solution: Before we move forward with the solution of this given question, let us first understand some basic concepts:
Manganese oxide is the inorganic compound with the formula $Mn{O_2}$ . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules.
$Mn{O_2}$ is also used as a pigment and as a precursor to other manganese compounds, such as $KMn{O_4}$ . It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols.
Step 1: In this step we will write the equation of the given reaction:
Manganese oxide reacts with $HCl$ and releases $C{l_2}$​ gas forming $MnC{l_2}$​ and water. The reaction of hydrogen chloride with $Mn{O_2}$​ was used by Carl Wilhelm Scheele in the original isolation of chlorine gas.
$Mn{O_2} + \,\,4HCl\,\, \to \,\,MnC{l_2}\,\, + \,\,C{l_2}\, + \,\,2{H_2}O$
And hence the required gas is Chlorine gas.

Thus, the correct option is (B).

Note: Naturally occurring manganese dioxide contains impurities and a considerable amount of manganese(III) oxide. The predominant application of $Mn{O_2}$ is as a component of dry cell batteries: alkaline batteries and so-called Leclanché cells, or zinc–carbon batteries. Approximately $500,000$ tonnes are consumed for this application annually. Other industrial applications include the use of $Mn{O_2}$ as an inorganic pigment in ceramics and in glassmaking.