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Some Basic Concepts of Chemistry question

2019 · 12 Apr · Shift 2 · Q14

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Some Basic Concepts of Chemistry
2019 · 12 Apr · Shift 2 · Q14

Some Basic Concepts of Chemistry question

2019 · 12 Apr · Shift 2 · Q14

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1

Thermal decomposition of a Mn compound (X) at 513 K results in compound Y,

MnO_2

and gaseous product.

MnO_2

reacts with

NaCl

and concentrated

H_2O_4

to give a pungent gas Z. X, Y and Z, respectively, are :

A
$KMnO_4$ , $K_2MnO_4$ and $Cl_2$
B
$K_2MnO_4$ , $KMnO_4$ and $SO_2$
C
$K_3MnO_4$ , $K_2MnO_4$ and $Cl_2$
D
$K_2MnO_4$ , $KMnO_4$ and $Cl_2$

View written solutionFree

Correct answer: A

Identify the reaction of the manganese compound $X$ on heating

A well-known thermal decomposition reaction is:

$2KMnO_4 \xrightarrow{513\,K} K_2MnO_4 + MnO_2 + O_2$

So, on heating $KMnO_4$ , the products are:

$K_2MnO_4$
$MnO_2$
a gaseous product $O_2$

Thus,

$X = KMnO_4, \qquad Y = K_2MnO_4$

Identify gas $Z$ formed from $MnO_2$ with $NaCl$ and concentrated acid

$MnO_2$ oxidizes chloride ions in presence of concentrated sulfuric acid to give chlorine gas:

$2NaCl + MnO_2 + 2H_2SO_4 \rightarrow MnSO_4 + Na_2SO_4 + 2H_2O + Cl_2$

The pungent gas formed is:

$Z = Cl_2$

Match with the options

We found:

$X = KMnO_4$
$Y = K_2MnO_4$
$Z = Cl_2$

This corresponds to Option A.

Check other options briefly

B: starts with $K_2MnO_4$ and gives $KMnO_4$ on decomposition — not correct.
C: $K_3MnO_4$ is not the relevant known compound here.
D: again reverses $KMnO_4$ and $K_2MnO_4$ .

Hence the correct answer is A.

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