Q12 / 105 · NTA Abhyas (JEE Main) 2020 · Chemistry · d and f Block Elements

Pick out the incorrect statement

A
$M n O_{2}$ dissolves in conc. HCl, but does not form $M n^{4 +}$ ions
B
$M n O_{2}$ oxidizes hot concentrated $H_{2} S O_{4}$ liberating oxygen
C
$K_{2} M n O_{4}$ is formed, when $M n O_{2}$ is fused KOH is oxidized by air, $K N O_{3}, P b O_{2}$ or $N a B i O_{3}$
Correct answer
D
Decomposition of acidic $K M n O_{4}$ is not catalysed by sunlight

Solution

Decomposition of acidic

K M n O_{4}

is catalysed by sunlight.

4 M n O_{4}^{-} + 4 H^{+} \to 4 M n O_{2} + 3 O_{2} + 2 H_{2} O

A. On dissolution,

{MnO}_{2}

forms

M n^{2 +}

ions and HCl is oxidized to

C l_{2}

M n O_{2} + 4 HC l^{-} \to M n^{2 +} + 2 C l^{-} + C l_{2} + H_{2} O

H_{2} S O_{4}

is oxidized by

M n O_{2}

2 M n O_{2} + 2 H_{2} S O_{4} \to 2 M n S O_{4} + O_{2} + 2 H_{2} O

M n O_{2} + 2 K O H + \frac{1}{2} O_{2} \to \underset{G r e e n}{K_{2} M n O_{4}} + H_{2} O

Hence, the correct answer is option: 'D'.