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JEE Main levelSingle correct optionDifficulty 2 of 3qc083

White $Mn (OH) X_{2}$ , exposed to air, slowly turns brown. This is because manganese is oxidised from

A $+ 2$ to $+ 7$ , giving $MnO X_{4} X^{-}$
B $+ 2$ to $+ 3$ , giving $Mn (OH) X_{3}$ as a stable white solid
C $+ 2$ to $+ 4$ , giving hydrated $MnO X_{2}$ / $MnO (OH) X_{2}$
D $+ 2$ to $0$ , giving finely divided manganese

Answer: C

Atmospheric oxygen oxidises

Mn (OH) X_{2}

to brown hydrated manganese(IV) oxide,

MnO (OH) X_{2}

, in which Mn has gone from

+ 2

to

+ 4

. Oxidation to permanganate requires a strong oxidant such as

NaBiO X_{3}

.

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