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4. d and f- block elements — Chemistry STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceChemistry4. d and f- block elements1 Mark
MCQ
When $KMnO_4$ solution is added to hot oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time. This is because
  • ✓
    $Mn^{2+}$ acts as auto catalyst
  • B
    $CO_2$ is formed
  • C
    Reaction is exothermic
  • D
    $MnO_4^-$ catalyses the reaction.
✓

Answer

Correct option: A.
$Mn^{2+}$ acts as auto catalyst
a
Here, $KMnO _4$ is a reactant in the reaction which forms $Mn ^{2+}$ which acts as an auto-catalyst. The reaction is slow initially because $MnO _4{ }^{-}$is getting converted to $Mn ^{2+}$ but once $Mn ^{2+}$ forms, the reaction becomes faster due to the catalytic action.

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