Q56 / 180 · AIIMS 2018 (27 May) · Chemistry

In acidic medium, which of the following becomes colourless?

  • Correct answer
    A
    $\mathrm{MnO}_4^{-}$
  • B
    $\mathrm{MnO}_4^{2-}$
  • C
    $\mathrm{CrO}_4^{2-}$
  • D
    $\mathrm{FeO}_4^{2-}$

Solution

$\mathrm{MnO}_4^{-}$changes from purple to colourless in acidic solution while $\mathrm{MnO}_4^{2-}$ is stable in acidic medium. Yellow coloured $\mathrm{CrO}_4^{2-}$ changes to orange coloured $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ on acidifying and $\mathrm{FeO}_4^{2-}$ decomposes.

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

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