In acidic medium, which of the following becomes colourless?
In acidic medium, which of the following becomes colourless?
$\mathrm{MnO}_4^{-}$
$\mathrm{MnO}_4^{2-}$
$\mathrm{CrO}_4^{2-}$
$\mathrm{FeO}_4^{2-}$
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.