Question

To an aqueous solution containing anions a few drops of acidified $ KMn{{O}_{4}} $ are added. Which one of the following anions, if present will not decolourise the $ KMn{{O}_{4}} $ solution?

• A. $ {{I}^{-}} $
• B. $ CO_{3}^{2-} $
• C. $ {{S}^{2-}} $
• D. $ NO_{2-}^{{}} $
• E. $ C{{l}^{-}} $

Answer 1

Answer: (B)

In $ CO_{3}^{2-}, $ C is present in its highest oxidation state, ie, +4 state, so its further oxidation is not possible, it only undergoes reduction. Acidified $ KMn{{O}_{4}} $ is a strong oxidizing agent, but it cannot oxidize $ CO_{3}^{2-} $ . Hence, it will not be decolorized by $ CO_{3}^{2-} $ .