Question

Explain why does colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium.

Answer 1

Hey !!

KMnO₄ acts as oxidising agent. It oxidises oxalic acid to CO₂ and itself changes to Mn²⁺ ion which is colourless.

5C₂O₄²⁻ + 2MnO⁻₄+ 16H⁺ ----> 2Mn²⁺ + 8H₂O + 10CO₂

→ 2MnO²⁻₄ (Coloured)

→ 2Mn²⁺ (Colourless)

Good luck !!

Answer 2

Due to reduction of $MnO_{4} ^{-}$  to $Mn^{2+}$  the colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium.

Explanation:

• The oxidizing agent  $KMnO_{4}$ is used.
• It converts oxalic acid to $Co_{2}$ before converting to the colourless Mn$Mn^{2+}$ ion.

$5C_{2} O_{4} ^{-} + 2MnO_{4} ^{-} + 16 H^{+}$   →  $2Mn^{2+} + 8H2_{O} + 10CO_{2}$

           (Coloured)                  (Colourless)

• When oxalic acid is added to acidic solution of $KMnO_{4}$ it color disappear due to reduction of $MnO_{4} ^{-}$ (which is coloured) to $MnO_{4} ^{-}$ which is colorless.
• Pure oxalic acid is used to standardize potassium permanganate. A redox reaction is involved.

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