A pale-pink solution gives a white precipitate with NaOH that browns in air. How many moles of NaBiO3 are required to oxidise one mole of the cation completely to MnO4^- in nitric acid, and what is the cation?

JEE Advanced levelSingle correct optionDifficulty 3 of 3qc102

A pale-pink solution gives a white precipitate with $NaOH$ that browns in air. How many moles of $NaBiO X_{3}$ are required to oxidise one mole of the cation completely to $MnO X_{4} X^{-}$ in nitric acid, and what is the cation?

The white precipitate that browns in air and the pale-pink ion indicate

Mn X^{2 +}

. Mn goes

+ 2 \to + 7

(5 electrons), while

Bi (V) \to Bi (III)

takes 2 electrons, so

5/2 = 2.5

mol per mole, matching

2 Mn X^{2 +} + 5 NaBiO X_{3} + 14 H X^{+} 2 MnO X_{4} X^{-} + 5 Bi X^{3 +} + 5 Na X^{+} + 7 H X_{2} O