A pale yellow solid A is formed when sodium burns in excess air. A reacts with ice-cold dilute H2SO4 to give Na2SO4 and a compound B. B alone is then used to decolourise acidified KMnO4. The number of moles of KMnO4 decolourised by the B obtained from 1 mol of A is:

JEE Advanced levelSingle correct optionDifficulty 3 of 3sb149

A pale yellow solid A is formed when sodium burns in excess air. A reacts with ice-cold dilute $H X_{2} SO X_{4}$ to give $Na X_{2} SO X_{4}$ and a compound B. B alone is then used to decolourise acidified $KMnO X_{4}$ . The number of moles of $KMnO X_{4}$ decolourised by the B obtained from 1 mol of A is:

A is

Na X_{2} O X_{2}

Na X_{2} O X_{2} + H X_{2} SO X_{4} Na X_{2} SO X_{4} + H X_{2} O X_{2}

, so 1 mol A gives 1 mol B (

H X_{2} O X_{2}

). In acid,

5 H X_{2} O X_{2} + 2 KMnO X_{4} + 3 H X_{2} SO X_{4} 5 O X_{2} + 2 MnSO X_{4} + K X_{2} SO X_{4} + 8 H X_{2} O

, so 1 mol

H X_{2} O X_{2}

reacts with

2/5 = 0.4

mol of

KMnO X_{4}