A paper dipped in a dil. H 2 SO 4 solution of ' X ' upon treatment with SO 2 gas turns into green. The compound ' X ' is :

Chemistry · p-Block Elements (Group 15-18)

JEE Main 2026 — 5 April, Evening Shift — Question 65

A paper dipped in a dil. $\mathrm{H}_{2} \mathrm{SO}_{4}$ solution of ' X ' upon treatment with $\mathrm{SO}_{2}$ gas turns into green. The compound ' X ' is :

Option A:
KI-starch
Option B:
$\mathrm{KMnO}_{4}$
Option C:
$\mathrm{Pb}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}$
Option D:
$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$
Correct

Answer: D

Step-by-step solution

$\mathrm{SO}_{2}$ gas acts as reducing agent.

\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+\mathrm{SO}_{2} \xrightarrow{\mathrm{H}_{2} \mathrm{SO}_{4}} \underset{\text { Green solution }}{\mathrm{Cr}_{2}}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{SO}_{4}^{2-}

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 5 April, Evening Shift
Subject: Chemistry
Chapter: p-Block Elements (Group 15-18)
Topic: Compounds of Sulphur - preparation and properties