JEE Main 2026 — Apr 2, Shift 1 — Chemistry solution

JEE Main2026Apr 2, Shift 1Chemistry

Which of the following sets includes all the species that will change the orange colour of $K_{2} C r_{2} O_{7}$ in acidic medium ?

A
$F e^{2 +}, S n^{2 +}, I^{-}, S^{2 -}$
B
$S^{2 -}, F e^{3 +}, I^{-}, C_{2} O_{4}^{2 -}$
C
$F e^{2 +}, N O_{2}^{-}, S O_{2}, S n^{4 +}$
D
$F e^{3 +}, S O_{4}^{2 -}, S^{2 -}, S n^{4 +}$

Solution

Acidified $K_{2} C r_{2} O_{7}$ is a strong oxidising agent (orange $C r_{2} O_{7}^{2 -}$ is reduced to green $C r^{3 +}$ ). Only reducing species can decolourise it.

Inspecting the options, set (1) contains four species, each of which can be oxidised:

$F e^{2 +} \to F e^{3 +}$ , $S n^{2 +} \to S n^{4 +}$ , $I^{-} \to I_{2}$ , $S^{2 -} \to S$ .

The other options contain ions that are already in their highest stable oxidation state ( $F e^{3 +}$ , $S n^{4 +}$ , $S O_{4}^{2 -}$ ) and so cannot reduce the dichromate. Hence option (1) is correct.

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