JEE Main 2025 Jan 24 Shift 2, Chemistry Q8: Colour, Magnetism And Stability Of Co-ordination Compounds

JEE Main2025Jan 24, Shift 2Chemistry

Find the compound 'A' from the following reaction sequences.

$A aqua regia B (1) K N O_{2} ∣ N H_{4} O H (2) A c O H yellow ppt$

A
ZnS
B
CoS
C
MnS
D
NiS

Solution

The diagnostic yellow precipitate obtained on treatment with $K N O_{2}$ in $N H_{4} O H$ / $A c O H$ is potassium hexanitritocobaltate(III), $K_{3} [C o (N O_{2})_{6}]$ , which is a classical confirmatory test for $C o^{2 +}$ .

Working backwards:

$C o S aqua regia C o C l_{2} (1) K N O_{2} / N H_{4} O H (2) A c O H K_{3} [C o (N O_{2})_{6}] ↓ (yellow)$

Among the given sulphides only $C o S$ leads to this yellow precipitate, so $A = C o S$ .

Correct option: (2)

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JEE Main 2025 Jan 24 Shift 2, Chemistry Q8: Colour, Magnetism And Stability Of Co-ordination Compounds

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