An ammoniacal metal salt solution gives a brilliant red… — JEE Main 2023 Chemistry PYQ

JEE Main 2023 · 24 Jan · Shift 1 · Paper-1(B.E./B. Tech.)

An ammoniacal metal salt solution gives a brilliant red precipitate on addition of dimethylglyoxime. The metal ion is:

A.
$\text{Cu}^{2+}$
B.
$\text{Fe}^{2+}$
C.
$\text{Ni}^{2+}$
D.
$\text{Co}^{2+}$

Show answer and solution

Correct option: C

Solution

Ni²⁺ reacts with dimethylglyoxime (DMG) in an ammoniacal (slightly basic) medium to form a characteristic brilliant red/scarlet precipitate of nickel dimethylglyoximate, [Ni(DMG)₂]. This is the classic qualitative test for Ni²⁺, where two DMG molecules chelate the nickel ion through N and O donors, forming a square planar, insoluble red complex. No other common metal ion produces this distinctive red precipitate with DMG under these conditions.

[JEE Main 2023 · 24 Jan · Shift 1 · Paper-1(B.E./B. Tech.)]

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