A reagent which gives brilliant red precipitate with Nickel ions in basic medium is

Solution

Chemistry ma’am · 3 steps

Rosy red precipitate in ammonia is the signature of nickel with dimethylglyoxime; learn this pair by heart.

1. The nickel test. In Group IV analysis, Ni²⁺ is confirmed by adding dimethylglyoxime (DMG) to an ammoniacal solution. A bright rosy red (cherry red) precipitate of nickel dimethylglyoximate forms.

   Ni²⁺ + 2 dmgH₂ → [Ni(dmgH)₂] v + 2H⁺

2. Why basic medium. Each DMG molecule loses one H⁺ when it binds nickel. Ammonia removes this H⁺ and pushes the reaction forward. In acid, the complex does not form.

   Reagent	Main use in salt analysis	Colour seen
   Dimethylglyoxime	Ni²⁺ in ammoniacal solution	rosy red precipitate
   Sodium nitroprusside	S²⁻ (sulphide ion)	violet or purple colour
   meta-Dinitrobenzene	Not a test for metal cations	no red precipitate with Ni²⁺
   Neutral FeCl₃	Acetate ion and phenols	deep red or violet colour

3. So. The reagent is dimethylglyoxime, option (a).

The idea to keep. Tie each confirmatory reagent to its ion: DMG for Ni²⁺ (rosy red, ammoniacal), nitroprusside for S²⁻, neutral FeCl₃ for acetate. Cation tests and anion tests use different reagents.

Answer from the NTA final answer key. Solution by PrepWiser.