JEE Main · 2024 · 29 Jan 2024 · Shift 2 · Practical and Analytical Chemistry

On passing a gas, ' X ', through Nessler's reagent, a brown precipitate is obtained. The gas ' X ' is

(A) $H_{2} S$
(B) $CO_{2}$
(C) $NH_{3}$ ✓ Correct
(D) $Cl_{2}$

Answer: (C)

Solution

Nessler's reagent is an alkaline solution of potassium tetraiodomercurate(II),

K_{2} [Hg I_{4}]

, used to detect ammonia.

When ammonia gas is passed into it, it reacts to form the brown precipitate known as iodide of Millon's base:

2 K_{2} [Hg I_{4}] + N H_{3} + 3 KOH \to iodide of Millon’s base ↓ (brown) + 7 KI + 2 H_{2} O

Neither

H_{2} S

C O_{2}

nor

C l_{2}

gives this characteristic brown precipitate with Nessler's reagent.

The gas X is ammonia,

N H_{3}

JEE Main · 2024 · 29 Jan 2024 · Shift 2 · Single correct option

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