JEE Main · 2023 · Shift-IIeasyDNF-033

Formula for Nessler's reagent is:

d & f-Block Elements · Class 12 · JEE Main Previous Year Question

Question

Formula for Nessler's reagent is:

Options
  1. a

    KHg2I2\text{KHg}_2\text{I}_2

  2. b

    KHgI3\text{KHgI}_3

  3. c

    K2HgI4\text{K}_2\text{HgI}_4

  4. d

    HgI2\text{HgI}_2

Correct Answerc

K2HgI4\text{K}_2\text{HgI}_4

Detailed Solution

Nessler's Reagent:

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

Formula: K2[HgI4]\text{K}_2[\text{HgI}_4] (potassium tetraiodomercurate)

Composition:

  • K: potassium
  • Hg: mercury (in +2 state)
  • I: iodine (4 iodide ions)

Use: Detection of NH3\text{NH}_3 / NH4+\text{NH}_4^+ ions — gives a brown precipitate (Millon's base) with ammonia: NH3+K2[HgI4]Hg2NIH2O (brown ppt)\text{NH}_3 + \text{K}_2[\text{HgI}_4] \rightarrow \text{Hg}_2\text{N}\cdot\text{I} \cdot \text{H}_2\text{O} \text{ (brown ppt)}

Answer: Option (3) — K2HgI4\text{K}_2\text{HgI}_4

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