On passing a gas, 'X', through Nessler's reagent, a brown precipitate is obtained. The gas 'X' is
- Cl2
- CO2
- NH3
- H2S
Answer
(3) NH3
Solution
Nessler's reagent = alkaline K2HgI4; it is the test for NH3 / NH4+:
2K2HgI4 + NH3 + 3KOH
brown pptHgO Hg(NH2)I + 7KI + 2H2O
∵ the brown precipitate (iodide of Millon's base) is given only by NH3 ⇒ X = NH3
Cl2, CO2, H2S give no brown precipitate.
Answer: (3)