Question

The chemical formula of Nessler's reagent is .

• A. $H_{2}NHgOHgI$
• B. $K_2\left[Hg{I}_4\right]$
• C. $[FeS{O}_4.NO]$

Answer 1

The correct option is B $K_2\left[Hg{I}_4\right]$

Nessler's reagent $\left(K_2\right[Hg{I}_4\left]\right)$ is used to detect ammonia.
It is prepared by mixing 2g potassium iodide in 5ml water. To this solution, 3g of mercury (II) iodide is added, and the resulting solution is made to 20ml. Finally, 40g potassium hydroxide (30 %) is added to provide the alkaline base.