Question

The ion or group detected by ${\text{K}}_{\text{2}}{\text{[HgI}}_{\text{4}}\text{]}$ is _______.

Answer 1

Potassium mercuric iodide

• Potassium mercuric iodide ${\mathrm{K}}_2\left[{\mathrm{HgI}}_4\right]$ is known as Nessler’s reagent.
• The ion or group detected by ${\text{K}}_{\text{2}}{\text{[HgI}}_{\text{4}}\text{]}$ is the ammonium ion.

Chemical reaction

• On passing the gas through Nessler’s reagent, a brown coloration or precipitate of basic mercury(II) amido-iodine is formed.
• The chemical reaction is as follows-
• $2{\mathrm{K}}_2{\mathrm{HgI}}_4+{\mathrm{NH}}_3+3\mathrm{KOH}\to \mathrm{HgO}.\mathrm{Hg}({\mathrm{NH}}_2)\mathrm{I}+7\mathrm{KI}+2{\mathrm{H}}_2\mathrm{O}$

The ion or group detected by ${\text{K}}_{\text{2}}{\text{[HgI}}_{\text{4}}\text{]}$ is the ammonium ion $\left({\mathrm{NH}}_4^{+}\right)$.