$\mathrm{K}_2\left[\mathrm{Hgl}_4\right]$ detects the following ion

• A

  $\mathrm{Cl}^{-}$
• B

  $\mathrm{NO}_2^{-}$
• C

  $\mathrm{NO}_3^{-}$
• Correct answer
  D

  $\mathrm{NH}_4^{+}$

Solution

Analysis of $\mathrm{NH}_4^{+}$cation Take small amount of salt in the test tube and add NaOH and heat. Add Nessler's reagent $\left[\mathrm{K}_2 \mathrm{H}_3 \mathrm{I}_4\right]$ to the solution, brown ppt is obtained. It confirmed $\mathrm{NH}_4^{+}$ion.

Hence, the correct answer is option: 'D'.