Question

In Nessler's reagent for the detection of ammonia the active species is

• A. $Hg _{2} Cl _{2}$
• B. $Mg ^{2+}$
• C. $Hg _{2} I _{2}$
• D. $HgI _{4}{ }^{2-}$

Answer 1

Answer: (D)

Nessler's reagent gives brown ppt. of iodide of Millon's base with ammonium salt.
$
\left[ HgI _{4}\right]^{2-}+ NH _{4} Cl +4 OH ^{-} \rightarrow \underset{\text { Iodide of million base (Brown ppt) }}{ NH _{2} HgOHgI }+ I ^{-}+ Cl ^{-}+3 H _{2} O
$