Calomel $\left(\mathrm{Hg}_{2} \mathrm{Cl}_{2}\right)$ on reaction with ammonium hydroxide gives

(A) $\mathrm{HgNH}_{2} \mathrm{Cl}$

(B) $\mathrm{NH}_{2}-\mathrm{Hg}-\mathrm{Hg}-\mathrm{Cl}$

(C) $\mathrm{Hg}_{2} \mathrm{O}$

JEE Main · 2005 · 08 May 2005 · Offline · Practical and Analytical Chemistry

Calomel

(Hg_{2} Cl_{2})

on reaction with ammonium hydroxide gives

(A) $HgNH_{2} Cl$ ✓ Correct
(B) $NH_{2} - Hg - Hg - Cl$
(C) $Hg_{2} O$
(D)HgO

Answer: (A)

Solution

Calomel,

Hg X_{2} Cl X_{2}

, undergoes disproportionation when treated with ammonium hydroxide, the mercury(I) splitting into mercury(0) and mercury(II). The reaction

Hg X_{2} Cl X_{2} + 2 NH X_{4} OH Hg + Hg (NH X_{2}) Cl + NH X_{4} Cl + 2 H X_{2} O

throws down a black deposit of finely divided mercury alongside white mercury(II) amidochloride. The nitrogen-bearing product named among the choices is

HgNH X_{2} Cl

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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