Question

State True or False.

(A) is ${Hg}_2{Cl}_2$ (calomel).

• A. True
• B. False

Answer 1

The correct option is A True

The given statement is True.
(A) is $H{g}_{2}C{l}_2$ (calomel). It makes part of calomel electrode and is insoluble in water.
(A) is blackened by ammonia forming (B).
$\underset{\text{(A)}}{H{g}_{2}C{l}_2}+2N{H}_3\to \underset{\text{(B)}}{[Hg+Hg(N{H}_2\left)Cl\right]}\downarrow +N{H}_{4}Cl$
(B) is soluble in aqua regia forming (C).
$\underset{\text{(B)}}{[Hg+Hg(N{H}_2\left)Cl\right]}+3Cl\text{from aqua regia}\to \underset{\text{(C)}}{2HgC{l}_2}$
(C) gives orange ppt with KI but ppt dissolves in excess of KI forming (D).
$\underset{\text{(C)}}{HgC{l}_2}+2KI\to \underset{\text{(D)}}{Hg{I}_2}\downarrow \text{(orange)}+2KCl$