To a solution of a substance, gradual addition of ammonium hydroxide results in a brownish black precipitate which does not dissolve in excess of `NH_(4)OH`. However, when KI (no in excess) is added to the original solution, a green precipitate is formed. The solution contained:

Options

A. lead salt
B. silver salt
C. mercurous salt
D. copper salt

Answer

C

Explanation

`{:(Hg_(2)^(2+)overset(NH_(4)OH)rarrubrace(Hg+HgO.Hg(NH_(2))NO_(2))_("Black")darr),(darrKI),(underset(("Green ppt."))(Hg_(2)I_(2)darr)):}`