Question

To a solution of a substance gradiual addition of ammonium hydroxide result in a black precipitate which does not dissolve in excess of `NH_(4)OH` however when HCI is added to the original solution a white precipitate is formed .The solution contained
A. Lead salt
B. Silver salt
C. Mercurous salt
D. Copper salt

Answer 1

Correct Answer - c
`HgCI_(2)` is white insoluble salt
`Hg_(2)CI_(2)+2NH_(4)OH rarr ubrace(Hg+HgO.Hg(NH_(2))CI)_("Black")`
`+NH_(4)CI +2H_(2)O`