The presence of Hg^(2+) ions is detected as its sulphide in group IIA of qualitative analysis. The black HgS is one of the least soluble precipitate known (K_(sp) = 4 xx 10^(-54)). Aqua regia and sodium sulphide (2M) dissolve the black precipitate. potassium iodide when added slowly to the solution contaning Hg^(2+) ions, a red precipitate is formed which dissolves in excess KI to form a colourless soluble complex. when NH_(4)CI solution is added to the above colourless soluble complex containing some NaOH, a brown precipitate is formed. when to a warm alkaline aqueous solution of Hg(NO_(3))_(2) a solution a ammonium chloride is added, a white precipitate is obtained. The brown precipitate formed is due to the formation of:

The presence of Hg^(2+) ions is detected as its sulphide in group IIA

1.	The presence of Hg^(2+) ions is detected as its sulphide in group IIA of qualitative analysis. The black HgS is one of the least soluble precipitate known (K_(sp) = 4 xx 10^(-54)). Aqua regia and sodium sulphide (2M) dissolve the black precipitate. potassium iodide when added slowly to the solution contaning Hg^(2+) ions, a red precipitate is formed which dissolves in excess KI to form a colourless soluble complex. when NH_(4)CI solution is added to the above colourless soluble complex containing some NaOH, a brown precipitate is formed. when to a warm alkaline aqueous solution of Hg(NO_(3))_(2) a solution a ammonium chloride is added, a white precipitate is obtained. The brown precipitate formed is due to the formation of:
Answer» oxy-dimercuric ammonium iodide potassium tetraiodomercurate (II) ammonium tetraiodomercurate (II) (a) and (b) both Solution :`HgSdarr + Na_(2)S rarr Na_(2)[HgS_(2)]` (soluble) `K_(2)HgI_(4)+NH_(4)CI +KOH rarr HgO.HG(NH_(2))I` `Hg^(2+) +Co^(2+)+4SCN^(-) rarr UNDERSET(("Deep BLUE crystalline ppt"))(Co[Hg(SCN)_(4)]darr)` `2HG^(2+) +NO_(3)^(-) +4NH_(3)+H_(2)O rarr HgO.underset(("White ppt"))(Hg(NH_(2))NO_(3)darr +3NH_(4)^(+)`