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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. Identify the incorrect statement with respect to Hg(II) salts. |
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Answer» `Hg^(2+)` ions in the presence of DILUTE (M) hydrochloric acid gives initially a white PRECIPITATE of `Hg(II)` chloro sulphide with `H_(2)S` which then reacts with further quantity of `H_(2)S` to form black precipitate of `HgS`. `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)^(+)` |
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