Water is added to a group chloride precipitate and heated. After heating some wh
ID: 1031970 • Letter: W
Question
Water is added to a group chloride precipitate and heated. After heating some white precipitate remains The supernatant is separated from the precipitate while hot and treated with K2CrO4 (aq) producing a bright yellow precipitate. The white precipitate remaining from the first step is treated with NH3 (aq) and dissolves completely. When this ammoniacal solution is acidified with nitric acid, a white precipitate forms Sort the statements from the paragraph above into bins indicating what information the statement provided Does not indicate Indicates possible presence of A Confirms Indicates Confirms Indicates Confirms absence f bence of any Ag+ 2+ Pb Hg2 2+ Hg2 2+ ion Which cations 2. After heating some white ppt remains 1. Water is added to the group chloride ppt and heated 5. When the ammoniacal are present in this solution? solution is acidified with nitric acid, a white ppt forms 3. The supernatant is separated from the ppt while hot and treated with K2CrO4(aq) producing a bright yellow ppt 4. The white ppt remaining from the first step is treated with NH3 Ag and dissolves completely Hg2 2+ 2+ PbExplanation / Answer
when heating precipitate in hot water, some precipitate dissolves : Pb2+ present (PbCl2 soluble in hot water)
the filtrate treated with K2CrO4 gives yellow precipitate : Pb2+ confirmed (forms PbCrO4)
The remaining precipitate is made basic by adding NH3 solution, dissolves : Ag+ present (forms Ag(NH3)2Cl)
Adding HNO3 forms white precipitate again : Ag+ confirmed (forms AgCl)
So,
1. Does not indicate presence or absence of any cation
2. Indicates possible presence of Ag+ and Hg2^2+
3. confirms presence of Pb2+
4. indicates absence of Hg2^2+
5. Confirms presence of Ag+
Cations present in solution
Ag+
Pb2+
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