Question

Water is added to a group chloride precipitate and heated. The precipitate seems unaffected by heating The supernatant is separated from the precipitate while hot and treated with K2CrO4 (aq) but no precipitate forms. The white precipitate remaining from the first step is treated with NH3 (aq) and turns a grey/black color. When the ammoniacal supernatant is acidified with nitric acid, a white precipitate forms Sort the statements from the paragraph above into bins indicating what information the statement provided Indicates possible presence of Ag and Hg2 Does not indicate presence or Confirms presence of Indicates Confirms presence of Ag+ Confirms presence of РЬ Indicates absence of Pb absence f absence of any 2+ Hg2 2+ ion 1. Water is added to the group chloride ppt and heated 4. The white ppt remaining from the first step is treated with NH3 and turns a grey/black color. 3. The supernatant is separated from the ppt while hot and treated with K2CrO4 (aq) but no ppt forms 5. When the ammoniacal supernatant is acidified with nitric acid, a white ppt forms 2. The ppt seems unaffected by heating Which cations are present in this solution? Pb 2+ Hg22 Ag

Answer 1

Precipitate remains undissolved in hot water : presence of Ag+ and/or Hg2^2+

supernatant did not form precipitate with K2CrO4 : Pb2+ absent

Precipitate treated with NH3 turns grey black : Hg2^2+ present

ammonical supernatant acidified with HNO3, forms white precipitate : Ag+ present

So,

1. Does not indicate presence of absence of any ions

2. Indicates presence of Ag+ and Hg2^2+

3. indicates absence of Pb2+

4. Confirms presence of Hg2^2+

5. confirms presence of Ag+

Cations present in solution,

Ag+

Hg2^2+