A soltuion may contain Pb 2+ , Hg 2 2+ ,and Ag + ions, a white precipitate forme

Question

A soltuion may contain Pb2+, Hg22+,and Ag+ ions, a white precipitate formed upon the addition of 6M HCL solution. Some of the white precipitate dissolved in hot waters. the solution was decanted from the remaining white solid A. The addition of amonium carbonate to the decanted solution afforded a white precipitate B. The white solid A was then treated with 6M NH3 in which afforded a black solid. Which ions are present, which ions are absent or which may remain undetermined? Idicate if any test(s) are needed to verify the prescence of the undetermined ion.

Present:

Absent:

Yet to be determined:

Explanation / Answer

When HCl is added to a solution that may contain Ag, Pb², and Hg², All three can form white precipitates. However PbCl, if present, will dissolve in hot water. Since the precipitate dissolve in hot water, Pb² is present. When ammonia is added, Hg² will form a black precipitate.

So, based on the description, Pb² is absent, Hg² is present, and Ag remains undetermined

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