An unknown solution may contain any of the seven cations listed below. One stude

Question

An unknown solution may contain any of the seven cations listed below. One student preformed a series of experiments to determine what ions are in the solution. Based upon the experiments performed by the students, the results are as follows:

a) On addition of 6 M HCl, a white precipitate results. The white precipitate is then mixed with NH3 where it dissolves.

b) When acidic H2S is added to the unknown, a black precipitate results, and is dissolved in NH3 giving a deep blue color.

c) When ammonium carbonate, concentrated ammonia, and ammonium chloride are added to the unknown, a clear solution results.

Classify the following ions as present, absent, or undetermined. (input the whole word)

Silver:

Alumininum:

Barium:

Calcium:

Sodium:

Iron:

Copper:

Explanation / Answer

a)

addition of HCl in acidic conditions... will precipitate

Ag, Pb and/or Hg

all three are white so we cant know for sure which is which

b)

adding H2S will precipitate

Ag2S; PbS and HgS; all balck, so this wont help

c)

if adding NH3 dissolves the product, ther eis NO Hg

then

from th elist, there is only Silver (Ag+) possible

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