A solution containing a mixture of metal cations was treated as follows. 1. Dilu

Question

A solution containing a mixture of metal cations was treated as follows. 1. Dilute HCl was added and a precipitate formed. The precipitate was filtered off. 2. H2S was bubbled through the acidic solution. No precipitate formed. 3. The pH was raised to about 9 and H2S was again bubbled through the solution. A precipitate formed and was filtered off. 4. Finally, sodium carbonate was added to the filtered solution and no precipitate formed. 2+ What can be said about the presence of each of these groups of cations in the original solution? Cation Group Description Present in the original solution? O Ag, Pb, HG | form insoluble chlorides | At least one of these ions was present. Bi3, Cd + , Cu2+ , Hg" 2+ , form acid-insoluble At least one of these ions was present. Sh3Sulfides Pb2+ , Sbt, Sn2+ , Sn 4+ AP+ Co2+, Cr3+, Fe2+ | form base-insoluble Fe3+ , Ni 2+ , Mn2+ , Zn 2+ | sulfides or hydroxides None of these ions were present. Ba2+ , Ca2+ , Mo2, Sr2 + | form insoluble carbonates | None of these ions were present. completely soluble Li, NatK, NH , unknown All of these ions were present At least one of these ions was present. unknown None of these ions were present Incorrect.

Explanation / Answer

Since it formed precipitate with HCl hence first answer will be 'at least one of these ions were present'

No precipitate in case of acidic H2S hence second answer will be 'none of these ions were present'

Precipitate formed in case of H2S bubbling in basic solution hence third answer will be ' at least one of these ions was present'

No precipitate formed with sodium carbonate hence the fourth answer will be ' none of these ions were present'

In the last case in which solvent it is dissolved that is unknown hence the fifth answer will be ' unknown ,

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