8/13/2016 11:55 PM A 87.9/100 G 8/12/2016 02:07 PM Grade book Print Calculator l

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8/13/2016 11:55 PM A 87.9/100 G 8/12/2016 02:07 PM Grade book Print Calculator l Periodic Table Question 22 of 22 Sapling Learning macmillan learning A solution containing a mixture of metal cations was treated with dilute HCl and no precipitate formed. Next, H2S was bubbled through the acidic solution. A precipitate formed and was filtered off. Then, the pH was raised to about 8 and H2S was again bubbled through the solution. A precipitate again formed and was filtered off. Finally, the solution was treated with a sodium carbonate solution, which resulted in no precipitation. Which metal ions were definitely present, which were definitely absent, and which may or may not have been present in the orginal mixture? Definitely present Definitely absent Possibly present A Previous 3 Give Up & View Solution Check Answer Next Exit Hint

Explanation / Answer

Observation -

(1) No precipitate with dil. HCl - It means group 1 cations are absent. (Hg22+, Ag+ , Pb2+)

Hg22+, Ag+ are definitely absent

(2) Precipitate appeared when H2S is bubbled. It means group II cation is present

Group II cations - Bi3+ , Pb2+, Hg2+, Sn4+, Cu2+ may be present

(Note: Pb2+ occurs both in group I and group II)

(3) After raising the pH and again adding H2S, preciptate occurs. It means group III or IV is also present in the mixture.

Group III cations - Fe2+, Cr3+ definitely absent.

Group IV cations - Zn2+ is definitely present. (Since precipitate occurs on passing H2S in basic medium)

(4) No precipitate with carbonate. Group V is absent. Ca2+ is definitely absent

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