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

ID: 825330 • Letter: A

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. Again, a precipitate formed and was filtered off.

3. The pH was raised to about 9 and H2S was again bubbled through the solution. No precipitate formed.

4. Finally, sodium carbonate was added and no precipitate formed.


What can be said about the presence of each of these groups of cations in the original solution?

a) Ag+; Pb2+; Hg2^2+ description: form insoluble chlorides

b) Bi3+; Cd2+; Cu2+; Hg2+; Pb2+; Sb3+; Sn2+; Sn4+ description: form acid-insoluble sulfides

c) Al3+; Co2+; Cr3+; Fe2+; Fe3+; Ni2+; Mn2+; Zn2+ description: form base-insoluble sulfides or hydroxides

d) Ba2+; Ca2+; Mg2+; Sr2+ description: form insoluble carbonates

e) Li+; Na+; K+; NH4+ description: completely soluble


The answer choices for matching to each group are: *choices can be used more than once*

All of these ions are present

None of these ions are present

Unknown

At least one of these ions were present



Explanation / Answer

might be present:

Pb(NO3)2
Cd(NO3)2
Na2SO4
definitely present: definitely absent:
unfortunately I got this part completely wrong after trying different combinations of the above 3. maybe you'll have better luck
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