Answer Happy

1. Precipitation of Group B cations:
The Group B cations are the only cations in our qualitative
analysis scheme that form insoluble hydroxides upon the
addition of 6M ammonia. Addition of 6M NH3 separates the
Group B cations from Groups C & D.
The reaction for Bi3+ is.:
Bi3+(aq) + 3H2O(l) + 3NH3(aq) -> Bi(OH)3(s) +
3NH4+(aq)

The reactions for the other ions are similar to this, however
for Fe3+ we need to recall that it is present in the HCl(aq)
solution as a complex ion.
In the space below, write the balanced net ionic
chemical
equation, including phase labels, for the precipitation of
the FeCl4– when NH3(aq) is added.
2. Removal of Any Contaminating Lead
Cations:
PbCl2 is somewhat soluble. Therefore, some lead may not
precipitate as PbCl2 during the group A analysis. If Pb2+ is
present in your unknown, your Group B-D supernatant may
contain some residual Pb2+ that will precipitate with your
Group B cations upon addition of the NH3(aq) due to the
very low solubility of Pb(OH)2. In this case, it is necessary
to
remove the Pb2+ contaminant. This is accomplished by
adding sulfuric acid; the Group B hydroxides will dissolve
while any Pb2+ ion will form insoluble PbSO4.
In the space below, write the balanced net ionic
chemical
equation, including phase labels, for the dissolving of
Cr(OH)3 using sulfuric acid.








In the space below, write the balanced net ionic
chemical
equation, including phase labels, for the precipitation of
Pb2+(aq) ions using sulfuric acid.