This qualitative analysis applet
involves cations that can be classified in three
groups:
| Group
I: Pb2+, Ag+ |
|
|
Group
II: Cu2+ |
|
|
Group
III: Fe2+, Ni2+,
Mn2+ |
In choosing your
strategy for separating and identifying these
cations, consider the following hints.
1.
The Group I cations form insoluble chlorides.
(Add a squirt of 6M HCl.) PbCl2(s)
will dissolve in hot water.
2.
Group II sulfides are insoluble in acidic
solution. (Add a squirt of 6M HCl, a squirt of
thioacetamide, and heat in the water bath.)
3.
Group III sulfides are insoluble in basic
solution. (Add another squirt of thioacetamide,
heat, and then add concentrated ammonia.)
After
making precipitates, remember to centrifuge,
separate solid from centrifugate, and save both
for more testing. Further confirmatory tests can
be devised from the reactions listed in the
applet.
Exercise.
Use the applet below to test an unknown sample
which contains one type of cation. You can
practice with known samples. The identity
of a "true unknown" can only be
revealed by an instructor of teaching assistant
who is officially using this applet.
To
use the Lab Bench, drag the dropper and spatulas
to the test tubes to add reagents. A tube will
become red when it is ready to receive reagent.
Test tubes can be dragged to the waste can, the
pH paper, the hot plate and the centrifuge. Wait
for some response from the receiving apparatus
before releasing the tube.
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