Qualitative Analysis of Cations

This qualitative analysis applet involves cations of lead, silver, copper, iron, nickel, and mangenese, 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.