Identifying ions

Method

Flame tests

1. Students should set up a Bunsen burner on a heatproof mat.
2. They should label test tubes with each of the chloride solutions and add 1cm depth of each solution to the tubes using a disposable pipette.
3. Next, they should dip the nichrome wire loop into the first test tube and then hold the loop in a blue Bunsen flame.
4. Their observations should be recorded in a table.
5. Students should clean the wire loop by carefully holding the loop in the flame until no colour change is seen.
6. The steps above are then repeated for the other known chloride solutions.

Carbonate test

1. Students should label 5 test tubes with the available sodium solutions provided.
2. Again, they should add 1cm depth of each sodium solution into the relevantly labelled test tubes.
3. In a sixth labelled test tube, they should add 1cm depth of limewater.
4. To the sodium tubes, one by one, students should add 1ml of Hydrochloric Acid to each of them. If they see bubbles, they must quickly transfer some of the gas using a clean pipette and bubble this through the limewater in the sixth test tube. They may need to add a couple of pipettes full of gas in order to instigate the colour change.
5. They should repeat the process for the remaining sodium solutions and record their observations in their table.

Sulfate test

1. Students should label 5 test tubes with the available sodium solutions provided.
2. Again, they should add 1cm depth of each sodium solution into the relevantly labelled test tubes.
3. A few drops of Hydrochloric Acid is added to each tube along with 1cm d.epth of Barium Chloride.
4. Any observations should be recorded in their table.

Halide test

1. Students should label 5 test tubes with the available sodium solutions provided.
2. Again, they should add 1cm depth of each sodium solution into the relevantly labelled test tubes.
3. A few drops of Nitric Acid are then added to each of the tubes along with add 1cm depth of Silver Nitrate.
4. Any observations should be recorded in their table.

Testing the unknown solution

1. Students should now repeat each of the above tests on the unknown solution and record their observations. They then compare this with the known samples they have already tested.
2. Can they identify the positive metal ion in the unknown?
3. Can they also identify the non-metal ion?

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