Identifying Ions GCSE Chemistry Practical
Use chemical tests to identify the ions in unknown single ionic compounds.
Students use flame testing, the carbonate test, the sulfate test and the halide test to identify an unknown chemical. They will carry out each of the chemical tests on a range of known chemicals, noting down any observations. They will then apply their knowledge to an unknown chemical, in order to identify it.
The students' use of equipment and chemicals in a safe manner is also observed during the practical session.
These experiments can easily be spread over two practical sessions.
Equipment (per participant)
• Safety goggles
• Bunsen burner
• Heatproof mat
• Spatula
• Flame test loop
• Test tubes
• Test tube rack
• Pipette
• Chinagraph pencil
• Hydrochloric Acid (0.4M)
• Barium Chloride (0.1M)
• Nitric Acid (0.4M)
• Silver Nitrate (0.05M)
• Lithium Chloride
• Sodium Chloride
• Calcium Chloride
• Potassium Chloride
• Copper Chloride
• Sodium Carbonate
• Sodium Sulfate
• Sodium Bromide
• Sodium Iodide
• CLEAPSS Hazcards: 10A, 19A, 26, 47A, 47B, 67, 87, 92, 95A
Method
Flame tests
- Students should set up a Bunsen burner on a heatproof mat.
- 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.
- Next, they should dip the nichrome wire loop into the first test tube and then hold the loop in a blue Bunsen flame.
- Their observations should be recorded in a table.
- Students should clean the wire loop by carefully holding the loop in the flame until no colour change is seen.
- The steps above are then repeated for the other known chloride solutions.
Carbonate test
- Students should label 5 test tubes with the available sodium solutions provided.
- Again, they should add 1cm depth of each sodium solution into the relevantly labelled test tubes.
- In a sixth labelled test tube, they should add 1cm depth of limewater.
- 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.
- They should repeat the process for the remaining sodium solutions and record their observations in their table.
Sulfate test
- Students should label 5 test tubes with the available sodium solutions provided.
- Again, they should add 1cm depth of each sodium solution into the relevantly labelled test tubes.
- A few drops of Hydrochloric Acid is added to each tube along with 1cm d.epth of Barium Chloride.
- Any observations should be recorded in their table.
Halide test
- Students should label 5 test tubes with the available sodium solutions provided.
- Again, they should add 1cm depth of each sodium solution into the relevantly labelled test tubes.
- A few drops of Nitric Acid are then added to each of the tubes along with add 1cm depth of Silver Nitrate.
- Any observations should be recorded in their table.
Testing the unknown solution
- 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.
- Can they identify the positive metal ion in the unknown?
- Can they also identify the non-metal ion?
Video produced by revisechemistrywithmrb,
practical GCSE Chemistry tutorials by a specialist Chemistry teacher with over 25 years experience.
Technician tips
• Students could be advised to thoroughly rinse their test tubes in between each set of chemical tests to reduce the amount of glassware used.
• Carbonate deposits from the limewater test can be removed from glassware using 1M Hydrochloric Acid.
• Always consult the CLEAPSS method for diluting concentrated acids.
• 0.4M Nitric Acid is made up in a fume cupboard wearing a face shield or splash-proof goggles and chemical resistant gloves. 13mls of concentrated acid is added slowly with stirring to 300mls of water. The solution will become warm. Water is then added to make it up to 500mls.
• 0.4M Hydrochloric Acid is made wearing eye protection by diluting the 4M stock solution by 10x.
• 0.1M Barium Chloride is made wearing eye protection by dissolving 6.11g of the solid into 250mls of water.
• To prepare the 0.05M Silver Nitrate Solution, wearing splash-proof goggles and disposable gloves, 2.12g of the solid is dissolved in 250mls of deionised or distilled water.
• 0.4M Lithium Chloride Solution is made up wearing eye protection and 4.24g of the solid is dissolved in 250mls of water.
• 0.4M Sodium Chloride is made up wearing eye protection by dissolving 5.84g of the solid in 250mls of water.
• 0.4M Calcium Chloride is made up wearing eye protection by dissolving 21.92g of the solid in 250mls of water.
• 0.4M Potassium Chloride is made up wearing eye protection by dissolving 7.46g of the solid in 250mls of water.
• 0.4M Copper Chloride is made up wearing eye protection by dissolving 17.04g of the solid in 250mls of water.
• 0.4M Sodium Carbonate is made up wearing eye protection by dissolving 28.6g of the solid in 250mls of water.
• 0.4M Sodium Iodide is made up wearing eye protection by dissolving 14.99g of the solid in 250mls of water.
• 0.4M Sodium Bromide is made up, wearing eye protection, by dissolving 10.29g of the solid in 250mls of water.
To do this practical you will need
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