Chemical Tests
A student is given five unlabelled beakers with solid white powders. Each powder could be:
Lithium chloride
Copper chloride
Potassium chloride
Calcium chloride
Sodium chloride
Describe a chemical test to identify the contents of each beaker.
[6 marks]
Test for Metal Ions
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To decontaminate it, dip nichrome wire into Concentrated Hydrochloric Acid.
To test for metal ions:
Dip the wire into the powder
Hold it onto the tip of a blue flame
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Observe the flame colour:
Lilac = Potassium
Orange-red = Calcium
Crimson = Lithium
Yellow = Sodium
Green = Copper
A student is given an unknown sodium salt.
The student thinks it could be:
sodium carbonate
sodium sulphate
sodium chloride
sodium bromide
sodium iodide.
Describe the three chemical tests to prove if the salt contains carbonate ions, sulphate ions and halide ions in this order.
[6 marks]
Test for Carbonate Ions
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Add dilute acid. (1 mark)
Observe whether limewater turns milky. (1 mark)
If yes, Carbon Dioxide is present. So it is a Carbonate.
Test for Sulphate Ions
-
Add dilute Hydrochloric Acid. (1 mark) This removes any present Carbonate ions.
Add Dilute Barium Chloride. (1 mark)
Observe whether a white precipitate is seen. (1 mark)
If yes, sulphate ions are present.
Test for Halide Ions
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Add dilute Nitric Acid. (1 mark) This removes any present Carbonate ions. Do NOT use Hydrochloric Acid as it will react with Silver Nitrate.
Add dilute Silver Nitrate Solution. (1 mark)
Observe the colour of the precipitate: (1 mark)
If white, chloride ions are present
If cream, bromide ions are present
If yellow, iodide ions are present
