1. Sulphate Anion Tests

2. What are we testing to find?
This test is to confirm the presence of sulphate ions.
Sulphate ions are negatively charged (SO42-) therefore they are anions.

3. How do we do the test? Place the sample solution in a test tube.
First add a few drops of hydrochloric acid using the dropper.
Then add barium chloride solution to the sample, using a dropper.
Observe if any precipitate is formed.

4. What results might we get?
If sulphate anions (SO42-) were present in the sample then we will observe a white precipitate.
This can be represented by an equation, here with the example of copper sulphate
CuSO4 (aq) + BaCl2 (aq) → CuCl2 (aq) + BaSO4 (s)
The copper and chloride ions can be removed from the equation and we can write this as an ionic equation, where only the reacting ions are used
SO42- (aq) + Ba2+ (aq) → BaSO4 (s)

5. Why does this test work?
Most sulphate salts are insoluble. One notable exception is barium sulphate, which is a white solid.
If we add barium chloride solution, which we know to be soluble to a sulphate, then the barium ions and the sulphate ions will form the insoluble salt, which precipitates.

6. Watch this video to see the test in action

7. Summary
We can test for the presence of sulphate anions by adding barium chloride in the presence of hydrochloric acid to the sample, and if we will see a white precipitate formed the presence of sulphate ions is confirmed.