Telling dilute sulphuric acid apart from hydrochloric and nitric acid
Three dilute acids look identical: colourless, sharp, all turning blue litmus red. Barium chloride solution tells them apart in one step. Added to dilute sulphuric acid, it throws down insoluble barium sulfate as a white precipitate; added to dilute hydrochloric or dilute nitric acid, nothing precipitates at all, because barium chloride and barium nitrate are both freely soluble. A precipitate that shows up in exactly one of the three flasks is the identification — no smell, no colour, no other difference to go on.
6 steps · Sulphuric Acid · Study of Compounds
What you will use
Apparatus
- Sulphuric acid test
- Hydrochloric acid test
- Nitric acid test
Chemicals
- Dilute Sulfuric Acid
- Barium Chloride Solution
- Dilute Hydrochloric Acid
- Dilute Nitric Acid
The steps
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Pour dilute sulphuric acid into the first flask.
Colourless, the same as every dilute acid on this bench.
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Add barium chloride solution to it.
A white precipitate forms at once — barium sulfate.
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Pour dilute hydrochloric acid into the second flask.
Colourless, indistinguishable by eye from the first flask before the test.
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Add barium chloride solution to it.
Nothing precipitates — the flask stays clear.
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Pour dilute nitric acid into the third flask.
Colourless, the same starting point as the other two flasks.
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Add barium chloride solution to it.
Nothing precipitates here either — the flask stays clear.
What it shows
Only the sulphate ion pairs with barium to form something insoluble: BaCl₂ + H₂SO₄ → BaSO₄↓ + 2HCl. Barium chloride added to hydrochloric acid changes nothing — both are already chlorides — and barium nitrate, the product with nitric acid, stays fully dissolved. A white precipitate in exactly one of the three tubes is the entire test: dilute sulphuric acid is the one that clouds.