Testing for Sulfate Ions

To identify the presence of sulfate ions in a solution, follow these steps:

1. To acidify the sample, add a few drops of dilute hydrochloric acid (HCl).

2. Then, add a few drops of dilute barium chloride (BaCl2) solution to the sample.

3. If sulfate ions are present in the solution, a white precipitate of barium sulfate (BaSO4) will form. The reaction is:

Ba²⁺ (aq) + SO4²⁻ (aq) → BaSO4 (s)

For example, if we have a solution of magnesium sulfate (MgSO4), the reaction would be:

BaCl2 (aq) + MgSO4 (aq) → BaSO4 (s) + MgCl2 (aq)

By observing the formation of the white precipitate, we can confirm the presence of sulfate ions in the sample.

An illustration demonstrating a chemical test for sulphate ions. On the left is a test tube containing a clear solution labelled 'Magnesium Sulphate Solution'. In the centre is another test tube, where a hand is depicted adding drops from a dropper into the solution, leading to the formation of a 'Milky White Precipitate of Barium Sulphate' at the bottom. To the right is a third test tube with the milky precipitate settled at the bottom. Below the illustration, the process is described: "Adding a small amount of Barium Chloride Solution to Magnesium Sulfate Solution (which contains dissolved sulfate ions in dilute hydrochloric acid)." Accompanying this description is the chemical reaction "BaCl2 + MgSO4 → BaSO4 + MgCl2". A note at the bottom states: "A milky white precipitate of barium sulphate is formed which indicates the presence of sulphate ions."

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