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.