Question on Qualitative Analysis

Few drops of Barium Chloride are added to aqueous solutions of the following 2 compounds.

(1) Sodium Shulphate

(2) Sodium Carbonate

Which one of the compounds given above forms a white precipitate that is insoluble in dilute HCl?

Answer:

The answer is Sodium Sulphate. Sodium Sulphate reacts with Barium Chloride to give Barium Sulphate while Sodium Carbonate will give Barium Carbonate.

If Barium Sulphate and Barium Carbonate react with HCl the reactions would be as follows;

BaSO₄ + 2HCl = BaCl₂ + H₂SO₄

BaCO₃ + 2HCl = BaCl₂ + H₂CO₃

HCl can not release H₂SO₄ from BaSO₄ as H₂SO₄ is a stronger acid than HCl whereas it can release H₂CO₃ from BaCO₃ as H₂CO₃  is a weaker acid than HCl. So Sodium Sulphate forms a white precipitate with Barium Chloride that is insoluble in dilute HCl.