Negative ions- Sulphate test (Edexcel GCSE Chemistry Combined Science): Revision Notes

Sulphate ions $\ce{(SO4^2−​) }$ can be tested using a solution of barium chloride $\ce{BaCl2}$ mixed with dilute hydrochloric acid $(HCl)$. When this mixture is added to a solution containing sulphate ions, a white precipitate of barium sulphate $\ce{BaSO4}$ forms.

This reaction occurs as the larger sulphate ions displace the chloride ions in barium chloride:

The appearance of a white precipitate indicates the presence of sulphate ions in the solution.