State how you would test a solution for the presence of sulfate ions? Explain, using an ionic equation, what you would expect to observe in the presence of sulfate ions.

You would add barium chloride solution to the sample to be tested. Group II sulfate solubility decreases down the group - with barium sulfate being insoluble. We would expect to see a heavy white precipitate of barium sulfate, according to the equation: Ba²⁺ (aq) + SO₄^2- (aq) => BaSO₄ (s).