A student tests an unknown solution for sulfate ions.
She adds dilute hydrochloric acid to the solution, followed by a few drops of barium chloride solution.
Why does she need to add dilute hydrochloric acid in this test?
To increase the pH of the solution.
Chloride ions are needed for the test to work.
To react with and remove any carbonate ions that would also form a white precipitate.
The test only works under alkaline conditions.
41 exam-style questions on OCR GCSE Chemistry Identifying the products of chemical reactions. Each one has a worked solution and a mark scheme showing where the marks go.