A student is testing an unknown solution, XXX, to determine if it contains sulfate ions (SO42−\text{SO}_4^{2-}SO42−).
They followed this method:
Step 1: Acidify a 2 cm3 sample of solution X X\,X by adding a few drops of dilute sulfuric acid.
Step 2: Add a few drops of barium chloride solution.
Step 3: Record the observation.
The student observed a thick white precipitate and concluded that solution X X\,X contained sulfate ions.
This is not a valid conclusion because of the experimental method used.
Explain one improvement that the student could make to their method to obtain a valid result.
Practise Edexcel GCSE Chemistry Qualitative analysis: tests for ions with exam-style questions for Foundation and Higher tier. 127 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
