A student is given a clear, colourless aqueous solution of an unknown organic compound. Which of the following tests and subsequent observations would confirm that the solution is acidic?
Adding a few drops of phenolphthalein indicator, resulting in the solution turning a deep pink colour.
Dipping a strip of red litmus paper into the solution, which subsequently turns blue.
Adding solid NaHCO3\text{NaHCO}_3NaHCO3, resulting in effervescence of a gas that turns limewater cloudy.
Adding aqueous BaCl2\text{BaCl}_2BaCl2, resulting in the formation of a dense white precipitate.
Practise Edexcel GCSE Chemistry Acids with exam-style questions for Foundation and Higher tier. 100 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.