The table shows the colours of three indicators over different pH ranges.
| Indicator | Colour below the pH shown | pH at which colour changes | Colour above the pH shown |
|---|---|---|---|
| methyl orange | red | 3.1 to 4.4 | yellow |
| bromothymol blue | yellow | 6.0 to 7.6 | blue |
| phenolphthalein | colourless | 8.2 to 10.0 | pink |
A few drops of each indicator are added to separate samples of solution X. Methyl orange turns yellow, bromothymol blue turns yellow and phenolphthalein stays colourless. Which conclusion about solution X is correct?
X is neutral, because phenolphthalein stays colourless
X is acidic, with a pH between 4.4 and 6.0
X is alkaline, because methyl orange turns yellow
X is acidic, with a pH below 3.1
44 exam-style questions on Edexcel GCSE Chemistry 4.1 Acids, covering 4.1.1 Acids, alkalis and the pH scale, 4.1.2 Hydrogen ion concentration and pH, 4.1.3 Dilute and concentrated, weak and strong acids, 4.1.4 Bases, alkalis and the reactions of acids, 4.1.5 Chemical tests for hydrogen and carbon dioxide, 4.1.6 Neutralisation as a reaction of acids with bases, 4.1.7 Preparing soluble salts, and 4.1.8 Solubility rules and preparing insoluble salts. Each one has a worked solution and a mark scheme showing where the marks go.