A technician tests water from four heating systems using two different methods.
| Water sample | Universal indicator paper result | pH meter result |
|---|---|---|
| A | approximately 6 | 6.4 |
| B | approximately 7 | 6.8 |
| C | approximately 7 | 7.3 |
| D | approximately 8 | 7.7 |
Which water sample is closest to neutral? Explain why the pH meter results allow a more certain choice than the universal indicator paper results.
87 exam-style questions on AQA GCSE Chemistry 10.1 Using the Earth's resources and obtaining potable water, covering 10.1.1 Using the Earth's resources and sustainable development, 10.1.2 Potable water, 10.1.3 Waste water treatment, and 10.1.4 Alternative methods of extracting metals. Each one has a worked solution and a mark scheme showing where the marks go.