A student added sodium carbonate powder to 25.0 cm3 of dilute hydrochloric acid and measured the pH after each addition.
The table below shows their results:
| Mass of sodium carbonate added (g) | pH |
|---|---|
| 0.0 | 1.5 |
| 0.2 | 1.7 |
| 0.4 | 1.9 |
| 0.6 | 2.2 |
| 0.8 | 2.8 |
| 1.0 | 7.0 |
| 1.2 | 9.8 |
| 1.4 | 10.3 |
| 1.6 | 10.5 |
Explain, in terms of the ions present, why the pH starts at a low value and ends at a higher, alkaline value.
276 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.