A student adds sodium hydroxide solution, 5 cm35\,\mathrm{cm^{3}}5cm3 at a time, to 25 cm325\,\mathrm{cm^{3}}25cm3 of dilute hydrochloric acid. They measure the pH with a pH meter after each addition.
| Volume of sodium hydroxide solution added (cm3\mathrm{cm^{3}}cm3) | pH |
|---|---|
| 0 | 1.0 |
| 5 | 1.2 |
| 10 | 1.6 |
| 15 | 7.0 |
| 20 | 12.3 |
| 25 | 12.5 |
Statement 1: The mixture was neutral after 15 cm315\,\mathrm{cm^{3}}15cm3 of sodium hydroxide solution had been added.
Statement 2: After 10 cm310\,\mathrm{cm^{3}}10cm3 had been added, the mixture contained an excess of hydroxide ions.
Statement 3: After 25 cm325\,\mathrm{cm^{3}}25cm3 had been added, the mixture contained more hydroxide ions than hydrogen ions.
Which statements are correct?
1 only
1 and 2 only
1 and 3 only
1, 2 and 3
112 exam-style questions on OCR GCSE Chemistry 3.3 Types of chemical reactions, covering 3.3.1 Oxidation and reduction in terms of oxygen, 3.3.2 Acids, alkalis and neutralisation, 3.3.3 The pH scale and measuring pH, 3.3.4 Oxidation and reduction in terms of electrons, 3.3.5 Dilute and concentrated, weak and strong acids, and 3.3.6 Hydrogen ion concentration and pH. Each one has a worked solution and a mark scheme showing where the marks go.