A trainee technician repeats the same acid–alkali titration four times.
| Titration | Initial burette reading / cm3\mathrm{cm^3}cm3 | Final burette reading / cm3\mathrm{cm^3}cm3 | Observation |
|---|---|---|---|
| 1 | 0.30 | 25.10 | This was the rough titration and the acid was added quickly throughout. |
| 2 | 1.20 | 25.75 | There was an air bubble in the burette jet before the initial reading. There was no bubble after the titration. |
| 3 | 2.40 | 26.60 | The jet was full and the acid was added drop by drop while the flask was swirled near the end point. |
| 4 | 5.10 | 29.20 | The jet was full and the acid was added drop by drop while the flask was swirled near the end point. |
Calculate the titre for each titration.
Calculate the mean titre that the technician should use.
Explain why the titre calculated for titration 2 is greater than the volume of acid that was delivered into the conical flask.
152 exam-style questions on OCR GCSE Chemistry 5.1 Monitoring chemical reactions, covering 5.1.1 The technique of titration, 5.1.2 Theoretical mass, percentage yield and atom economy, 5.1.3 Concentration of a solution in mol/dm3, 5.1.4 Concentration calculations and titration results, 5.1.5 Molar gas volume and volumes of gases in reactions, and 5.1.6 Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.