A student uses a pipette to transfer 25.0 cm325.0\,\mathrm{cm^{3}}25.0cm3 of dilute sulfuric acid into a conical flask. Potassium hydroxide solution is added from a burette.
Before titration 1, the student fills the burette but does not open the tap to fill the jet. There is an air bubble in the jet. The air bubble is no longer present after titration 1.
The student refills the burette before the liquid level reaches the tap and completes three more titrations.
| Titration | Titre (cm3\mathrm{cm^{3}}cm3) |
|---|---|
| 1 | 24.45 |
| 2 | 24.10 |
| 3 | 24.15 |
| 4 | 24.10 |
Explain why the titre for titration 1 is greater than the other titres.
The student refills the burette before the liquid level reaches the tap and carries out another titration. Calculate an estimate for the next titre. Explain your answer.
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.