A student uses acid in a burette to titrate the same fixed volume of an alkali of known concentration. The acid and alkali react in a 1:1 ratio.
In every titration, the student continues adding acid after the first permanent colour change before recording the final burette reading.
| Titration | Recorded titre / cm3\text{cm}^3cm3 |
|---|---|
| 1 | 22.60 |
| 2 | 22.65 |
| 3 | 22.60 |
The student states, "The results are concordant, so their mean must give an accurate value for the concentration of the acid."
Explain whether the student's statement is correct. Predict whether the concentration calculated using the recorded titres will be higher or lower than the true concentration.
151 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.