A student carried out a series of titrations to determine the concentration of a standard sodium carbonate solution. The student titrated 20.0 cm3 samples of the sodium carbonate solution against dilute hydrochloric acid.
The results of the four titrations are shown in the table below.
| Titration 1 | Titration 2 | Titration 3 | Titration 4 | |
|---|---|---|---|---|
| Final burette reading (cm3^{3}3) | 21 | 21.55 | 20.95 | 23.15 |
| Initial burette reading (cm3^{3}3) | 0 | 1.20 | 0.50 | 1.85 |
| Volume of acid added (cm3^{3}3) | 21 | 20.35 | 20.45 | 21.30 |
Two of the titrations should not be used to calculate the mean volume of acid required.
Identify these two titrations and give a reason why each should be excluded from the calculation.
Practise Edexcel GCSE Chemistry Quantitative analysis with exam-style questions for Foundation and Higher tier. 100 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.