Titration
3 marks · Easy| Titration | Initial burette reading / cm³ | Final burette reading / cm³ |
|---|---|---|
| 1 | 0.70 | 18.35 |
| 2 | 1.40 | 19.80 |
| 3 | 2.00 | 20.45 |
Calculate the titre (volume delivered) for Titration 1.
Which titration is likely to be the rough (trial) titration? Give a reason for your answer.
Suggest why the average titre is calculated using only concordant results.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 17.65 cm³
(b) Titration 1; its volume is not close to the others (not concordant).
(c) To improve accuracy and remove results that may have procedural errors.
Common mistakes: using all titres for average even if not concordant
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Subtracts initial from final reading for Titration 1: 18.35 - 0.70 = 17.65 cm³. (follow-through)
B1 (b) · 1 mark · States Titration 1 is rough; reason: volume is not similar to others.
B1 (c) · 1 mark · Mentions concordant titres improve reliability/accuracy by excluding anomalous values.
Worked solution
| Titration | Initial burette reading / cm³ | Final burette reading / cm³ |
|---|---|---|
| 1 | 0.70 | 18.35 |
| 2 | 1.40 | 19.80 |
| 3 | 2.00 | 20.45 |
(a) Titre for Titration 1 = 18.35 – 0.70 = 17.65 cm³
(b) Titration 1 is rough because its result is not close to Titration 2 or 3.
(c) Only concordant (closely agreeing) results are used to remove errors and get accurate mean.