Question 20N.3.sl.TZ0.2f
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.sl.TZ0.2f |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Comment | Question number | f | Adapted from | N/A |
An investigation was carried out to determine the effect of chain length of the alcohol on the equilibrium constant, , for the reversible reaction:
The reactants, products and the catalyst form a homogeneous mixture.
Fixed volumes of each alcohol, the ethanoic acid and the sulfuric acid catalyst were placed in sealed conical flasks.
At equilibrium, the flasks were placed in an ice bath, and samples of each flask titrated with to determine the ethanoic acid concentration present in the equilibrium mixture.
The following processed results were obtained.
© International Baccalaureate Organization 2020
Comment on the magnitudes of random and systematic errors in this experiment using the answers in (e).
[2]
Any two:
large percentage error means large systematic error «in procedure» ✔
small percentage uncertainty means small random errors ✔
random errors smaller than systematic error ✔
Award [2] for “both random and systematic errors are significant.”
Of the many students that obtained the mark most did through the first alternative and a lesser percentage through the third. Many students were unable to relate their calculations from 2e (percentage error and percentage uncertainty) to systematic error and random error. They either compared the calculations to incorrect errors or in some cases did not discuss the errors at all. Once again this points to a general lack on experimental understanding.
