Question 20N.3.sl.TZ0.1d
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.sl.TZ0.1d |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | d | Adapted from | N/A |
In order to determine the oil content of different types of potato crisps (chips), a student weighed of crushed crisps and mixed them with of non-polar solvent.
She assumed all the oil in the crisps dissolved in the solvent.
The student then filtered the mixture to remove any solids, and gently heated the solution on a hot plate to evaporate the solvent.
She measured the mass of the oil that remained from each type of crisps
Suggest one source of error in the experiment, excluding faulty apparatus and human error, that would lead to the following:
[2]
Experimental mass greater than actual mass of oil in crisps:
other substances «in the crisps» are soluble in the solvent
OR
not all the solvent evaporates ✔
Experimental mass less than actual mass of oil in crisps:
not all oil dissolved/extracted ✔
Accept “oil evaporated” OR “oil burned/decomposed” OR “oil absorbed by the filter” OR “assumption «all oil dissolved» was wrong” for M2.
Do not accept examples of human errors OR faulty apparatus.
Even weak candidates scored at least one point and often both. One common pitfall was to invert the arguments or provide answers excluded by the stem. A frequent incorrect answer was identification of faulty apparatus and human error which was specifically excluded in the question.