Question 22M.2.SL.TZ1.c(ii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.SL.TZ1.c(ii) |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Suggest | Question number | c(ii) | Adapted from | N/A |
Suggest an explanation, other than product being lost from the crucible or reacting with nitrogen, that could explain the yield found in (b)(iii).
[1]
incomplete reaction
OR
Mg was partially oxidised already
OR
impurity present that evaporated/did not react ✔
Accept “crucible weighed before fully cooled”.
Accept answers relating to a higher atomic mass impurity consuming less O/O2.
Accept “non-stoichiometric compounds formed”.
Do not accept "human error", "wrongly calibrated balance" or other non-chemical reasons.
If answer to (b)(iii) is >100%, accept appropriate reasons, such as product absorbed moisture before being weighed.
Quite a few students realised that incomplete reaction would lead to this, but only 30% of students gave a correct answer rather than a non-specific guess, such as "misread balance" or "impurities".
