DP Chemistry (first assessment 2025)
Question 22M.2.HL.TZ2.6c(ii)
| Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.HL.TZ2.6c(ii) |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | c(ii) | Adapted from | N/A |
c(ii).
[Maximum mark: 2]
22M.2.HL.TZ2.6c(ii)
(c(ii))
Explain the electron domain geometry of SO3.
[2]
Markscheme
three electron domains «attached to the central atom» ✔
repel/as far away as possible /120° «apart» ✔
Examiners report
Most were focussed on the shape itself instead of explaining what led them to suggest that shape; number of electron domains allowed most candidates to get one mark and eventually a mention of bond angles resulted in only 35% getting both marks. In general, students were not able to provide clear explanations for the shape (not a language issue) but rather were happy to state the molecular geometry which they knew, but wasn't what was actually required for the mark.
Syllabus sections
Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.4—The valence shell electron pair repulsion (VSEPR) model enables the shapes of molecules to be predicted from the repulsion of electron domains around a central atom. Predict the electron domain geometry and the molecular geometry for species with up to four electron domains.