DP Chemistry (last assessment 2024)
Question 19M.2.sl.TZ1.3c(ii)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.2.sl.TZ1.3c(ii) |
| Level | sl | Paper | 2 | Time zone | TZ1 |
| Command term | Outline | Question number | c(ii) | Adapted from | N/A |
c(ii).
[Maximum mark: 1]
19M.2.sl.TZ1.3c(ii)
This question is about compounds of sodium.
Sodium peroxide is used in diving apparatus to produce oxygen from carbon dioxide.
2Na2O2 (s) + 2CO2 (g) → 2Na2CO3 (s) + O2 (g)
(c(ii))
Outline why bond enthalpy values are not valid in calculations such as that in (c)(i).
[1]
Markscheme
only valid for covalent bonds
OR
only valid in gaseous state [✔]
Examiners report
Most students didn’t gain a mark and “values are average” was the most common incorrect answer. The fact this was an ionic compound did not register with them. Some students did gain a mark for stating that the substances were not in a gaseous state.
