DP Chemistry (last assessment 2024)
Question 19M.2.hl.TZ2.a(ii)
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.hl.TZ2.a(ii) |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Write | Question number | a(ii) | Adapted from | N/A |
a(ii).
[Maximum mark: 2]
19M.2.hl.TZ2.a(ii)
Dinitrogen monoxide, N2O, causes depletion of ozone in the stratosphere.
Dinitrogen monoxide in the stratosphere is converted to nitrogen monoxide, NO (g).
Write two equations to show how NO (g) catalyses the decomposition of ozone.
[2]
Markscheme
NO (g) + O3 (g) → NO2 (g) + O2 (g) [✔]
NO2 (g) + O3 (g) → NO (g) + 2O2 (g) [✔]
Note: Ignore radical signs.
Accept equilibrium arrows.
Award [1 max] for NO2 (g) + O (g) → NO (g) + O2 (g).
Examiners report
Many candidates recalled the first equation for NO catalyzed decomposition of ozone only. Some considered other radical species.
