DP Chemistry (last assessment 2024)
Question 22M.2.hl.TZ2.7a(iii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.hl.TZ2.7a(iii) |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Justify | Question number | a(iii) | Adapted from | N/A |
a(iii).
[Maximum mark: 1]
22M.2.hl.TZ2.7a(iii)
The overall equation for the production of hydrogen cyanide, HCN, is shown below.
CH4 (g) + NH3 (g) +O2 (g) → HCN (g) + 3H2O (g)
(a(iii))
Justify whether a 1.0 dm3 solution made from 0.10 mol NH3 and 0.20 mol HCl will form a buffer solution.
[1]
Markscheme
no AND is not a weak acid conjugate base system
OR
no AND weak base «totally» neutralized/ weak base is not in excess
OR
no AND will not neutralize small amount of acid ✔
Accept “no AND contains 0.10 mol NH4Cl + 0.10 mol HCl”.
Examiners report
Poorly answered revealing little understanding of buffering mechanisms, which is admittedly a difficult topic.
