DP Chemistry (last assessment 2024)
Question 22M.1.sl.TZ2.20
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.1.sl.TZ2.20 |
| Level | sl | Paper | 1 | Time zone | TZ2 |
| Command term | Deduce | Question number | 20 | Adapted from | N/A |
20.
[Maximum mark: 1]
22M.1.sl.TZ2.20
What is the strongest acid in the equation below?
H3AsO4 + H2O H2AsO4− + H3O+ Kc = 4.5 × 10−4
A. H3AsO4
B. H2O
C. H2AsO4−
D. H3O+
[1]
Markscheme
D
Examiners report
A challenging question that combined interpreting the implications of the value of the equilibrium constant with the Brønsted-Lowry concept. Most candidates focused on BL theory and the forward reaction only. 36% of the candidates answered the question correctly by selecting the acid involved in the backward reaction.