DP Chemistry (first assessment 2025)
Question 22N.1A.HL.TZ0.23
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.HL.TZ0.23 |
| Level | HL | Paper | 1A | Time zone | TZ0 |
| Command term | Apply | Question number | 23 | Adapted from | N/A |
23.
[Maximum mark: 1]
22N.1A.HL.TZ0.23
Which of these changes would shift the equilibrium to the right?
[Co(H2O)6]2+ (aq) + 4Cl− (aq) [CoCl4]2− (aq) + 6H2O (l)
I. Addition of 0.01 M HCl
II. Addition of concentrated HCl
III. Evaporation of water
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
[1]
Markscheme
C
Examiners report
This proved to be the most difficult question on the paper with <30% of candidates deducing which changes would shift the equilibrium to the right and success rate seemed to be only weakly related to overall performance. The most popular answer was (D), indicating that most students did not realise that adding dilute HCl would add much more water than Cl−.
Syllabus sections
Reactivity 2. How much, how fast and how far? » Reactivity 2.3—How far? The extent of chemical change » Reactivity 2.3.4—Le Châtelier’s principle enables the prediction of the qualitative effects of changes in concentration, temperature and pressure to a system at equilibrium. Apply Le Ch.telier’s principle to predict and explain responses to changes of systems at equilibrium.