DP Chemistry (first assessment 2025)
Question 20N.1B.SL.TZ0.c
| Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.1B.SL.TZ0.c |
| Level | SL | Paper | 1B | Time zone | TZ0 |
| Command term | Suggest | Question number | c | Adapted from | N/A |
c.
[Maximum mark: 1]
20N.1B.SL.TZ0.c
Suggest why the titration must be conducted quickly even though a low temperature is maintained.
[1]
Markscheme
equilibrium shifts to left
OR
more ethanoic acid is produced «as ethanoic acid is neutralized»
OR
prevents/slows down ester hydrolysis ✔
Accept “prevents equilibrium shift” if described correctly without direction.
Examiners report
Not well answered and of the few students that replied correctly most referred to preventing equilibrium shift and few candidates identified the direction of the shift. It was rather common to see answers where Le Chatelier's principle was stated without any attempt in adapting it to the context. Very few students described the specific equilibrium shift that could occur during the titration, changing the results.
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.