Question 20N.3.sl.TZ0.c
| Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.3.sl.TZ0.c |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | c | Adapted from | N/A |
An investigation was carried out to determine the effect of chain length of the alcohol on the equilibrium constant, , for the reversible reaction:
The reactants, products and the catalyst form a homogeneous mixture.
Fixed volumes of each alcohol, the ethanoic acid and the sulfuric acid catalyst were placed in sealed conical flasks.
At equilibrium, the flasks were placed in an ice bath, and samples of each flask titrated with to determine the ethanoic acid concentration present in the equilibrium mixture.
The following processed results were obtained.
© International Baccalaureate Organization 2020
Suggest why the titration must be conducted quickly even though a low temperature is maintained.
[1]
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.
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.
