Question 20N.3.sl.TZ0.d
| Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.3.sl.TZ0.d |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | Question number | d | 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
An additional experiment was conducted in which only the sulfuric acid catalyst was titrated with . Outline why this experiment was necessary.
[1]
to determine volume/moles of used up by the catalyst/sulfuric acid «in the titration»
OR
to eliminate/reduce «systematic» error caused by acid catalyst ✔
Do not accept “control” OR “standard” alone.
Some students achieved on mark. Many answers referred simple to "control" or "standard" underlining the lack of some skills as also identified in the Internal assessment. Once again very few students had the specific details necessary to explain why this separate titration was needed in their response to receive a mark.
