Question 19M.3.sl.TZ2.15
| Date | May 2019 | Marks available | [Maximum mark: 8] | Reference code | 19M.3.sl.TZ2.15 |
| Level | sl | Paper | 3 | Time zone | TZ2 |
| Command term | Determine, Outline, Predict, State | Question number | 15 | Adapted from | N/A |
A student synthesized aspirin, acetylsalicylic acid, in a school laboratory.
Predict one absorption band present in an infrared (IR) spectrum of aspirin, using section 26 of the data booklet.
[1]
Any one of:
1050–1410 «cm–1 due to C–O» [✔]
1700–1750 «cm–1 due to C=O in acids and esters» [✔]
2500–3000 «cm–1 due to O–H in acids» [✔]
2850–3090 «cm–1 due to C–H in alkanes and arenes» [✔]
This was a very well answered question. Even weak candidates were able to identify one correct wavenumber.
0.300 g of crude aspirin was dissolved in ethanol and titrated with sodium hydroxide solution, NaOH (aq).
NaOH (aq) + C9H8O4 (in ethanol) → NaC9H7O4 (aq) + H2O (l)
Determine the mass of aspirin which reacted with 16.25 cm3 of 0.100 mol dm−3 NaOH solution.
[2]
n(aspirin) «= n(NaOH) = × 0.100 mol dm–3 » = 1.625 × 10–3 «mol» [✔]
m(aspirin) «= 1.625 × 10–3 mol × 180.17 g mol–1 » = 0.293 «g» [✔]
Note: Award [2] for correct final answer.
This was a fairly well answered question with most students receiving both marks and many receiving one mark.
Determine the percentage purity of the synthesized aspirin.
[1]
« × 100% » = 97.7 «%» [✔]
This was a reasonably well answered question but quite a few students still struggled with what should have been a basic calculation, even when using ECF from the previous question.
Outline how aspirin can be chemically modified to increase its solubility in water.
[1]
convert to a salt
OR
react with sodium hydroxide/NaOH [✔]
Note: Accept other reactions forming soluble salts.
Accept “to ionize” but not “more polar”.
This question was reasonably answered by most students although some candidates confused the modification of aspirin into an ionic salt with the modification of the side chain of penicillin.
State why aspirin should not be taken with alcohol.
[1]
synergistic effect/increased toxicity
OR
increased risk of stomach/intestines bleeding/ulcers/heartburn
OR
increased risk of liver toxicity/damage
OR
increased risk of nausea/vomiting [✔]
This question was well answered.
Outline two factors which must be considered to assess the greenness of any chemical process.
[2]
Any two of:
energy requirements «during production» [✔]
use of toxic materials «during production» [✔]
use of solvents «that are not recycled» [✔]
emission of toxic by-products [✔]
quantity of waste produced
OR
atom economy [✔]
Note: Accept “E-factor/carbon efficiency/% of carbon in reactants vs products” for M1.
Accept references to materials being/not being recycled for M3.
This question was not very well answered by some students. Some students gave vague answers or responses not related to the concept of Green chemistry.