DP Chemistry (last assessment 2024)

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Question 19M.3.hl.TZ2.22

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Date May 2019 Marks available [Maximum mark: 6] Reference code 19M.3.hl.TZ2.22
Level hl Paper 3 Time zone TZ2
Command term Determine, Outline, Predict, State Question number 22 Adapted from N/A
22.
[Maximum mark: 6]
19M.3.hl.TZ2.22

A student synthesized aspirin, acetylsalicylic acid, in a school laboratory.

(a)

Predict one absorption band present in an infrared (IR) spectrum of aspirin, using section 26 of the data booklet.

[1]

Markscheme

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» [✔]

Examiners report

This was a very well answered question. Even weak candidates were able to identify one correct absorption band present in an infrared spectrum of aspirin.

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)

(b(i))

Determine the mass of aspirin which reacted with 16.25 cm3 of 0.100 mol dm−3 NaOH solution.

[2]

Markscheme

n(aspirin) «= n(NaOH) =  16.25  c m 3 1000 × 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.

Examiners report

A significant number of candidates were able to calculate the mass of aspirin correctly.

(b(ii))

Determine the percentage purity of the synthesized aspirin.

[1]

Markscheme

«  0.293  g 0 .300 g × 100 % »= 97.7 «%»  [✔]

Examiners report

A significant number of candidates were able to calculate the percentage purity of aspirin correctly although some managed an ECF mark.

(c)

Outline how aspirin can be chemically modified to increase its solubility in water.

[1]

Markscheme

convert to a salt
OR
react with sodium hydroxide  [✔]

 

Note: Accept other reactions forming soluble salts.

Accept “to ionize” but not “more polar”.

Examiners report

This part was reasonably answered by most candidates.

(d)

State why aspirin should not be taken with alcohol.

[1]

Markscheme

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   [✔]

Examiners report

This part was well answered by the majority of the candidates.

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