DP Chemistry (last assessment 2024)

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Question 20N.3.sl.TZ0.11b

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Date November 2020 Marks available [Maximum mark: 1] Reference code 20N.3.sl.TZ0.11b
Level sl Paper 3 Time zone TZ0
Command term Suggest Question number b Adapted from N/A
b.
[Maximum mark: 1]
20N.3.sl.TZ0.11b

Aspirin is formed by reacting salicylic acid with ethanoic anhydride. The structure of aspirin is given in section 37 of the data booklet.

(b)

Aspirin crystals are rinsed with water after recrystallization to remove impurities.
Suggest why cold water is used.

[1]

Markscheme

to avoid dissolving the crystals/aspirin ✔

Accept “to avoid loss of product” OR “aspirin is less soluble in cold water”.

Examiners report

While there were many good answers it was worrying to correct as many where the student clearly didn't establish a connection between solubility and purification. Many incorrect responses indicated the cold water was to "stay below the melting point of the aspirin" rather than relate it to the solubility of the final product.

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