DP Chemistry (last assessment 2024)

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Question 19M.2.hl.TZ1.h

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.2.hl.TZ1.h
Level hl Paper 2 Time zone TZ1
Command term Suggest Question number h Adapted from N/A
h.
[Maximum mark: 1]
19M.2.hl.TZ1.h

Benzoic acid, C6H5COOH, is another derivative of benzene.

Suggest how benzoic acid, Mr = 122.13, forms an apparent dimer, Mr = 244.26, when dissolved in a non-polar solvent such as hexane.

[1]

Markscheme

«intermolecular» hydrogen bonding    [✔]

 

Note: Accept diagram showing hydrogen bonding.

Examiners report

The other question where only 10 % of the candidates earned a mark. Few identified hydrogen bonding as the reason for carboxylic acids forming dimers. There were many G2 forms stating that the use of the word “dimer” is not in the syllabus, however the candidates were given that a dimer has double the molar mass and the majority seemed to understand that the two molecules joined together somehow but could not identify hydrogen bonding as the cause.

Syllabus sections