DP Chemistry (last assessment 2024)

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Question 20N.3.hl.TZ0.6a(ii)

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Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.3.hl.TZ0.6a(ii)
Level hl Paper 3 Time zone TZ0
Command term Deduce Question number a(ii) Adapted from N/A
a(ii).
[Maximum mark: 2]
20N.3.hl.TZ0.6a(ii)
(a(ii))

Proteins are polymers of amino acids.

The mixture is composed of glycine, Gly, and isoleucine, Ile. Their structures can be found in section 33 of the data booklet.

Deduce, referring to relative affinities and Rf, the identity of A1.

[2]

Markscheme

Ile AND larger Rf ✔

more soluble in non-polar solvent «mobile phase»
OR
not as attracted to polar «stationary» phase ✔

Only award M2 if Ile is identified in M1.

Examiners report

Few candidates recognised that A1 was Ile so no marks were scored. Even of those candidates that did identify A1 as IIe, many did not mention larger Rf and therefore M1 was lost. There appeared to be in general, poor understanding of the basic principles of paper chromatography.

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