DP Chemistry (last assessment 2024)

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Question 19N.3.hl.TZ0.15

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Date November 2019 Marks available [Maximum mark: 6] Reference code 19N.3.hl.TZ0.15
Level hl Paper 3 Time zone TZ0
Command term Compare and contrast, Describe, Explain Question number 15 Adapted from N/A
15.
[Maximum mark: 6]
19N.3.hl.TZ0.15
(a)

Describe the function of chlorophyll in photosynthesis.

[2]

Markscheme

absorbs/traps light «energy» ✔

initiates redox reactions
OR
transfers electrons ✔

(b)

Compare and contrast the structures of starch and cellulose.

One similarity:

One difference:

[2]

Markscheme

One similarity:
1−4/glycosidic linkage
OR
glucose monomers/residues ✔

NOTE: Accept “both are polysaccharides”.

One difference:
starch has α-glucose AND cellulose has β-glucose «monomers»
OR
starch can form coiled/spiral/helical chains «and straight chains» AND cellulose cannot/can only form straight chains/can only form a linear structure
OR
starch «in amylopectin» also has 1−6 glycosidic links AND cellulose does not ✔

NOTE: Accept "cellulose has alternate glucose monomers upside down with respect to each other AND starch does not".

(c)

Explain why maltose, C12H22O11, is soluble in water.

[2]

Markscheme

«solubility depends on forming many» H-bonds with water ✔
maltose has many hydroxyl/OH/oxygen atom/O «and forms many H-bonds» ✔

NOTE: Reference to “with water” required.
Accept “hydroxy” for “hydroxyl” but not “hydroxide/OH–”.
Reference to many/several OH groups/O atoms required for M2.

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