| Date | May 2018 | Marks available | 2 | Reference code | 18M.3.sl.TZ2.9 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | 9 | Adapted from | N/A |
Question
Explain the solubility of vitamins A and C using section 35 of the data booklet.
Markscheme
Vitamin A:
fat soluble/soluble in non-polar solvents AND non-polar/long hydrocarbon backbone/chain
Vitamin C:
water soluble AND contains 4 hydroxyl groups/contains many hydroxyl groups/forms «many» H-bonds with water
Accept “Vitamin A: fat soluble/soluble in non-polar solvents as it contains only one hydroxyl group whose H-bonds with water are not strong enough to overcome London/dispersion/vdW forces between Vitamin A molecules”.
Accept “lipid” for “fats”.
Accept “alcohol” OR “hydroxy” OR “OH groups” for “hydroxyl” but not “hydroxide”.
Award [1 max] for “Vitamin A: fat soluble AND Vitamin C: water soluble” with no or incomplete explanation.
[2 marks]
Examiners report
Syllabus sections
- 20N.3.sl.TZ0.7a: The diverse functions of biological molecules depend on their structure and shape. Classify...
- 19N.3.hl.TZ0.14c: Vitamins are organic compounds essential in small amounts. State the name of one functional...
- 19N.3.sl.TZ0.10a: State the name of one functional group common to all three vitamins shown in section 35 of...
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19M.3.hl.TZ1.13:
Ascorbic acid and retinol are two important vitamins.
Explain why ascorbic acid is soluble in water and retinol is not. Use section 35 of the data booklet.
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18N.3.sl.TZ0.5b:
Suggest why it is advisable for those living in northerly or southerly latitudes (that is away from the equator) to take vitamin D supplements during the winter.
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19M.3.hl.TZ2.11c:
Lecithin aids the body’s absorption of vitamin E.
Suggest why vitamin E is fat-soluble.
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19M.3.sl.TZ2.7d:
Lecithin aids the body’s absorption of vitamin E.
Suggest why vitamin E is fat-soluble.
- 17N.3.sl.TZ0.10b: State one function of vitamin D in the body.
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17M.3.sl.TZ1.13d:
The solubility of a vitamin depends on its structure.
Identify the vitamin given in section 35 of the data booklet that is the most soluble in water.
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19M.3.sl.TZ1.10:
Ascorbic acid and retinol are two important vitamins.
Explain why ascorbic acid is soluble in water and retinol is not. Use section 35 of the data booklet.
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18M.3.sl.TZ1.7c.ii:
Predict the solubility of retinol (vitamin A) in body fat, giving a reason. Use section 35 of the data booklet.
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17M.3.sl.TZ2.11:
Suggest, in terms of its structure, why vitamin D is fat-soluble using section 35 of the data booklet.
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17N.3.sl.TZ0.10a:
Explain, at the molecular level, why vitamin D is soluble in fats. Use section 35 of the data booklet.
- 20N.3.hl.TZ0.8a: The diverse functions of biological molecules depend on their structure and shape. Classify...
