Question 19M.3.hl.TZ1.13
Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.hl.TZ1.13 |
Level | hl | Paper | 3 | Time zone | TZ1 |
Command term | Explain | Question number | 13 | Adapted from | N/A |
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.
[2]
ascorbic acid: many hydroxyl/OH groups AND retinol: few/one hydroxyl/OH group
OR
ascorbic acid: many hydroxyl/OH groups AND retinol: long hydrocarbon chain [✔]
ascorbic acid: «many» H-bond with water
OR
retinol: cannot «sufficiently» H-bond with water [✔]
Note: Do not accept “OH−/hydroxide”.
Explanations of why ascorbic acid is soluble in water and retinol is not were poor. Very few referred to the ability to form hydrogen bonds with water. Some said “hydroxide” instead of “hydroxyl” and thus failed to score a mark. Commonly, candidates scored 1 mark for saying that ascorbic acid has many hydroxyl groups and retinol has a long hydrocarbon chain.
