DP Chemistry (last assessment 2024)
Question 19N.3.hl.TZ0.12b
| Date | November 2019 | Marks available | [Maximum mark: 2] | Reference code | 19N.3.hl.TZ0.12b |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Compare | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 2]
19N.3.hl.TZ0.12b
Stearic acid (Mr = 284.47) and oleic acid (Mr = 282.46) have the same number of carbon atoms. The structures of both lipids are shown in section 34 of the data booklet.
(b)
The chemical change in stored fats causes rancidity characterized by an unpleasant smell or taste.
Compare hydrolytic and oxidative rancidity.
[2]
Markscheme
NOTE: Award [1] for any two sites or conditions from any of the four listed.
Accept “high temperature” for “heat”. Accept "lipase" for "enzyme".
Do not accept just “double bond”.
Accept “air” for “oxygen” and “UV/sun” for “light”.
Ignore any reference to heat/high temperature as a condition for oxidative.
