DP Chemistry (first assessment 2025)
Question 19M.2.HL.TZ2.b
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ2.b |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Suggest | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 2]
19M.2.HL.TZ2.b
Alcohol levels in the breath can also be determined using IR spectroscopy.
Suggest, giving a reason, which bond’s absorbance is most useful for detecting ethanol in breath.
Bond:
Reason:
[2]
Markscheme
Bond:
C–O
OR
C–H [✔]
Reason:
cannot use O–H bonds as in water «found in breath» [✔]
Note: Accept “C–O/C–H «bonds in molecules in breath» most likely to be in ethanol”.
Do not apply ECF here.
Examiners report
Most candidates incorrectly identified O-H, failing to realise it is unsuitable due to its abundant presence in the breath.
Syllabus sections
Structure 3. Classification of matter » Structure 3.2—Functional groups: Classification of organic compounds » Structure 3.2.9—Infrared (IR) spectra can be used to identify the type of bond present in a molecule. Interpret the functional group region of an IR spectrum, using a table of characteristic frequencies (wavenumber/cm–1).