| Date | May 2019 | Marks available | 2 | Reference code | 19M.3.hl.TZ1.19 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Deduce | Question number | 19 | Adapted from | N/A |
Question
Aspirin can be obtained from salicylic acid.
Additional information can be obtained from the 1H NMR spectrum of aspirin.
Unreacted salicylic acid may be present as an impurity in aspirin and can be detected in the infrared (IR) spectrum.
Name the functional group and identify the absorption band that diff erentiates salicylic acid from aspirin. Use section 26 of the data booklet.
Name:
Absorption band:
Deduce the protons responsible for signals X and Y by marking them on the structure of aspirin in (a). Use section 27 of the data booklet.
Identify the splitting pattern of signals X and Y.
X:
Y:
Markscheme
Name:
hydroxyl [✔]
Absorption band:
3200–3600 «cm–1» [✔]
Note: Accept “phenol” OR “alcohol” but not “hydroxide”.
correct X [✔]
correct Y [✔]
Note: X and Y must be near the Hs.
X: singlet AND Y: singlet [✔]
Examiners report
Many candidates scored a mark for naming a functional group that differentiates salicylic acid from aspirin. Some incorrectly said ether or carboxylic acid. Many candidates also scored for identifying the absorption band although 1700-1750 was a popular incorrect answer.
There was considerable confusion with indicating protons responsible for 1H NMR signals. Often entire functional groups were circled or carbon atoms and not hydrogen atoms were circled.
There was also great difficulty in identifying the splitting pattern of the signals. It was rare to see both signals identified as singlets.
Syllabus sections
-
18M.3.hl.TZ2.11a:
Hemoglobin’s oxygen dissociation curve is shown at a given temperature. Sketch the curve on the graph at a higher temperature.
- 17N.3.hl.TZ0.14b: Outline the change in oxidation state of the iron ions in heme groups that occurs when...
-
18M.3.hl.TZ1.10a:
Outline why anthocyanins are coloured.
-
17M.3.hl.TZ2.14a:
Explain the shape of the curve from 0 to X kPa.
-
17M.3.hl.TZ1.16a:
Explain the shape of the curve at low oxygen partial pressure up to about 5 kPa.
-
18M.3.hl.TZ2.11b:
Outline two differences between normal hemoglobin and foetal hemoglobin.
- 18N.3.hl.TZ0.11a: A graph showing saturation of oxygen against partial pressure of oxygen is shown. Explain...
-
17M.3.hl.TZ2.14b:
Explain why carbon monoxide is toxic to humans.
-
19M.3.hl.TZ2.13a:
Outline why the complex formed between Fe2+ and oxygen is red. Refer to the diagram above and section 17 of the data booklet.
- 19M.3.hl.TZ2.13b(ii): Sketch another line to show the effect of an increase in body temperature on the oxygen...
-
17N.3.hl.TZ0.14a:
State the half-equation for the reduction of molecular oxygen to water in acidic conditions.
-
17M.3.hl.TZ1.16b.ii:
Outline the effect of decreasing pH on the oxygen saturation of hemoglobin.
-
17M.3.hl.TZ1.16b.i:
Sketch a graph on the axes above to show the effect of decreasing pH on the binding of oxygen to hemoglobin (the Bohr Effect).
- 16N.3.hl.TZ0.16b: With reference to its chemical structure, outline whether this pigment is found in aqueous...
- 16N.3.hl.TZ0.16a: Outline why this molecule absorbs visible light.
-
16N.3.hl.TZ0.16c:
A student investigated the ability of anthocyanins to act as pH indicators. He extracted juice from blackberries and used a UV-vis spectrophotometer to produce absorption spectra at different pH values. His results are shown below.
Deduce the colour of the juice at each pH, giving your reasoning. Use section 17 of the data booklet.
- 19N.3.hl.TZ0.15a: Describe the function of chlorophyll in photosynthesis.
- 19N.3.hl.TZ0.14a: The graph shows the change in oxygen partial pressure in blood, measured at different pH...
-
19M.3.hl.TZ1.11b:
The absorption spectrum of chlorophyll a is shown below.
Suggest how the combination of chlorophyll a and carotenoids is beneficial for photosynthesis.
-
18M.3.hl.TZ1.10b:
Explain why the blue colour of a quinoidal base changes to the red colour of a flavylium cation as pH decreases.
-
19M.3.hl.TZ1.11a:
The absorption spectrum of β-carotene is shown below.
Explain its colour in terms of its absorption bands. Use section 17 of the data booklet.
-
19M.3.hl.TZ2.13b(i):
Explain the shape of the curve.
- 20N.3.hl.TZ0.6c(i): Proteins are polymers of amino acids. Sketch and label two oxygen dissociation curves, one...
-
19M.3.hl.TZ1.19b(ii):
Identify the splitting pattern of signals X and Y.
X:
Y:
-
20N.3.hl.TZ0.6c(ii):
Proteins are polymers of amino acids.
Explain why the affinity for oxygen of foetal hemoglobin differs from that of adult hemoglobin.
-
18N.3.hl.TZ0.11b:
Explain why carbon monoxide is very toxic and how it may be possible to treat carbon monoxide poisoning.
