Question 23M.3.SL.TZ2.11
| Date | May 2023 | Marks available | [Maximum mark: 6] | Reference code | 23M.3.SL.TZ2.11 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Determine, Explain, Identify, Suggest, Write | Question number | 11 | Adapted from | N/A |
Photosynthesis enables green plants to store energy from sunlight as glucose.
Write the equation for photosynthesis.
[1]
6CO2 (g) + 6H2O (l) → C6H12O6 (aq) + 6O2 (g) ✓
Identify the structural feature that allows chlorophyll to absorb light.
Use section 35 of the data booklet.
[1]
conjugated «electronic» structure/delocalized «pi» electrons/alternate «single and» double bonds ✓
Accept “many/delocalized double bonds”.
Do not accept “tetrapyrrole group” alone without reference to idea of conjugation.
Explain how photosynthesis is being employed to control global warming.
[2]
reduces/sequesters CO2/carbon dioxide «concentration from atmosphere» ✓
«planting» more plants/trees ✓
Do not accept “carbon capture” alone for M1.
Do not accept just “plants/trees” alone for M2.
Glucose can be converted to ethanol through fermentation:
C6H12O6 (aq) → 2C2H5OH (aq) + 2CO2 (g)
Determine the energy efficiency of this conversion in terms of the enthalpies of combustion of the reactants and products. Use section 13 of the data booklet.
[1]
«(2x −1367 / −2803) × 100 =» 97.54 %
OR 2.46 % loss «in energy efficiency» ✓
Suggest one reason, other than energy density and specific energy, why ethanol may be considered a more useful fuel than glucose.
[1]
liquid
OR
easier ignition
OR
more volatile ✓
Accept “complete combustion more likely”“
OR
“better octane rating”
OR
“engine must be converted in order to use glucose”.
Do not accept “less viscous”.