| Date | November 2019 | Marks available | 1 | Reference code | 19N.3.sl.TZ0.14 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | State | Question number | 14 | Adapted from | N/A |
Question
Ethanol is a biofuel that can be mixed with gasoline.
Write the equation for the complete combustion of ethanol.
Outline the evidence that relates global warming to increasing concentrations of greenhouse gases in the atmosphere.
Explain, including a suitable equation, why biofuels are considered to be carbon neutral.
State the type of reaction that occurs when ethanol reacts with vegetable oil to form biodiesel.
Markscheme
C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (l) ✔
Any two of:
«showing strong» correlation between «atmospheric» CO2 concentration/greenhouse gas concentration and average «global/surface/ocean» temperature ✔
lab evidence that greenhouse gases/CO2 absorb(s) infrared radiation ✔
«advanced» computer modelling ✔
ice core data ✔
tree ring data ✔
ocean sediments / coral reefs / sedimentary rocks data ✔
NOTE: Do not accept “global warming” for “average temperature”.
Do not accept “traps/reflects heat” OR “thermal energy”.
Evidence must be outlined and connected to data.
Accept references to other valid greenhouse gases other than carbon dioxide/CO2, such as methane/CH4 or nitrous oxide/N2O.
biofuel raw material/sugar/glucose formed by photosynthesis
OR
biofuel raw material/sugar/glucose uses up carbon dioxide during its formation
OR
biofuel from capturing gases due to decaying organic matter formed from photosynthesis ✔
6CO2 (g) + 6H2O (l) → C6H12O6 (aq) + 6O2 (g) ✔
NOTE: Accept arguments based on material coming from plant sources consuming carbon dioxide/carbon for M1.
transesterification
OR
«nucleophilic» substitution/SN ✔
Examiners report
Syllabus sections
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18M.3.sl.TZ1.11a.ii:
State the formula of a fuel that might be produced from the vegetable oil whose formula is shown.
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18M.3.hl.TZ1.13b:
State the formula of a fuel that might be produced from the vegetable oil whose formula is shown.
- 16N.3.sl.TZ0.14a: State the equation for the complete transesterification of the triglyceride given below with...
- 18N.3.sl.TZ0.11c.ii: Describe how vegetable oils can be converted to a more suitable fuel.
- 18N.3.sl.TZ0.11c.i: State a physical property of vegetable oils that makes them very difficult to use as fuel in...
- 18N.3.sl.TZ0.11b: Light can be absorbed by chlorophyll and other pigments. Consider molecules A and B...
- 18N.3.hl.TZ0.14b.i: State a physical property of vegetable oils that makes them very difficult to use as fuel in...
- 18N.3.hl.TZ0.14b.ii: Describe how vegetable oils can be converted to a more suitable fuel.
-
17M.3.sl.TZ1.15d:
Determine the specific energy, in kJg−1, and energy density, in kJcm−3, of a particular biodiesel using the following data and section 1 of the data booklet.
Density = 0.850 gcm−3; Molar mass = 299 gmol−1;
Enthalpy of combustion = 12.0 MJmol−1.
- 17N.3.sl.TZ0.15b: Vegetable oils are too viscous for use as liquid fuels. Describe, using an equation, how a...
-
18M.3.hl.TZ1.13a:
Outline the major technical problem affecting the direct use of vegetable oils as fuels in internal combustion engines and the chemical conversion that has overcome this.
-
17M.3.sl.TZ1.15b:
Deduce the formula of the biodiesel formed when the vegetable oil shown is reacted with the reagents in (a).
- 17N.3.sl.TZ0.15a: State the structural feature of chlorophyll that enables it to absorb visible light.
-
17M.3.sl.TZ2.12b:
Coloured molecules absorb sunlight. Identify the bonding characteristics of such molecules.
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19M.3.hl.TZ1.17c:
Biodiesel containing ethanol can be made from renewable resources.
Suggest one environmental disadvantage of producing biodiesel from renewable resources.
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19N.3.sl.TZ0.14a:
Write the equation for the complete combustion of ethanol.
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16N.3.sl.TZ0.14b:
Outline why the fuel produced by the reaction in (a) is more suitable for use in diesel engines than vegetable oils.
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18M.3.sl.TZ2.14b:
Outline why the ester product of this reaction is a better diesel fuel than pentyl octanoate.
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19M.3.sl.TZ1.13c:
Biodiesel containing ethanol can be made from renewable resources.
Suggest one environmental disadvantage of producing biodiesel from renewable resources.
-
18M.3.sl.TZ2.14a:
Deduce the equation for the transesterification reaction of pentyl octanoate, C7H15COOC5H11, with methanol.
-
17M.3.sl.TZ1.15c:
Explain, in terms of the molecular structure, the critical difference in properties that makes biodiesel a more suitable liquid fuel than vegetable oil.
-
19N.3.sl.TZ0.14c:
Explain, including a suitable equation, why biofuels are considered to be carbon neutral.
-
19M.3.sl.TZ2.12a:
The structure of chlorophyll is given in section 35 of the data booklet.
State the feature of the chlorophyll molecule that enables it to absorb light in the visible spectrum.
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17M.3.sl.TZ1.15a:
State two reagents required to convert vegetable oil to biodiesel.
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20N.3.sl.TZ0.9d:
A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a mixture over the use of pure gasoline. Exclude any discussion of cost.
-
19M.3.sl.TZ2.12b:
Evaluate the use of biodiesel in place of diesel from crude oil.
Strength:
Limitation:
-
18M.3.sl.TZ1.11b:
Outline why biofuels are considered more environmentally friendly, even though they produce more carbon dioxide per kJ of energy than petroleum based fuels.
- 20N.3.hl.TZ0.11d: A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a...
-
18M.3.sl.TZ1.11a.i:
Outline the major technical problem affecting the direct use of vegetable oils as fuels in internal combustion engines and the chemical conversion that has overcome this.
-
19M.3.hl.TZ2.17:
This question is about biofuel.
Evaluate the use of biodiesel in place of diesel from crude oil.
- 20N.3.sl.TZ0.9e: Contrast the molecular structures of biodiesel and the vegetable oil from which it is formed.
