| Date | November 2019 | Marks available | 2 | Reference code | 19N.3.sl.TZ0.14 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | 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
-
17M.3.sl.TZ2.14c.iii:
Suggest a reason why syngas may be considered a viable alternative to crude oil.
- 16N.3.sl.TZ0.12a: Discuss how the octane number changes with the molecular structure of the alkanes.
-
18M.3.sl.TZ1.10a:
Identify an element, other than carbon and hydrogen, found at significant concentrations in fossil fuels.
-
17M.3.sl.TZ2.14c.ii:
The Fischer-Tropsch process, an indirect coal liquefaction method, converts CO(g) and H2(g) to larger molecular weight hydrocarbons and steam.
Deduce the equation for the production of octane by this process.
-
19M.3.hl.TZ1.15c(i):
Methane can also be obtained by fractional distillation of crude oil.
[Source: Image used with kind permission of science-resources.co.uk]
Draw a circle on the diagram to show where the methane fraction is withdrawn.
-
19M.3.sl.TZ1.11c(i):
Methane can also be obtained by fractional distillation of crude oil.
Draw a circle on the diagram to show where the methane fraction is withdrawn.
- 16N.3.sl.TZ0.12b: Catalytic reforming and cracking reactions are used to produce more efficient fuels. Deduce...
-
19M.3.hl.TZ1.17a:
Ethanol has a Research Octane Number (RON) of 108.6.
Outline how higher octane fuels affect engine performance.
-
19M.3.hl.TZ2.15a:
Crude oil can be converted into fuels by fractional distillation and cracking.
Contrast these two processes.
-
17N.3.sl.TZ0.13a:
“Knocking” in an automobile (car) engine can be prevented by increasing the octane number of the fuel. Explain, including an equation with structural formulas, how heptane, C7H16, could be chemically converted to increase its octane number.
- 19N.3.sl.TZ0.12b(i): Reforming reactions are used to increase the octane number of a hydrocarbon fuel. Suggest...
- 19N.3.sl.TZ0.12a: Suggest why a high-octane number fuel is preferable.
- 19N.3.sl.TZ0.12b(ii): The 1H NMR spectrum of one of the products has four signals. The integration trace shows a...
-
18M.3.sl.TZ2.10b.i:
Formulate an equation for the cracking of C16H34 into two products with eight carbon atoms each.
-
19M.3.sl.TZ1.13a:
Ethanol has a Research Octane Number (RON) of 108.6.
Outline how higher octane fuels affect engine performance.
-
18N.3.sl.TZ0.10a:
Formulate equation(s) for the conversion of coal and steam to methane.
-
18M.3.sl.TZ2.10c.ii:
The performance of hydrocarbons as fuels can be improved by catalytic reforming.
Outline how catalytic reforming increases a fuel’s octane rating.
-
19M.3.sl.TZ2.10a:
Crude oil can be converted into fuels by fractional distillation and cracking.
Contrast these two processes.
-
18M.3.sl.TZ2.10b.ii:
Identify, giving a reason, which product in (b)(i) could be used in petrol (gasoline).
-
18M.3.sl.TZ2.10c.i:
Outline how higher octane fuels help eliminate “knocking” in engines.
-
19M.3.hl.TZ2.15c:
Hydrocarbons need treatment to increase their octane number to prevent pre-ignition (knocking) before they can be used in internal combustion engines.
Describe how this is carried out and the molecular changes that take place.
-
19M.3.hl.TZ1.15c(ii):
List the following products, which are also obtained by fractional distillation, according to decreasing volatility: asphalt, diesel, gasoline, lubricating motor oil.
-
18N.3.hl.TZ0.13c:
Calculate the mass, in kg, of carbon dioxide produced by the complete combustion of 72.0 dm3 octane, C8H18.
Density of C8H18 = 703 g dm−3
C8H18 (l) + 12.5O2 (g) → 8CO2 (g) + 9H2O (g)
-
17M.3.sl.TZ1.16a:
State how these gases are produced, giving the appropriate equation(s).
- 20N.3.sl.TZ0.9b: State a class of organic compounds found in gasoline.
-
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.
-
18N.3.hl.TZ0.13a:
Formulate equation(s) for the conversion of coal and steam to methane.
-
17M.3.sl.TZ1.16b:
Outline how the carbon monoxide is then converted to a hydrocarbon fuel.
-
19M.3.sl.TZ1.11c(ii):
List the following products, which are also obtained by fractional distillation, according to decreasing volatility: asphalt, diesel, gasoline, lubricating motor oil.
- 20N.3.hl.TZ0.11d: A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a...
-
17M.3.sl.TZ2.14c.i:
Suggest an equation for the production of syngas from coal.
- 20N.3.hl.TZ0.11b: State a class of organic compounds found in gasoline.
-
19M.3.sl.TZ2.10c:
Hydrocarbons need treatment to increase their octane number to prevent pre-ignition (knocking) before they can be used in internal combustion engines.
Describe how this is carried out and the molecular changes that take place.
-
18M.3.sl.TZ1.10b:
Petroleum contains many hydrocarbons. Explain how these are separated by fractional distillation.
-
19M.3.sl.TZ1.13b:
Show that, for combustion of equal masses of fuel, ethanol (Mr = 46 g mol−1) has a lower carbon footprint than octane (Mr = 114 g mol−1).
-
20N.3.sl.TZ0.9c:
Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a car. Exclude any discussion of cost.
-
17N.3.sl.TZ0.13b:
Many like to refer to our “carbon footprint”. Outline one difficulty in quantifying such a concept.
-
18N.3.sl.TZ0.10c:
Calculate the mass, in kg, of carbon dioxide produced by the complete combustion of 72.0 dm3 octane, C8H18.
Density of C8H18 = 703 g dm−3
C8H18 (l) + 12.5O2 (g) → 8CO2 (g) + 9H2O (g)
-
20N.3.hl.TZ0.11c:
Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a car. Exclude any discussion of cost.
