| Date | November 2019 | Marks available | 1 | Reference code | 19N.3.sl.TZ0.12 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | 12 | Adapted from | N/A |
Question
Octane number is a measure of the performance of engine fuel.
Suggest why a high-octane number fuel is preferable.
Reforming reactions are used to increase the octane number of a hydrocarbon fuel.
Suggest the structural formulas of two possible products of the reforming reaction of heptane, C7H16.
The 1H NMR spectrum of one of the products has four signals. The integration trace shows a ratio of the areas under the signals of 9 : 3 : 2 : 2.
Deduce the structural formula of the product.
Markscheme
low knocking/auto-ignition
NOTE: Do not accept “pre-ignition”.
OR
more efficient fuel
NOTE: Accept “less CO2 emissions since knocking engine uses more fuel «to produce the same power»”.
OR
high compression
OR
more power extracted
OR
more air going into engine / turbocharging
OR
less engine damage ✔
Any two of:
NOTE: Accept skeletal formulas or full or condensed structural formulas.
Accept any other branched cycloalkane that contains 7 carbons.
Do not accept any alkenes.
Penalise missing hydrogens or bond connectivities once only in Option C.
Accept hydrogen as the second product if the first product is toluene or a cycloalkane.
NOTE: Accept a skeletal formula or a full or condensed structural formula.
Penalise missing hydrogens or bond connectivities once only in Option C.
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Draw a circle on the diagram to show where the methane fraction is withdrawn.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Draw a circle on the diagram to show where the methane fraction is withdrawn.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.TZ0.12b(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.
-
19N.3.sl.TZ0.14b:
Outline the evidence that relates global warming to increasing concentrations of greenhouse gases in the atmosphere.
-
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.
