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Date November 2019 Marks available 1 Reference code 19N.3.sl.TZ0.12
Level SL Paper 3 Time zone TZ0
Command term Deduce 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.

[1]
a.

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.

[2]
b(i).

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.

[1]
b(ii).

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 ✔

a.

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.

b(i).

NOTE: Accept a skeletal formula or a full or condensed structural formula.
Penalise missing hydrogens or bond connectivities once only in Option C.

b(ii).

Examiners report

[N/A]
a.
[N/A]
b(i).
[N/A]
b(ii).

Syllabus sections

Core » Topic 10: Organic chemistry » 10.1 Fundamentals of organic chemistry
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Options » C: Energy » C.2 Fossil fuels
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