DP Chemistry (last assessment 2024)

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Question 17N.3.sl.TZ0.13a

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Date November 2017 Marks available [Maximum mark: 3] Reference code 17N.3.sl.TZ0.13a
Level sl Paper 3 Time zone TZ0
Command term Explain Question number a Adapted from N/A
a.
[Maximum mark: 3]
17N.3.sl.TZ0.13a

Much of our energy needs are still provided by the refined products of crude oil.

(a)

“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.

[3]

Markscheme

CH3CH2CH2CH2CH2CH2CH3 → CH3CH(CH3)CH2CH(CH3)2

OR

CH3CH2CH2CH2CH2CH2CH3 → 

isomerisation/reforming/platforming/cracking

Pt/Re/Rh/Pd/Ir

OR

catalyst

A structural formula is only required for the organic product, not heptane.

Accept any correctly balanced equation showing increased branching or cyclization OR aromatization OR cracking.

Suitable supports for catalysts may be included for M3 (eg silica, alumina, zeolite) but the symbol or name of an appropriate metal must be given (typically a noble metal). Ignore temperature and other conditions.

Award M2 AND M3 for “catalytic isomerisation” OR “catalytic reforming” OR “catalytic cracking”.

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