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AQA A Level Chemistry

3.3.2
Alkanes

AQA 3.3.2 covers alkanes as saturated hydrocarbons: the fractional distillation of crude oil, thermal and catalytic cracking, complete and incomplete combustion, the pollutants from internal combustion engines and their removal, sulfur dioxide from fuels, and the free-radical substitution of methane by chlorine.

Exam Paper
Paper 2
7405/2
Specification Points
3.3.2.1 – 3.3.2.4
4 AQA sections
Topic Parts
4 parts
16 revision pages
Exam Board
AQA
AQA 7405
Specification Coverage

3.3.2 Alkanes – AQA A Level Chemistry

The following AQA specification points outline the knowledge and skills students are expected to demonstrate for Alkanes.

3.3.2 Alkanes

3.3.2.1
Fractional distillation of crude oil
Alkanes are saturated hydrocarbons.
Petroleum is a mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation.
3.3.2.2
Modification of alkanes by cracking
Cracking involves breaking C-C bonds in alkanes.
Thermal cracking takes place at high pressure and high temperature and produces a high percentage of alkenes (mechanism not required).
Catalytic cracking takes place at a slight pressure, high temperature and in the presence of a zeolite catalyst and is used mainly to produce motor fuels and aromatic hydrocarbons (mechanism not required).
Students should be able to:
1
explain the economic reasons for cracking alkanes
3.3.2.3
Combustion of alkanes
Alkanes are used as fuels.
Combustion of alkanes and other organic compounds can be complete or incomplete.
The internal combustion engine produces a number of pollutants including NOx, CO, carbon and unburned hydrocarbons.
These gaseous pollutants from internal combustion engines can be removed using catalytic converters.
Combustion of hydrocarbons containing sulfur leads to sulfur dioxide that causes air pollution.
Students should be able to:
1
explain why sulfur dioxide can be removed from flue gases using calcium oxide or calcium carbonate
3.3.2.4
Chlorination of alkanes
The reaction of methane with chlorine.
Students should be able to:
1
explain this reaction as a free-radical substitution mechanism involving initiation, propagation and termination steps