6B: Alkanes Flashcards
Use PPQs for spec points: 16
What is the general formula for alkanes?
Cn H2n+2
What sort of hydrocarbons are alkanes and cycloalkanes?
Saturated hydrocarbons
Describe cracking of hydrocarbons and why it is useful.
The thermal decomposition of alkanes.
Forms shorter chain alkanes, which have higher demand.
Forms alkenes, which are used in making plastics.
Define reforming of hydrocarbons.
The processing of straight-chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion.
What pollutants are formed during the combustion of alkane fuels?
Carbon monoxide,
oxides of nitrogen and sulfur,
carbon particulates,
unburned hydrocarbons
What problem arises from carbon monoxide formed from the combustion of fuels?
Toxic
What problem arises from oxides of nitrogen and sulfur formed from the combustion of fuels?
Acid rain
How does the use of a catalytic converter solve some problems caused by pollutants?
Catalyses the conversion of toxic carbon monoxide and nitrogen oxides to non-toxic CO2 and N2
What alternative fuels can be used instead of non-renewable fossil fuels?
Biodiesel,
alcohols derived from renewable sources such as plants
What is a radical,
how is it represented in mechanisms,
and how is it formed?
A species with an unpaired electron,
represented in mechanisms by a single dot,
formed by homolytic fission of a covalent bond
Reaction of alkanes with oxygen in air:
Products
Complete combustion: Carbon dioxide and water
Incomplete combustion: Carbon monoxide and water
Describe the reaction:
Alkane -> carbon dioxide + water
React with oxygen in air,
Complete combustion.
Describe the reaction:
Alkane -> carbon monoxide + water
React with oxygen in air,
Incomplete combustion.
Reaction of alkanes with halogens:
Condition,
Mechanism,
Products.
UV light,
Free radical substitution,
Haloalkane + hydrogen halide
Describe the reaction:
Alkane -> haloalkane
React with halogens under UV light,
Free radical substitution.
