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Alkanes

  • 8 subtopics
  • 24 things to know
  • Unit AS 2

What Alkanes covers

Alkanes is examined in Unit AS 2, Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry, and drawn on again in Unit AS 3, Basic Practical Chemistry. It covers alkanes as saturated hydrocarbons, boiling points of alkanes and van der Waals' forces, boiling points of branched isomers, complete and incomplete combustion of alkanes, pollutants from alkane fuels and the atmosphere, catalytic converters, radicals, homolytic fission and heterolytic fission and free radical substitution of alkanes.

Where it is assessed

Unit AS 2

Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry, and again in Unit AS 3, Basic Practical Chemistry.

Check the CCEA specification ↗

The 8 subtopics

Each one has its own page.

What you need to know

Answer each one before you reveal it.

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Key term

Explain, in terms of van der Waals' forces, why boiling point rises with chain length.

Key term

Why does an alkane boil at a much lower temperature than an alcohol of similar relative molecular mass?

Evaluation

Give one argument in favour of continuing to burn hydrocarbon fuels and one argument against.

Key term

Outline how a heterogeneous catalyst brings about a reaction between two gases.

Key term

What is meant by the term hydrocarbon?

Key term

Explain, in terms of van der Waals' forces, why a branched alkane boils at a lower temperature than its unbranched isomer.

Key term

Which two products are always formed when an alkane burns completely?

Key term

Define the term radical.

Process

What type of mechanism operates when methane reacts with chlorine?

Key term

Why are alkanes described as saturated hydrocarbons?

Key term

Which of pentane and 2,2-dimethylpropane has the higher boiling point?

Key term

What condition is needed for the complete combustion of an alkane?

Key term

Name five pollutants produced during the combustion of alkane fuels.

Key term

What is the purpose of a catalytic converter in a car exhaust?

Key term

How is a radical represented in a chemical equation?

Key term

What conditions are required for the halogenation of an alkane?

Key term

State the general formula of the alkanes.

Key term

Why do van der Waals' forces act between all molecules?

Key term

Two isomers contain exactly the same number of electrons, so why do they boil at different temperatures?

Key term

Write the equation for the complete combustion of methane.

Process

How is carbon monoxide formed when a fuel burns in an engine?

Key term

Which metals are used as the catalyst in a catalytic converter?

Key term

Write the equation for the homolytic fission of a chlorine molecule.

Key term

Write the overall equation for the reaction of methane with chlorine to give chloromethane.

Take Alkanes further

The same content, four other ways.

Questions from this topic

Each one with the model answer underneath.

  1. 1

    What is meant by the term hydrocarbon?

    Model answer

    A hydrocarbon is a compound containing the elements carbon and hydrogen only.

  2. 2

    Why are alkanes described as saturated hydrocarbons?

    Model answer

    Every bond between the carbon atoms is a single bond, so each molecule already holds the largest possible number of hydrogen atoms and cannot take up any more.

  3. 3

    State the general formula of the alkanes.

    Model answer

    The alkanes have the general formula CₙH₂ₙ₊₂.

  4. 4

    Give the molecular formula of the unbranched alkane containing eight carbon atoms.

    Model answer

    Putting n = 8 into CₙH₂ₙ₊₂ gives the molecular formula C₈H₁₈.

  5. 5

    What type of bond joins the carbon atoms in an alkane?

    Model answer

    The carbon atoms are joined by single covalent sigma bonds formed by the head-on overlap of orbitals.

  6. 6

    State the bond angle around each carbon atom in an alkane and explain it.

    Model answer

    The bond angle is 109.5°, because each carbon atom has four bonding pairs of electrons that repel one another equally into a tetrahedral arrangement.

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Alkanes revision questions

What does Alkanes cover in CCEA A-Level Chemistry?
8 subtopics: alkanes as saturated hydrocarbons, boiling points of alkanes and van der waals' forces, boiling points of branched isomers, complete and incomplete combustion of alkanes, pollutants from alkane fuels and the atmosphere, catalytic converters, radicals, homolytic fission and heterolytic fission and free radical substitution of alkanes. Each one has its own page with questions and model answers.
How is Alkanes organised?
By the CCEA 1110 specification, subtopic by subtopic, so it matches the order you are taught it in.

Every question in Alkanes, on a schedule.

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