Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Crude oil consists of a complex blend of hydrocarbon molecules. Fractional distillation is used to separate the hydrocarbons in crude oil because the different hydrocarbon molecules have different boiling points.
(a)[2]

Explain why the hydrocarbon molecules found in crude oil have varying boiling points.

(b)[1]

Suggest why some hydrocarbon molecules are further processed by cracking.

(c(i))[1]

Write the equation for the cracking reaction where one mole of dodecane, $\text{C}_{12}\text{H}_{26}$, is cracked to form two moles of ethene and one mole of a different hydrocarbon molecule.

(c(ii))[1]

Give the full name of the process that produces poly(ethene) from ethene.

(c(iii))[2]

Give two reasons why poly(ethene) should be reused or recycled instead of simply being thrown away.

(c(iv))[2]

A section of a polymer chain, made by the same kind of process as poly(ethene), is shown. Give the displayed formula of the monomer that was used to make this polymer.

(iii)[2]

Give two reasons why poly(ethene) should be reused or recycled instead of simply being discarded.

(iv)[2]

A section of a polymer chain, made by the same process type as poly(ethene), is shown. Give the displayed formula of the monomer from which this polymer was made.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Hydrocarbon molecules of different sizes contain different numbers of electrons

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