Chemistry 9701 · AS & A Level · 10.2

10.2 — practice question

Alkanes belong to a homologous series of organic molecules. They are usually unreactive and are often employed as fuels.
(a)[2]

Define the term homologous series.

(b)[2]

Give two reasons to account for the general unreactivity of alkanes.

(c)[1]

Alkanes with low relative molecular mass, $M_r$, are more useful than those in heavier crude oil fractions. Name the process used to obtain alkanes with low $M_r$ from heavier crude oil fractions.

(d(i))[2]

Hexane, $\mathrm{C_6H_{14}}$, has four structural isomers. Fig. 3.1 shows hexane and two of its structural isomers. Complete Fig. 3.1 by drawing the structures of C and D, the other two structural isomers of hexane.

(d(ii))[3]

A, B and hexane have different boiling points. Put A, B and hexane in order of increasing boiling point. Explain your answer.

(e(i))[1]

Hexane can be converted into compounds E and F at high temperature and pressure. Fig. 3.2 shows the reaction scheme involving hexane, E and F. Identify a suitable reagent for reaction 3.

(e(ii))[2]

Use the data in Fig. 3.2 and in Table 3.1 to calculate the enthalpy change of reaction 2, $\Delta H_2$.

(e(iii))[1]

Write an equation for the complete combustion of hexane.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: (family of molecules / compounds / series with) the same general formula

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