Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Heptane, $\text{C}_7\text{H}_{16}$, is an unwanted part of petrol because it combusts very violently and causes ‘knocking’ in an engine.
(a(i))[2]

State the meanings of the terms structural isomers and chiral.

(a(ii))[4]

Give the structures and names of the two structural isomers of $\text{C}_7\text{H}_{16}$ that contain a chiral centre.

(b(i))[1]

Write an equation for the complete combustion of heptane.

(b(ii))[1]

Write an equation for the incomplete combustion of heptane leading to the production of a solid pollutant.

(b(iii))[1]

Incomplete combustion can also release unburnt hydrocarbons. State one environmental consequence of this.

(c(i))[1]

Name the mechanism of the reaction between heptane and chlorine in the presence of UV light. $\text{C}_7\text{H}_{16} + \text{Cl}_2 \rightarrow \text{C}_7\text{H}_{15}\text{Cl} + \text{HCl}$

(c(ii))[5]

Describe this mechanism, using suitable equations and including the names of each stage in the process.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: Structural isomers: share the same molecular formula but have different structural formulae

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