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Edexcel IGCSE Chemistry 4.25 unsaturated hydrocarbons

Practise unsaturated-hydrocarbon questions by using displayed formulae to identify C=C bonds and carbon-hydrogen-only composition.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • State that unsaturated compounds contain a carbon-carbon double bond or multiple bond.
  • Explain from a displayed formula why ethene or ocimene is an unsaturated hydrocarbon.

4.25 Unsaturated hydrocarbons question 1

[Maximum number: 4]

Ocimene is an organic compound that gives some plants their particular smell.
The molecular formula of ocimene is C10H16\mathrm{C}_{10} \mathrm{H}_{16}

Question (a)

(a)

The displayed formula of ocimene is

Figure for Question (a) — Edexcel IGCSE Chemistry

Explain why ocimene is described as an unsaturated hydrocarbon.

[ 3 ]

Question (b)

(b)

Ocimene is an alkene.

[ 1 ]

Question (i)

(i)

Many alkenes have the general formula CnH2n\mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}}

Suggest why ocimene does not have this general formula.

[ 1 ]
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