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Edexcel IGCSE Chemistry alkenes

Practise alkene questions by identifying C=C bonds, drawing isomers and using bromine water to recognise addition reactions.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • Explain unsaturation from a C=C bond and hydrocarbon status from carbon and hydrogen only.
  • Draw displayed formulae for alkene isomers from molecular formulae such as C4H8.
  • Use bromine water decolourisation and dibromo products to identify addition reactions.

Covered syllabus points

4.23 Alkene functional group4.24 Alkene general formula4.25 Unsaturated hydrocarbons4.26 Alkene structures and isomers4.27 Alkene addition with bromine4.28 Bromine-water test

(d) Alkenes question 1

[Maximum number: 4]

This question is about hydrocarbons.

Question (a)

(a)

Another homologous series of hydrocarbons is the alkenes.

Alkenes are unsaturated hydrocarbons.

[ 4 ]

Question (i)

(i)

Give the general formula for the alkenes.

[ 1 ]

Question (ii)

(ii)

State the meaning of the term unsaturated.

[ 1 ]

Question (iii)

(iii)

Describe a test to show that a hydrocarbon is unsaturated.

[ 2 ]

(d) Alkenes question 2

[Maximum number: 5]

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.

[ 2 ]

Question (i)

(i)

Which of these types of reaction occurs between ocimene and bromine?

A

addition

B

polymerisation

C

precipitation

D

substitution

[ 1 ]

Question (ii)

(ii)

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 ]

(d) Alkenes question 3

[Maximum number: 2]

This question is about alkanes and alkenes.

Question (a)

(a)

Ethane and ethene each react with bromine, but under different conditions.

[ 1 ]

Question (i)

(i)

Give the colour change that occurs when ethene reacts with bromine water.

[ 1 ]

Question (b)

(b)

The diagram shows the displayed formulae of two compounds in the homologous series of alkenes.

Figure for Question (b) — Edexcel IGCSE Chemistry
[ 1 ]

Question (i)

(i)

Draw the displayed formula of another alkene that is an isomer of these two alkenes.

[ 1 ]
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