CAIE IGCSE Chemistry 11.5 Alkenes Question Bank

Practise alkene reactions and tests by using C=C bonding, cracking equations, bromine water and addition-product reasoning.

Exam points

use C=C and bromine water decolourisation to recognise unsaturated compounds
complete cracking equations that form alkenes, hydrogen or smaller alkanes
explain addition reactions from a single product and a reacting carbon-carbon double bond

Covered syllabus points

11.5.1—Bonding in alkenes includes a double 11.5.2—Manufacture of alkenes and hydrogen by 11.5.3—Reasons for the cracking of larger 11.5.4—Test to distinguish between saturated 11.5.5—In an addition reaction only one 11.5.6—Alkene addition reactions with

[Maximum number: 1]

State one gas which:

is unsaturated

[Maximum number: 3]

The chemical equation for the complete combustion of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ , is shown.

\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2}+3 \mathrm{H}_{2} \mathrm{O}

The energy released when one mole of ethanol undergoes complete combustion is 1280 kJ .
Part of the energy level diagram for this reaction is shown.

Figure for Question 11.5 Alkenes question 2 — CAIE IGCSE Chemistry

(a)

Dodecane is an alkane containing 12 carbon atoms. Ethanol can be manufactured from dodecane in a two-stage process.

In stage 1, each molecule of dodecane is converted into three molecules of ethene and one molecule of another hydrocarbon.

[ 3 ]

(i)

Name the process which occurs in stage 1.

[ 1 ]

(ii)

Write a chemical equation for the reaction which occurs in stage 1.

In stage 2, ethene reacts with steam to produce ethanol.

[ 2 ]

$\mathrm{C}_{12} \mathrm{H}_{26} \rightarrow 3 \mathrm{C}_{2} \mathrm{H}_{4}+\mathrm{C}_{6} \mathrm{H}_{14}$

M1 $\mathrm{C}_{12} \mathrm{H}_{26}$

M2 rest of equation

[Maximum number: 2]

Fluorine is a Group VII element. Fluorine forms compounds with metals and non-metals.

Tetrafluoroethene is an unsaturated compound with the formula $\mathrm{C}_{2} \mathrm{~F}_{4}$ . Tetrafluoroethene is the monomer used to make the polymer poly(tetrafluoroethene).

Describe a test to show that tetrafluoroethene is unsaturated.
test
observations

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Covered syllabus points

11.5 Alkenes question 1

11.5 Alkenes question 2

Question (a)

Question (i)

Question (ii)

11.5 Alkenes question 3