Edexcel IGCSE Chemistry 4.17 Catalytic Cracking

Practise converting long-chain alkanes into shorter alkanes and alkenes using the required catalyst and temperature.

Exam points

state 600–700°C with silica, alumina or zeolite as the cracking catalyst
balance carbon and hydrogen atoms when completing a cracking equation
identify products as a mixture containing shorter-chain alkanes and alkenes

[Maximum number: 3]

Crude oil is a mixture of hydrocarbons.

(a)

Catalytic cracking is used to convert long-chain alkanes into shorter-chain alkanes.

[ 1 ]

(i)

Name the catalyst used in catalytic cracking.

[ 1 ]

alumina / silica

Accept:
- aluminium oxide
- silicon dioxide
- $\ce{Al2O3}$
- $\ce{SiO2}$
- zeolite(s)
- aluminosilicate(s)

(b)

Catalytic cracking also produces alkenes.
$\ce{C11H24}$ can undergo cracking to give pentane ( $\ce{C5H12}$ ) and two different alkenes.
Complete the equation for this cracking reaction.

$\ce{C11H24}$ -> $\ce{C5H12}$ + ................................ + ................................

[ 2 ]

$\ce{C11H24 -> C5H12 + C2H4 + C4H8}$

Marking guidance:
- Alkenes can be in either order.
- 1 mark for $\ce{C2H4}$ .
- 1 mark for $\ce{C4H8}$ .

Allow:
- $\ce{C6H12}$ / $\ce{2C3H6}$ / $\ce{C3H6}$ + $\ce{C3H6}$ for 1 mark
- correct displayed formulae

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4.17 Catalytic cracking question 1

Question (a)

Question (i)

Question (b)