5.1 Cracking Hydrocarbons

Question 1

How can large hydrocarbon molecules be broken down?

Answer 1

By cracking

Question 2

What 2 ways can cracking be done?

Answer 2

By heating a mixture of hydrocarbon vapours and steam to a very high temperature, or by passing hydrocarbon vapours over a hot catalyst

Question 3

What happens during cracking?

Answer 3

Thermal decomposition reactions produce a mixture of smaller molecules

Question 4

What are some of the smaller molecules produced from cracking called?

Answer 4

Alkanes

Question 5

What are alkanes useful as?

Answer 5

Fuels

Question 6

What type of hydrocarbons are alkanes?

Answer 6

Saturated

Question 7

What is the general formula for hydrocarbons?

Answer 7

CnH2n+2

Question 8

What are the other smaller molecules produced from cracking?

Answer 8

Alkenes

Question 9

What are alkenes?

Answer 9

Unsaturated hydrocarbons because they contain fewer hydrogen atoms than alkanes with the same number of carbon atoms

Question 10

What is the general formula for an alkene?

Answer 10

CnH2n

Question 11

What is an example of a cracking reaction?

Answer 11

Decane –> pentane, propene and ethene

Question 12

What do alkenes have?

Answer 12

A double bond that makes them more reactive

Question 13

What type of conditions are needed for cracking?

Answer 13

800 degrees celsius and a catalyst