Cracking

Question 1

Describe the purpose of cracking.

Answer 1

• It is the thermal decomposition of large, saturated hydrocarbon molecules (alkanes) into smaller, more useful ones, some of which are unsaturated (alkenes)
• It involves breaking strong covalent bonds, so you need lots of energy

Question 2

Explain why cracking is necessary.

Answer 2

• Longer molecules produced from fractional distillation need to be cracked into smaller ones as there’s more demand for products like petrol and diesel
• Alkene molecules produced by cracking can be used to make polymers (plastics)

Question 3

State the conditions for the process of cracking.

Answer 3

• Aluminium oxide catalyst
• 400°C - 700°C
• 70 atmospheres of pressure

Question 4

Recall which fractions are non-renewable fossil fuels obtained from crude oil.

Answer 4

• Petrol
• Kerosene
• Diesel oil

Question 5

Recall from where methane gas is obtained.

Answer 5

It is a non-renewable fossil fuel found in natural gas