Cracking Hydrocarbons

Question 1

Describe long chain hydrocarbons

Answer 1

• high boiling point
• viscous
• darker in colour

Question 2

Describe short chain hydrocarbons

Answer 2

• low boiling point
• less vicious
• paler colour

Question 3

What is cracking a form of

Answer 3

Thermal decomposition

Question 4

What does cracking produce

Answer 4

Alkenes and short chain hydrocarbons

Question 5

What are the benefits of cracking

Answer 5

• alkenes can be used to make polymers
• large hydrocarbons are not efficient, don’t flow easily and are hard to ignite
• large HDC burn with a smokey flame while shorter HDC burn with a clean flame
• higher demand for shorter HDC
• large HDC do not release much energy per given mass

Question 6

What are the conditions for cracking

Answer 6

• catalyst = aluminium oxide or silica

- 600-700°C

Question 7

Describe cracking

Answer 7

• heat the parrafin
• heat the catalyst
• the parrafin will vaporise and cracks as it passes over the heated catalyst
• small alkanes collect at the end of the boiling tube, while alkene gas is collected over water