7.4 Organic Chemistry (catalytic cracking and steam cracking)

Question 1

What is the equation for catalytic cracking?

Answer 1

long chain alkane –> shorter chain alkane + alkene

Question 2

What is cracking?

Answer 2

The process in which long chain hydrocarbons are split into shorter, more useful hydrocarbons

Question 3

What type of reaction is cracking?

Answer 3

thermal decomposition reaction

Question 4

What are the conditions for catalytic cracking?

Answer 4

• reactant heated to vapour
• reactant passed over a hot catalyst

Question 5

What are the conditions for steam cracking?

Answer 5

• heated to vapour
• mixed with steam and heated to high temperatures

Question 6

Describe the process of catalytic cracking? (3)

Answer 6

1. Heat the long chained hydrocarbons until they vaporise into a gas
2. The vapour is passed over hot powdered aluminium oxide catalyst
3. This breaks the long chain molecules on the surface of the catalyst, into a shorter alkane and an alkene

Question 7

Describe the process of steam cracking?

Answer 7

1. Heat the long-chained hydrocarbons unti they vapourise into a gas
2. Mix vapour with steam and heat to a very high temperature
3. This produces short chained hydrocarbons

Question 8

What are the products of cracking?

Answer 8

alkane and alkene

Question 9

What are the products of cracking used as?

Answer 9

used as polymers and starting materials for synthesis

Question 10

How is steam cracking different from catalytic cracking?

Answer 10

• there is no catalyst involved in steam cracking
• instead the vapourised long chain hydrocarbon is mixed with steam at very high temperatures

Question 11

True or false. In cracking, the number of carbon and hydrogen atoms in the reactants and products are always balanced?

Answer 11

true

Question 12

How can the long chains produced by fractional distillation be made shorter?

Answer 12

through cracking