Cracking Crude Oil

Question 1

What does cracking mean?

Answer 1

Splitting up long chain hydrocarbons

Question 2

“a lot of longer molecules produced from fractional distillation are turned into smaller ones by the process of cracking” is this correct?

Answer 2

Yes

Question 3

What do long chain hydrocarbons form?

Answer 3

Thick gloppy liquids like tar which aren’t very useful

Question 4

What are some useful products of cracking long chain hydrocarbons?

Answer 4

• petrol for cars
• paraffin for jet fuels
• ethene for making plastics

Question 5

What type of reaction is cracking?

Answer 5

A thermal decomposition reaction ~ breaking molecules down by heating them

Question 6

What are the steps of cracking?

Answer 6

1) heat the long chain hydrocarbon to vaporise it (turn to a gas)
2) the vapour is hen passed over a powdered catalyst at a temp of 400 - 700 (degrees celsius)
3) aluminium oxide is the catalyst used
4) the long chain molecules split apart or “crack”on the surface of the catalyst
5) the products of cracking are alkanes and unsaturated hydrocarbons called alkenes

Question 7

Alkenes have what type of bond?

Answer 7

A double bond (C=C)

Question 8

Why are alkenes knows as ‘unsaturated’?

Answer 8

Because they can make as many bonds as they want (the double bond can open up, allowing the 2 carbon atoms to bond with other atoms)

Question 9

What is the formula for alkenes?

Answer 9

Cn H2n

Question 10

Is ethene has 2 carbon atoms, how many hydrogen atoms does it have?

Answer 10

C2 H(2x2) = 4

Question 11

How can you test for an alkene?

Answer 11

By adding the substance to bromine water ~ an alkene will decolourise the bromine water - turning it from Orange to colourless. This is because the double bond has opened up and formed bonds with the bromine