Alkenes

Question 1

Describe catalytic cracking

Answer 1

Decomposition of long chain alkanes –> shorter chain alkanes and alkenes
600-700 degrees
silica or alumina

Question 2

Why is cracking necessary

Answer 2

Shorter chains = higher demand e.g. petrol
(more useful)
produces alkenes used in making polymers and ethanol

Question 3

What is the functional group of alkenes

Answer 3

> C=C<
Double bond

Question 4

What is the general formula for alkenes

Answer 4

CnH2n

Question 5

Why are alkenes classified as unsaturated

Answer 5

They contain a double bond

Question 6

Describe reaction of alkenes with bromine

Answer 6

UV light not needed
Addition reaction (across =)
Colour change (orange –> colourless)
test for presence of alkene

Question 7

How does bromine water help distinguish between alkane and alkene

Answer 7

In absence of UV light alkanes will not react to bromine. Water will stay orange
Alkanes will, so colour change to colourless