Reactions Of Alkenes

Question 1

Which are more reactive: alkenes or alkanes?

Answer 1

Alkenes

Question 2

Why are alkenes more reactive than alkanes?

Answer 2

This is because they contain a Pi bond and therefore the electrons in the Pi bond are more exposed. The Pi bond therefore breaks easily.

Question 3

Which is weaker the sigma bond or the Pi bond?

Answer 3

The Pi bond.

Question 4

What type of reactions do alkenes undergo?

Answer 4

Addition reactions

Question 5

Name four addition reactions of alkenes?

Answer 5

Hydrogen in the presence of a nickel catalyst
Halogens
Hydrogen halides
Steam in the presence of an acid catalyst

Question 6

What is formed from a hydrogenation reaction?

Answer 6

An alkane

Question 7

What is the alkene mixed with in a hydrogenation reaction?

Answer 7

Hydrogen

Question 8

Where is the hydrogen atom added in hydrogenation?

Answer 8

Across a double bond.

Question 9

At what temperature does hydrogenation occur?

Answer 9

432K

Question 10

In what type of reaction are the reactants passed over a nickel catalyst?

Answer 10

Hydrogenation

Question 11

How many bonds are hydrogenated in a hydrogenation reaction.

Answer 11

All of them so long as there is enough hydrogen molecules.

Question 12

How many hydrogen atoms are added to the double bond during hydrogenation?

Answer 12

2 atoms are added (so 1 molecule)

Question 13

What is the product of the halogenation of alkenes?

Answer 13

Haloalkane

Question 14

At what temperature does halogenation take place?

Answer 14

Room temperature

Question 15

What does bromine water test for?

Answer 15

Unsaturation

Question 16

What will happen to the bromine water if added to an alkene?

Answer 16

It will become colourless.

Question 17

Why does the bromine water turn colourless if added to an alkene?

Answer 17

Bromine is added across the double bond.

Question 18

What colour is unreacted bromine water?

Answer 18

Orange

Question 19

What happens if bromine water is added to an alkane?

Answer 19

Nothing- no bromine is added to the compound and so the bromine water stays orange.

Question 20

How should bromine water be added to a solution?

Answer 20

Dropwise

Question 21

What is the product of a reaction involving an alkene and a gaseous hydrogen halide?

Answer 21

A haloalkane

Question 22

What happens in the reaction of alkenes and halogen halides if the alkene is a liquid?

Answer 22

The hydrogen halide is bubbled through it.

Question 23

What does two liquid hydrogen halides can be reacted with an alkene to form a haloalkane?

Answer 23

Concentrated hydrochloric acid
Concentrated hydrobromic acid
These are essentially solutions of the hydrogen halides in water.

Question 24

In the reaction of alkenes and hydrogen halides, what state is the hydrogen halide usually in?

Answer 24

Gaseous unless it is concentrated HCl or concentrated HBr.

Question 25

What is formed in a hydration reaction?

Answer 25

Alcohols

Question 26

What catalyst is used in hydration?

Answer 26

Phosporic acid

Question 27

What is the formula of phosphoric acid?

Answer 27

H3PO4

Question 28

What is the alkene reacted with in hydration reactions?

Answer 28

Steam

Question 29

Where is the steam added?

Answer 29

Across the double bond.

Question 30

What reaction is used widely in industry?

Answer 30

Hydration- ethanol is produced from ethane.

Question 31

How many possible products are there in hydration reactions and reactions involving hydrogen halides?

Answer 31

There are many possible reactions.