Alkenes

Question 1

What is an alkene?

Answer 1

An unsaturated hydrocarbon

Question 2

What is a hydrocarbon?

Answer 2

A compound that contains only carbon and hydrogen

Question 3

What is an unsaturated compound?

Answer 3

A compound that contains double bonds

Question 4

What is the general formula for alkenes?

Answer 4

CnH2n

Question 5

What type of isomerism can alkenes exhibit?

Answer 5

Geometric isomerism

Question 6

What are stereoisomers?

Answer 6

Isomers that have the same molecular formulae but a different spatial arrangement of atoms

Question 7

Why do alkenes exhibit geometric isomerism?

Answer 7

There is restricted rotation around the double bond

Question 8

When does geometric isomerism arise?

Answer 8

it arises when:

• there is restricted rotation around the double bond
• there are two different groups atoms attached at both ends of the double bond

Question 9

What is an electrophile?

Answer 9

A lone pair acceptor

Question 10

What is an addition reaction?

Answer 10

A reaction where a molecule joins to an unsaturated molecule to form a saturated molecule

Question 11

What is carbocation?

Answer 11

A positive ion with the positive charge on a carbon atom

Question 12

Why are alkenes reactive?

Answer 12

There is a high electron density in the double bond

Question 13

What types of bonds are in double covalent bond?

Answer 13

Pi and Sigma bonds

Question 14

Why Pi bonds vulnerable to attack by electrophiles?

Answer 14

They are exposed and have a high electron density

Question 15

What is an electrophile?

Answer 15

A lone pair acceptor

Question 16

What can be used to test for unsaturation?

Answer 16

Bromine water

Question 17

What happens when a solution is made containing an alkene and bromine water?

Answer 17

The solution decolourises

Orange to colourless

Question 18

Why does bromine water decolourise the solution?

Answer 18

The Br atom is added onto the double bond by electrophilic addition

Question 19

What is formed when alkenes react with hydrogen halide?

Answer 19

Halogenalkanes

Question 20

What happens when hydrogen halides are added onto unsymmetrical alkenes?

Answer 20

Two products are produced

Major and minor

Question 21

What determines the atom economy of each product formed?

Answer 21

The stability of the carbocation intermediate determines the atom economy of each product

Question 22

What is an alkyl?

Answer 22

Alkanes with a hydrogen removed

Question 23

What happens when there are more alkyl groups around a carbocation?

Answer 23

The carbocation becomes more stable because there are more alkyl groups feeding electrons towards the positive charge

Question 24

What is the stability of a primary carbocation?

Answer 24

Least stable

Question 25

What is the stability of a tertiary carbocation?

Answer 25

Most stable

Question 26

What is formed when alkenes react with cold, concentrated sulfuric acid?

Answer 26

Alkyl hydrogensulfates

Question 27

What is formed when water is added to the alkyl hydrogensulfate in warm conditions?

Answer 27

An alcohol is formed

Question 28

Alkyl hydrogensulfates are formed through what type of reaction?

Answer 28

Electrophilic addition

Question 29

An alcohol is formed through what type of reaction?

Answer 29

Hydrolysis

Question 30

What is hydrolysis reaction?

Answer 30

A reaction where a molecule is split by the addition of water

Question 31

What is the purpose of the sulfuric acid in the reaction?

Answer 31

It is a catalyst because it is regenerated

Question 32

What is a polymer?

Answer 32

A long chained molecule formed from lots of repeated molecules joined together

Question 33

What is a monomer?

Answer 33

A small molecule repeated many times making a polymer

Question 34

Give examples of polymers

Answer 34

DNA Proteins Synthetics

Question 35

What is an addition polymer?

Answer 35

A polymer made from alkenes when they act as monomers because their double bonds open up joining together to long chains

Question 36

What are the properties of polyalkanes?

Answer 36

Unreactive Non-polar Saturated

Question 37

Why are polyalkanes unreactive?

Answer 37

The C-C and C-H bonds are strong

Question 38

What are the properties of long,straight chains?

Answer 38

Rigid | Strong

Question 39

What are the properties of short, branched chains?

Answer 39

Flexible | Weak

Question 40

What happens as the length of the chains increases?

Answer 40

The longer the polymer chains, the closer together they can get and the stronger the van der Waals forces between the chains

Question 41

How can polymers be modified?

Answer 41

They can be modified using plasticisers which makes them more flexible

Question 42

How do plasticisers make polymers more flexible?

Answer 42

The plasticiser molecules get between the polymer chains and push them apart The intermolecular forces between the chains weaken Therefore, the chains slide more making the polymer easy to bend

Question 43

What is PVC formed from?

Answer 43

Chloroethene

Question 44

What are the properties of rigid PVC?

Answer 44

Long, closely packed polymer chains Hard Brittle

Question 45

What is rigid PVC be used for?

Answer 45

Drainpipes | Window frames

Question 46

What are the properties of plasticised PVC?

Answer 46

Flexible compared to rigid PVC

Question 47

What is plasticised PVC used for?

Answer 47

Electrical cable insulation Flooring tiles Clothing