Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AQA A Level Chemistry > 3.4 Alkenes > Flashcards

3.4 Alkenes Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

What is an alkene?

A

Unsaturated hydrocarbons with a C=C double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the general formula of an alkene?

A

CnH2n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why is there no rotation about the C=C double bond?

A

Due to the pi orbital - electron density above and below the single bond, which holds the carbon atoms in place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Are they more or less reactive than alkanes? Why?

A

More reactive, due to high electron density of double bond and the fact that the pi-bond is slightly easier to break

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What intermolecular forces of attraction do they have

A

Only van de Waals due to non-polar bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Are they soluble in water?

A

No, non-polar bonds (van de Waals < hydrogen bonds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Name and describe the three different types of isomers alkenes can have

A

Chain isomers - Branched chains
Position isomers - C=C on different double bonds
Geometric E-Z isomers - Z is when 2 highest number atomic chains are on the same side of the double bond; E is when they’re on opposite sides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Write an equation for the complete combustion of pent-2-ene

A

CH3CH=CHCH2CH3 + 7.5 O2 —> 5CO2 + 5H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is an electrophile

A

Electron deficient atoms / ions which accept a pair of electrons (here from the C=C double bond)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the most stable carbocation intermediate? Why?

A

Alkyl groups have a positive inductive effect, so the most stable carbocation is the one bonded to most other carbon atoms i.e. A tertiary carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Major products will be formed from which kind of carbocations?

A

Tertiary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What conditions are needed for the electrophilic addition of H2O to an alkene?

A

Acid catalyst, usually phosphoric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the products for the electrophilic addition of H2O to an alkene?

A

An alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What conditions are need for the electrophilic addition of a hydrogen halide to an alkene?

A

Room temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What conditions are needed for the electrophilic addiction of a halogen molecule to an alkene

A

Room temperature and organic solvent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does a molecule with a non-polar bond react as if it is an electrophile

A

C=C double bond with high electron density induces a temporary dipole in the halogen molecule —> δ+ atom attracted to double bond

17
Q

How would turn the product (from sulphuric acid + ethene) into an alcohol and how does this show that sulphuric acid catalyses the addition of water to an alkene?

A

Add water
H2SO4 reforms, showing it catalyses the hydration of alkenes

18
Q

What is an addition polymer?

A

Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule

19
Q

What are monomers? What form do they usually take?

A

Molecules which combine to make a monomer
Usually have a C=C double bond which breaks to leave a repeating pattern

20
Q

Give three uses of poly(chloroethene) / PVC

A

Drainpipes
Vinyl
Aprons

21
Q

Give two examples of plasticisers

A

Esters and phthalates

22
Q

What are plasticisers?

A

Small molecules which get between polymer chains to force them apart and allow them to slide over one another

23
Q

How do the physical properties of PVC change due to a plasticiser? What applications does this lead to?

A

PVC with a plasticiser become flexible, used for aprons
Without a plasticiser, PVC is rigid and used for drainpipes

24
Q

Why do many things containing C-C and C-H bonds not decompose easily?

A

Bonds are non-polar so not attacked by enzymes

25
Q

Why is a lack of biodegradability in compounds with C-C and C-H bonds a problem?

A

Disposal is very problematic

26
Q

What is mechanical recycling?

A

Where plastics are separated into different types, washed, ground down, melted and re-moulded

27
Q

What is mechanical recycling used for?

A

Soft drinks bottles —> fleeces

28
Q

What is feedstock recycling?

A

Plastics heated to a temperature which breaks polymer bonds, leaving original monomers which can be made into new polymers

29
Q

What is feedstock recycling used for?

A

Making totally new plastics

30
Q

What is a problem with recycling?

A

Each time a thermosoftening plastic is melted down and remoulded, their properties degrade, so they can only be remoulded a limited number of times

AQA A Level Chemistry (34 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions