Organic Chemistry - Alkanes and Alkenes Flashcards Preview

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Flashcards in Organic Chemistry - Alkanes and Alkenes Deck (33):
1

What does saturated mean?

There are no double or triple bonds.

• Alkanes are saturated.

2

What does unsaturated mean?

Contains a double/triple/etc bond.

• Alkenes are unsaturated.

3

What is general formula for Alkanes?

CnH2n+2

4

What is the general formula for Alkenes?

CnH2n

5

What are isomers?

Molecules with the same molecular formula, but different structural formulae.

6

What happens when methane reacts with bromine in the presence of UV light?

bromomethane is formed

7

What does homologous series mean?

A homologous series is "family" of organic compounds which:

- contain the same functional group therefore similar chemical properties

- differ from one another by CH₂

- because they get larger they have a trend in physical properties (like the fractions in crude oil)

8

How to test for an Alkenes?

Add ethene to bromine water, shake it, and it will become colourless. Addition reaction.

9

How can polymers be made?

• addition polymerisation

• condensation polymerisation

10

What is addition polymerisation?

The joining together or many small molecules called monomers.

11

What is condensation polymerisation?

• Two different monomers are added to create a polymer, which also produces a small molecule, which is normally water, but sometimes HCl.

12

What's an example of condensation polymerisation?

• The making of nylon.

13

How can ethanol be produced?

• fermentation

• production from ethene

14

Uses of polypropene

• ropes

• crates

15

Uses of polyethene

• plastic bags

• plastic bottles

16

Uses of polychloroethene

• drainpipes

• replacement windows

17

What are the problems associated with disposing of polymers?

• Polymers or plastics cannot be broken down due to their many strong covalent bonds they are inert (unreactive).

• The methods of disposal are landfill or incineration.

18

What does biodegradable mean?

Something which can decompose in the ground and is broken down by living organisms/bacteria.

19

What happens during the hydration of ethene?

  • Ethene and steam are passed over phosphoric acid (acts as a catalyst) to create ethanol.
  • Temperature is about 300ºC.
  • Pressure is at about 60-70 atmospheres.
  • C2H4 + H2O → C2H5OH. 

20

What happens during the manufacture of ethanol using fermentation?

  • A sugar (e.g. glucose) in converted into ethanol using yeast.
  • The temperature is about 30ºC.
  • The pressure is normal.

21

What are the advantages of producing ethanol by hydration?

  • Quite cheap because ethene (which comes from crude oil) is not very expensive and not much is wasted.
  • The rate of reaction is very fast.
  • The product made is of a very high quality (pure).
  • Low labour costs

22

What are the disadvantages of producing ethanol using hydration?

  • Ethene comes from crude oil, which is a finite resource and therefore will run out.
  • The process is done at a high temperature and high pressure and it is a continuous process, so the equipment needed is expensive.

23

What are the advantages of fermentation to produce ethanol?

  • Sugar and yeast are both renewable resources.
  • Equipment needed is quite basic and quite cheap.

24

What are the disadvantages of fermentation to produce ethanol?

  • The ethanol is impure (and not very concentrated) and needs to be distilled and purified.
  • The rate of reaction is very slow.
  • It is done as a batch process and therefore labour costs are quite expensive.

25

What happens during the dehydration of ethanol?

  • The water is removed from ethanol to produce ethene in a dehydration reaction.
  • Ethanol vapour is passed over a hot catalyst of aluminium oxide (Al2O3) which provides a large surface area for the reaction.
  • C2H5OH → C2H4 + H2

26

What is made during the complete combusion of alkanes?

Complete combusion occurs when there is plenty of oxygen to burn with the alkane.

  • alkane + oxygen → carbon dioxide + water (+ energy)
  • CH4 + 2O2 → CO2 + 2H2O

27

What is made during the incomplete combustion of alkanes?

Incomplete combustion occurs when there is not enough oxygen to burn with the alkane.

  • alkane + oxygen → carbon + carbon monoxide + carbon dioxide + water (+ energy)
  • the symbol equation depends on how much oxygen is present 

28

What would the repeat unit for poly(ethene) look like?

A image thumb
29

What would the repeat unit for poly(propene) look like?

A image thumb
30

What would the repeat unit for poly(chloroethene) look like?

A image thumb
31

Complete the chemical equation for the reaction between ethene and bromine water

C2H4 + Br

C2H4Br2

32

Why is the second method a safer way to measure the boiling points of organic compounds?

Q image thumb

Organic compounds are flammable, so the second method reduces the risk of fire. 

33

What is a raw material which can be used as a source of C6H12O6?

Cane sugar / sugar beet.