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Grace Chemistry IGCSE > Topic 12 - Organics > Flashcards

Topic 12 - Organics Flashcards

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1
Q

Define hydrocarbon

A

A compound made up of only C and H atoms

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2
Q

Define crude oil

A

Mixture of millions of hydrocarbon s

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3
Q

How is crude oil processed?

A

Through fractional distillation

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4
Q

Describe the fractional distillation of crude oil

A

1) oil enters the fractionating column, heated until most of it has turned into a gas (bitumen is drained off at the bottom)
2) the column is hotter at the bottom and colder at the top
3) each molecule rises as a gas until it reaches its boiling point, then it condensed into a liquid; longer hydrocarbons have high BPs
4) each different hydrocarbon has a different boiling point - because of this, they all condense at different heights in the column
5) therefore molecules with similar boiling points are separated into the same columns
6) bubble caps in the fractionating column stop the separates liquids from running back down the column and remixing

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5
Q

What is the order of hydrocarbons in terms of boiling points

A 
Refinery gases
Gasoline
Kerosene
Diesel 
Fuel oil
Bitumen
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6
Q

Describe refinery gases

A

BPs less than 0°C

CH4 -> C4H10

Fuel for home Heating

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7
Q

Describe gasoline

A

BPs between 0°C and 150°C

C5H12 -> C9H20

Fuel for cars

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8
Q

Describe kerosene

A

BPs between 150°C and 200°C

C10H22 -> C14H30

Fuel for planes

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9
Q

Describe diesel

A

BPs between 200°C and 300°C

C15H32 -> C19H40

Fuel for trucks

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10
Q

Describe fuel oil

A

BPs between 300°C and 400°C

C20H42 ->C29H50

Fuel for ships

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11
Q

Describe bitumen

A

BPs more than 400°C

C30H62 and up

Used for making roads

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12
Q

Define alkanes

A

The main type of hydrocarbon found in fuel oil

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13
Q

Describe the general formula for alkanes

A

CnH2n+2

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14
Q

What is a homologous series?

A
  • same general formula
  • similar chemical reactions
  • trends in physical properties
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15
Q

What are isomers ?

A
  • same molecular formula

* different structural formula

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16
Q

State the names and formulas of the first 5 alkanes

A

1) methane (CH4)
2) ethane (C2H6)
3) propane (C3H8)
4) butane (C4H10)
5) pentane (C5H12)

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17
Q

Define saturated

A

Only containing single bonds

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18
Q

Why is CO toxic

A
  • binds irreversibly to haemoglobin

* reduces the amount of oxygen which can be transported

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19
Q

What is needed for alkane substitution and what does it produce

A

UV light

Haloalkanes (e.g. bromomethane)

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20
Q

What is needed for catalytic cracking

A

Powdered aluminium oxide (lowers Ea)

650°C (achieves Ea)

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21
Q

Why is catalytic cracking necessary

A

Oil supply is mostly long hydrocarbon chains

Oil demand is for shorter hydrocarbon chains

Catalytic cracking shortens alkane chains while also producing useful alkenes

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22
Q

State the general formula of alkenes

A

CnH2n

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23
Q

What is the functional group of alkenes

A

C=C

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24
Q

Define unsaturated

A

Does not only contain single bonds

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25
Q

What is an addition reaction with bromine used for

A

To tell the difference between alkanes and alkenes

26
Q

Describe and explain an addition reaction with bromine

A

1) Add the substance to bromine
2) shake it
3) if it stays the same, the substance is an alkane. If it goes colourless (the bromine has been used up), it is an alkene
4) this is because the bromine atoms add into the molecule where the gaps were, breaking the double bond (because the electrons from bromine repel the shared pair) and forming the haloalkane dibromoethane.

27
Q

What is needed for addition polymerisation of alkenes?

A

High temperature (breaking one of the C=C)

High pressure (joining them into a long chain)

28
Q

Describe polyethene

A 
H    H
          |     | 
—(— C - C —)— 
          |     |        n
         H    H

used: bags, drinks bottles

29
Q

Describe polypropene

A 
H     CH3
          |      |   
—(— C - C —)—
          |      |       n 
          H    H

Uses: crates, ropes

30
Q

Describe polychloroethene

A 
H     Cl
          |      | 
—(— C - C —)—
          |      |       n 
         H     H

Uses: guttering, wire insulators

31
Q

Describe polytetrafluoroethene (PTFE)

A 
F     F
          |      |
—(— C - C —)—
          |      |       n
          F     F

Uses: non-stick surfaces

32
Q

Why is it difficult to dispose of addition polymers ?

A

They are inert (unreactive -> don’t biodegrade) because the carbon-carbon bonds in the polymer chain are very strong and aren’t easily broken

Don’t burn because it can release toxic gases

33
Q

How can you dispose of addition polymers ?

A

1) recycle/ reuse
2) landfills
3) incinerate (use the energy released to generate electricity)

34
Q

What is the problem with incinerating addition polymers

A

It releases toxic gases:
• hydrogen chloride
• hydrogen cyanide

35
Q

What is the functional group for alcohols?

A

O-H

36
Q

What is the general formula for alcohols?

A

CnH2n+1OH

37
Q

What are the two ways of making ethanol?

A

1) hydration of ethane

2) fermentation of glucose

38
Q

Describe the hydration of ethene

A

Addition reaction, reversible

Ethene + water (steam) -> ethanol

Conditions:
• 300°C
• 65atm
• catalyst phosphoric acid (H3PO4)

Pros:
• really fast
• cheap because ethene is cheap and not much is wasted
• makes pure ethanol

Cons:
• high energy cost
• crude oil- raw material - non-renewable, will soon become v expensivo

39
Q

Describe the fermentation of glucose

A

Glucose -> 2 ethanol + 2CO2

Conditions:
• yeast (contains enzymes- naturally occurring catalysts)
• 30°C (optimum for yeast enzymes)
• without O2 (otherwise ethanoic acid is formed)

Pros:
• low energy cost
• sugar cane is renewable, as is yeast

Cons:
• makes impure ethanol -> needs to be distilled and purified
• slow

40
Q

What are the methods of alcohol oxidation?

A

1) combustion
2) microbial oxidation
3) potassium dichromate (VI) in dilute sulfuric acid : acidified

41
Q

Describe alcohol combustion

A

alcohol + oxygen -> CO2 + H20

Burns cleanly: blue, almost invisible flame

42
Q

Describe microbial oxidation of alcohols

A

Microbes contain enzymes, use alcohols as an energy source. They use oxygen in the air to oxidise alcohols

Alcohol + 2[o] -> carboxylic acid + water

43
Q

Describe the reaction between alcohols and acidified potassium dichromate (VI)

A

Alcohol + 2[o] -> carboxylic acid + water

Colour change: orange -> green

Oxidising agent = dichromate (VI)

44
Q

How to draw carboxylic acids

A

Functional group is

C=O
|
O - H

Fill up other C’s with H’s

45
Q

What happens when a carboxylic acid dissociates

A

Carboxylic acid loses the H in its functional group which becomes H+, the leftover O becomes O-

The substance “anoate” and is a salt
These salts always have 1- charge

46
Q

Describe the reaction between alcohols and carboxylic acids

A

Alcohol + carboxylic acid -> ester + water

47
Q

How do you draw an Ester?

A

Lose the H from the functional group of the carboxylic acid, lost the OH functional group of the alcohol

48
Q

What is the functional group of an Ester?

A

C=O
|
O

49
Q

How to make an ester in the lab

A

1) add a few drops of concentrated sulfuric acid into a boiling tube using a dropping pipette
2) add 10 drops of ethanoic acid
3) add an equal volume of ethanol
4) place the billing tube in a beaker of water and place on a tripod
5) beat using a Bunsen burner until the water starts to boil, then turn off the Bunsen
6) after 1 minute, remove the tube and allow it to cool
7) once cooled, pour the mixture into a test tube of sodium carbonate solution and mix - a layer of ester should form on top of the solution

50
Q

How to name an Ester:

A

Take the prefix of the alcohol and add ‘yl’ suffix - this is the first word

The second word is the name of the salt formed

51
Q

Describe ester properties

A
  • Smell sweet (like pear drops)
  • Volatile- evaporate easily
  • Used in perfumes
  • Used to make food flavourings
52
Q

What are the ways in which isomers are recognised?

A
  • different shaped carbon chains; straight or branched chains. These isomers have similar chemical properties, but their physical properties (e.g BP) differ
  • functional group in different place cause different physical properties
  • different functional groups. Could have the same number of carbon, oxygen and hydrogen atoms but have a different functional group- causes very different physical and chemical properties
53
Q

What is catalytic cracking?

A
  • a form of thermal decomposition
  • long-chain alkanes are split into more useful short-chain alkanes and alkenes
  • the alkane is heated until it is vaporised, it then breaks down when it comes into contact with the catalyst
54
Q

How does the combustion of fossil fuels cause acid rain?

A

1) when fossil fuels are burnt, sulfur dioxide and nitrogen oxides may be produced
2) the sulfur dioxide comes from the sulfur impurities in the hydrocarbon fuels
3) nitrogen oxides are created when the temperature is high enough for the nitrogen and the oxygen in the air to react- this often happens in car engine. Nitrogen oxides include nitrogen monoxide (NO) and nitrogen dioxide (NO2)
4) when sulfur dioxide and nitrogen oxides mix with the water vapour in the clouds they form dilute sulfuric and nitric acid
5) acid rain chases lakes to become acidic- many plants and animals die as a result

55
Q

Describe butene

A
  • but-1-ene has the C=C connecting the first and second C atoms
  • but-2ene has the C=C connecting the second and third C atoms
56
Q

Describe vinegar

A
  • Ethanoic acid dissolved in water

* Used for flavouring and preserving foods

57
Q

What are polymers?

A

Substances of high average relative molecules mass made up by joining lots of monomers (small, repeating units)

The monomers that make up addition polymers have a double covalent bond

58
Q

What is condensation polymerisation

A

Reacting two different types of monomer forms bonds between them, making polymer chains

Each monomers has to contain at least 2 functional groups, one on each end of the molecule. Each functional group reacts with the functional group of another monomer, creating long chains of alternating monomers.

For each new bond that forms, a molecule of water is lost

59
Q

How do polyesters form?

A

When docarboxylic acid monomers and diol monomers react together, forming an ester link

  O      O                     H  H
  ||      ||                      |    |
nC — C        + n HO-C-C-OH     —>
  ||      ||                      |    |
 HO    OH                  H   H
      O  O      H  H
      ||  ||       |    |        
-|—C-C-O-C-C-O—|- n     + 2n H2O
                    |    |
                   H   H
60
Q

Describe polyesters

A
  • some are biodegradable, m own as biopolyesters; they can be broken down by bacteria and other living organisms in the environment over time
  • because they can decompose, their pollutant effect is reduced

Grace Chemistry IGCSE (21 decks)

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