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Chemistry > Topic 9: Hydrocarbons, Alchols And Carboxylic Acids > Flashcards

Topic 9: Hydrocarbons, Alchols And Carboxylic Acids Flashcards

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1
Q

What is a hydrocarbon?

A

Molecular compounds that contain only carbon and hydrogen.

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2
Q

What are alkanes and what is their general formula?

A

Alkanes are a group of hydrocarbon molecules based on a chain of carbon atoms. They have the general formula CnH2n+2.

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3
Q

What are the first 4 members of the alkane homologous series?

A

Number of carbon in chain: Alkane: Molecular formula:
1 Methane CH4
2 Ethane C2H6
3 Propane C3H8
4 Butane C4H10

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4
Q

What does saturated mean?

A

Molecules are saturated if all the carbon covalent bonds are single bonds e.g alkanes.

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5
Q

What does unsaturated mean?

A

Hydrocarbon which at least 1 double covalent bond between the adjacent carbon atoms are unsaturated.

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6
Q

What is the general formula for alkenes?

A

CnH2n

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7
Q

What are the first three members of the alkene homologous series?

A

Ethene C2H4
Propane C3H6
Butene C4H8

It is not possible for their to be (meth)ene with one carbon because there cannot be a double covalent bond and there has to be because alkenes are unsaturated.

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8
Q

What is an isomer?

A

Molecules with the same molecular formula but a different arrangement of of atoms are called isomers.

A functional group can be in different places in molecules with the same functional formula.

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9
Q

Give an example of an isomer of butene:

A

Butene has 2 isomers. The second one is But-2-ene. The double covalent bond is between the 2nd and 3rd carbon atoms.

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10
Q

What is produced when hydrocarbons burn in a plentiful supply of oxygen?

A

Carbon dioxide and water are formed. During consumption oxidisation occurs. If all the hydrocarbons are fully oxidised, the products are only water and CO2. This is called complete combustion.

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11
Q

What is the difference between complete and incomplete combustion?

A

Complete combustion: combustion of hydrocarbons with enough oxygen present to convert all the fuel into carbon dioxide and water.

Incomplete combustion: when a substance reacts only partially with oxygen such as when carbon burns in air carbon dioxide, carbon monoxide and soot (unburnt particles of carbon).

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12
Q

What is the reaction for when methane burns in air?

A

Methane + oxygen ➡️ carbon dioxide + water

CH4 (g) + 2O2 (g) ➡️ CO2 (g) + 2H2O (g)

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13
Q

What is bromine water?

A

Bromine water is a dilute solution of bromine in water, Br2 (aq). It has an orange brown colour.

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14
Q

What colour is bromine water?

A

Organs-brown

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15
Q

How can you test for alkenes using bromine water?

A

When bromine water (orange-brown) colour is mixed with alkenes a chemical reaction occurs, leading to colourless products. Alkanes do not cause decolorisation and so bromine water is used to test between alkanes and alkenes.

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16
Q

Why do alkenes when recanted with bromine water produce colourless products?

A

Because the C=C bond reacts with the bromine to form a colourless product. (Alkanes do not have a C=C bond so don’t produce colourless products). The bromine is therefore removed from the solution, which loses its colour.

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17
Q

What colour is bromine gas?

A

Orange-brown

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18
Q

Does bromine gas react with alkanes?

A

Yes

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19
Q

What is an addition reaction?

A

This is a reaction in which reactants combine to form one larger product and molecule and no other products.

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20
Q

What happens when bromine gas reacts with ethene (an alkene)?

A

It reacts with ethene to produce a colourless liquid called 1,2-dibromoethane. The ‘di’ in the name of the product means 2 and the numbers show that the 2 bromine atoms are attached to different carbon atoms. If they were attached to the same carbon atom it would be called 1,1-dibromoethane.

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21
Q

What do alcoholic drinks contain?

A

Ethanol

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22
Q

What is the functional group for alcohols?

A

OH

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23
Q

What can ethanol be used for?

A

Alcohols, fuel for vehicles and as a raw material for the chemical industry.

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24
Q

What is the formula for ethanol?

A

C2H5OH

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25
Q

What is a sugar?

A

Surfers are small soluble substances that belong to a group called carbohydrates. (Compounds made of carbon, hydrogen and oxygen). Many fruits (such as grapes). Ethanol on alcoholic drinks is made from sugars.

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26
Q

What carbohydrate do seeds contain?

A

Starch, which is a long polymer.

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27
Q

How is starch made into alcohol?

A

Starch must be broken down into sugars in order to make alcoholic drinks.

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28
Q

How are seeds used to make alcohol?

A

Seeds are germinated, before using them to make ethanol because, during this process, enzymes in seeds naturally turn starch into sugars.

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29
Q

What seeds make what type of alcohol?

A

Beer - barley seeds
Wine - grapes
Whiskey - barely seeds
Vodka - wheat seeds

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30
Q

What is fermentation?

A

When plant material containing sugars is mixed with water and yeast. Enzymes in the yeast turn the sugars into ethanol and carbon dioxide.

Glucose ➡️ ethanol + carbon dioixde

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31
Q

During fermentation what must be controlled?

A

The temperature and the pH must be carefully controlled, to help the enzymes work as their best.

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32
Q

What type of respiration is yeast fermentation?

A

It is a type of anaerobic respiration and only occurs in the absence of oxygen.

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33
Q

What is the limitation of fermentation?

A

It only produces alcohol concentrations up to 15% as higher concentration kill the yeast cells.

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34
Q

How are more concentrated solutions of alcohol (ethanol) formed?

A

Concentrated solutions of ethanol are formed by fractional distillation. This works because the boiling point of ethanol (78°C) is lower than the boiling point of water (100°C).

The heated liquids evaporate and their vapours cool as they rise up the fractionating column. As the ethanol has a lower boiling point, it remains as a gas for longer and separates from the water. As a result the first fraction, or distillate, that is collected contains a higher % of ethanol.

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35
Q

What is an organic compound?

A

These have a central framework of carbon atoms, onto which hydrogens and other atoms are attached.

36
Q

How did ethanol and ethane differ?

A

Ethanol differs from a similar organic compound called ethane by having an additional oxygen atoms. They have very different properties and are each in a different family or homologous series of a compound. Ethane belongs to the alkane series and ethanol belongs to the alcohol series.

37
Q

What do compounds in the same homologous series have in common?

A
  • all have the same general formula
  • have similar chemical reactions
  • display a trend in properties
  • have simulator names
38
Q

What is the general formula for alcohols?

A

CnH2n+1OH

39
Q

What are the first 4 alcohols?

A

Methanol CH3OH
Ethanol C2H5OH
Propanol C3H7OH
Butanol C4H9OH

40
Q

What similar chemical properties do all alcohols share?

A
  • produce carbon dioxide and water in complete combustion.
  • can be oxidised to form compounds called carboxylic acids.
  • react with reactive metals, such as sodium,forming hydrogen gas as one of the products.
41
Q

What is a functional group?

A

The atom or group of atoms in a molecule that is responsible for its main chemical reactions.
Alcohols all the the same functions group -OH.
Carboxylic acids all have the same functional grouP - COOH.

42
Q

What are some of the uses of alcohols?

A

Solvents for…

  • cosmetics
  • medical drugs
  • varnishes
  • to drink
  • fuels
43
Q

What is a renewable source?

A

Source if raw materials that will not run out.

44
Q

When wine is left in the open air what does it turn into and why?

A

It turns into vinegar due to a reaction between ethanol and oxygen. The product is ethanoic acid. This oxidisation reaction occurs naturally in the presence of a certain bacteria.

(Vinegar can be made from any dilute ethanol solution like wine, cider or beer)

45
Q

What are the first 4 members of the carboxylic acid homologous series?

A

Methanoic acid - HCOOH
Ethanoic acid - CH3COOH
Propanoic acid - C2H5COOH
Butanoic acid - C3H7COOH

46
Q

What is the general formula for carboxylic acids?

A

CnH2n+1COOH

Contain the functional group COOH.

47
Q

How are most carboxylic acids generally formed?

A

They are formed by the gentle oxidation of alcohols using oxidising agents (e.g hot copper oxide.)

48
Q

What similar chemical properties do all carboxylic acids have?

A
  • all form a solution with a pH lower than 7.
  • react with metals to form a salt and hydrogen.
  • react with bases to form a salt and water.
  • react with carbonates to form carbon dioxide, a salt and water.
49
Q

What is the acidic properties of carboxylic acids due to?

A

This is due to the presence of the -COOH group. In a solution this group forms a hydrogen ion, while the rest of the molecules forms the negative ions that makes the salt. E.g propanoic acid forms propanoate ions, which makes propanoate salt.

50
Q

What substance is used to test for carbonate rocks?

A

Vinegar can be used to test for carbonate rocks like chalk and limestone (calcium carbonate). The ethanoic acid ‘fizzes’, producing carbon dioxide gas.

51
Q

What are plastics made from?

A

Polymers.

52
Q

What are polymers?

A

A polymer is a large molecule made from lots of small molecules called monomers, joined together.

53
Q

What is polymerisation?

A

The process in which monomers join together to form a polymer.

54
Q

Why can polymer molecules not be given a specific relative molecular mass?

A

The polymer molecules can be different lengths so they therefore cannot have a specific relative formula mass. But in general a polymer HAS A HIGH AVERAGE RELATIVE MOLECULAR MASS.

55
Q

Give an example of an addition polymerisation reaction:

A

Poly(ethene)/polythene is a polymer found when a large number of ethene monomers join together. Ethene molecules have a double covalent bond between the carbon atoms. One of the bonds in the double bond breaks open and another ethene molecule adds on. This process happens again and again, forming a long chain. The process is called addition polymerisation.

56
Q

What is a synthetic polymer?

A

Synthetic polymers are manufactured in a laboratory or a factory.

E.g poly(ethene)

57
Q

What is a repeating unit?

A

The part of the polymer that can be repeated many times to form the polymer chain.

The repeating unit shows how the monomer has changed and how it repeats throughout the polymer chain. The repeating unit does not have double bonds but has bond lines passing through the brackets to show there is another repeating unit joined on each side.

58
Q

Give some examples of naturally occurring polymers:

A
  • DNA
  • Starch
  • Proteins
59
Q

What is a naturally occurring polymer?

A

A substance that exists naturally as a polymer in plants and animals e.g DNA, Starch and proteins.

60
Q

What polymer is starch made from?

A

Starch is a polymer made from sugar.

61
Q

What polymers are proteins made from?

A

Amino acids.

62
Q

How is poly(ethene) formed?

A

It is formed when thousands of ethene molecules undergo addition polymerisation.

63
Q

Why can polymers be made from alkene monomers?

A

Because they all contain C=C double bonds.

64
Q

How can you work out the monomer from the formula for the polymer?

A

Remove the bracket and the extension bond lines that go through them, and then draw a double bind between the 2 carbon atoms. Keep all the other atoms or groups of atoms the same.

65
Q

What are the properties and uses of poly(ethene)?

A

Common name: polythene
Properties: flexible, cheap, good insulator
Uses: plastic bags, plastic bottles, cling film, polytunnels.

66
Q

What are the properties and uses of poly(propene)?

A

Common name: polypropylene
Properties: flexible, does not shatter
Uses: buckets, bowls, crates, ropes, carpets.

67
Q

What are the properties and uses of poly(chloroethene)?

A

Common name: polyvinyl chloride/PVC
Properties: tough, good insulator, can be made hard or flexible.
Uses: window frames, gutters, pipes, insulation for electrical wires.

68
Q

What are the properties and uses of poly(tetrafluoroethene)?

A

Common name: PTFE, Teflon
Properties: tough, slippery
Uses: non-stock coatings for frying pans and kitchen utensils, burette taps, stain-proofing clothing and carpets.

69
Q

What are plastic bottles made from and what are the benefits from using this material?

A

Many plastic bottles are made from PET (poly(ethylene terephthalate)), which is a polyester. The bottles are:

  • strong
  • lightweight
  • shatter-resistant
  • recyclable (can be made into items such as plastic garden furniture or fibres for carpets or fleece jackets).
70
Q

What is condensation polymerisation?

A

When monomers join together and eliminate a small molecule,
such as water.

(Polyesters are synthetic polymers made by condensation polymerisation.)

71
Q

What is an ester and what is its functional group?

A

Esters are organic compounds that contain the functional group -COO-.

72
Q

What is a functional group?

A

An atoms or or group that is responsible for the properties and reactions of a compound.

73
Q

How are esters formed?

A

Esters are formed when a carboxylic acid reacts with an alcohol, in the presence of a catalyst. This is a condensation reaction because water is also produced.

74
Q

What is a polyester?

A

A long chain of molecules that contain many ester links.

75
Q

What functional groups do the monomers that form a polyester contain?

A

The alcohol and carboxylic acid functional group. To form a long chain, each monomer must have 2 functional groups, one at each need of the molecule.

76
Q

Hie are different polyesters formed?

A

Different polyesters can be formed by using monomers with different numbers of carbon atoms.

77
Q

In general how are polyesters used?

A

Used in the manufacturing of synthetic fibres for weaving into fabrics for clothes and sheets.

78
Q

How is crude oil separated and purified?

A
  • Crude oil is separates into fractions by fractional distillation.
  • the fractions are further purified by, cracked and refined to produce useful chemicals.
79
Q

Where do most of the monomers needed to make synthetic polymers come from?

A

Most of the monomers needed to make synthetic polymers are obtained from crude oil.

80
Q

What type of resource is crude oil?

A

Crude oil is a finite resource and is therefore non-renewable, so chemists will need to find new sources of monomers in the future.

81
Q

Define the term biodegradable:

A

This means that they rot because microbes can feed on them and break them down. E.g wood and paper.

82
Q

Why is it useful that most synthetic polymers are not biodegradable?

A

Most synthetic polymers are useful for many purposes because they are not biodegradable and so they last for a long term. HOWEVER THIS ALSO MEANS THEY DO NOT ROT WHEN TNEY ARE THROWN AWAY WHICH IS A PROBLEM.

83
Q

What is the problem with non-biodegradable plastic materials?

A

Non-biodegradable plastic materials in the rubbish will last for many years. Some waste is incinerated (burned) and the energy released can be used to generate electricity. However all plastic produce CO2, a greenhouse gas, and some plastics produce toxic substances when they are burnt. Most of these toxic substances can be removed from the waste gases, but this forms toxic ash, which must be disposed of safely.

84
Q

How can we reduce the amount of waste that goes to landfill sites?

A

By reducing the amounts of materials we use and also by reusing materials. E.g reusing plastic bags instead of just throwing them away after a single use. If an item cannot be reused anymore, or may be possible to recycle it by processing it to make a new item. This will also help to conserve the supplies of crude oil.

85
Q

What are the uses of poly(styrene)?

A

Egg boxes, foam packaging.

86
Q

It is difficult to recycle polymers because many steps are needed to obtain a new item. These steps are:

A

1) collect the waste -this may involve kerbside collection or people taking it to collection points.
2) sort the waste into different types of polymers - this is often done by hand, which is time-consuming and expensive.
3) dispose of waste that cannot be recycled in a landfill site.
4) clean the polymers and grind them into chippings.
5) purify the chippings.
6) melt the chippings and then process them into a new product.

87
Q

Why are codes and symbols used on plastic items.

A

To show what they’re made of so it is easier for sorting.

Chemistry (14 decks)

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