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Chemistry > Unit 2.1 Basic Concepts And Hydrocarbons > Flashcards

Unit 2.1 Basic Concepts And Hydrocarbons Flashcards

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1
Q

Why can carbon form so many compounds?

A

A carbon atom can:

  • Form bonds with other carbon atoms to make chains and rings
  • Form a single, double or triple bond to another carbon atom
  • Bond with atoms of other elements
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2
Q

Definition of hydrocarbon

A

Organic compounds that contain carbon and hydrogen only

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3
Q

Definition of saturated hydrocarbon

A

A hydrocarbon with single bonds only

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4
Q

Definition of unsaturated hydrocarbon

A

A hydrocarbon containing carbon-to-carbon multiple bonds

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5
Q

Definition of aliphatic hydrocarbon

A

A hydrocarbon with carbon atoms joined together in straight (unbranched) or branched chains

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6
Q

Definition of alicyclic hydrocarbon

A

A hydrocarbon with carbon atoms joined together in a ring structure

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7
Q

Definition of functional group

A

The part of the organic molecule responsible for its chemical reactions

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8
Q

Definition of homologous series

A

A series of organic compounds with the same functional group but with each successive member differing by CH2

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9
Q

Definition of alkane

A

Saturated straight-chained hydrocarbon with single C-C bonds only

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10
Q

Definition of alkyl group

A

An alkane with a hydrogen atom removed

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11
Q

What is the suffix (ending of the word) and formula for an aldehyde?

A

Suffix: -al
Formula: -CHO

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12
Q

What is the suffix and formula for a ketone?

A

Suffix: -one
Formula: C-CO-C

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13
Q

What is the suffix and formula for a carboxylic acid?

A

Suffix: -oic acid
Formula: -COOH

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14
Q

Definition of general formula

A

The simplest algebraic formula of a member of a homologous series

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15
Q

What does a displayed formula do?

A

Shows the relative positioning of all the atoms in a molecule and the bonds between them

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16
Q

What does a structural formula do?

A

Shows the minimal detail for the arrangement of atoms in a molecule

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17
Q

What is the structural formula of propane?

A

CH3CH2CH3

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18
Q

What is a skeletal formula?

A

A simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups

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19
Q

Definition of structural isomers

A

Molecules with the same molecular formula but with different structural arrangements of atoms

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20
Q

Name 2 structural isomers of C4H10

A

E.g. Butane, 2-methylpropane

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21
Q

Definition of stereoisomers

A

Compounds with the same structural formula, but with a different arrangement in space

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22
Q

Definition of E/Z isomerism

A

A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond

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23
Q

What are the 2 criteria that a molecule must satisfy to have E/Z isomerism?

A
  • A carbon-carbon double bond must be present

- Each carbon in the double bond must be attached to 2 different groups

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24
Q

Definition of cis-trans isomerism

A

A special type of E/Z isomerism in which there is a non-hydrogen group and hydrogen on each C of a C=C double bond

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25
Q

What is homolytic fission?

A

The breaking of a covalent bond, with one of the bonded electrons going to each going to each atom, forming 2 radicals

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26
Q

What is heterolytic fission?

A

The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation and an anion

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27
Q

What is a radical?

A

A species with an unpaired electron

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28
Q

What is a nucleophile?

A

An atom that is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond

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29
Q

What is an electrophile?

A

An atom that is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond

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30
Q

What is an addition reaction?

A

A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
2 products —-> 1 product

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31
Q

What is a substitution reaction?

A

A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms
2 reactants —–> 2 products

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32
Q

What is an elimination reaction?

A

The removal of a molecule from a saturated molecule to make an unsaturated molecule
1 reactant —-> 2 products

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33
Q

What is fractional distillation?

A

A fossil fuel made from naturally decaying plants and animals that once lived in ancient seas, millions of years ago
It is a mixture of different hydrocarbons

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34
Q

How is crude oil refined?

A

By fractional distillation

35
Q

How does fractional distillation work?

A
  • It takes place in a fractionating column
  • The crude oil is first vaporised by heating and is then passed into the fractionating column
  • The gases pass up the column through a series of bubble caps
  • The column is hotter at the bottom than at the top
  • When the gases reach a temp that is lower than their boiling point, they condense into a liquid
  • The liquid fractions are then tapped off into storage containers
36
Q

What condenses near the top of the column, and why?

A

Short-chained hydrocarbons; lower boiling points

37
Q

What effect does increasing the chain length of alkanes have on the boiling point?

A
  • As the chain length increases, the boiling point increases because the intermolecular forces between the molecules get stronger
  • There are more points of contact between the molecules, so there are more van der Waals’ forces between the molecules
  • So more energy is needed (and therefore a higher temp) to separate the molecules
38
Q

What effect does branching have on the boiling point of an alkane?

A

A branched isomer has a lower boiling point than the unbranched isomer with the same molecular mass:
- The branched alkane has fewer points of contact between molecules
- So there are fewer van der Waals’ forces between the molecules
- Branched molecules cannot get as close to each other as unbranched ones
- This reduces the intermolecular forces between the molecules
So less energy is required to separate the molecules

39
Q

What happens when short-chain alkanes are burnt in a plentiful supply of oxygen?

A

They form carbon dioxide and water

40
Q

What happens when alkanes are burnt in a limited supply of oxygen?

A
  • They undergo incomplete combustion

- Form carbon monoxide and water

41
Q

What is cracking?

A

The break down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes

42
Q

What is isomerisation?

A
  • A form of cracking

- Unbranched alkanes are converted into branched alkanes

43
Q

What is reforming?

A
  • A form of cracking

- Aliphatic (straight-chain or branched) hydrocarbons are converted into cyclic or aromatic hydrocarbons

44
Q

What can crude oil be used for? Give 3 examples.

A
  • As a source of fuel
  • Plastics
  • Pharmaceuticals
  • Cosmetics
  • To make roads
  • Dyes
  • Inks
45
Q

Why can burning hydrocarbons be bad for the environment?

A

Releases atmospheric pollutants, such as:
- Carbon monoxide
- Carbon dioxide
- Nitrogen oxides
- Sulfur dioxide
The release of these gases could be causing global warming

46
Q

What fuels could be used instead of hydrocarbons from fossil fuel?

A

Biofuel: - derived from recently living material (e.g. Plants, animal waste)
Ethanol: - made by fermenting sugar and other carbohydrates
- burns efficiently in a plentiful supply of oxygen, to give CO2 and oxygen
Bioethanol: - A fuel oil derived from natural sources such as plants
- Can be used 100% pure, but it is usually blended with normal diesel

47
Q

What is radical substitution?

A

A type of substitution reaction in which a radical replaces a different atom or group of atoms

48
Q

What are alkenes?

A

Unsaturated hydrocarbons with at least 1 C=C double bond

49
Q

What happens in the formation of a double bond?

A
  • A σ-bond is formed directly between 2 carbon atoms by the overlap of orbitals. Each carbon atom contributes 1 electron to the electron pair in the σ-bond
  • A π-bond is formed above and below the plane of the carbon atoms, by sideways overlap of p-orbitals. Each carbon atom contributes 1 electron from a p-orbital to the electron pair in the π-bond
50
Q

What does the π-bond in an alkene do?

A
  • It fixes the carbon atoms in position, at either end of the double bond
  • This prevents any rotation of the bond
51
Q

In alkenes, how is each carbon involved in the double bond?

A
  • 3 of its electrons are used in the formation of 3 σ-bonds

- 1 of its electrons is used in the formation of a π-bond

52
Q

What is the shape of an alkene molecule?

A
  • 3 regions of electron density surround each carbon atom in the double bond
  • Pairs of electrons repel each other as far apart as possible to minimise repulsions
  • The electron pairs repel each other to give a trigonal planar shape, with bond angles of approx. 120°
53
Q

Why are alkenes more reactive than alkanes?

A 
Because of the C=C double bond:
- A double bond is stronger than a single bond
- A π-bond is weaker than a σ-bond
When an alkene reacts:
- The π-bond breaks
- The σ-bond remains intact
54
Q

What type of bond is between the 2 carbon atoms in an alkane?

A

A σ-bond

55
Q

What type of reactions do alkenes typically take part in?

A

Addition reactions

56
Q

What happens to an alkene in an addition reaction?

A
  • A small molecule is added across the double bond, causing the π-bond to break
  • 2 reactant molecules react together to form 1 product molecule
  • An unsaturated alkene reacts and forms a saturated product
57
Q

What happens when hydrogen is added to an alkene?

A
  • The hydrogen adds across the double bond and an alkane is formed
  • This is a reduction reaction
  • It is sometimes known as hydrogenation
58
Q

What conditions are required for the addition of hydrogen to an alkene?

A
  • A temp of 150°C

- A nickel catalyst

59
Q

What happens when halogens are added to alkenes?

A
  • The halogen adds across the double bind to give a di-substituted halogenoalkane
  • The reaction is sometimes known as halogenation
    It is a rapid reaction at room temperature
60
Q

What happens when a hydrogen halide is added to an alkene?

A
  • It adds across the double bond

- Produces a halogenoalkane

61
Q

What happens when steam is added to an alkene?

A

An alcohol is produced

62
Q

What conditions are required for the addition of steam to an alkene?

A
  • High temperature and pressure

- Phosphoric acid catalyst

63
Q

Why is the double bond in alkenes a region of high electron density?

A

Because of the π-electrons in the double bond

64
Q

What happens when hydrogen bromide is added to an alkene? (Electrophilic addition)

A
  • Bromine is more electronegative than hydrogen, causing a dipole
  • The electron pair in the π-bond is attracted to the slightly positive hydrogen atom, causing the double bond to break
  • A new bond forms between 1 of the carbon atoms and the hydrogen atom
  • The H-Br bond breaks by heterolytic fission, with the electron pair going to the bromine
  • A bromide ion and a carbocation are formed
  • The carbocation is unstable, so it quickly reacts with the bromide ion to form the organic product
65
Q

How is bromine added to an alkene?

A

By electrophilic addition

66
Q

What is a polymer?

A

A long molecular chain built up from monomer units

67
Q

What is a monomer?

A

A small molecule that combines with many other monomers to form a polymer

68
Q

How can vegetable oil be hardened to make margarine?

A

By hydrogenation:
- Adds hydrogen molecules across the double bonds in an addition reaction
- Alters the individual molecule in the oil in such a way that the oil partially solidifies and hardens
By adding hydrogen bonds across different numbers of the many double bonds, you can harden the oil by different amounts

69
Q

Why is partial hydrogenation of unsaturated fats thought to be unhealthy?

A
  • Can transform some cis double bonds into trans double bonds as a by-product
  • These trans fats are thought to be bad for health
70
Q

What is addition polymerisation?

A

The process in which unsaturated alkene molecules (monomers) add on to a growing polymer chain one at a time, to form a very long saturated molecular chain (the addition polymer)

71
Q

What are the 2 different industrial processes in which addition polymerisation is carried out?

A

Radical polymerisation

The Ziegler-Natta process

72
Q

What conditions are required for radical polymerisation? What does it produce?

A
  • Temp of 200°C
  • Very high pressure
    Leads to branching of the polymer chain and the production of polymer mixtures
73
Q

What conditions are required for the Ziegler-Natta process?

A
  • Temp of 60°C

- Specialist catalysts such as TiCl3 and Al(C2H5)2Cl

74
Q

What happens in the Ziegler-Natta process?

A
  • The alkene is passed over the catalyst
  • The conversion is low
  • Any unreacted alkane is recycled and passed over the catalyst repeatedly
75
Q

What is a repeat unit?

A
  • A specific arrangement of atoms that occurs in the structure over and over again
  • They are included in brackets, outside of which is the symbol ‘n’
76
Q

Why are addition polymers difficult to dispose of?

A
  • Don’t usually react with the substances placed inside them

- Fairly durable and do not break down naturally

77
Q

Why is it important to recycle polymers?

A
  • They are non-biodegradable

- They are rapidly filling up landfill space

78
Q

How are polymers recycled?

A

-The different types of plastics are separated from each other
Reclamation:
- They are mechanically chopped into small flakes
- Then washed to remove any impurities
These flakes can be melted + remoulded to form new materials

79
Q

How can polymer waste be used?

A
  • Polymers can be burnt under controlled conditions to produce heat energy, which can be harnessed to make electricity
  • Polymers can be converted into synthesis gas (a mixture of hydrogen and carbon monoxide). Hydrocarbons and synthesis gas can be used as a chemical feedstock for conversion into useful products or as a fuel at oil refineries
  • PVC can be recycled by dissolving it in solvents (to separate it from other scrap) then recovering it from the solvent by precipitation
80
Q

What are bioplastics?

A
  • Plastics that are biodegradable or compostable
  • They break down as a result of bacterial activity
  • Produce carbon dioxide and water when they degrade
81
Q

What are bioplastics made from?

A

Renewable raw materials such as:

  • Starch
  • Maize
  • Cellulose
  • Lactic acid
82
Q

Describe how hydrogen can be used in the manufacture of margarine

A

Unstaurated oils reacted with hydrogen in the prescence of a nickel catalyst

83
Q

What does ‘curly arrow’ represent?

A

The movements of electron pairs

Chemistry (4 decks)

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