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Chemistry (Tara) > Organic chem - 2 > Flashcards

Organic chem - 2 Flashcards

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1
Q

What are the 4 points about crude oil?

A
  1. Crude oil is a fossil fuel. It is formed by the decomposition of dead bodies of creatures that died millions of years ago.
  2. It is pumped from under the ground or sea.
  3. Thick, black, viscous, pungent liquid , = no use in this form.
  4. It is found in large quantities in countries like Iran,
    the North Sea, the USA, Russia etc.
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2
Q

What does crude oil consist of?

A

A mixture of hydrocarbons –> mixture means not chemically combined

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3
Q

What does the types of hydrodro carbons present in oil depend on?

A

Where it is found in the world.

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4
Q

What can the hydrocarbons be?

A

They may be small chained molecules e.g ethane, or may consist of many carbon atoms.

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5
Q

What are the smaller hydrocarbons (b.p & uses?

A

They are volatile & low boiling points. Used as fuels or chemical feedstock.

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6
Q

What are the larger hydrocarbons like?

A

They are heavy and may be used in heavy industry or may be broken down into smaller molecules (thermal or catalytic cracking)

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7
Q

What is fractional distillation?

A

Fractional distillation is a process that is used to separate the crude oil into its components.

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8
Q

Why can fractional distillation method be used?

A

This method can be used as the oil is a mixture of molecules.

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9
Q

What is the principle involved in fractionation of crude oil?

A

The principle involved is that the oil is separated into ‘fractions’ on the basis of the different boiling points of the compounds.

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10
Q

What is a positive of the principle?

A

These ‘fractions’ are now more useful and can be used for various purposes.

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11
Q

What is the first stage in the fractionation of crude oil?

A
  1. The crude oil is heated to high temperatures and is fed into large fractionating towers. These towers may be 80m high.
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12
Q

What is the second stage in the fractionation of crude oil?

A
  1. The tower is kept at a high temperature at the bottom.
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13
Q

What is the third stage in the fractionation of crude oil?

A
  1. As you go up the tower there are trays present to collect the ‘fractions’.
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14
Q

What is the fourth stage in the fractionation of crude oil?

A
  1. The temperature decrease as you ascend the tower.
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15
Q

What is the fifth stage in the fractionation of crude oil?

A
  1. As the crude oil rises up the tower the fractions will reach a temperature that is just bellow their boiling point and turn into liquids which collect on the tray.
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16
Q

What is the sixth stage in the fractionation of crude oil?

A
  1. The heavier hydrocarbons will condense first, while the lighter hydrocarbons will rise higher and condense higher up the tower.
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17
Q

What is C1-C4?

1 + 2

A
  • Gas
  • Refinery fuel
  • Liquefied from propane or butane gas (LPG).
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18
Q

What is C5-C10?

1 + 2

A
  • Light gasoline

- Motor fuel –> what we get petrol from

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19
Q

What is C7-C10?

1 + 2

A
  • Naptha (v.important)
  • Petrol
  • Feedstock for petrochemical industry
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20
Q

What is C10-C14?

1 + 2

A
  • Kerosene
  • Fuel for planes
  • Paraffin lamps/stoves
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21
Q

What is C14-C40?

3

A
  • Gas oil and heavy gas oil
  • Diesel oil
  • Lubricating oil for engines
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22
Q

What is C35 and upwards?

1 + 3

A
  • Residue
  • Heavy industrial fuel
  • Used in catalytic cracking
  • Bitumen for road surfaces
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23
Q

What is natural gas a mixture of?

A

Natural gas is a mixture of hydrocarbons.

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24
Q

What is natural gas usually made up of?

A

Usually made up of methane, ethane, propane and butane.

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25
Q

Where in the world are gas fields made up mainly of methane (95%)?

A

The North Sea and Kinsale gas fields.

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26
Q

What is the natural gas in the USA mainly made up of?

A

Propane and butane.

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27
Q

What are propane and butane sold as in Europe?

A

Sold as liquefied petroleum gas (LPG)

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28
Q

Does natural gas have an odour?

A

No its odourless.

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29
Q

What compounds are added to the natural gas before distribution and why?

A

Mercaptans, for safety reasons

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30
Q

Why is mercaptans added for safety reasons?

A

Mercaptans have a strong smell so this alerts to a leakage.

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31
Q

What do a lot of industries that are using natural gas as a reactant have to do?

A

The mercaptans have to be removed if it is going to be used as a raw material.

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32
Q

What must the petrol and oxygen do to ensure the engine runs smoothly?

A

The petrol and oxygen must ignite and explode evenly at the correct time to ensure the engine runs smoothly.

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33
Q

What causes auto-ignition (‘knocking’)

A

It is caused by poor quality petrol (long straight molecules)

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34
Q

When does ‘knocking’ happen?

A

‘Knocking’ happens if the petrol and oxygen explode due to an increase in pressure in the engine instead of the explosion being caused by a spark (from the spark plugs)

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35
Q

What does ‘knocking’ damage?

A

It can damage the engine and lead to loss of power.

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36
Q

What happens if the petrol is rich in straight chained hydrocarbons?

A

Auto-ignition occurs.

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37
Q

How does petrol rich in branched chained hydrocarbons burn?

A

Burns more smoothly and efficiently

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38
Q

Draw the structural formula of 2,2,4-trimethylpentane.

A

Drawn

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39
Q

Draw and name the other reference molecule.

A

Heptane, drawn

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40
Q

What is the octane number of 2,2,4 trimethylpentane?

A

100

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41
Q

What is the octane number of heptane?

A

0

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42
Q

Define octane number

A

The measure of the tendency of a fuel to resist auto-ignition.

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43
Q

Why is 2,2,4 trimethylpentane (iso-octane) given an octane number of 100?

A

As it is one of the most efficient.

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44
Q

In straight chained hydrocarbons, the shorter the alkane the ………. the octane number.

A

Higher

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45
Q

In branched-chained hydrocarbons, the grater the number of branches the ……… the octane number.

A

Higher

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46
Q

Do cyclic and aromatic hydrocarbons have a high or low octane number?

A

High

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47
Q

What octane number can a ‘good’ quality petrol have?

A

97

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48
Q

What are the 3 structural features of alkanes that prevent autoignition?

A
  1. Short chained
  2. Highly branched
  3. Cyclic/aromatic i.e benzene
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49
Q

What is the first solution to auto-ignition? (additive)

A
  • Add lead to the petrol.

- Added in the from of tetraethyl lead

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50
Q

Is leaded petrol safe?

A

No it is toxic, harmful to the environment and peoples health. (Phased out due to this reason)

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51
Q

Is unleaded petrol more or less expensive?

A

More expensive

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52
Q

What does isomerisation (reforming) involve? (2nd solution to auto ignition)

A
  • It involves changing straight-chained hydrocarbons into branched-chained isomers.
  • Burns more smoothly = higher octane number.
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53
Q

What does dehydrocyclization (reforming) involve? (3rd solution to auto-ignition)

A
  • Involves the conversion of straight-chained hydrocarbons to form ring compounds.
  • The converted into aromatic compounds.
  • Done in the presence of a catalyst. = ‘dehydro’ = high octane number & carcinogenic.
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54
Q

What does catalytic cracking (reforming) involve? (4th solution to auto-ignition)

A
  • Involves breaking down long chained hydrocarbons for which there is a low demand into short chained molecules for which there is a high demand = higher octane number & highly branched.
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55
Q

What is addition of oxygenates? (last solution to auto-ignition)

A

The addition of oxygen compounds to the petrol

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56
Q

What are the two types of addition oxygenates?

A
  • Addition of alcohols i.e methanol (octane no. 114)

- Addition of ethers i.e methyl tert-butyl ether (octane no.118)

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57
Q

What does (a) addition of alcohols & (b) addition of ethers do?

A

(a) Increase the octane number of the petrol and (b) they also cause less pollution as they reduce the level of carbon monoxide in the exhaust fumes.

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58
Q

Define reforming

A

Reforming involves changing straight chained hydrocarbons into branched chained hydrocarbons or cyclic hydrocarbons.

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59
Q

Define cracking

A

Cracking involves changing long chained hydrocarbons for which there is low demand, into short chained hydrocarbons for which there is high demand.

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60
Q

Define auto-ignition

A

The early explosion of petrol-air mixture caused by increasing pressure in the engine.

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61
Q

Define octane number

A

The octane number of a fuel is the measure of its tendency to resist ‘knocking’.

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62
Q

What is a catalytic converter?

A

A catalytic converter is fitted to car exhausts to reduce pollution from the exhaust fumes.

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63
Q

What do exhaust fumes contain if leaded petrol is used?

A
  • Carbon monoxide, nitrogen monoxide, nitrogen dioxide, lead compounds & unburned hydrocarbons.
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64
Q

What does the catalytic converter do?

A

It changes harmful gases into harmless gases.

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65
Q

What is an example of a catalytic converter changing these harmful gases to harmless gases?

A

CO + NO –> CO2 + 1/2 N2

=> able as it has a high energy triple bond.

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66
Q

What does the catalytic converter contain and where?

A

It contains catalysts such as platinum, palladium and rhodium inside a stainless steel case.

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67
Q

What does the inside of a converter look like?

A

A honeycomb

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68
Q

What does the honeycomb arrangement in the converter allow for?

A
  • A large surface area = increased removal of harmful gases into harmless gases such as carbon dioxide and nitrogen.
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69
Q

What does the lifetime of a converter depend on?

A
  • The type of petrol used
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70
Q

Does the lifetime of a converter shorter when using leaded or unleaded petrol?

A

Leaded

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71
Q

What is the policy that all new cars are fitted with catalytic converters?

A
  • EU, 1993
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72
Q

Why is ethene a very important organic compound?

A

As it is the ‘building block’ from which many plastics are made.

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73
Q

In the laboratory what is ethene prepared by?

A

A dehydration reaction of ethanol. Dehydration means removing water. This is an example of an elimination reaction.

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74
Q

What is the apparatus for the preparation ethene?

A
  • Boiling tube
  • Retort stand
  • Glass tubing
  • Water bath
  • Test tubes
  • Bunsen burner
  • Rubber bung
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75
Q

What are the materials for the preparation of ethene?

A
  • Ethanol
  • Aluminium oxide
  • Water
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76
Q

What is the physical appearance of ethene?

A

Colourless with a sweetish smell.

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77
Q

What is ethenes solubility in water?

A

The gas in insoluble in water as water is a polar solvent and ethene is non-polar therefore ethene does not form hydrogen bonds with water. This is why ethene can be collected by the displacement of water.

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78
Q

What is the combustion of ethene?

A
  • When a lighted taper is placed in a test tube of ethene a luminous flame is observed. A small amount of smoke may also be produced. If limewater is added after burning, the limewater goes ‘milky’.
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79
Q

What is the first test for unsaturation in ethene?

A

Addition of bromine - when bromine water is added to ethene an addition reaction occurs. The bromine adds across the double bond to form 1,2-dibromo ethane. Colour change from red/brown to colourless proves unsaturation.

80
Q

What is the equation for the addition of bromine in ethene?

A

C2H4 + Br2 –> C2H4Br2

C2H4 +Br2 –> 1,2-dibromoethane

81
Q

What is the second test for unsaturation in ethene?

A
  • Addition of dilute potassium manganate - a dilute solution of potassium manganate is light purple in colour. When this solution is added to ethene gas and shaken the purple colour of the solution goes colourless. This test also proves the presence of carbon - carbon double bond & unsaturation
82
Q

What is ethyne used for?

A
  • Used for cutting and welding metals as when burned in oxygen it can reach temperatures over 3000’C
83
Q

What is the equation for the preparation of ethyne?

A

CaC2 + 2H2O –> C2H2 + Ca(OH)2

Calcium dicarbide reacts with water to produce ethyne and calcium hydroxide.

84
Q

What is the apparatus for the preparation of ethyne?

A
  • Dropping funnel
  • Buchner flask
  • Glass tubing
  • Conical flask
  • Two holed rubber bung
  • Test tubes
  • Water bath
85
Q

What are two solid impurities that are present in the calcium dicarbide?

A
  • Calcium phosphide, Ca3P2

- Calcium sulfide, CaS

86
Q

What are two gaseous impurities in the ethyne gas collected?

A
  • Phosphine, PH3

- Hydrogen sulfide H2S

87
Q

How are the gaseous impurities removed?

A

Removed by bubbling the impure ethyne gas through acidified copper (II) sulfate solution.

88
Q

What are the physical properties of ethyne gas?

A

Colourless gas with a sweetish smell if pure.

89
Q

What is ethynes insolubility in water?

A
  • Insoluble in water, as water is a pure solvent and ethyne being non-polar does not form hydrogen bonds with water. This is why ethyne can be collected by the displacement of water.
90
Q

What is the combustion of ethyne?

A
  • Very dangerous and must be done in a fume cardboard.
  • Burns with a smoky luminous flame.
  • Smoke is due to an unburned carbon.
  • To ensure no soot = use an excess of oxygen when burning.
91
Q

What is the first test for proving the unsaturation of ethyne?

A

Addition of bromine - when bromine is added across the carbon-carbon triple bond the red-brown colour of the bromine goes colourless thus proving that the ethyne is unsaturated.

92
Q

What is the second test for the unsaturation?

A

Addition of dilute potassium manganate (VII) - the purple colour of the manganate (VII) solution goes colourless also proving the presence of a multiple bond (carbon-carbon triple bond) hence ethyne is unsaturated.

93
Q

Classify C3H6 as having one, two or three tetrahedrally bonded carbon atoms

A

Three

94
Q

Butane is a major component of LPG. What do the letters LPG stand for?

A

Liquefied petroleum gas

95
Q

Draw two structural isomers of butane

A

Drawn

96
Q

Methane is a major component of natural gas. Why are mercaptans added to natural gas?

A

To give an odour / to detect leaks

97
Q

Methane is a major component of natural gas. What environmental change of or effect is associated with the release of methane to the atmosphere?

A

Greenhouse effect / global warming

98
Q

Methane is a major component of natural gas. Apart from leaking pipes, name a major source from which methane is released in the atmosphere ?

A

Fossil fuels/ oil / coal

99
Q

What structural feature of 2,2,4 trimethylpentane results in it having a high octane rating? Give one other structural feature which increases the octane number of a hydrocarbon?

A

(1) Branching / short chain

(2) Aromatic / ring

100
Q

Describe the appearance of calcium carbide

A

black / dark

101
Q

Write a balanced equation for the reaction between water and calcium carbide.

A

CaC₂ + H₂O –> C₂H₂ + CaO

102
Q

What is observed when a sample of ethyne gas in burned in air? Write a balanced equation for the combustion of ethyne in oxygen.

A
  • luminous bright flame / sooty flame

- C₂H₂ + 2.5O₂ –> 2CO₂ + H₂O

103
Q

Ethyne, C2H2, is described as an unsaturated hydrocarbon. Describe a test you could carry out to show that ethyne is unsaturated.

A

Bromine is added across the carbon-carbon triple bond the red-brown colour of the bromine goes colourless.

104
Q

Ethyne, C2H2, is described as an unsaturated hydrocarbon. Write an equation for the reaction taking place during a test that proves ethyne’s unsaturation and name the organic product.

A

Equation = C₂H₂ +Br₂ –> C₂H₂Br₂

Organic product = Dibromoethene

105
Q

The common name for ethyne has, C2H2, is acetylene. Give one major use of the gas.

A

Cutting metals / welding metals

106
Q

What is the function of the glass wool in the preparation of ethene?

A

Keeps ethanol at the end of the test tube.

107
Q

Describe the appearance of aluminium oxide.

A

White powder (solid)

108
Q

State and explain two safety precaution which should be observed when carrying out the experiment to prepare a sample of ethene.

A
  1. Keep gas away from flames - because gas is flammable.

2. Disconnect tube - to prevent suckback.

109
Q

Write a balanced equation for the reaction involved in the preparation of ethene.

A

C₂H₅OH → C₂H₄ + H₂0

110
Q

If the ethene produced is bubbled through an acidified solution of potassium manganate (VII), the solution is decolourised showing that ethene is unsaturated. What is meant by the term unsaturated?

A

Unsaturated - undergoes addition reactions

111
Q

Describe the flame that would be observed when a combustion test is carried out on a sample of ethene gas. Write a balanced equation for the combustion of ethene in excess oxygen.

A

Flame - luminous smoky flame

Equation - C₂H₄ + 3O₂ → 2CO₂ + 2H₂0

112
Q

Give the name and formula of the solid which is heated using the Bunsen burner in the preparation of ethene.

A

Aluminium oxide

113
Q

Identify the solid which is used to keep the ethanol at the end of the test tube.

A

Glass wool

114
Q

What precaution should be observed when heating is stopped in the preparation of ethene? Why is this necessary?

A
  • Dismantle the apparatus

- To prevent suck-back

115
Q

Give one major use of ethene gas.

A

Manufacture of polythene / make PVC

116
Q

Naphtha and gas oil are two of the hydrocarbon fractions obtained from the fractional distillation of crude oil. How are the molecules of the naphtha fraction differ from the molecules of the gas oil fraction?

A

Naphtha have shorter chains / less carbon atoms

117
Q

Name the homologous series to which propane and butane belong. Draw the structural formula of propane. (L.C)

A

Alkanes

CH₃CH₂CH₃ - DRAW!

118
Q

Propane and butane have boiling points of -42.1°C and -0.5°C, respectively. Explain why propane has a lower boiling point than butane. (L.C)

A

Propane smaller with fewer electrons, therefore weaker intermolecular forces.

119
Q

What is meant by saying that compounds are structural isomers? Draw the structural formula of the isomer of butane (L.C)

A

Structural isomers are molecules with the same molecular formula but different structural formulas.
- (CH₃)₂CHCH₃

120
Q

Give the name or chemical formula of the solid X used in the preparation of ethene. What is the colour of this solid? (L.C)

A

Aluminium oxide

White

121
Q

Write a balanced equation for the reaction involved in the preparation of ethene. What term describes this type of reaction. (L.C)

A

C₂H₅OH → C₂H₄ + H₂O

- Elimination

122
Q

State four precautions that should be observed when carrying out the preparation of ethene by this method. (L.C)

A
  • Keep gas from flame
  • Safety glasses
  • Tie hair back
  • Air-tight stopper
123
Q

Explain the term unsaturated (L.C)

A

Contains a multiple bond between two carbon atoms.

124
Q

Give the name or formula of the solid Y used in the preparation of ethyne in the school laboratory. Describe the appearance of this solid. (L.C)

A

Calcium dicarbide

Black / grey

125
Q

Describe a test you could carry out on a sample of either gas to show that it is unsaturated. What would you observe during the test? (L.C)

A

Test - Add bromine water until decolorises

Observe - Double carbon-to-carbon bond present

126
Q

Give a major use of ethene. (L.C)

A

Manufacture of polythene

127
Q

Give a major use of ethyne (L.C)

A

Cutting metals / welding metals

128
Q

Both ethene and ethyne can be burned in air. What is most noticeable difference seen when these combustions are carried out in a school laboratory? (L.C)

A

Ethene less luminous/smoky

129
Q

Write a balanced equation for the complete combustion of ethene. (L.C)

A

C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

130
Q

Write a balanced equation for complete combustion of ethyne. (L.C)

A

2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

131
Q

Dehydrocyclisation is one of the processes used to increase the octane numbers of hydrocarbons. What two changes to the hydrocarbon molecules occur during this process? (L.C)

A
  • Removal of hydrogen

- Ring formation

132
Q

Ethanol is an example of an oxygenate. Give another example of an oxygenate. Give two reasons why oxygenates are added to petrol. (L.C)

A
  • Methanol
  • Raise octane number
  • Decrease knocking
133
Q

Crude oil is separated into a number of fractions in oil refining. Name the two fractions which contain molecules with the carbon chain lengths needed for petrol. (L.C)

A
  • Light gasoline

- Naptha

134
Q

What is meant by the octane number of a fuel? (L.C)

A

The measure of the tendency of fuel to resist auto-ignition.

135
Q

The two hydrocarbons used as references when establishing the octane number of a fuel are heptane and 2,2,4 - trimethylpentane. Draw the structure of each of these molecules. (L.C)

A

Drawn

136
Q

Give the name and formula of the solid A which is heated using the Bunsen Burner. (ethene prep) (L.C)

A

Aluminium oxide / Al₂O₃

137
Q

Identify the solid B which is used to keep the ethanol at the end of the test tube. (ethene prep) (L.C)

A

Glass wool

138
Q

What precautions should be observed when heating is stopped? Why is this necessary? (ethene prep) (L.C)

A

Remove the delivery tube from the trough of water and

disconnect tube from test tube to prevent suck-back.

139
Q

Give one major use of ethene gas. (L.C)

A

Manufacture of polythene

140
Q

In which fraction of crude oil do pentane and its isomers occur? (L.C)

A

Light gasoline

141
Q

Naptha and gas oil are two of the hydrocarbon fractions obtained from the fractional distillation of crude oil. How do the molecules of the naptha fraction differ from the molecules of the gas oil fraction. (L.C)

A

Naptha have shorter chains and gas oil have longer chains

142
Q

Bitumen is a residue fraction obtained from crude oil. Give one use for bitumen. (L.C)

A

Road surfacing / roofing

143
Q

What is catalytic cracking? What is its economic importance in oil refining? (L.C)

A

Cracking involves changing long chained hydrocarbons for which there is low demand, into short chained hydrocarbons for which there is high demand.

144
Q

What is the function of the glass wool? (prep ethene)(L.C)

A

Keeps ethanol at the end of test tube to avoid wetting the aluminium oxide.

145
Q

Identify the solid X and describe its appearance. (prep ethene) (L.C)

A

Aluminium oxide

White powder

146
Q

State and explain two safety precautions which should be observed when carrying out the student experiment (prep of ethene) (L.C)

A

Keep away from gas as gas is flammable

Air-tight stopper as it stops ethene escaping

147
Q

Write a balanced equation for the reaction involved in this preparation. (ethene) (L.C)

A

C₂H₅OH → C₂H₄ + H₂O

148
Q

Define the term unsaturated. (L.C)

A

Contains only single bonds around carbon atoms.

149
Q

Describe how you would carry out another test to confirm that ethene is unsaturated. (other than potassium manganate) (L.C)

A

Add bromine water

Red / orange / yellow → colourless

150
Q

Describe the flame that would be observed when a combustion test is carried out on a sample of ethene gas. (L.C)

A

Yellow / luminous / smoky sooty flame

151
Q

Write a balanced equation for the combustion of ethene in excess oxygen. (L.C)

A

C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

152
Q

Identify the liquid x and the solid y (prep of ethyne gas) (L.C)

A 
X = water
Y = calcium dicarbide
153
Q

Describe the appearance of calcium dicarbide. (L.C)

A

Black / dark

154
Q

Write a balanced equation for the reaction between water and calcium dicarbide. (L.C)

A

2C₂H₂ + 5O₂ → 2CO₂ + 2H₂O

155
Q

Butane is a major component of LPG. What do the letters LPG stand for? (L.C)

A

Liquefied petroleum gas

156
Q

Draw the two structural isomers of butane. (L.C)

A

Drawn

157
Q

Why are mercaptans added to natural gas? (L.C)

A

To give an odour to detect leaks

158
Q

What environmental change or effect is associated with the release of methane to the atmosphere? (L.C)

A

Greenhouse effect / global warming / reducing ozone damage

159
Q

Apart from leaking pipes, name a major source from which methane is released to the atmosphere? (L.C)

A

Fossil fuels / oil / coal

160
Q

What structural feature of 2,2,4-trimethylpentane results in it having a high octane rating? (L.C)

A

Branching / methyl branches

161
Q

Give a structural feature which increase the octane number of a hydro carbon other than branching. (L.C)

A

Ring

162
Q

Classify C₃H₆ as having one, two or three tetrahedrally bonded carbon atoms. (L.C)

A

One

163
Q

What is meant by octane number? (L.C)

A

The measure of the tendency of a fuel to resist auto-ignition.

164
Q

What is meant by the term structural isomer? (L.C)

A

Molecules with the same molecular formulas but different structural formulas.

165
Q

Give two features of alkanes that make them less prone to ‘knocking’. (L.C)

A
  • Short chained

- Highly branched

166
Q

What are mercaptans used for? (L.C)

A

Are used to alert to leakage as they have a strong smell (from the sulfur).

167
Q

Oxygenates are often added to petrol. Give an example of an oxygenate and explain why it is added to petrol. (L.C)

A

Addition of alcohol, to increase the octane number of the petrol and they cause less pollution as they reduce the level of carbon monoxide in the exhaust fumes.

168
Q

What lead compound used to be added to petrol? Explain why it was added to the petrol and give a reason why it is no longer added to petrol. (L.C)

A

Tetraethyl lead

  • Allowed the petrol to burn smoothly
  • Toxic, harmful to environment and people’s health.
169
Q

Petrol is obtained from crude oil in an oil refinery. Name the process used to obtain the petrol from crude oil. (L.C)

A

Fractional distillation

170
Q

Explain the term catalytic cracking and briefly say why it is used? (L.C)

A

Involves changing long chained hydrocarbons for which there is low demand, into short chained hydrocarbons for which there is high demand.
- It is used to prevent auto-ignition (knocking)

171
Q

Name two features of the structure of alkanes that would make them less prone to knocking. (L.C)

A
  • Short chained

- Highly branched

172
Q

Give the name and structural formula of the substance found in petrol that is given an octane number of 100. (L.C)

A

2,2,4 trimethylpentane

C₈H₁₈ / (CH₃)2CHCH₂C(CH₃)₃

173
Q

Give a wide scale use of ethyne. (L.C)

A

Cutting and welding metals

174
Q

Describe what you would see if ethyne is burned. Write a balanced equation for this reaction. (L.C)

A

A smoky luminous flame

2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

175
Q

Name the reagent you would use to show that ethyne is unsaturated and describe what you would observe when this reagent is applied to a sample of ethyne gas and shaken. (L.C)

A

n

176
Q

Explain the term unsaturated hydrocarbon. (L.C)

A

N

177
Q

Phosphine gas often occurs as an impurity in ethyne. How would you remove the phosphine from the ethyne? (L.C)

A

N

178
Q

Draw diagrams to represent the structure of (i) benzene and (ii) methylbenzene. (L.C)

A

Drawn

179
Q

Methylbenzene is often used I the laboratory in preference to benzene. Give a reason for this. (L.C)

A

N

180
Q

What does aromatic compound mean? (L.C)

A

Aromatic - contains a benzene ring in the structure

Compound - A substance that is made up of two or more elements combined together chemically.

181
Q

Is benzene water soluble? Give a reason for your answer. (L.C)

A

N

182
Q

Describe what you would expect to see if a test tube of ethyne is burned in air. (L.C)

A

N

183
Q

Ethyne is an unsaturated compound. Describe how you could demonstrate this in the laboratory. (L.C)

A

N

184
Q

Write an equation for the combustion of methane in excess air. Where are you most likely to encounter methane in your life. (L.C)

A

N

185
Q

Oil refining separated crude oil into a number of different fractions. Discuss the industrial process. (L.C)

A

N

186
Q

Outline a use for mercaptans. (L.C)

A

N

187
Q

Define octane number. (L.C)

A

The octane number of a fuel is the measure of its tendency to resist ‘knocking’.

188
Q

Discuss methods of improving the efficiency in the internal combustion engine when a mixture of petrol and air is drawn into the cylinder and ignited by a spark. (L.C)

A

M

189
Q

By using alternatives to lead, how can we say that the combustion of petrol becomes more environmentally friendly? (L.C)

A

N

190
Q

Octane and 2,2,4-trimethylpentane are structural isomers. Why is it possible to separate these isomers by fractional distillation? (L.C)

A

N

191
Q

Write a balanced equation for the production of ethyne in the laboratory. (L.C)

A

N

192
Q

Give the name or formula of an impurity present in the ethyne gas produced. (L.C)

A

N

193
Q

Give the name or formula of a compound present that would have given rise to this impurity. (L.C)

A

N

194
Q

Suggest a way of removing the gaseous impurity from the ethyne gas produced. (L.C)

A

N

195
Q

Give an everyday use of ethyne. (L.C)

A

Cutting and welding metals

196
Q

Classify C₃H₇OH as having one, two or three tetrahedrally bonded carbon atoms. (L.C)

A

Three

197
Q

Classify CH₃COCH₃ as having one, two or three tetrahedrally bonded carbon atoms. (L.C)

A

Two

Chemistry (Tara) (50 decks)

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