Organic chem - 2 Flashcards
(197 cards)
1
Q
What are the 4 points about crude oil?
A
- Crude oil is a fossil fuel. It is formed by the decomposition of dead bodies of creatures that died millions of years ago.
- It is pumped from under the ground or sea.
- Thick, black, viscous, pungent liquid , = no use in this form.
- It is found in large quantities in countries like Iran,
the North Sea, the USA, Russia etc.
2
Q
What does crude oil consist of?
A
A mixture of hydrocarbons –> mixture means not chemically combined
3
Q
What does the types of hydrodro carbons present in oil depend on?
A
Where it is found in the world.
4
Q
What can the hydrocarbons be?
A
They may be small chained molecules e.g ethane, or may consist of many carbon atoms.
5
Q
What are the smaller hydrocarbons (b.p & uses?
A
They are volatile & low boiling points. Used as fuels or chemical feedstock.
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)
7
Q
What is fractional distillation?
A
Fractional distillation is a process that is used to separate the crude oil into its components.
8
Q
Why can fractional distillation method be used?
A
This method can be used as the oil is a mixture of molecules.
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.
10
Q
What is a positive of the principle?
A
These ‘fractions’ are now more useful and can be used for various purposes.
11
Q
What is the first stage in the fractionation of crude oil?
A
- The crude oil is heated to high temperatures and is fed into large fractionating towers. These towers may be 80m high.
12
Q
What is the second stage in the fractionation of crude oil?
A
- The tower is kept at a high temperature at the bottom.
13
Q
What is the third stage in the fractionation of crude oil?
A
- As you go up the tower there are trays present to collect the ‘fractions’.
14
Q
What is the fourth stage in the fractionation of crude oil?
A
- The temperature decrease as you ascend the tower.
15
Q
What is the fifth stage in the fractionation of crude oil?
A
- 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.
16
Q
What is the sixth stage in the fractionation of crude oil?
A
- The heavier hydrocarbons will condense first, while the lighter hydrocarbons will rise higher and condense higher up the tower.
17
Q
What is C1-C4?
1 + 2
A
- Gas
- Refinery fuel
- Liquefied from propane or butane gas (LPG).
18
Q
What is C5-C10?
1 + 2
A
- Light gasoline
- Motor fuel –> what we get petrol from
19
Q
What is C7-C10?
1 + 2
A
- Naptha (v.important)
- Petrol
- Feedstock for petrochemical industry
20
Q
What is C10-C14?
1 + 2
A
- Kerosene
- Fuel for planes
- Paraffin lamps/stoves
21
Q
What is C14-C40?
3
A
- Gas oil and heavy gas oil
- Diesel oil
- Lubricating oil for engines
22
Q
What is C35 and upwards?
1 + 3
A
- Residue
- Heavy industrial fuel
- Used in catalytic cracking
- Bitumen for road surfaces
23
Q
What is natural gas a mixture of?
A
Natural gas is a mixture of hydrocarbons.
24
Q
What is natural gas usually made up of?
A
Usually made up of methane, ethane, propane and butane.
25
Where in the world are gas fields made up mainly of methane (95%)?
The North Sea and Kinsale gas fields.
26
What is the natural gas in the USA mainly made up of?
Propane and butane.
27
What are propane and butane sold as in Europe?
Sold as liquefied petroleum gas (LPG)
28
Does natural gas have an odour?
No its odourless.
29
What compounds are added to the natural gas before distribution and why?
Mercaptans, for safety reasons
30
Why is mercaptans added for safety reasons?
Mercaptans have a strong smell so this alerts to a leakage.
31
What do a lot of industries that are using natural gas as a reactant have to do?
The mercaptans have to be removed if it is going to be used as a raw material.
32
What must the petrol and oxygen do to ensure the engine runs smoothly?
The petrol and oxygen must ignite and explode evenly at the correct time to ensure the engine runs smoothly.
33
What causes auto-ignition ('knocking')
It is caused by poor quality petrol (long straight molecules)
34
When does 'knocking' happen?
'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)
35
What does 'knocking' damage?
It can damage the engine and lead to loss of power.
36
What happens if the petrol is rich in straight chained hydrocarbons?
Auto-ignition occurs.
37
How does petrol rich in branched chained hydrocarbons burn?
Burns more smoothly and efficiently
38
Draw the structural formula of 2,2,4-trimethylpentane.
Drawn
39
Draw and name the other reference molecule.
Heptane, drawn
40
What is the octane number of 2,2,4 trimethylpentane?
100
41
What is the octane number of heptane?
0
42
Define octane number
The measure of the tendency of a fuel to resist auto-ignition.
43
Why is 2,2,4 trimethylpentane (iso-octane) given an octane number of 100?
As it is one of the most efficient.
44
In straight chained hydrocarbons, the shorter the alkane the ………. the octane number.
Higher
45
In branched-chained hydrocarbons, the grater the number of branches the ……… the octane number.
Higher
46
Do cyclic and aromatic hydrocarbons have a high or low octane number?
High
47
What octane number can a 'good' quality petrol have?
97
48
What are the 3 structural features of alkanes that prevent autoignition?
1. Short chained
2. Highly branched
3. Cyclic/aromatic i.e benzene
49
What is the first solution to auto-ignition? (additive)
- Add lead to the petrol.
| - Added in the from of tetraethyl lead
50
Is leaded petrol safe?
No it is toxic, harmful to the environment and peoples health. (Phased out due to this reason)
51
Is unleaded petrol more or less expensive?
More expensive
52
What does isomerisation (reforming) involve? (2nd solution to auto ignition)
- It involves changing straight-chained hydrocarbons into branched-chained isomers.
- Burns more smoothly = higher octane number.
53
What does dehydrocyclization (reforming) involve? (3rd solution to auto-ignition)
- 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.
54
What does catalytic cracking (reforming) involve? (4th solution to auto-ignition)
- 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.
55
What is addition of oxygenates? (last solution to auto-ignition)
The addition of oxygen compounds to the petrol
56
What are the two types of addition oxygenates?
- Addition of alcohols i.e methanol (octane no. 114)
| - Addition of ethers i.e methyl tert-butyl ether (octane no.118)
57
What does (a) addition of alcohols & (b) addition of ethers do?
(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.
58
Define reforming
Reforming involves changing straight chained hydrocarbons into branched chained hydrocarbons or cyclic hydrocarbons.
59
Define cracking
Cracking involves changing long chained hydrocarbons for which there is low demand, into short chained hydrocarbons for which there is high demand.
60
Define auto-ignition
The early explosion of petrol-air mixture caused by increasing pressure in the engine.
61
Define octane number
The octane number of a fuel is the measure of its tendency to resist 'knocking'.
62
What is a catalytic converter?
A catalytic converter is fitted to car exhausts to reduce pollution from the exhaust fumes.
63
What do exhaust fumes contain if leaded petrol is used?
- Carbon monoxide, nitrogen monoxide, nitrogen dioxide, lead compounds & unburned hydrocarbons.
64
What does the catalytic converter do?
It changes harmful gases into harmless gases.
65
What is an example of a catalytic converter changing these harmful gases to harmless gases?
CO + NO --> CO2 + 1/2 N2
| => able as it has a high energy triple bond.
66
What does the catalytic converter contain and where?
It contains catalysts such as platinum, palladium and rhodium inside a stainless steel case.
67
What does the inside of a converter look like?
A honeycomb
68
What does the honeycomb arrangement in the converter allow for?
- A large surface area = increased removal of harmful gases into harmless gases such as carbon dioxide and nitrogen.
69
What does the lifetime of a converter depend on?
- The type of petrol used
70
Does the lifetime of a converter shorter when using leaded or unleaded petrol?
Leaded
71
What is the policy that all new cars are fitted with catalytic converters?
- EU, 1993
72
Why is ethene a very important organic compound?
As it is the 'building block' from which many plastics are made.
73
In the laboratory what is ethene prepared by?
A dehydration reaction of ethanol. Dehydration means removing water. This is an example of an elimination reaction.
74
What is the apparatus for the preparation ethene?
- Boiling tube
- Retort stand
- Glass tubing
- Water bath
- Test tubes
- Bunsen burner
- Rubber bung
75
What are the materials for the preparation of ethene?
- Ethanol
- Aluminium oxide
- Water
76
What is the physical appearance of ethene?
Colourless with a sweetish smell.
77
What is ethenes solubility in water?
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.
78
What is the combustion of ethene?
- 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'.
79
What is the first test for unsaturation in ethene?
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
What is the equation for the addition of bromine in ethene?
C2H4 + Br2 --> C2H4Br2
| C2H4 +Br2 --> 1,2-dibromoethane
81
What is the second test for unsaturation in ethene?
- 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
What is ethyne used for?
- Used for cutting and welding metals as when burned in oxygen it can reach temperatures over 3000'C
83
What is the equation for the preparation of ethyne?
CaC2 + 2H2O --> C2H2 + Ca(OH)2
| Calcium dicarbide reacts with water to produce ethyne and calcium hydroxide.
84
What is the apparatus for the preparation of ethyne?
- Dropping funnel
- Buchner flask
- Glass tubing
- Conical flask
- Two holed rubber bung
- Test tubes
- Water bath
85
What are two solid impurities that are present in the calcium dicarbide?
- Calcium phosphide, Ca3P2
| - Calcium sulfide, CaS
86
What are two gaseous impurities in the ethyne gas collected?
- Phosphine, PH3
| - Hydrogen sulfide H2S
87
How are the gaseous impurities removed?
Removed by bubbling the impure ethyne gas through acidified copper (II) sulfate solution.
88
What are the physical properties of ethyne gas?
Colourless gas with a sweetish smell if pure.
89
What is ethynes insolubility in water?
- 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
What is the combustion of ethyne?
- 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
What is the first test for proving the unsaturation of ethyne?
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
What is the second test for the unsaturation?
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
Classify C3H6 as having one, two or three tetrahedrally bonded carbon atoms
Three
94
Butane is a major component of LPG. What do the letters LPG stand for?
Liquefied petroleum gas
95
Draw two structural isomers of butane
Drawn
96
Methane is a major component of natural gas. Why are mercaptans added to natural gas?
To give an odour / to detect leaks
97
Methane is a major component of natural gas. What environmental change of or effect is associated with the release of methane to the atmosphere?
Greenhouse effect / global warming
98
Methane is a major component of natural gas. Apart from leaking pipes, name a major source from which methane is released in the atmosphere ?
Fossil fuels/ oil / coal
99
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?
(1) Branching / short chain
| (2) Aromatic / ring
100
Describe the appearance of calcium carbide
black / dark
101
Write a balanced equation for the reaction between water and calcium carbide.
CaC₂ + H₂O --> C₂H₂ + CaO
102
What is observed when a sample of ethyne gas in burned in air? Write a balanced equation for the combustion of ethyne in oxygen.
- luminous bright flame / sooty flame
| - C₂H₂ + 2.5O₂ --> 2CO₂ + H₂O
103
Ethyne, C2H2, is described as an unsaturated hydrocarbon. Describe a test you could carry out to show that ethyne is unsaturated.
Bromine is added across the carbon-carbon triple bond the red-brown colour of the bromine goes colourless.
104
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.
Equation = C₂H₂ +Br₂ --> C₂H₂Br₂
| Organic product = Dibromoethene
105
The common name for ethyne has, C2H2, is acetylene. Give one major use of the gas.
Cutting metals / welding metals
106
What is the function of the glass wool in the preparation of ethene?
Keeps ethanol at the end of the test tube.
107
Describe the appearance of aluminium oxide.
White powder (solid)
108
State and explain two safety precaution which should be observed when carrying out the experiment to prepare a sample of ethene.
1. Keep gas away from flames - because gas is flammable.
| 2. Disconnect tube - to prevent suckback.
109
Write a balanced equation for the reaction involved in the preparation of ethene.
C₂H₅OH → C₂H₄ + H₂0
110
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?
Unsaturated - undergoes addition reactions
111
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.
Flame - luminous smoky flame
| Equation - C₂H₄ + 3O₂ → 2CO₂ + 2H₂0
112
Give the name and formula of the solid which is heated using the Bunsen burner in the preparation of ethene.
Aluminium oxide
113
Identify the solid which is used to keep the ethanol at the end of the test tube.
Glass wool
114
What precaution should be observed when heating is stopped in the preparation of ethene? Why is this necessary?
- Dismantle the apparatus
| - To prevent suck-back
115
Give one major use of ethene gas.
Manufacture of polythene / make PVC
116
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?
Naphtha have shorter chains / less carbon atoms
117
Name the homologous series to which propane and butane belong. Draw the structural formula of propane. (L.C)
Alkanes
| CH₃CH₂CH₃ - DRAW!
118
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)
Propane smaller with fewer electrons, therefore weaker intermolecular forces.
119
What is meant by saying that compounds are structural isomers? Draw the structural formula of the isomer of butane (L.C)
Structural isomers are molecules with the same molecular formula but different structural formulas.
- (CH₃)₂CHCH₃
120
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)
Aluminium oxide
| White
121
Write a balanced equation for the reaction involved in the preparation of ethene. What term describes this type of reaction. (L.C)
C₂H₅OH → C₂H₄ + H₂O
| - Elimination
122
State four precautions that should be observed when carrying out the preparation of ethene by this method. (L.C)
- Keep gas from flame
- Safety glasses
- Tie hair back
- Air-tight stopper
123
Explain the term unsaturated (L.C)
Contains a multiple bond between two carbon atoms.
124
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)
Calcium dicarbide
| Black / grey
125
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)
Test - Add bromine water until decolorises
| Observe - Double carbon-to-carbon bond present
126
Give a major use of ethene. (L.C)
Manufacture of polythene
127
Give a major use of ethyne (L.C)
Cutting metals / welding metals
128
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)
Ethene less luminous/smoky
129
Write a balanced equation for the complete combustion of ethene. (L.C)
C₂H₄ + 3O₂ → 2CO₂ + 2H₂O
130
Write a balanced equation for complete combustion of ethyne. (L.C)
2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O
131
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)
- Removal of hydrogen
| - Ring formation
132
Ethanol is an example of an oxygenate. Give another example of an oxygenate. Give two reasons why oxygenates are added to petrol. (L.C)
- Methanol
- Raise octane number
- Decrease knocking
133
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)
- Light gasoline
| - Naptha
134
What is meant by the octane number of a fuel? (L.C)
The measure of the tendency of fuel to resist auto-ignition.
135
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)
Drawn
136
Give the name and formula of the solid A which is heated using the Bunsen Burner. (ethene prep) (L.C)
Aluminium oxide / Al₂O₃
137
Identify the solid B which is used to keep the ethanol at the end of the test tube. (ethene prep) (L.C)
Glass wool
138
What precautions should be observed when heating is stopped? Why is this necessary? (ethene prep) (L.C)
Remove the delivery tube from the trough of water and
| disconnect tube from test tube to prevent suck-back.
139
Give one major use of ethene gas. (L.C)
Manufacture of polythene
140
In which fraction of crude oil do pentane and its isomers occur? (L.C)
Light gasoline
141
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)
Naptha have shorter chains and gas oil have longer chains
142
Bitumen is a residue fraction obtained from crude oil. Give one use for bitumen. (L.C)
Road surfacing / roofing
143
What is catalytic cracking? What is its economic importance in oil refining? (L.C)
Cracking involves changing long chained hydrocarbons for which there is low demand, into short chained hydrocarbons for which there is high demand.
144
What is the function of the glass wool? (prep ethene)(L.C)
Keeps ethanol at the end of test tube to avoid wetting the aluminium oxide.
145
Identify the solid X and describe its appearance. (prep ethene) (L.C)
Aluminium oxide
| White powder
146
State and explain two safety precautions which should be observed when carrying out the student experiment (prep of ethene) (L.C)
Keep away from gas as gas is flammable
| Air-tight stopper as it stops ethene escaping
147
Write a balanced equation for the reaction involved in this preparation. (ethene) (L.C)
C₂H₅OH → C₂H₄ + H₂O
148
Define the term unsaturated. (L.C)
Contains only single bonds around carbon atoms.
149
Describe how you would carry out another test to confirm that ethene is unsaturated. (other than potassium manganate) (L.C)
Add bromine water
| Red / orange / yellow → colourless
150
Describe the flame that would be observed when a combustion test is carried out on a sample of ethene gas. (L.C)
Yellow / luminous / smoky sooty flame
151
Write a balanced equation for the combustion of ethene in excess oxygen. (L.C)
C₂H₄ + 3O₂ → 2CO₂ + 2H₂O
152
Identify the liquid x and the solid y (prep of ethyne gas) (L.C)
```
X = water
Y = calcium dicarbide
```
153
Describe the appearance of calcium dicarbide. (L.C)
Black / dark
154
Write a balanced equation for the reaction between water and calcium dicarbide. (L.C)
2C₂H₂ + 5O₂ → 2CO₂ + 2H₂O
155
Butane is a major component of LPG. What do the letters LPG stand for? (L.C)
Liquefied petroleum gas
156
Draw the two structural isomers of butane. (L.C)
Drawn
157
Why are mercaptans added to natural gas? (L.C)
To give an odour to detect leaks
158
What environmental change or effect is associated with the release of methane to the atmosphere? (L.C)
Greenhouse effect / global warming / reducing ozone damage
159
Apart from leaking pipes, name a major source from which methane is released to the atmosphere? (L.C)
Fossil fuels / oil / coal
160
What structural feature of 2,2,4-trimethylpentane results in it having a high octane rating? (L.C)
Branching / methyl branches
161
Give a structural feature which increase the octane number of a hydro carbon other than branching. (L.C)
Ring
162
Classify C₃H₆ as having one, two or three tetrahedrally bonded carbon atoms. (L.C)
One
163
What is meant by octane number? (L.C)
The measure of the tendency of a fuel to resist auto-ignition.
164
What is meant by the term structural isomer? (L.C)
Molecules with the same molecular formulas but different structural formulas.
165
Give two features of alkanes that make them less prone to 'knocking'. (L.C)
- Short chained
| - Highly branched
166
What are mercaptans used for? (L.C)
Are used to alert to leakage as they have a strong smell (from the sulfur).
167
Oxygenates are often added to petrol. Give an example of an oxygenate and explain why it is added to petrol. (L.C)
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
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)
Tetraethyl lead
- Allowed the petrol to burn smoothly
- Toxic, harmful to environment and people's health.
169
Petrol is obtained from crude oil in an oil refinery. Name the process used to obtain the petrol from crude oil. (L.C)
Fractional distillation
170
Explain the term catalytic cracking and briefly say why it is used? (L.C)
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
Name two features of the structure of alkanes that would make them less prone to knocking. (L.C)
- Short chained
| - Highly branched
172
Give the name and structural formula of the substance found in petrol that is given an octane number of 100. (L.C)
2,2,4 trimethylpentane
| C₈H₁₈ / (CH₃)2CHCH₂C(CH₃)₃
173
Give a wide scale use of ethyne. (L.C)
Cutting and welding metals
174
Describe what you would see if ethyne is burned. Write a balanced equation for this reaction. (L.C)
A smoky luminous flame
| 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O
175
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)
n
176
Explain the term unsaturated hydrocarbon. (L.C)
N
177
Phosphine gas often occurs as an impurity in ethyne. How would you remove the phosphine from the ethyne? (L.C)
N
178
Draw diagrams to represent the structure of (i) benzene and (ii) methylbenzene. (L.C)
Drawn
179
Methylbenzene is often used I the laboratory in preference to benzene. Give a reason for this. (L.C)
N
180
What does aromatic compound mean? (L.C)
Aromatic - contains a benzene ring in the structure
| Compound - A substance that is made up of two or more elements combined together chemically.
181
Is benzene water soluble? Give a reason for your answer. (L.C)
N
182
Describe what you would expect to see if a test tube of ethyne is burned in air. (L.C)
N
183
Ethyne is an unsaturated compound. Describe how you could demonstrate this in the laboratory. (L.C)
N
184
Write an equation for the combustion of methane in excess air. Where are you most likely to encounter methane in your life. (L.C)
N
185
Oil refining separated crude oil into a number of different fractions. Discuss the industrial process. (L.C)
N
186
Outline a use for mercaptans. (L.C)
N
187
Define octane number. (L.C)
The octane number of a fuel is the measure of its tendency to resist 'knocking'.
188
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)
M
189
By using alternatives to lead, how can we say that the combustion of petrol becomes more environmentally friendly? (L.C)
N
190
Octane and 2,2,4-trimethylpentane are structural isomers. Why is it possible to separate these isomers by fractional distillation? (L.C)
N
191
Write a balanced equation for the production of ethyne in the laboratory. (L.C)
N
192
Give the name or formula of an impurity present in the ethyne gas produced. (L.C)
N
193
Give the name or formula of a compound present that would have given rise to this impurity. (L.C)
N
194
Suggest a way of removing the gaseous impurity from the ethyne gas produced. (L.C)
N
195
Give an everyday use of ethyne. (L.C)
Cutting and welding metals
196
Classify C₃H₇OH as having one, two or three tetrahedrally bonded carbon atoms. (L.C)
Three
197
Classify CH₃COCH₃ as having one, two or three tetrahedrally bonded carbon atoms. (L.C)
Two
