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Fuels and Heats Of Reaction Flashcards

1
Q

Define octane number

A

It is a measure of the tendency of a fuel to resist knocking

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2
Q

What is the best fuel? ie the fuel with an octane number 100

A

2,2,4 Trimethylpentane

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3
Q

What is the worst fuel? ie the fuel with an octane number 0

A

Heptane

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4
Q

What are three ways that increase octane number?

A

-Adding a cyclic structure
-Increase branching
-Reduce chain length
-Adding oxygenates

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5
Q

Three ways of making petrol are what?

A

isomerisation
Catalytic cracking
dehydrocyclization

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6
Q

Three ways to make hydrogen are what?

A

-Electrolysis of water
-Steam reforming of natural gas
-produce in oil refineries when dehydrocycliasation is carried out

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7
Q

What are the disadvantages of hydrogen?

A

–Hydrogen is highly flammable in air
-Storage problems due to flammability
-transportation problems

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8
Q

What are the benefits of hydrogen?

A

–emits only water which is a clean product
–Reduces environmental pollution
–Reduce dependency on fossil fuels

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9
Q

What are the uses of hydrogen?

A

-Fuel
-Manufacture of ammonia
-Hydrogenating vegetable oils to manufacture margarine

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10
Q

What is knocking?

A

knocking is the pinging sound resulting from premature ignition of the fuel-air mixture.

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11
Q

Define organic chemistry

A

It is the study or compounds of carbon

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12
Q

What is a hydrocarbon?

A

It is a compound that contains only carbon and hydrogen

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13
Q

Name some common sources of hydrocarbons-

A

-Coal
-Natural gas (methane)
-Crude oil

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14
Q

What are fossil fuels ?

A

They are fuels that were formed from the remains of plants and animals that lived millions of years ago

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15
Q

What type of compounds are alkanes?

A

Saturated compounds- they contains only single bonds between atoms in a molecule

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16
Q

Name the first 5 alkanes

A

Methane
Ethane
Propane
Butane
Pentane

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17
Q

What happens to the molecular formula of alkanes as you go from 1-10

A

They increase by 2 hydrogens and 1 carbon

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18
Q

Name the alkanes going from 6-10

A

Hexane
Heptane
Octane
Nonane
Decane

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19
Q

Give the structural formula of pentane

A

CH3CH2CH2CH2CH3

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20
Q

What is another word for alkanes?

A

Paraffins

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21
Q

What is the general formula for alkanes?

A

CnH2n+2

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21
Q

Define a homologous series

A

It is a series of compounds with
-Similar chemical properties
-Show graduation in physical properties
-Have a general formula for its members
-Each member has a similar member of preparation
-Each member differs from the previous member by a CH2 unit

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22
Q

Define a structural isomer

A

They are compounds with the same molecular formula but different structural formula

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23
Q

Give an example of a structural isomer

A

Butane and Methylpropane

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24
What does IUPAC names refer to?
Their systemic names
25
What does a methyl group look like?
CH3
26
What does an ethyl group look like?
C2H5
27
WHAT DOES A PROPYL GROUP LOOK LIKE?
C3H7
28
What are the common alkyl groups?
Ethyl, methyl and propyl
29
If two alkyl groups are added and are the same what prefix should you add/?
di...... ....
30
How should you name a chain that has alkyl groups?
You should name them starting at the side that would give them the smallest numbers
31
What is the hydrocarbon called that forms a ring?
Cyclohexane
32
What are the alkenes?
They are compounds that are unsaturated meaning they contain one or more double or triple bonds between atoms in the molecule
33
What are the names of the first 4 alkenes?
Ethene Propene But-1-ene But-2-ene
34
If two carbon atoms have a single bond between them what shape is created?
Tetrahedral
35
If two carbon atoms have a double bond between them what shape is created?
Planer
36
What is the general formula for alkenes?
CnH2n
37
What state are the first three alkenes in?
Gases Then the next 11 are liquids and the last ones waxy solids
38
What happens to the boiling point of alkanes and alkenes?
As you move down the homologous series of alkanes, the boiling points generally increase. This trend is due to the increasing molecular size and mass of the alkanes. With each addition of a CH₂ unit, the molecular mass increases, leading to stronger van der Waals forces
39
What are alkynes?
These contain a triple carbon carbon bond so are highly unsaturated
40
What is the general formula of alkynes?
CnH2n-2
41
What alkyne do you need to know and what is its structure?
Ethyne - C2H2- H-C-triple bond-C-H
42
wHAT IS ETHYNE USED IN?
Gas used in oxyacetylene welding and cutting. It is used as it can be burned on controlled amounts of oxygen in temperatures of excess 3000 degrees c
43
What are aromatic compounds?
Are compounds that contain a benzene ring structure in their molecules
44
what is an aliphatic compounds?
Is an organic compound that consists of open chains of carbon atoms and closed chain compounds (ring) that resemble them in chemical properties.
45
What two points puzzled chemists about benzene?
Reactivity- it was predicted that benzene would be highly reactive due to the expected presence of three double bonds. in fact benzene was found to be very unreactive Bond Length- it satisfies the valencies of carbon and hydrogen, there is a problem about the alternating double and single bonds between carbon atoms. Bond lengths are meant to be the same length between a single carbon carbon bond and then double bonds are slightly smaller in length. But, in benzene all bond lengths are the same length whether single or double
46
Why is benzene unreactive?
47
What is fractional distillation?
It is a process used to separate crude oil into a number of useful parts. This process involves heating the crude oil and separating the various parts on the basis of their boiling points.
48
What are the names of the separated groups groups of similar compounds called?
Fractions
49
What is placed in the fractional distillation column?
Crude oil which mainly consists of hydrocarbons
50
Are alkenes soluble in water?
no alkene are non polar while water is polar so it is insoluble
51
what bonding is present in alkenes?
van der walls forces- which are non polar
52
what are alkenes soluble in?
non polar solvents eg cyclohexane
53
what is a non polar solvent example?
cyclohexane
54
How do you name a alkene\/
identify longest carbon chain number carbon chain starting from side with double bond closest If there is six carbons in the chain and the double bond is on carbon two- hex-2-ene Then identify functional group branch Place the name of this before the Hex-2-ene
55
What is a structural isomer\/
It is a compound with the same molecular formula but different molecular structure Has different properties- as they are different compounds
56
Are the alkanes polar or non polar and why?
Non polar as they have van der walls forces between molecules
57
Are alkanes soluble? in water
N as they are non polar compounds
58
What are alkanes soluble in?
non polar solvent like cyclohexane
59
What is it called when a hydrocarbons longest chain forms a closed ring /
Cyclo- something
60
Cyclohexane and cyclohexene are different why?
Cyclohexane contains all 6 carbon which are singly bonded to each other Whereas cyclohexene has 6 carbon atoms and a double bond
61
Are alkynes soluble or in soluble in water?
Insoluble in water as they have van der walls forces
62
What are aromatic hydrocarbons?
they are compounds which contain a benzene ring
63
Give some example of aromatic hydrocarbons?
ethylbenzene methylbenzene benzene
64
What is autoignition
It is the premature ignition of a fuel air mixture before a spark has been introduced
65
Does natural gas come from crude oil?
no it is found on its own in porous rock deep underground
66
WHat happens to a car if it uses fuel with a low octane number
Fuel can auto ignite causing -excessive wear on the engine -Loss of power
67
Crude oil is made of what
A mixture of different hydrocarbons
68
What affects octane number
Number of branches Length of chain Presence of rings
69
How does isomerisation raise octane number?
It changes straight chained alkanes into branched changed isomers
70
How does catalytic cracking raise octane number?
It involves using heat and a catalyst to break down long chain hydrocarbons into short chains
71
How does dehydrocyclization raise octane number?
Involves using a catalyst to change linear molecules into cyclic molecules
72
How does adding oxygenates raise octane number?
Is the addition of an oxygen containing compound eg methanol, ethanol and MTBE
73
How does adding lead raise octane number?
Adding lead compounds
74
Why was adding lead to increase octane number banned?
Lead is poisonous health hazard and poisons the metals in the catalytic converter in the car
75
What are examples of oxygenates?
methanol, ethanol and MTBE
76
What is an endothermic reaction
It is a reaction that gets cooler
77
wHat is an exothermic reaction
it is a reaction which gets hotter ie produces heat
78
What is the heat of reaction?
it is the energy change when the number of moles of reactants in the balanced equation react fully
79
What is the heat of combustion?
IT is the heat change when 1 MOLE of a substance is burned completely in excess oxygen
80
What is the heat of formation?
is the heat change of a compound that takes place when one mole of a compound is formed from its elements in their standard state
81
How do you measure heat of combustion
using a bomb calorimeter Place sample being tested into metal bomb with oxygen gas ignition WIRES IGNITE SMAPLE the SAMPLE IS BURNING SO HEATS SURROUNDING WATER Stirrers stir the mixture- heat equally spread thermometer reads increase in temp heat combustion can be then calculated
82
What products are always formed from the combustion of hydrocarbons?
Co2 and H20
83
wHAT MUST BE PRESNET FOR A COMBUSTION REACTION TO OCUUR
02
84
WHAT ORDER SHOULD YOU BALANCE AN EQUATION
C--H--O
85
HOW MANY MOLES OF FUEL SHOULD YOU HAVE IN YOUR EQUATION
1 Look at the definition it is when one mole of a substance is burned completely in excess oxygen
86
Define the kilogram calorific value
Is the value of the energy produced when 1kg of fuel is burned completely in oxygen
87
define bond energy
it is the energy require to break 1 mole of a certain covalent bond and separate the neutral atoms completely from each other
88
What are the elements that are in their standard state?
H2, Cl2, O2, N2, F2, I2, Br2
89
What is the heat of neutralisation?
It is the heat change when one mole oh H+ ions from an acid react with one mole of oh- ions from a base
90
1 mole of HCL will produce how many moles of H+
1 mole
91
what is hess's law
it states that the heat change for a reaction is independent of the pathway taken
92
what is the law of conversation of energy
it states that energy cannot be created or destroyed only transferred from one form to another
93

Chemistry (12 decks)

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