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Developing Fuels Flashcards

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1
Q

What is the enthalpy change for an exothermic reaction

A

Bond making so gives out heat energy and is a negative enthalpy change

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2
Q

What is enthalpy change

A

Change in heat energy during chemical reaction from reactants to surroundings

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3
Q

Standard enthalpy changes are measured under standard conditions, what are these conditions

A

25 degrees C/298K
1 atmosphere/1.01x10^5 Pa
1 moldm^-3
Chemicals need to be in preferred state at 25 degrees C

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4
Q

Standard enthalpy change of combustion

A

When 1 mole of substance is completely burned in oxygen under standard conditions

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5
Q

Explain a fuel combustion energy change experiment

A
  1. Known volume of water in copper calorimeter, record water temperature
  2. Record spirit burner mass (with fuel in)
  3. Burn till water 30 degrees C
  4. Take water temperature (max) reweigh burner
  5. Calculate energy transferred
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6
Q

What is the energy transferred equation

A 
Water mass (g) x 4.2 x temperature change(K)
M X C x delta T
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7
Q

How much is 1 gram in cm^3

A

1 g = 1 cm^3

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8
Q

Standard enthalpy change of formation

A

When 1 mole of compound is formed from elements in standard states

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9
Q

Why does standard enthalpy formation changes have to be calculated indirectly from enthalpy combustion change

A

Difficult to cause reactants to react under standard conditions so use standard enthalpy combustion change in an enthalpy cycle

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10
Q

What does Hess’s law state

A

Chemical reaction is independent of the route taken if initial, final conditions identical

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11
Q

Standard enthalpy change of reaction

A

Enthalpy change that occurs when reactants shown in balanced equation react under standard conditions to give standard state products

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12
Q

How is standard enthalpy neutralisation measured

A

From energy out when acid reacts with alkali in aqueous solutions

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13
Q

What is the neutralisation ionic equation

A

H(^+) (aq) + OH(^-) (aq) -> H20(l)

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14
Q

What is the enthalpy reaction change equation

A

All energy absorbed to break bonds - all energy released to make bonds

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15
Q

What is average bond enthalpy

A

Energy needed to break a mole of bonds in gas phase, averages over, any different compounds

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16
Q

How is bond enthalpy and bond length related

A

Positive nuclei attracted to shared electrons, two positive nuclei repel, as do electrons. Between two nuclei attractive and repulsive forces balance, this is bond length. Stronger attraction between atoms, higher bond enthalpy shorter bond length

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17
Q

How do you workout gas volumes from balanced symbol equations

A
  1. Find moles of one of the molecules mass/Mr
  2. Use balance equation to work out moles of molecule want to find volume of
  3. Moles x 24dm^3 (as 1 mole of amy gas)
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18
Q

How can you use a gas syringe to measure gas volume

A
  1. Attach gas syringe to reaction vessel opening
  2. Show total volume gas made (if more than one gas made won’t show how much of each)
  3. Reaction end when no change in volume
  4. Vigorous reactions can blow plunger out, careful
  5. Calculate number molecules in the volume
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19
Q

What has the highest entropy level

A 
Highest:
Gases
Aqueous solution
Liquid
Solid
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20
Q

What’s cracking

A

Larger molecule made into smaller molecules, solves supply and demand

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21
Q

What are the products of alkanes being cracked

A

Branched alkanes and branched alkenes
OR
Smaller alkanes and cycloalkanes

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22
Q

What are the products is cycloalkanes being cracked

A

Alkenes and branched alkenes

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23
Q

What are the products of alkenes being cracked

A

Smaller alkenes

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24
Q

What does a catalyst do

A

Speeds up chemical reaction, can be recovered chemically unchanged after reaction

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25
Q

What happens in a riser reactor

A

Hot vaporised hydrocarbons and zeolite catalyst fed in bottom of tube, forced up by steam

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26
Q

What is the problem in catalytic cracking

A

Coke forms on catalyst surface, eventually inactive, needs o be regenerated to overcome problem

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27
Q

What happens after the riser reactor

A

It goes into the separator and the steam carries cracked products away, leaving solid catalyst (goes into regenerator hot air blows off coke) back to base of reactor, repeat cycle

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28
Q

Why is no extra heating needed in riser reactor

A

Energy releases burning coke heats catalyst, energy transferred to feedstock, no extra heating

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29
Q

What is catalysis

A

Process that speeds up chemical reaction using catalyst

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30
Q

What is homogeneous catalysis

A

Reactants and catalyst in same physical state

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31
Q

What is a heterogeneous catalyst

A

Reactant and catalyst different physical states

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32
Q

What happens when a solid catalyst is used to increase reaction rate, (reaction occurs on solid surface)

A
  1. Reactants, atoms form binds on catalyst surface, they’re absorbed
  2. Bonds in reactant weakened
  3. Reactant bonds break
  4. New bonds form between reactants, held close to surface, for, products
  5. Weakens bond to catalyst surface, product released
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33
Q

Why can’t leaded petrol be used in cars with a catalytic converter

A

Heterogeneous catalysis, poison molecules absorbed stronger to catalyst surface than reactant molecule. Catalyst can’t catalyse a reaction of poison - inactive poison molecules block surface sites

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34
Q

What does the feedstock process do

A

Removes soulful compounds and prevents severe catalyst poisoning

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35
Q

What are zeolites

A

Complex large aluminium, silicon, oxygen lattices carrying negative charges

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36
Q

What is isomerisation

A

A molecule with the exact same atoms in a different arrangement

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37
Q

How does reforming occur

A

Uses platinum catalyst suspended on aluminium oxide with various promoters to make catalyst more efficient. Original ,molecules passed as vapours over solid catalyst at around 500 degrees C

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38
Q

What is a structural isomer

A

Have different structural arrangements of atoms but still same molecular formula

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39
Q

Why do atoms with same formula and different structure have different properties

A

Skeleton and functional group could be the same, only functional group attached to different carbon atom. Different physical properties, chemical properties may be different

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40
Q

What is the enthalpy change for an endothermic reaction

A

Bond breaking reaction that takes in heat energy so has a positive enthalpy change

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41
Q

What is photochemical smog made of

A

Mix of primary and secondary pollutants

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42
Q

What/how is ozone made

A

It is a secondary pollutant, not released into atmosphere directly, formed from chemical reactions occur when sunlight shines on mix of primary pollutants oxygen and water vapour

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43
Q

Why is ozone vital in stratosphere

A

Can cause toxic gas, high human health damage, is irritating, acts as greenhouse gas contributes to global warming

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44
Q

What does photochemical smog cause

A

Haziness, reduced visibility close to ground, eye/nose irritation, breathing difficulty, asthma enhanced

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45
Q

What is the complete combustion equation

A

Hydrocarbon + oxygen -> carbon dioxide + water

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46
Q

Why does incomplete combustion occur and what does it produce

A

If oxygen is limited combustion of hydrocarbons lead to water and either carbon monoxide/carbon (particulates) or both

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47
Q

What is the product of burning sulfur compounds in fuels

A

Sulfur dioxide

S + O2 -> SO2

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48
Q

How can nitrogen oxides form

A

Some made by burning nitrogen compounds in fuels, in low proportions
Nitrogen and oxygen in air react in high temperature if vechile engine

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49
Q

How is sulphuric acid formed

A

Sulfur dioxide and water react in lower atmosphere form weak sulphuric acid

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50
Q

How is strong sulfuric acid (VI) made

A

Sulfur dioxide oxidised to form sulfuric (VI) acid in stratosphere, reacts with atmosphere water

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51
Q

How is nitric acid formed

A

NO and NO2 react with water and oxygen to form nitric acid
2NO + 1 1/2O2 + H2O -> 2HNO3 nitric acid
NO2 + 1/2 O2 +H2O -> 2HNO3 nitric (V) acid, strong

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52
Q

What does acid rain cause

A

Breathing difficulties, corrodes limestone, kills forest/lake life

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53
Q

Why does more diesel have more complete combustion and how does it effect the environment

A

Higher temperature to run engine

Less carbon dioxide made but more nitrogen oxide

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54
Q

What/why are particulates a problem

A

Tiny particles of liquid in air

Settle in lungs decrease lung function

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55
Q

What do catalytic converters do

A

Catalyst reactions change pollutants to carbon dioxide, water, nitrogen occur naturally but under exhaust system conditions, go too slowly to remove pollutant

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56
Q

What do catalytic converters contain and what reactions do they speed up

A

Platinum/rhodium on honeycomb structure. They’re three way catalysts as speed up reactions
Carbon + oxygen -> carbon dioxide
Hydrocarbons -> carbon dioxide + water
Carbon monoxide + nitrogen oxide -> nitrogen + carbon dioxide (only for petrol)

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57
Q

What has be correct in catalyst system for it to work

A

Air and petrol mix carefully controlled, exact stoichiometric mix for fuel (ratio of hydrocarbon:oxygen for complete combustion)

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58
Q

What happens if there is too much fuel in the catalyst mix

A

If not enough oxygen for complete combustion, can’t remove carbon monoxide and hydrocarbons

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59
Q

What temperature does a platinum catalyst start working at

A

240 degrees C

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60
Q

If the platinum catalyst is alloyed with rhodium what is the temperature the catalyst starts working at

A

150 degrees C

61
Q

What is the main pollutant in Diesel engines

A

Carbon monoxide, hydrocarbons, particulates and nitrogen oxide compounds

62
Q

How are particulates removed by diesel

A

Particulate filters contain a variety of material e.g ceramic

63
Q

What is regeneration and when does it occur

A

Burn off carbon particles

Increase temperature, decided when by vehicle computer but increases fuel consumption

64
Q

How are nitrogen oxides reduced

A

By recycling exhaust gases cylinder, lowering temperature

65
Q

What are the biggest sources of air pollutant

A

Transport, industry and power generation

66
Q

How is sulfur dioxide removed from power stations

A

Using calcium oxide

67
Q

How are particulates removed from power stations

A

Using wet scrubbers (catch them in water droplets) from some car exhaust using filters

68
Q

How is carbon monoxide helped to fully combust in car petrol

A

Oxygenates are added

69
Q

How are emissions reduced

A

New vehicles not allowed to pollute above certain level
Yearly MOT includes emissions test
1992 compulsory new cars catalytic converter
Government tax pollution e.g raise fuel tax
Developing new fuels, cause less pollution

70
Q

What does fractional distillation do

A

Separates hydrocarbons in crude oil into useful fractions

71
Q

What are organic compounds sub-divided into

A

Homologous series

72
Q

What are alkanes

A

Hydrocarbons
Saturated compound
CnH2n+2

73
Q

What are cycloalkanes

A

Hydrocarbons
Saturated compounds
CnH2n

74
Q

What are alcohols

A

Contain oxygen
CnH2n+1+OH
-OH is hydroxyl group (functional group) can attach to carbon atom on chain

75
Q

What are alkenes

A

Unsaturated hydrocarbons

CnH2n

76
Q

What is a benzene and what causes it to be stable

A

Benzene has a ring of delocalised electrons

Quite stable due to double bond electrons delocalised round carbon ring

77
Q

What are benzene ring structures called

A

Arenes or aromatic compounds

78
Q

What are ethers

A

Oxygen atom attached to two aryl or alkyl groups

General formula R-O-R

79
Q

What are aliphatic compounds

A

Have carbon chains (not rings) e.g alkanes

80
Q

What are aromatic compounds

A

Contain delocalised electrons in ring e.g benzene

81
Q

What steps are in nomenclature (naming organic compounds)

A
  1. Count carbon atoms in longest continuous chain
  2. Main functional group of molecules gives end of name
  3. Number carbons in longest chain with main functional group on lowest possible number. If more than one longest, pick one with most side-chains
  4. Write carbon number functional groups on before suffix
  5. Side chains/less important functional groups added as prefixes in alphabetical order after number carbon atom each attached to
  6. If more than one identical side chain/functional group use di- (2)
82
Q

What occurs in addition polymerisation

A

Alkenes double bond opens and joins to make longer chains - polymers

83
Q

How are alkenes tested for

A

Bromine water to test for C=C double bond

  1. Shake alkene with orange bromine water, solution quickly decolourises
  2. Bromine added across double bond, for dibromoalkane
  3. Test for unsaturation
84
Q

What type of reaction is bromine reacting with alkene

A

Electrophilic addition

85
Q

What happens in the electrophilic addition reaction

A
  1. Double bond in alkene repels electrons in Br2, polarising Br-Br
  2. Br-Br bind induced polarisation, Br nearest to alkene slightly positive, other slightly negative
  3. Alkenes double bond opens as double bond has plenty of electrons, easily attacked by electrophiles, Br (positive) added to alkene
  4. Intermediate very unstable tries to bond, Br (7 in outer shell, only bond with one atom)
  5. Br attacks positive carbon
86
Q

What is carbocation

A

Organic ion with positively charged carbon atom

87
Q

What evidence is there for a electrophilic addition reaction mechanism

A

Once ethane reacts with bromine, form carbocation so can react with another Br- or Cl-

88
Q

How are bromoalkanes formed

A

Alkenes undergo hydrogen halide addition

89
Q

How can alcohols be made from alkenes

A

Hydrating alkenes with use of acid catalyst

  1. Cold concentrated acid reacts with alkene in electrophilic addition reaction
  2. Add cold water and warm products, hydrolysed, form alcohol, not all acid used up, acts as catalyst
90
Q

How can ethanol be made by steam hydration

A
  1. Ethene can be hydrated by steam at 300 degrees C and 60 atm with phosphoric (V) acid catalyst
  2. Reversible reaction low, reaction yield (5%) can recycle unreacted ethene gas, overall yield (95%)
91
Q

What makes alkanes more volatile and what does it change

A

Lower Mr

Burn easier as react oxygen, alkane must first be vaporised

92
Q

What is an isomer

A

Distinct compounds with different physical properties, often different chemical properties too

93
Q

What is a structural isomer

A

Have same molecular formula, atoms bonded different order. Have structural formulae. Various ways structural isomerism occur

94
Q

What is a chain isomers

A

Only one alkane corresponding to each of the molecular formula, need more than four or more carbon atoms different arrangements are chain isomers
Molecular formula is same, different structure lead to different properties

95
Q

When does position isomerism occur

A

When there’s an atom/group of atoms substituted in carbon chain/ring, functional groups. Occurs when functional group in different positions in molecules

96
Q

What is functional group isomerism

A

Same molecular formula and different functional group, as have different functional group, in different homologous series

97
Q

What is E/Z isomerism a type of

A

Stereoisomerism

98
Q

How would you change an Z molecule into an E vice versa

A

Spin one end of molecule round in relation to other end of molecule round in relation to other end. Must break li bond in double bond first

99
Q

What would the name of the stereoisomers be if the Hydrogens are across the double bond

A

E isomer

100
Q

What would the name of the stereoisomers be if the Hydrogens are both above or both below

A

Z isomer

101
Q

What would the name of the stereoisomers be if there are no hydrogens but e.g two CH3 on opposite sides of the bond

A

Trans isomer

102
Q

What would the name of the stereoisomers be if there are no hydrogens but e.g two CH3 on the same side of the bond

A

Cis isomer

103
Q

What causes E/Z isomerism

A

Restricted rotation around C=C double bond

104
Q

Why are single bonded carbon atoms arranges like a tetrahedron

A

Molecules take shape allows all electrons pairs to get as far from each other as can

  1. Carbon atom makes four single bonds, molecule doesn’t lie flat. Atoms form 3D tetrahedral structure
  2. Angle between any two covalent bonds (109.5)
  3. Show bonds are as far apart as can be using wedges and dotted lines
  4. Shape round each carbon atom means sing,e bonded carbon atoms
105
Q

If double bond, atoms bonded to carbon what shape is made

A

Trigonal planar

106
Q

What is a single bond in organic molecules made of. When are they made

A

Sigma bonds
Formed when two orbitals overlap in straight line between two atoms
Highest electron density between two positive nuclei
Sigma bonds usually strong

107
Q

What is a double bond made of

A

Sigma and Pi bond made when two p orbitals overlap sideways

Pi bond weaker than sigma, double bond less than twice as strong as single bond

108
Q

What happens when an alkene reacts with e.g bromine

A

Breaks double bonds and Br bonds to it

109
Q

What effects how a hydrocarbon burns in an engine

A

The higher the octane rating the more smoothly it burns

110
Q

What occurs in preignition and which molecule is more prone to it

A

Straight chain molecules
Petrol and air mix compressed tend to explode, second explosion a spark passed through double explosion causing knocking in engine

111
Q

How can octane rating be increased

A

Rearranging straight chain molecules into isomers with branched chains

112
Q

Why is it likely that butane content in petrol is likely to be lowered

A

Volatile, responsible for evaporative emissions

Causes ozone formation and photochemical smogs

113
Q

Why is butane in petrol if it has bad environmental effects

A

Helps petrol perform well in modern engines

If removed must be replaced

114
Q

What is a renewable fuel

A

Don’t add to greenhouse gases(or other pollution) are carbon neutral
Carbon dioxide still given out in making e.g solar panels

115
Q

What are the objections of using renewable fuels

A

Not sufficiently reliable

Need lots of e.g wind turbines and get a fraction of energy supplied by fossil fuels (but won’t last forever)

116
Q

What are biofuels made of

A

Derived from renewable plant and animal matter

117
Q

How is biodiesel made

A

Chemically reducing fats, oils with alcohol producing fatty acid esters - trans-esterfication

118
Q

How is bioethanol made

A

Ethanol made by sugar fermentation (from crops e.g maize)

119
Q

How is biogas made

A

Breakdown of organic waste matter

120
Q

What are the advantages of biodiesel over diesel

A

Make from waste oil rather than fossil fuel oils
Carbon neutral
Some diesel vehicles can run on pure biodiesel (most are regular mixes)
Biodegradable if spill
Contains barely any sulfur, less oxides of sulfur emission
Less particulates, carbon monoxide, hydrocarbons than petrol and diesel

121
Q

What are the disadvantages of biodiesel

A

Makes more nitrogen oxides

122
Q

What is a benefit of biofuel use

A

Biofuels made carbon dioxide when burnt, which plants absorb while grow so carbon neutral

123
Q

What is an advantage of biodiesel/gas

A

Can make from landfill waste

124
Q

What is a problem of biofuel use

A

Need to modify engine to be able to use high methanol concentration

125
Q

How can hydrogen gas be used

A

Burned in modified engine

Used in fuel cell (convert hydrogen to oxygen to water, chemical process makes electricity) water only waste made

126
Q

How can hydrogen be obtained

A

From sea water, takes energy to extract it. Method to extract it determines how environmentally friendly fuel is e.g if renewable source wind, hydrogen fuel nearly carbon neutral
Hydrogen like an energy carrier

127
Q

Why is transporting and storing hydrogen difficult

A

Highly flammable, needs liquefying due to low energy to volume ratio of hydrogen gas
Will need a whole new fuel supply infrastructure e.g pipelines

128
Q

What are the advantages of using hydrogen instead of fossil fuels

A

Renewable made by water electrolysis
Stored, sent down pipelines in same way methane is
Used in internal engine combustion/fuel cells to make electricity
Makes no carbon dioxide/monoxide or hydrocarbons when burnt

129
Q

What are the disadvantages of using hydrogen instead of fossil fuels

A

Production from water often uses electricity fro, fossil fuel power stations
Less energy dense than petrol, doesn’t release a much energy per gram as petrol
Oxides of nitrogen still made at high temperatures a hydrogen interval combustion engine runs at

130
Q

Why may hydrogen economy be beneficial

A

Would use hydrogen as storing distributing energy. Systems costed over lifetime use, distributing hydrometer by pipeline maybe be cheaper than transmitting energy

131
Q

What does a fuel cell do in a small car and what is the main product

A

Generate electricity and convert chemical energy from fuel into electricity in a chemical reaction with oxygen/oxidising agent in electrochemical cell
Main product is water

132
Q

What is the main problem of cars running in hydrogen

A

Large gas volume required to get mileage equivalent to fuel tank of petrol
Needs storing compactly, could store as liquid in high pressure fuel tank

133
Q

What is liquefied petroleum gas from crude oil distillation also called. How is it stored

A

Auto gas when used in cars
Under pressure store hydrocarbons as liquids
Petrol vehicles can convert to run on both fuels - need bigger fuel tank

134
Q

What does auto gas work in best

Why is it better for the environment

A

High performance engines
Makes 20% less carbon dioxide per mile than petrol as higher carbon to hydrogen ratio
Makes less unguents hydrocarbons, nitrogen oxides than petrol

135
Q

Why is petrol better economically than auto gas

A

Lower road tax and fuel tax

136
Q

What is the bad thing about auto gas

A

Not many LPG filling stations

137
Q

What is liquid natural gas mainly from

A

Oil, natural gas fields

138
Q

What must occur for methane to be liquefied

A

Pressure and cooled below -160 degrees C

139
Q

What changes in the petrol when it is colder

A

Petrol difficult to vaporise, harder to start car so use different blend. More volatile components (more small molecule hydrocarbons)

140
Q

When does the fuel and air mix to ignite

A

Just before the piston at the cylinder top when mix is compressed and heats up

141
Q

What is the ideal gas equation

A 
pV=nRT
p pressure (Pa)
V volume (m^3)
n gas amount (moles)
R gas constant (JK^-1mol^-1)
T temperature (K)
142
Q

Why is it difficult to have affordable clean energy

A

Increasing competitions from other countries for available supplies, higher prices
Supplies maybe be disrupted by political issues

143
Q

What is the prefix or suffix for alkanes

A

-ane

144
Q

What is the prefix or suffix for side-chains in branched alkanes

A

Alkyl-

-yl

145
Q

What is the prefix or suffix for alkanes

A

-ene

146
Q

What is the prefix or suffix for haloalkanes/halogenalkanes

A

chloro-
bromo-
iodo-

147
Q

What is the prefix or suffix for alcohol

A

-ol

148
Q

What is the prefix or suffix for cycloalkanes

A

cyclo-

-ane

149
Q

What is the prefix or suffix for arenes

A

-benzene

Chemistry (5 decks)

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