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Flashcards in Fuels Deck (65):

(1) Which row of the table describes propene?

hydrocarbon, unsaturated


(2) Propene can form the polymer poly(propene).
Draw a diagram to show the part of a poly(propene) molecule formed from two
propene molecules.

correct repeating unit(1)
• two correct units shown with
continuation bonds (1)


(2) ) Describe a test that shows that molecules of propene contain carbon to carbon double

bromine (water) (1)
• (bromine water) turns (from
orange) to colourless/or is
decolourised (1)


(1) C10H22 → 2C3H6 + C4H10
decane propene butane
Give the total mass of products formed if 17 g of decane is cracked in this way

17 (g)


(2) Explain what is meant by cracking.

break down of hydrocarbons /
large molecules / alkanes (1)
• into small(er) molecules (1)


(2) Explain why it is necessary to crack crude oil fractions that contain large

less demand for (fractions
containing) large molecules ORA
• large molecules are less useful
ORA (1)


(2) Suggest two reasons why it is usually difficult to burn different hydrocarbon fuels
efficiently in the same appliance.

• fuels can be in different
states / specific example
• different sized molecules(1)
• different viscosities (1)
• different boiling point /
vaporisation temperatures
• different ease of ignition
/some fuels more flammable
• different amounts of air /
oxygen needed (1)


(1) The fuels that can be used in the stove are obtained by the fractional distillation of
crude oil.
Which of these statements about the fractions obtained by the fractional distillation
of crude oil is correct?

diesel oil is used as a fuel for some trains


(3) Ethane, C2H6, is present in crude oil.
Write the balanced equation for the complete combustion of ethane.

2C2H6 + 7O2 → 4CO2 + 6H2O
• reactant formulae (1)
• product formulae (1)
• balancing correct formulae


(6) ) Petrol is the fuel used in many car engines.
Research is being carried out into the use of hydrogen instead of petrol.
Evaluate the advantages and disadvantages of using hydrogen rather than petrol as a
fuel for cars.

• plenty of water / raw material
• limited supplies of crude oil
• hydrogen produces only water as waste
• petrol produces carbon dioxide
• carbon dioxide (emissions) may cause global warming
• hydrogen has to be produced
• requires energy / electricity to produce it
• producing electricity from non-renewable sources produces
carbon dioxide
• expensive to produce
• problems of storage of large volumes of flammable gas
• stronger / heavier / bigger tanks needed
• hydrogen a gas, petrol a liquid, hydrogen leaks more likely
• limited outlets / conversion costs
• shorter distance between refuelling


(1) Which of the following statements is true

molecules in diesel are larger than molecules in petro


(2) Explain what is meant by cracking.

• break down of
/ alkanes) (1)
• into smaller
/ alkanes) (1)


(3) Explain why ethene is described as an unsaturated hydrocarbon

(molecule) containing
(carbon-carbon) double /
multiple bond (1)
• contains (atoms of)
carbon and hydrogen (1)
• only (1)


(2) Describe what you would see when a sample of ethene is shaken with
bromine water

orange/brown/yellow (1)
• to colourless (1)


(6) Explain how the presence of sulfur in fossil fuels can lead to damage to the
environment and how the amount of damage can be reduced.

cause of acid rain
• burning sulfur
• produces sulfur dioxide
• escapes into atmosphere
• dissolves in rain water
• forming acidic solution / sulfurous / sulfuric acid
• falls to the ground as acid rain
effect of acid rain
• acidification of lakes
• kills fish
• kills trees / forests
• damage / erosion of stonework
reduction of damage
• calcium carbonate
• from limestone
• may be converted into calcium hydroxide
• waste gases from power stations
• passed through carbonate or hydroxide
• removing sulfur dioxide


(1) Natural gas is a good fuel because

it produces no solid waste on complete combustion


(2) The complete combustion of fossil fuels releases gases into the atmosphere.
Explain how these gases could cause an increase in the temperature of the Earth

carbon dioxide / water
vapour (released into the
atmosphere) (1)
• absorbs OWTTE heat
(radiated from Earth)(1)


(1) State an advantage of replacing fossil fuels with biofuels made from plants

(biofuels) renewable / plants
remove carbon dioxide from
atmosphere / conserves fossil


(2) Explain a disadvantage of replacing fossil fuels with biofuels made from plants.

(growing crops for
biofuels) requires land (1)
• less land for food
production / less food /
deforestation / destroys
habitat / food prices
increase (1)


(6) Incomplete combustion of methane can occur in gas heaters such as the one
shown in the photograph.
Explain how incomplete combustion occurs and the problems it can cause.

• lack of / insufficient oxygen
• {blocked burner jets / poor servicing} leads to lack of oxygen
• poor ventilation leads to lack of oxygen
• complete combustion cannot take place
• produces carbon / soot
• produces carbon monoxide
• wastes fuel
• soot stains / damages decorations etc
• soot causes health problems
• soot may block gas jets
• carbon monoxide is toxic
• combines with haemoglobin / forms carboxyhaemoglobin
• prevents blood carrying oxygen
• no oxygen reaches cells / no respiration / death


(1) For which fractions does the demand exceed the supply?

LPG, petrol and diesel


(2) Explain why cracking is needed.

use of {fractions / large molecules /
long chain hydrocarbons} of {less
demand / less useful / lower value}
/ ORA (1)
• to meet demand / small molecules
needed (1)


(1) As the number of carbon atoms in the molecules of a hydrocarbon increases

the boiling point of the hydrocarbon


(1) What is the formula of a molecule of ethene?



(2) Ethene can be converted into poly(ethene).
Write a balanced equation for this reaction.

ignore n missing on polymer structure
LHS (1) RHS (1)
(where X could be CH3 or similar


(2) Explain why some people are concerned about the increase in the amount of
carbon dioxide in the atmosphere.

greenhouse gas / traps heat in
atmosphere (1)
• may lead to increasing global
temperature / global warming (1)


(2) Explain how the product of combustion of these sulfur impurities affects the environment.

sulfur dioxide formed (during
combustion of fuel) (1)
• sulfur dioxide {dissolves in rain /
forms acid (rain)} (1)
• an effect of acid rain e.g. harms
{fish / plants / statues / buildings} /
lowers pH of lakes (1)


(2) Explain the difference between non-renewable and renewable fuels

• e.g. fossil fuels (1)
• when used, not replaced (in a
reasonable time) / finite supply (1)
Renewable fuels
• produced {from plants / electrolysis
(to produce hydrogen)} (1)
• (therefore) when used, able to be
(quickly) replaced (1)


(6) Evaluate the advantages and disadvantages of using bioethanol, instead of petrol,
as a fuel for cars.

Advantages of bioethanol
• is renewable / petrol is finite / takes a long time to form crude
• crops to make bioethanol regrown quickly/takes a long time to
form crude oil
• use reduces demand on fossil fuels
• carbon dioxide is removed from air when growing crops (which
are used in ethanol production)
• may be sulfur impurities in petrol, none in ethanol / ethanol is
less polluting than petrol (does not produce sulphur dioxide )
• ethanol burns more completely, petrol does not
Disadvantages of bioethanol
• less readily available than petrol / fewer filling stations than for
petrol (in UK but not in some countries)
• lots of crops needed to generate sufficient fuel to replace petrol
• less farmland available for growing food crops
• currently few cars are built to run on bioethanolbioethanol fuel
(in cars) runs out faster / over shorter distances / less energy


(3) Write the balanced equation for the overall reaction that takes place when the
hydrogen reacts with oxygen in the fuel cell.

2 H2 + O2 → 2 H2O (3)


(1) Apart from the possibility of an explosion, state another disadvantage of using
hydrogen, rather than diesel, as a fuel for buses.

requires {electricity / energy} for
electrolysis (1)
• must be stored in {heavy / strong /
pressurised} cylinders (1)
• gas can escape easily (1)
• fewer fuel stations (1)


(1) Crude oil is a mixture of mainly



(1) Fuel oil is used as a fuel in

power station furnaces


(3) Write the balanced equation for the complete combustion of methane.

CH4 + 2O2 → CO2 + 2H2O


(1) When 1 g of methane is burnt, 56 kJ of heat energy is produced.
Calculate the heat energy produced when 1 g of octane is burnt.

48 (kJ) (1)
5472 /114 = 48 (kJ) (1)
5472/114 (1)


(2) ) State two factors that make a good fuel.

easy to ignite / low boiling point /
low viscosity (1)
{burns readily/easily} /
not produce too much {soot/ash/
smoke} / burns with
{clean/blue} flame / burns
cleanly (1)
easy to {store/


(2) Draw the structure of a propene molecule, showing all of the bonds

one C=C in a three consecutive
carbon atom molecule (1)
rest of structure correct, ignore
bond angles, conditional on first
marking point(1)


(1) One molecule of decane, C10H22, can be cracked to produce one molecule of
propene and one molecule of an alkane X only.
The formula of a molecule of alkane X is



(3) Given a sample of each gas, describe a test to show which gas is propane and
which gas is propene.

add bromine (water) / aqueous
bromine (and shake the tube)(1)
stays orange / no change / does
not go colourless in
{propane/alkane} (1)
turns colourless / decolorises in
{propene/alkene} (1)


(6) Explain how poly(propene) molecules are formed from propene molecules and
relate the properties of poly(propene) to its uses.

Making the polymer
many propene molecules
join/react together
form a long chain
polymerisation reaction
propene is the monomer
propene is unsaturated / has a double bond
poly(propene) has single bonds
propene is a gas and forms poly(propene) which is a solid
the C=C bond breaks / opens up

Properties of poly(propene) with related uses
property – flexible, low density (lightweight), shatterproof, high
softening point, non-toxic, strong, tough, good insulator, water
proof, resistant to corrosion, long lasting, can be moulded into
shape, can be made into fibres
Uses of poly(propene)
use – to make plastic bags, packaging, buckets, bowls, food
containers, ropes, carpets, thermal underwear, Thinsulate
items, toys, bottles, bottle caps, laboratory equipment, medical
equipment, pipes, car bumpers, crates, furniture, tubing


(1) ) One of the gases in the table is present in a much larger amount in today’s
State the name of this gas



(1) A gas not named in the table makes up about 21% of today’s atmosphere.
State the name of this gas



(1) The amount of carbon dioxide in the early atmosphere was reduced by

(the gas dissolving in oceans)


(2) Explain why it is difficult to be certain about the composition of the Earth’s early

no humans on Earth (1)
• no measurements taken
• different sources conflict
• websites may refer to
different times (1)


(2) All of the oxygen in this sample of air reacted to form copper oxide.
After the reaction, the volume of gas remaining was 41cm3
Calculate the percentage of oxygen in this sample of air

50 – 41 (1) M1
(= 9)
9/50 x 100 (1) M2
(= 18)


(1) ..................Cu + O2 → ..................CuO

2 Cu + O2 → 2 CuO


(1) This fraction is more difficult to ignite than most other fractions and is used as
a fuel in large ships.

fuel oil


(1) This fraction is obtained from the top of the fractionating column.



(1) This fraction has a higher boiling point than kerosene and is used as a fuel for
some cars.

diesel oil


(1) Which of these cannot be a product of burning hydrocarbon fuels?



(2) 2CH4 + ................O2 → 2CO + ................H2O

2CH4 + 3 O2 (1)
• 2CO + 4 H2O (1)


(2) Explain how carbon monoxide can cause death.

(carbon monoxide)
combines with
haemoglobin/red blood
cells (1)
• lack of oxygen (to
brain/cells) (1)


(2) Explain a problem caused by growing plants to produce biofuels.

uses up
(farm)land/space/area (to
grow crops for fuel) (1) M1
• less (farm)land to grow
crops for food (1) M2
• can cause food prices to
rise (1) M3
• (could lead to) food
poverty (1) M4
• (could lead to)
deforestation/soil erosion
(1) M5


(1) Which of the following statements about alkenes is correct?

alkenes are unsaturated


(2) Explain a problem caused by the disposal of polymers.

non biodegradable (1)
persist in landfill sites (1)
produce gases/fumes when
burnt (1) M1
gases may be toxic/harmful (1)
cannot be recycled (1)
new {raw material/crude oil}
needed (1)


(6) Explain the properties required of a good fuel.

A good fuel should
Burning considerations
• ignite easily
• burn easily
• release a lot of /sufficient heat energy when it
is burnt
Usage considerations
• be safe to use
• be safe/easy to transport
• be {safe/easy/convenient} to store
• be reasonably cheap
Supply considerations
• readily available/good supply
• be renewable/sustainable/not finite
Products considerations
• not produce (much) solid/ash when burnt
• not produce much/any smoke
• contain little/no sulfur
• not produce {toxic/harmful} gases/fumes
• carbon neutral
• not produce too much carbon dioxide or other
named gas such as sulfur dioxide or greenhouse gases


(1) When the experiment is complete there is a danger that water will rise up the
delivery tube into the hot test tube.
State what you would do to prevent this

remove delivery tube from water
before stopping heating


(1) C12H26 → C2H6 + C6H12 + X
X is



(1) State what is meant by unsaturated.

contains a {double/multiple}


(3) Propane and propene are bubbled through separate samples of bromine water.
Describe what you would see in these tests.

bromine water is orange
• propane: (remains) orange
/ no colour change (1)
• propene: becomes
colourless /decolourises


(2) In industry, long chain hydrocarbon molecules are cracked to form shorter chain
hydrocarbon molecules.
Explain why this process is important.

shorter chain molecules are
more useful ORA (1)
• demand for shorter chain
molecules ORA (1)
• meets demand
• reduces the excess of longer
chain molecules (1)
• (cracking) produces alkenes
• alkenes used to make
polymers (1)


(1) Which of these is the formula of a molecule of a hydrocarbon?



(2) Draw the structure of a molecule of propene, showing all covalent bonds.

carbon skeleton correct including
double bond (1)
rest of molecule correct (1)


(3) Methane burns in oxygen to form carbon dioxide and water.
Write the balanced equation for this reaction.

CH4 + 2O2 → CO2 + 2H2O


(6) Describe the advantages and disadvantages of using bio-methane rather than
natural gas as a source of energy.

• renewable / sustainable
• more plants can be grown
• crops use up carbon dioxide and produce oxygen
when growing /photosynthesising
• carbon neutral because the carbon produced during
combustion is used when growing the plants
• does not use up crude oil/non-renewable resources

• crops grown for bio-fuels use up land
• land could otherwise be used to provide homes / less
farmland available for growing food crops
• lots of crops required to provide a small amount of
• bad season reduces availability
• carbon emissions due to transport and production if