Developing Fuels practise questions

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1. DF10: Governments and car manufacturers have both investigated ways of reducing
the emissions from car engines. One possible way is the use of `lean burn' technology
for petrol engines.
A lean burn engine uses more air to burn a fixed mass of fuel than does a normal
engine. This reduces the amount of carbon monoxide produced in the exhaust gases.
(i) Suggest why less carbon monoxide is formed.
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[1]
(ii) DF10: The amount of nitrogen monoxide, NO, produced is also less in lean burn
engines.
Suggest and explain a possible reason why this is the case.
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[2]
[Total 3 marks]
2. EL6: Nitromethane, CH3NO2,
does not burn as quickly as petrol.
One of the more spectacular pollutants in drag car racing is flames of burning
nitromethane being emitted from the exhaust.
The products formed from this burning `nitro' are carbon dioxide, water and nitrogen
gas.
(i) Write a balanced equation for the burning of nitromethane.
[3]
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DF10: Exhaust gases from petrol fuelled cars may be less spectacular, but toxic
pollutants such as nitrogen monoxide, NO, are present in the exhaust emitted.
Explain the origin of nitrogen monoxide emitted by p
etrol engines.
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[3]
[Total 6 marks]
3. DF10: Heterogeneous catalysts play an extremely important role in many chemical
reactions, including the control of polluting emissions and in the manufacture of various
chemicals.
(a) Many cars now have `threeway' catalytic converters fitted. The following diagram
illustrates how they work.…read more

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The threeway catalytic converter involves both a reduction and an
oxidation phase. Why is the conversion of NOx
to N2
described as
reduction?
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[1]
(b) (i) Diesel exhaust contains a higher proportion of particulates than petrol
exhaust. Particulates are very small solid soot particles.
Suggest and explain why diesel fuel produces more particulates than petrol.
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[3]
(ii)
Diesel engines without catalytic converters produce less NOx than an
equivalent petrol engine.
Explain the formation of NOx in petrol engines.…read more

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DF5: Heterogeneous catalysts are often used in the reforming process. The process is
called `platforming' when the catalyst is platinum metal. Coke (from side reactions in
the process) reduces the efficiency of the catalyst.
Describe the stages involved in heterogeneous catalysis and explain why the formation
of coke can cause the platinum to become ineffective.
In your answer, you should use appropriate technical terms, spelled correctly.
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DF5
5.
The diagram illustrates a model for heterogeneous catalysis.
The following phrases describe some of the steps labelled on the above diagram.
Write the numbers of the step or steps corresponding to each phrase.
Bonds in reactants weaken and break
Step(s) .................................................
New bonds in products form
Step(s) .................................................
Diffusion from catalyst surface
Step(s) .................................................…read more

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DF5
6. Catalysts also play a role in the oil industry in the production of more useful
hydrocarbons from longer chain fractions.
Zeolite catalysts replaced the traditional silica/alumina catalysts in the 1960s.
The following box illustrates some of the reactions catalysed by zeolites.
(i)
Use words from the following list to describe reactions A to
D.
isomerisation reforming cracking
reaction A ....................................................
reaction B ....................................................
reaction C ....................................................
reaction D ....................................................
[4]
(ii) By what type of formula are the molecules represented?
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Suggest one
reason why the hydrocarbon formed in reaction B is more useful
than the hydrocarbon it is made from.
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[1]
[Total 10 marks]
DF8
7. The longer a car engine runs, the more exhaust gases are produced. Use the steps
below to obtain an estimate of the volume of exhaust gases produced by a car each
second.
The equation for the complete combustion of heptane vapour in the car engine is
shown below,
Assume that petrol is pure heptane (C7H
16)
.…read more

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Calculate the volume of exhaust gases produced per second.
One mole of molecules of the exhaust gases occupies 60 dm3
at the high
temperature in the exhaust.
3 ­1
answer ........................ dm s
[1]
[Total 5 marks]
DF5
8. Catalytic converters can reduce still further the pollution from lean burn engines.
Catalytic converters use a precious metal such as platinum spread thinly over a
honeycomb support. The platinum acts as a heterogeneous catalyst.
(i) What is meant by the terms
heterogeneous a
nd catalyst?
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