Green Chemistry Q

8/13/2019 Green Chemistry Q

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1. The enthalpy change of combustion of two fuels is listed below.

fuel enthalpy of combustion/kJ mol 1

hydrogen, H 2 2 !

octane, " H1 ##1!

$a% "alculate the enthalpy change per unit mass for each of the fuels.

Hydrogen&

'ctane&

(3)

$b% (uggest, gi)ing two reasons, which substance is the more useful as a fuel for motor carsand gi)e your reasoning.

*eason 1.................................................................................................................

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*eason 1.................................................................................................................

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$c% (uggest one disad)antage of using the fuel chosen in $b%

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(Total 6 marks)

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2. The following table shows some properties of two different fuels.

+uel Hydrogen thanol

+ormula H 2 " 2H#'H-oiling temperature / " 2#2

nthalpy of combustion per gram / kJ 10 !

"ost per tonne / 1!! #!!

$a% 3rite e4uations to show the complete combustion of&

$i% hydrogen ..........................................................................................................

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$ii% ethanol .............................................................................................................

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$b% Hydrogen and ethanol are used as motor car fuel. (uggest the ad)antages anddisad)antages of each of these fuels in this application. 5se the table, and your answers to

part $a% abo)e to help you.

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(Total 9 marks)

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3. *ead the passage below on EMISSION CONTROL straight through and then more carefully,in order to answer the following 4uestions.

EMISSION CONTROL

6hotochemical smog, a brown ha7e 8ust abo)e the hori7on, was first obser)ed in 9os :ngeles inthe 1;0!s. *esearch showed that the smog was produced by the action of sunlight on aircontaining a )ariety of pollutants, many of them produced by burning fuels.

the most efficient is thestoichiometric ratio. This is the ratio of air to fuel which, in theory, leads to completecombustion of the fuel. too muchfuel will mean insufficient o=ygen in the e=haust fumes. The e=haust system must therefore befitted with o=ygen sensors linked back to an electronically controlled fuel in8ection system.

fficiency is also impro)ed by incorporating other @platinum groupB metals such as rhodium and

sometimes palladium.

"atalysts for dieselAengined )ehicles ha)e to include an efficient filter to remo)e carbon particles. This leads to a further problem because the solid carbon $soot% needs to be burned toallow the filter to continue to work effecti)ely. (oot combustion needs a temperature of #!! G!! " and the e=othermic reaction with o=ygen can raise it to as much as 1!!! ",which candamage the filter. This problem has been tackled by first con)erting all nitrogen o=ides tonitrogen dio=ide $?' 2% using a platinum catalyst, and then using the nitrogen dio=ide to o=idisethe carbon, a reaction which takes place at 2!! ".

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Iou are not asked to summarise the whole passage, nor to include e4uations in your summary.

#t t$" "n% o& 'o r s mmar' stat" t$" n m "r o& *or%s 'o $a+" s"%.

Credit will be i!en for answers written in ood En lish, usin complete sentences and usin technical words correctly and chemical names rather than formulae. A!oid copyin lon

sections from the ori inal te"t. #umbers count as one word, as do standard abbre!iations, units and hyphenated words. Any title you i!e your passa e does not count in your word total.

There are penalties for the use of words in e=cess of 12!.(Total , marks)

4. *ead the passage on @-5


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Non $lorin" l"a $"s to t$" r"s "


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$a% ?ame sodium hypochlorite, ?a'"l, using (tock notation.

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$b% =plain what is meant by a &r"" ra%i al .

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$c% T:F9s can act as catalysts in the pero=ide bleaching process. =plain how catalystsincrease the rate of a reaction.

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$d% Cescribe the TH* key features of an "n+ironm"ntall' "ni n process.

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$e% (uggest why a m lation of dio=ins in the food chain may be harmful to people.

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(Total , marks)

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5. This 4uestion is about some of the chemicals used in car engines and their reactions.

$a% "ompound , shown below, is one component of petrol.

H M " M M " M M " M M " M M " M H

H " H H H H

H " H H H" H

1

1 1

$i% ?ame .

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$ii% Ei)e the "m!iri al formula of .

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$iii% can be made by cracking decane, " 1! H22.

:ssuming only one other product forms in a cracking reaction, deduce themol" lar formula of this other product.

(1)

$i)% 3hat is the sign of the enthalpy change for the reaction in which decane iscracked Ei)e a reason for your answer.

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$)%


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$iii% : te=tbook says RThe catalytic con)erter con)erts the gases coming out of theengine into less harmful onesS.

(tate, with a reason, which of the four gases in the e4uation in $ii% you consider to be l"ast harmful.

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$i)% The diagram below shows the reaction profile for the change which occurs in thecatalytic con)erter.

, n e r g y

2 ? ' $ g % N 2 " ' $ g %

? $ g % N 2 " ' $ g %2 2

6 r o g r e s s o f r e a c t i o n

'n the diagram, show the acti)ation energy, E : .

:dd a line showing the reaction profile if no catalyst is present.(2)

(Total 12 marks)

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6. $a% "hlorofluorocarbons, "+"s, are useful compounds as they are nonAflammable andunreacti)e.


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,. $i%+ormula of substance (tandard enthalpy of formation / kJ mol 1

"H 0 $g% #

' 2 $g% !

"' 2 $g% ;0H2' $g% 202

The e4uation for the complete combustion of methane at 1#! " is&

"H 0$g% N 2'2$g% Q "' 2$g% N 2H2'$g%

5se the gi)en data to calculate the enthalpy of combustion of methane under theseconditions.

(2)

$ii% Thestan%ar% enthalpy of combustion of methane is ;1 kJ mol 1 .

=plain why this is )ery different from the )alue you ha)e calculated in $a%$i%.

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$iii% Here are some data about different fuels&

?ame +ormula (tandard state nergy e)ol)ed per gram / kJ*elati)e cost

per kJ

hydrogen H2 gas 10 2

octane " H1 li4uid 0 .0 !

(tate and e=plain the ad)antages and disad)antages of using hydrogen compared withoctane as a fuel for aeroplanes.

5se the data in the table abo)e and your knowledge of the combustion of fuels to helpyou.

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(Total , marks)

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7. 3hich of the following is not a greenhouse gas

# "H 0

- "' 2

C H2'

/ ? 2(Total 1 mark)

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9. 3hich of the following fuels has the smallest carbon footprint

# petrol made from crude oil

- hydrogen made from methane

C ethanol made from sugar

/ coal(Total 1 mark)

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18. 3hich of the following would not lead to a greater sustainability in an industrial process

# using a catalyst that impro)es atom economy

- running the reaction at a higher temperature

C using biofuels to run the process

/ recycling waste products(Total 1 mark)

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11. "hlorine was used in swimming pools as a bactericide.

The amount of chlorine present can be determined by adding e=cess potassium iodide solutionto a known )olume of swimming pool water. This reacts to form iodine&

"l 2$a4% N 2< $a4%


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$a% $i% The record of measurements re)eals faults both in the procedure and the recordingof measurements. (tate one fault in each of these.

6rocedure .........................................................................................................

*ecording of measurements .............................................................................

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$ii% "alculate the number of moles of sodium thiosulfate used in the titration.

(1)

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$iii% 5se your answer to $ii% to calculate the number of moles of iodine which reacted.

(1)

$i)% Ceduce the concentration of chlorine, in mol dm , in the swimming pool water.

(1)

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$b% The disinfecting action of chlorine in swimming pools is due to the presence of chloric$


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$ii% (uggest on" other reason why the use of chlorine is undesirable in swimming pools.

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$iii% Ei)e the formula for calcium chlorate$


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$i)% "hlorine dio=ide, "l' 2, undergoes a disproportionation reaction when it reactswith water.

0"l' 2 N 2H2' H"l' N H"l'

=plain, in terms of o=idation numbers, why this is a disproportionation reaction.

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$c% Ciscuss and e=plain the science communityBs ad)ice that "+"s should no longer be usedin aerosols, foams and refrigerants. (upport your answer with one or more e4uations.

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(Total 1, marks)

Documents

Green Chemistry Q