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Dubai English Speaking College

Q1.Glucose can decompose in the presence of microorganisms to form a range of products.One of these is a carboxylic acid (M r = .!" containing #!.$% carbon and #.&% hydrogenby mass.

(a" Deduce the empirical and molecular formulas of the carboxylic acid formed.

Empirical formula = ...................... 'olecular formula = ......................(4)

(b" Ethanol is formed by the fermentation of glucose. student carried out this fermentation reaction in a beaker using an a)ueoussolution of glucose at a temperature of *& +C in the presence of yeast.

,rite an e)uation for the reaction occurring during fermentation.

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(1)

(c" -n industry this fermentation reaction is carried out at /& +C rather than *& +C.

Suggest one ad0antage and one disad0antage for industry of carrying out thefermentation at this higher temperature.

d0antage ......................................................................................................

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Disad0antage .................................................................................................

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(d" 1he method used by the student in part (b" 2ould result in the ethanol beingcontaminated by ethanoic acid.

3o2 does this contamination occur4

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(e" Gi0e two differences bet2een the infrared spectrum of a carboxylic acid and that ofan alcohol other than in their fingerprint regions.7se Table A on the Data Sheet.

Difference 6 ...................................................................................................

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Difference * ...................................................................................................

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(Total 10 marks)

Q2. lcohol A (C3/"*C3C3(O3"C3/ undergoes reactions separately 2ith acidified potassiumdichromate(8-" and 2ith concentrated sulfuric acid.

(a" Deduce the -75C name for alcohol A.

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(1)

(b" Dra2 the structure of the organic product B formed 2hen A is oxidised in thereaction 2ith acidified potassium dichromate(8-".

(1)

(c" 12o isomeric alkenes C and D are formed 2hen A is dehydrated in the reaction2ith concentrated sulfuric acid.

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9ame the mechanism for this dehydration reaction.

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(d" Dra2 the structure of each isomer.

-somer C -somer D

(2)

(e" 9ame the type of structural isomerism sho2n by C and D.

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(1)

(f" :ist alcohol A product B and isomer C in order of increasing boiling point.

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(1)

(g" Dra2 the structure of the isomer of A that is not oxidised by acidified potassiumdichromate(8-".

(1)

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(h" Dra2 the structure of the isomer of A that cannot be dehydrated to form an alkeneby reaction 2ith concentrated sulfuric acid.

(1)(Total 9 marks)

Q3.Ethanol can be oxidised by acidified potassium dichromate(8-" to ethanoic acid in a t2o;stepprocess.

ethanol ethanal ethanoic acid

(a" -n order to ensure that the oxidation to ethanoic acid is complete the reaction iscarried out under reflux.

Describe 2hat happens 2hen a reaction mixture is refluxed and 2hy it is necessaryin this case for complete oxidation to ethanoic acid.

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(b" ,rite a half;e)uation for the o0erall oxidation of ethanol into ethanoic acid.

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(1)

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(c" 1he boiling points of the organic compounds in a reaction mixture are sho2n in thefollo2ing table.

Compoun ethanol ethanal ethanoic acid

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contained ethanal and did not contain ethanoic acid.

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(Total 1& marks)

Q4.Ethanol is an important fuel.

(a" dilute a)ueous solution of ethanol can be produced by the fermentation of ana)ueous solution of glucose.-t is claimed that the ethanol obtained from this solution is a carbon;neutral biofuel.

,rite an e)uation for this fermentation reaction.

Gi0e two other essential conditions for this reaction to produce a good yield ofethanol.

9ame a process used to produce a much more concentrated solution of ethanolfrom a dilute a)ueous solution.

State the meaning of the term carbon'neutral in the context of this biofuel.

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(b" student carried out a laboratory experiment to determine the enthalpy change2hen a sample of ethanol 2as burned. 1he heat produced 2as used to 2arm some2ater in a copper calorimeter. 1he student found that the temperature of

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(c" 'ean bond enthalpies can be used to calculate enthalpies of reaction.

(i" Gi0e the meaning of the term mean bon entalp.

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(2)

(ii" Consider the mean bond enthalpy data in the follo2ing table.

C*+ C*C C*, ,-, C-, ,*+

ean bon entalp #k/ mol 1

#6* /# />!to be

calculated!& #>/

7se the data in the table abo0e and the e)uation sho2n to calculate a 0aluefor the bond enthalpy for the O=O double bond in an oxygen molecule.

C3/C3*O3(g" /O*(g" *CO*(g" /3*O(g" FH = @6*

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Q%.Ethanoic acid propyl ethanoate and propan;6;ol are all colourless li)uids. Esters do not gi0e a positi0e result 2ith any of the usual tests for functional groups.

State ho2 you could use chemical tests to sho2 the presence of ethanoic acid andpropan;6;ol in a mixture of the acid the alcohol and the ester.

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Q&. sample of *;methylpropan;*;ol 2as contaminated 2ith butan;*;ol. 1he student separatedthe t2o alcohols using chromatography.

-dentify a reagent or combination of reagents that the student could use to distinguishbet2een these alcohols. State 2hat 2ould be obser0ed for each alcohol.

eagent(s" ..............................................................................................................

Obser0ation 2ith *;methylpropan;*;ol ....................................................................

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Obser0ation 2ith butan;*;ol ....................................................................................

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Q.-n each of the follo2ing )uestions you should dra2 the structure of the compound in thespace pro0ided.

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(a" Dra2 the structure of the alkene that 2ould form 6*;dibromo;/;methylbutane 2henreacted 2ith bromine.

(1)

(b" Dra2 the structure of the alcohol 2ith molecular formula C#36!O that is resistant tooxidation by acidified potassium dichromate(8-".

(1)

(c" Dra2 the structure of the alkene that has a peak due to its molecular ion at m/z =#* in its mass spectrum.

(1)

(d" Dra2 the structure of the organic product 2ith M r =

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(a" -n a)ueous solution some glucose molecules ha0e the follo2ing structure.

(i" Deduce the empirical formula of glucose.

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(1)

(ii" Consider the infrared spectrum of solid glucose.

,a0enumber H cm @6

State 2hy it is possible to suggest that in the solid state 0ery fe2 moleculesha0e the structure sho2n.ou may find it helpful to refer to Table 1 on the Data Sheet.

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(b" -n the absence of oxygen an a)ueous solution of glucose can be fermented toproduce ethanol for use in alcoholic drinks.

,rite an e)uation for this fermentation reaction.Gi0e two other essential conditions for the production of ethanol in this fermentation.

E)uation

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Condition 6 ......................................................................................................

Condition * ......................................................................................................(3)

(c" ny ethanol present in the breath of a drinker can be detected by using abreathalyser.1he ethanol is con0erted into ethanoic acid. 1he breathalyser has negati0e andpositi0e electrodes. current is measured and displayed in terms of alcohol content.

1he o0erall redox e)uation is as follo2s

C3/C3*O3(-" O*(g" C3/COO3(-" 3*O(-"

(i" Dra2 the displayed formula for ethanoic acid.

(1)

(ii" Deduce a half;e)uation for the reduction of atmospheric oxygen to 2ater inacidic solution at one electrode of the breathalyser.

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(1)

(iii" Deduce a half;e)uation for the oxidation of ethanol in 2ater to ethanoic acid atthe other electrode of the breathalyser.

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(1)

(i0" 1he earliest breathalysers used laboratory chemicals to oxidise the ethanol to

ethanoic acid. Detection 2as by a colour change.

-dentify a reagent or combination of reagents that you 2ould use in the

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laboratory to oxidise ethanol to ethanoic acid.State the colour can"e that you 2ould expect to see.

eagent or combination of reagents .......................................................

Colour change .........................................................................................(2)

(d" 1he fermentation of glucose from crops is the main method for the production ofethanol. 1he product is called bioethanol. 1he European 7nion has declared thatbioethanol is carbon;neutral.

(i" State the meaning of the term carbon-neutral .

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(ii" Other than carbon;neutrality state the ma!n ad0antage of the use of glucosefrom crops as the ra2 material for the production of ethanol.

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(1)

(iii" Gi0e one disad0antage of the use of crops for the production of ethanol.

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(1)(Total 13 marks)

Q9.aking po2der contains sodium hydrogencarbonate and an acid or a mixture of acids. Oneacid that may be in baking po2der is */;dihydroxybutanedioic acid. 1his has the

molecular formula C#3>O> and it is often referred to as tartaric acid.

(a" Dra2 the structural formula of tartaric acid.

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(1)

(b" ,rite an e)uation for the reaction of tartaric acid (C#3>O>" 2ith sodiumhydrogencarbonate to form a salt carbon dioxide and 2ater.

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(1)

(c" Substances that contain carbonate or hydrogencarbonate ions can be used toconfirm the presence of an acid.

-dentify one other substance that could be used to confirm the presence of acidgroups in tartaric acid.State the obser0ation you 2ould make 2hen this other substance is added to ana)ueous solution of tartaric acid.

Substance ......................................................................................................

Obser0ation ....................................................................................................

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(d" -t is kno2n that tartaric acid contains alcohol and carboxylic acid functional groupsonly. test can be used to sho2 that tartaric acid contains secondary alcohol groups nottertiary alcohol groups.

(i" -dentify a reagent for this test and state the obser0ation you 2ould make foreach type of alcohol.

eagent ................................................................................................

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Obser0ation for secondary alcohol .......................................................

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Obser0ation for tertiary alcohol .............................................................

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(ii" Suggest 2hy this test cannot be used to distinguish bet2een a primaryalcohol and a secondary alcohol.

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(1)

(e" aking po2der usually contains starch. Starch is added to absorb any 2ater 0apourthat may come into contact 2ith the baking po2der 2hen the container is opened.

Deduce a reason 2hy this 2ater 0apour needs to be absorbed.

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(f" Sodium hydrogencarbonate in baking po2der forms carbon dioxide during theproduction of bread and cakes.

Suggest one ad0antage of ha0ing an acid in baking po2der.

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(g" Safety information indicates that tartaric acid and its salts can act as muscle toxins.1hese can cause paralysis and possible death.

Suggest one reason 2hy the use of tartaric acid in baking po2der is not a haIard tohealth.

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(Total 11 marks)

Q10.'ethanol (C3/O3" is an important fuel that can be synthesised from carbon dioxide.

(a" 1he table sho2s some standard enthalpies of formation.

CO*(g" 3*(g" C3/O3(g" 3*O(g"

J3f ƟHkB mol @6 @ /$# ! @ *!6 @ *#*

(i" 7se these standard enthalpies of formation to calculate a 0alue for thestandard enthalpy change of this synthesis.

CO*(g" /3*(g" C3/O3(g" 3*O(g"

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(ii" State 2hy the standard enthalpy of formation for hydrogen gas is Iero.

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(1)

(b" State and explain 2hat happens to the yield of methanol 2hen the total pressure isincreased in this synthesis.

CO*(g" /3*(g" C3/O3(g" 3*O(g"

Effect on yield ................................................................................................

Explanation ....................................................................................................

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(c" 1he hydrogen re)uired for this synthesis is formed from methane and steam in are0ersible reaction. 1he e)uation for this reaction is sho2n belo2.

C3#(g" 3*O(g" C!(g" /3*(g" J3 = *!> kB mol @6

State and explain 2hat happens to the yield of hydrogen in this reaction 2hen the

temperature is increased.

Effect on yield ................................................................................................

Explanation ....................................................................................................

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(d" 1he methanol produced by this synthesis has been described as a carbon;neutralfuel.

(i" State the meaning of the term carbon-neutral .

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(ii" ,rite an e)uation for the complete combustion of methanol.

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(1)

(iii" 1he e)uation for the synthesis of methanol is sho2n belo2.

CO*(g" /3*(g" C3/O3(g" 3*O(g"

7se this e)uation and your ans2er to part (d"(ii" to deduce an e)uation torepresent the o0erall chemical change that occurs 2hen methanol beha0es asa carbon;neutral fuel.

E)uation ...............................................................................................(1)

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(e" student carried out an experiment to determine the enthalpy change 2hen asample of methanol 2as burned.

1he student found that the temperature of 6#! g of 2ater increased by

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(a" eaction 1 produces a 6&% a)ueous solution of ethanol.-t is claimed that the ethanol produced in this 2ay is a carbon;neutral biofuel.

,rite an e)uation for eaction 1 and name the process.

,rite an e)uation for the complete combustion of ethanol.

Explain 2hy the ethanol produced by this process may not be a carbon-neutral biofuel.

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(b" Gi0e a reagent and conditions for eaction 2.

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C3/C3*r

C3/C3*O3

9ame and outline a mechanism for eaction 2.

Suggest one reason other than safety 2hy this method is not used in industry tomake ethanol.

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(c" eaction 3 is used in industry.

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3*C =C3* C3/C3*O3

-dentify a suitable catalyst for eaction 3.

-dentify the type of reaction.

Gi0e two conditions in addition to the presence of a catalyst necessary foreaction 3 to produce a high yield of ethanol.

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(Total 1% marks)

Q12.1he reaction of butane;6#;diol 2ith butanedioic acid produces the polymer 5S used inbiodegradable packaging and disposable cutlery.utanedioic acid is produced by t2o different processes.

rocess 1

• )ueous sodium hydroxide reacts 2ith 6#;dibromobutane to make butane;6#;diol.

K utane;6#;diol is oxidised to butanedioic acid.

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rocess 2

• Glucose reacts 2ith carbon dioxide in the presence of microorganisms to producebutanedioic acid directly.

K 1he carbon dioxide used in this process is obtained from a local factory thatproduces bioethanol.

(a" Deduce one safety reason and one en0ironmental reason 2hy rocess 2 ispreferred to rocess 1.

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(b" (i" 9ame and outline a mechanism for the follo2ing reaction that occurs inrocess 1.

rC3*C3*C3*C3*r

9aO3 rC3*C3*C3*C3*O3

9ar

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(3)

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(ii" 1he infrared spectra sho2n are those of three compounds.

Compound A 6#;dibromobutaneCompound B butane;6#;diolCompound C butanedioic acid

-dentify the compound responsible for each spectrum by 2riting the correctletter A B or C in the box next to each spectrum.

ou may find it helpful to refer to Table 1 on the Data Sheet.

(3)

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(c" -n the production of bioethanol glucose (C>36*O>" is con0erted into a dilute a)ueoussolution of ethanol and carbon dioxide.

Gi0e the name of this process and state tree essential conditions necessary toproduce a good yield of ethanol.

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(d" State the class of alcohols to 2hich the diol butane;6#;diol belongs.

-dentify a suitable reagent or combination of reagents for the con0ersion of butane;6#;diol into butanedioic acid (3OOCC3*C3*COO3".

,rite an e)uation for this oxidation reaction using LOM to represent the oxidisingagent.

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(Total 1% marks)

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1.(a" 5ercentage of oxygen by mass = 6!! @ #!.$ @ #.& = .>1

C 3 O

%Di0ide by Ar

= /.#6 = #.& = /.#6

1

Di0ide by smallest =

9earest 2hole number ratio = 6 ? / 6./* ? / 6 ? /

= / N /.$> N /

9earest integer ratio = / N # N /1

Empirical formula C/3#O/

Empirical formula mass = = molecular formula mass

1herefore molecular formula is same as the empirical formula ; C/3#O/1

(b" C>36*O> *C*3&O3 *CO*1

(c" d0antage @ ethanol is produced at a faster rate1

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Disad0antage @ more energy is used H re)uired in the reaction1

(d" ir gets in H oxidation occurs1

(e" lcohol O3 absorption in different place (/*/!@/&&! cm @6" from acid O3absorption (*&!!@/!!! cm @6"

1

1he C=O in acids has an absorption at 6>!@6

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Allow (CH 3 )2 C=CHCH 31

Allow (CH 3 )2 CHCH=CH 2 1

(e" 5osition1

(f" C

1

(g"

Allow (CH 3 )2 C(OH)CH 2 CH 31

(h"

Allow (CH 3 )3CCH 2 OH 1

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3.(a" mixture of li)uids is heated to boiling point for a prolonged time 1

8apour is formed 2hich escapes from the li)uid mixture is changed back intoli)uid and returned to the li)uid mixture

1

ny ethanal and ethanol that initially e0aporates can then be oxidised1

(b" C3/C3*O3 3*O C3/COO3 #3 #e @

1

(c" 'ixture heated in a suitable flask H container

A labelled setc! "llustrat"n# t!ese po"nts scores t!e mars1

,ith still head containing a thermometer 1

,ater cooled condenser connected to the still head and suitable cooledcollecting 0essel

1

Collect sample at the boiling point of ethanal1

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Cooled collection 0essel necessary to reduce e0aporation of ethanal1

(d" 3ydrogen bonding in ethanol and ethanoic acid or no hydrogen bonding in

ethanal1

-ntermolecular forces H dipole;dipole are 2eaker than hydrogen bonding1

(e" eagent to confirm the presence of ethanalN

dd 1ollensA reagent H ammoniacal sil0er nitrate H a)ueous sil0er nitratefollo2ed by 6 drop of a)ueous sodium hydroxide then enough a)ueousammonia to dissol0e the precipitate formed

,6

dd ehlingAs solution1

,arm

M2 and M3 can onl$ be awarded "% M& "s #"'en correctl$ 1

esult 2ith 1ollenAs reagentN

Sil0er mirror H black precipitate

,6

esult 2ith ehlingAs solutionN

ed precipitate H orange;red precipitate1

eagent to confirm the absence of ethanoic acid

dd sodium hydrogencarbonate or sodium carbonate

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1

esultP no effer0escence obser0edP hence no acid present1

M can onl$ be awarded "% M "s #"'en correctl$

,6

eagentP add ethanol and concentrated sulfuric acid and 2arm

esultP no s2eet smell H no oily drops on the surface of the li)uid

hence no acid present1&5

4.(a"

1 C>36*O> 2C3/C3*O3(*C*3&O3"

2CO*

*enal"se C 2 H + O %or et!anol "n M1.

2 and 3

Mar M2 and M3 "ndependentl$,

ny two conditions !n an orer for 2 and 3 from

• (enIymes from" yeast or Iymase

K *& +C Q 1 Q #* +C O *$ Q 1 Q /6&

K anaerobic H no oxygen H no air O neutral p3

A lac o% ox$#en can mean e"t!er w"t!out ox$#en or not!a'"n# enou#! ox$#en and does not ensure no ox$#ent!ere%ore onl$ cred"t .lac o% ox$#en "% "t "s 0ual"%"ed,

*enal"se 1bacter"a 1p!osp!or"c ac"d 1!"#! pressure us"n#t!e l"st pr"nc"ple,

4 (fractional" distillation or G:C

#nore re%erence to 1a0ueous or 1water ("e not part o% t!e l"st pr"nc"ple),

% Carbon;neutral !n t!s conte7t means

1here is no net H o0erall (annual" carbon dioxide H CO* emission to theatmosphere

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1here is no change in the total amount H le0el of carbon dioxide H CO* presentin the atmosphere

4or M5 5 must be about CO2 and t!e atmosp!ere,

6!e "dea t!at t!e carbon d"ox"de / CO2 #"'en out e0uals t!e

carbon d"ox"de / CO2 t!at was taen "n %rom t!e atmosp!ere, 5

(b" 1 ) = m c J1 (this mark for correct mathematical formula"

4ull mars %or M1 M2 and M3 %or t!e correct answer .

n M1 do not penal"se "ncorrect cases "n t!e %ormula,

2 = (

% c = ,

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heat H energy needed in breaking H dissociating (a" co0alent bond(s"

#nore bond ma"n#,

2 a0eraged for that type of bond o0er different H a range of molecules Hcompounds

#nore re%erence to moles,2

(ii" 1

( reactants" R (proucts" = JH

,6

Sum of bonds broken R Sum of bonds formed = JH

,6

(C;C" (C;O" (O;3" &(C;3" /(O=O" @ #(C=O" @ >(O@3" = JH = R6*& )

4or ot!er "ncorrect or "ncomplete answers proceed as%ollows

@ c!ec %or an ar"t!met"c error (AE) w!"c! "s e"t!er a transpos"t"on error or an "ncorrect mult"pl"cat"on t!"s

would score 2 mars ( M1 and M2 ),% no AE c!ec %or a correct met!od t!"s re0u"res e"t!er acorrect c$cle w"t! 2CO2 and 3H 2 O OB a clear statement o%M1 w!"c! could be "n words and scores only M1.

2 (also scores 1"/#/>!#>/&(#6*" /(O=O"

(3231" (or 2& if O@3 cancelled"R #(!&" R >(#>/" = JH = R 6*

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%.-dentification of acid by suitable method eg named indicator named carbonate specifiedreacti0e metal

#nore an$ re%erence to t!e smell o% t!e ester,1

2ith expected results

o not allow t!e use o% an$ "nstrumental met!od e# ",r, orn,m,r, must be a c!em"cal test,

1

-dentification of alcohol by suitable method eg oxidation by acidified potassiumdichromate(8-"

1

2ith expected results1

45

&. cidified potassium dichromate

Accept words or %ormulae,

Accept ac"d"%"ed potass"um perman#anate, Accept 8ucas rea#ent (conc HCl DnCl 2 ) (cloud$ "n m"ns %or 2 "nstantl$ %or 3),

Mar on %or "ncomplete rea#ent,

ncorrect rea#ent CE = F / 3

nclus"on o% 6ollens etc w"t! ac"d"%"ed potass"um d"c!romate"s "ncorrect rea#ent,

7ot no react"on,

Either

Obs 2ith *;methylpropan;*;ol

9o 0isible change1

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Obs 2ith butan;*;ol

Orange to green (both colours needed"1

or

Obs 2ith *;methylpropan;*;ol orange

Obs 2ith butan;*;ol green

35

.(a" Structure for /;methylbut;6;ene

3*C=C3C3(C3/"*

An$ correct structural representat"on,

Cred"t .st"cs and re0u"re t!e double bond,1

(b" Structure for *;methylpropan;*;ol

(C3/"/CO3


Cred"t .st"cs,1

(c" Structure for propene

3*C=C3C3/


Cred"t .st"cs and re0u"re t!e double bond,1

(d" Structure for *;aminobutane

C3/C3*C3(93*"C3 /

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Cred"t .st"cs,1

45

.(a" (i" C3*O

Atoms "n an$ order

Accept a clear "nd"cat"on t!at C + H &2 O+ $"elds CH 2 O as t!eanswer

1

(ii" 9o peak H no absorption H no C=O in the ran"e 1&0 to 1%0 (cmR6"(suggesting no e0idence of C=O"

Allow t!e words .d"p .sp"e .low transm"ttance and.trou#! as alternat"'es %or absorpt"on

#nore re%erences to ot!er wa'enumbers1

(b" '6 C>36*O> 2C3/C3*O3 2CO*

*enal"se (C 2 H + O)

Allow mult"ples o% t!e e0uat"on "n M1

Either order '* (enIymes from" yeast or Iymase

'/ *& +C Q 1 Q #* +C O *$ Q 1 Q /6&

4or M2 and M3 #nore .a0ueous #nore .anaerob"c / absence o% ox$#en #nore .controlled pH#nore .warm

3

(c" (i" Displayed formula for C3/COO3

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All bonds must be drawn out but "#nore bond an#les1

(ii" O* #3

#eR

*3*O#nore state s$mbols

7e#at"'e c!ar#e on electron not essent"al

Accept mult"ples

Accept electrons subtracted %rom BHG1

(iii" C3/C3*O3 3*O C3/COO3 #3 #e @

(C*3>O or C*3&O3"

#nore state s$mbols

7e#at"'e c!ar#e on electron not essent"al

Accept mult"ples

Accept electrons subtracted %rom 8HG1

(i0" '6 cidified potassium or sodium dichromate

4or M1 "t must be a w!ole rea#ent and / or correct %ormulae

OR 3*SO# H *Cr *O

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(d" (i" n acti0ity 2hich has no net H o0erall (annual" carbon emissions to theatmosphere H air

6!e "dea t!at t!e carbon / CO2 #"'en out e0uals t!e carbon /

CO2 t!at was taen "n %rom t!e atmosp!ere / a"r

OR

n acti0ity 2hich has no net H o0erall (annual" greenhouse gasemissions to the atmosphere H air .

Answer must re%er to t!e atmosp!ere or a"r

OR

1here is no change in the total amount of carbon dioxide H carbonHgreenhouse gas present in the atmosphere H air

1

(ii" ene2able H sustainable O9:

#nore re%erences to #lobal warm"n# or #reen!ouse #ases1

(iii" An one statement about t!s process :rom

SubTect to 2eather H climate

#nore .batc!

OR

Depletes food supply O the land use for (specified" food

OR

e)uires use of H uses more fossil fuels

OR

9ot carbon;neutral O CO* produced during a named process (eghar0est transport etc."

OR

Slo2 process H slo2 rate of reaction H takes a long time (to gro2 crops"

OR

1his route leads to the production of a mixture of 2ater and ethanol Himpure ethanol that re)uires separation H further processing

1

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135

9.(a" 3OOCUC3O3UC3O3UCOO3

An$ su"table structural %ormula,

"spla$ed %ormula not re0u"red but bond se0uences must becorrect "% s!own,

1

(b" C#3>O> 9a3CO/ V C#3&O>9a CO* 3*O

OR

C#3>O> *9a3CO/ V C#3#O>9a* *CO* *3*O

Allow e0uat"ons based on t!e structural %ormula,

Allow mult"ples "nclud"n# %ract"ons,

Allow an$ structure %or C H + O or C H O+ 7a1

(c" Suitable named indicator (eg litmus methyl orange 7ni0ersal -ndicator" Hidentified reacti0e metal ('g Wn or e"

o not allow p!enolp!t!ale"n w"t!out explanat"on o% !ow acolour c!an#e would be seen,

ncorrect rea#ent c!em"cal error = F / 2 1

ppropriate colour in acid (eg red" H gas e0ol0ed

1

(d" (i" eagentN cidified potassium dichromate (solution"

% "ncomplete (correct) rea#ent lose M& but mar on,

ncorrect rea#ent c!em"cal error = F / 3

Allow ac"d"%"ed potass"um man#anate()1

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ObsN orange to green

*urple to colourless (solut"on),1

ObsN no (0isible" change

Allow 1no '"s"ble react"on but do not allow 1no react"onw"t!out 0ual"%"cat"on,

1

(ii" oth 2ould gi0e the same result H both oxidised by reagent H both react2ith the reagent or similar

Allow conse0uent"al answer %rom ("),

C!em"cal error "% rea#ent "n (") "s "ncorrect F / &1

(e" 1he 2ater 2ould allo2 the tartaric acid and sodium hydrogencarbonate toreact (before use"

#nore an$ re%erence to water react"n# w"t! t!e "n#red"ents,

#nore re%erences to pre'ent"on o% 1ca"n# or 1clump"n#,

#nore re%erences to s!el% l"%e w"t!out 0ual"%"cat"on, 1

(f" cid reacts (2ith 9a3CO/ H 9a*CO/" to form CO*

Allow 1neutral"ses (7aHCO3 / 7a2 CO3 ) to %orm CO2 ,1

(g" -t is only used in 0ery small )uantities

Allow 1decomposes "n t!e react"on,

o not allow 1reacts w"t!out 0ual"%"cat"on,

#nore re%erence to %ormat"on o% salts,1

115

10. (a" (i" 1 (coul be score b a correct matemat!cal e7press!on w!c

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must a? :or @ 49)

Correct answer #a"ns %ull mars

Cred"t & mar O789 %or I (? mol 5& )

4or ot!er "ncorrect or "ncomplete answers proceed as%ollows

@ c!ec %or an ar"t!met"c error (AE) w!"c! "s e"t!er a transpos"t"on error or an "ncorrect mult"pl"cat"on t!"s would score 2 mars ( M1 and M2 )

@ % no AE c!ec %or a correct met!od t!"s re0u"rese"t!er correct c$cle o% balanced e0uat"ons w"t! &C 3H 2 and&O2

OB a clear statement o% M1 w!"c! could be "n wordsand scores onl$ M1

3

(ii" -t is an element H elemental

#nore re%erence to .standard state

,6

y definition1

(b" 1 (1he yield" increases H goes up H gets more

% M& "s #"'en as .decreases / .no e%%ect / .no c!an#e t!enCE= F %or cl"p but mar on onl$ M2 and M3 %rom a blan M&

2 1here are more moles H molecules (of gas" on the left H of reactantsOR fe2er moles H molecules (of gas" on the rightH productsOR there are # moles Hmolecules (of gas" on the left and * moles H molecules on the

right.OR (e)uilibrium" shifts H mo0es to the side 2ith less moles H molecules

#nore .'olumes .part"cles .atoms and .spec"es %or M2

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3 Can onl score 3 !: 2 !s correct

1he (position of" e)uilibrium shifts H mo0es (from left to right" to oppose the increasein pressure

4or M3 not s"mpl$ .to oppose t!e c!an#e

4or M3 cred"t t!e e0u"l"br"um s!"%ts / mo'es (to r"#!t) to lower

/ decrease t!e pressure(6!ere must be a spec"%"c re%erence to t!e c!an#e t!at "sopposed)

3

(c" 1 ield increases goes up

2 1he (for2ard" reaction H to the right is endothermic O takes inH absorbsheat

OR

1he re0erse reaction H to the left is exothermic O gi0es out H releases heat

% M& "s #"'en as .decrease / .no e%%ect / .no c!an#e t!enCE= F %or cl"p but mar on onl$ M2 and M3 %rom a blan M1

Can onl score 3 !: 2 !s correct

3 1he (position of" e)uilibrium shifts H mo0es (from left to right" to oppose theincreasein temperature (Qo>)

4or M3 not s"mpl$ .to oppose t!e c!an#e

4or M3 cred"t t!e (pos"t"on o%) e0u"l"br"um s!"%ts / mo'es(#o$)

to absorb t!e !eat OR

to cool t!e react"on OR

to lower t!e temperature

(6!ere must be a spec"%"c re%erence to t!e c!an#e t!at "sopposed)

3

(d" (i" n acti0ity 2hich has no net H o0erall (annual" carbon emissions to theatmosphereOR n acti0ity 2hich has no net H o0erall (annual" greenhouse gas emissionsto the atmosphere.OR 1here is no change in the total amount H le0el of carbon dioxide HCO* carbonHgreenhouse gas present in the atmosphere.

6!e "dea t!at t!e carbon /CO2 #"'en out e0uals t!e carbon /CO2 t!at was taen "n %rom t!e atmosp!ere1

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(ii" C3/O3 1Y O* CO* 23*O

#nore state s$mbols

Accept mult"ples

1

(iii" 33* 1Y O* 33*O

#nore state s$mbols

OR

Accept mult"ples

23*

O*

23*

OExtra spec"es must be crossed t!rou#!

1

(e" 1 ) = m c J1

Award %ull mars %or correct answer

#nore t!e case %or eac! letter

OR ) = 6#! ? #.6 ?

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molecule.

*enal"se M %or %ormal c!ar#e on C o% t!e C5Lr or "ncorrect part"al c!ar#es on C5Lr

*enal"se once onl$ %or a l"ne and two dots to s!ow a bond,

or '# and '& a2ard full marks for an S96 mechanism

4or M and M max"mum & o% 2 mars "% wron# reactant "sused,

*enal"se M "% an extra arrow "s drawn %rom t!e Lr o% t!e C5Lr bond to %or example J IspanK

o not penal"se t!e use o% .st"cs

& One statement from

• 1he yield is (0ery" lo2 H not a high yield O elimination occurs H etheneformed

K 1he rate of reaction slo2

K romoethane has to be manufactured H made first

K romoethane is expensi0e

4or M+ "#nore re%erences to ot!er costs and expenses6

(c" 1 concentrated phosphoric acid H conc. 3/5O# OR concentrated sulfuric acid Hconc.

3*SO#

Answers "n an$ order

#nore re%erence to support med"um "n M&

2 hydration or (electrophilic" addition

or 3 an 4 an two :rom

o not appl$ t!e l"st pr"nc"ple to t!ese t!ree c!osen cr"ter"a"n M3 and M

• Excess ethene

OR Excess steam H 2ater H 3*O

OR remo0e the ethanol as it forms

OR recycle the ethene

K Specified 5ressure

&! atm Q 5 Q 6!! atm

OR &!!! k5a Q 5 Q 6!!!! k5a

OR & '5a Q 5 Q 6! '5a

K 3igh1emperature unless they gi0e a 0alue that is not in the ranges gi0en hereP

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OR /!! +C Q 1 Q >!! +C

OR &

Accept a re%erence to .low temperature "% t!e$ spec"%$ acorrect temperature ran#e or a correct temperature "n t!eran#e

4

1%5

12. (a" 1 a:et (!n rocess 1)

Sodium hydroxide H alkali is corrosi0e H harmful H caustic or sodium hydroxide isalkali(ne"

#nore re%erences to c!rom"um compounds

OR

romine compounds are toxic H poisonous

.Carbon-neutral alone "s "nsu%%"c"ent %or M2

2 n

#nore re%erences to #reen!ouse #ases

5rocess * could be used as a carbon sink H for carbon capture

OR

uses 2aste H recycled CO* H CO* from the factory H CO* from the bioethanol (or biofuel" production

OR

reduces or limits the amount of CO* released H gi0en out (into the atmosphere"

OR

5rocess * uses rene2able glucose H rene2able resource(s"2

(b" (i" '6 nucleophilic substitution

4or M1% &ot' wor!s re0u"red

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2 must sho2 an arro2 from the lone pair of electrons on the oxygen atom of the negati0ely charged hydroxide ion to the C atom.

*enal"se M2 "% co'alent 7aOH / JOH "s used

*enal"se one mar %rom M2 or M3 "% !al%-!eaded arrows areused

3 must sho2 the mo0ement of a pair of electrons from the C@r bond to ther atom. 'ark 3 independently pro0ided it is from the original molecule

*enal"se M3 %or %ormal c!ar#e on C o% t!e C5Lr or "ncorrect part"al c!ar#es on C5Lr

*enal"se once onl$ %or a l"ne and two dots to s!ow a bond,

or 2 and 3 a2ard full marks for an S96 mechanism

4or M2 and M3 max"mum & o% 2 mars %or t!e mec!an"sm "% wron# reactant "s used,

*enal"se M3 "% an extra arrow "s drawn %rom t!e Lr o% t!e C5Lr bond to %or example J I

Accept t!e correct use o% .st"cs

=B Te arrows ere are ouble'eae3

(ii" 1

2 C

3 3

(c" 1 fermentation

Mar M2 to M4 "ndependentl$

Tree con!t!ons !n an orer :or 2 to 4

*enal"se .bacter"a and .p!osp!or"c ac"d us"n# t!e l"st pr"nc"ple

2 (enIymes from" yeast or Iymase

3 *&+C Q 1 Q #*+C O *$ Q 1 Q /6&

#nore re%erence to .a0ueous or .water .closed conta"ner.pressure .lac o% ox$#en

.concentrat"on o% et!anol and .batc! process (",e, not part

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o% t!e l"st pr"nc"ple)

4 anaerobic H no oxygen H no air O neutral p34

(d" 1 primary O 6+ (alcohol"

Mar "ndependentl$

2 acidified potassium or sodium dichromate

4or M2 "t must be a w!ole rea#ent and/or correct %ormulae

OR 3*SO# H *Cr *O

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7404 Alcohols