equilibria ans

8/10/2019 Equilibria Ans

1/142

1. B[1]

2. (a) (i) Mark the two points independently, subject to the constraint inReject column

Effect:

(Equilibrium) shifts to the right (1

ALLOW: favours forward reaction / increase the amount of product/ increase the yield (of product)

Reason:

Eothermic (in forward direction) (1

NOTE: !ust(equilibrium) shifts in the eothermic directionscores (1 !

Equilibrium shifts to left will score (0) for (a)(i)

(ii) "irst mark:"ctivation energy for the reaction is too high / (if cooled) moleculeswould not have enough energy to react / few(er) molecules have therequired Ea/more molecules have energy #Eaat higher temperatures#R

not (technologically) feasible to cool the gases before they enter theconverter/costly to cool the gases (1

$econd mark:(cooling the gases would ma$e) the rate (too) slow /rate is faster if thetemperature is high (so the gases are not cooled) (1 !

Cooling the gases decreases the yield (of products) /an

incorrect Le Chatelier argument

(iii) Mark the two points independently, subject to theconstraint in Reject column

Effect:

(Equilibrium) shifts to the right

ALLOW: favours forward reaction / increase the amount of product /increase the yield of product (1

Reason:

%hifts / moves in the direction of fewer (moles of gas) molecules

ALLOWshifts in direction of fewer moles (of gas molecules) (1

INO!Eeffect on the rate !

Equilibrium shifts to left will score (0) for (a)(iii)

"#### fe$er atoms

1


2/142

(b) (i) (%n :&! / !& (1

(%n '

:&' / '& (1

NOTE%

(%n :ust !)&*(%n '

:ust ' scores (1 !

(ii) *+,& +-&& 'e,. * & 2-!*

ACCE&Tmultiples !

(iii) "g . "g&& e(,)/ "g , e(,). "g&

ACCE&TmultiplesINO!Estate symbols even if incorrect 0

"Ag ' e

Ag'

(iv) +"g & *+,& 1-& +"g&& * & !-!* (2

(1for multiplication of the silver half2equation by three or cq multiplefrom (b)(ii)

(1for rest of equation correctNOTE: Equation must be completely correct for the second mar$3

INO!Estate symbols even if incorrect !

if any e

are left in the final e*uation+ second mar, cannot -e

scored[13]

'. 4[1]

+. B[1]

. 4[1]

2


3/142

-. 4[1]

. "[1]

/. (a) (i) p4*)(*-p4-

-4*p4-)5(

+

!+p

.u

uu=

6artial pressure symbol can be shown in various ways eg ppp4* (4*)p etc

ALLOWp in upper or lower case round brac$etsINO!Eunits 0

0

1tate sym-ols gi2en as (l)

' in -ottom line

(ii) 6 4-+*- 7 138 (atm) (16 4* 7 138 (atm) (1

0 mar$ for recognition that pressures are equal

INO!Eunits !

(iii) 3p7 ((!!3!)/(138)!)

7 938!' (1

atm,0(1stand alone mark but must match e0pression used in (a(iii

#R

83!' 0916a,0/ 8!3' $6a,0(2

ALLOW;E from (a)(i) if inverted and/or (a)(ii) !

Ans$ers to other than 4 significant figures

(b) (i) 4-+*-: +3!4* : +3! (1for both values

4-+4*!-: 1


4/142

(ii)

!3'+

+!=310/>

!

!

(iii) 4orrect answer with or without wor$ing scores 2 marks

03F 09,'7 930!'ED- !

(1

D-& 7 031< 09,+

p- 7 !3=1/!3= (1

no ;E from an incorrect D-& !

5


6/142

(iv) p- 7 13= / 13FF (1

p- 7 p3a/ D-& 73a(when acid is half neutraliHed) (1 !

>'8 3a

(v) %igmoid curve starting between p- ! and 1 (!3=) ending between

p- 0! and 01 inclusive (1

with steep rise (may be vertical or gently sloping) of between + ,F units between p- < and 0!3 %loping section should not etendover more than 'cm+3 (1

Ihen 0!3' cm+ a*- added3 (1"AA*I tolerance for grid

Ceverse curves lose first mar$ +

(vi) "irst mark

;hymolphthalein more suitable as it changes(from colourless to blue) in steep region of titration(p- =3+ to 093


7/142

13. "[1]

11. (a) (i) !g(*+)!. !g* & 1*!& *!

4orrect formulae (1Balancing (1)44#5multiples or equation divided by ! %econd mar$ on correctspecies only Lgnore state symbols even if incorrect)44#5

!*1Etra oygen molecules on both sides in a balanced equation !

(ii) %tand alone mar$s

g!&/ agnesium ionsmaller or fewer electron shells/ greatercharge density (1#R

agnesium ionhas same charge (as calcium ion) but is smaller (1

4auses more polarisation /distortion of nitrate / anion (electron clouds)/ M* (bond)(1#R

g* produced has stronger lattice (1#R

production of g* is more eothermic (1

#Rreverse argument based on 4a!&

!@agnesium / calcium / atoms / molecules

(b) !a*+. !a*!& *!)44#5multiples or equation divided by ! Lgnore state symbols even ifincorrect)44#5

Etra oygen molecules on both sides in a balanced equation 0

(c) o asN3double bond would be shorter (than single bond) / shorter than dative(covalent) bond3)44#5

%tructure has double and single bonds (between and *)Oouble and single bonds have different lengths 0

Implication that the single co2alent and dati2e co2alent -onds

ha2e different lengths

7


8/142

(d) (i) ar$ independently Poes dar$er (brown) (1"AA*IPoes brownerLgnore comments on miture first becoming paler if volume increases

Equilibrium moves in the endothermic direction (1

#R

Equilibrium moves left as forward reaction is eothermic (1

Qor second mar$ )44#5Equilibrium moves left to counteract addition of heat / increase intemperature(1

#R

Ceaction removes added heat by moving left (1 !

ro$n (gas e2ol2ed)

(ii) Equilibrium moves right ("AA*I forwards) (so *!concentrationdecreases) (1#R

Ceaction reduces pressure (1

"s fewer moles / molecules("AA*I particles) (of gas) on C-% (1

%tand alone mar$s !

(e) "t ;!more molecules/collisions have energy greater than (or equal to)E"(1

;his can be shown on the diagram by indicating areas to right of vertical line

Energy must be at leastE"for successful collision / for reaction (1

#R%o more collisions have sufficient energy to react (1

Lgnore references to the average energy and speed of the molecules ![12]

12. B[1]

1'. 4[1]

1+. B[1]

8


9/142

1. "[1]

1-. B[1]

1. "[1]

1/. 4[1]

1. 4[1]

23. (a) (i) (p- 7) ,log D-&

*C(p- 7) ,log D-+*

&

*C

)ccept

Oefinition in words(Qor eample: Lt is minus / negative log(arithm) of the hydrogen ionconcentration)

Base 09 does not have to be there but reRect ln 0

Just"concentration of hydrogen ions

B curly -rac,ets

Dlog >'

(ii) (p- 7 2log 939099) 7 !(399) 0

If any units gi2en

9


10/142

(b) (i) D-+*& 7 E4**D4-

4**-ED4-,

+

+a3

*C

D-+*&

!

73aD4-+4**- (1ALLOW

D-" for D4-+4**- and D", for D4-+4**

, in rearranged epression

)ccept

D-& for D-+*&

D-+*& 7 S 03F' 09,F

*C

D-+*& 7 130=(' 09,1(mol dm,+) (1

p- 7 +3+= / +31ignore sf ecept one sf (1

;hird mar$ ;E from D-& only if p- less than

&.6. 7#RRE78 )&$5ER, 5%89 #R 5%89#8 5#R;%&

G0 / >

'0 8 salt0

10


11/142

(ii) "irst mark:

(Oilution/addition of water) shifts the equilibrium

4-+4**- 4-+4**,& -&/

4-+4**- & -!* 4-+4**,

& -+*&

to the riht*Cthe above stated in words such as: degree of dissociation increases/

proportion of dissociation increases/ more dissociation (as theethanoic acid is diluted) (1

$econd mark:

so the D-& is greater than epected/ so the decrease in D-& is less thanepected / so that the decrease in D-& is less than that forhydrochloric acid (1

Each mark is a stand alone mark.

ALTE!NATIHE !O?TE%

"irst mark:

D-& 7 S3a D-" *C (3a D-")T

*C

p- 7 Tp3a2 TlogD-" (1

$econd mark:

use of mathematical epression given (e3g3D-&

affected by factor of0/S09 on dilution *C substitution of numerical values into theequation) (1

INO!E: any comments or calculations relating to -4l(aq) !

!eFect Fust a reference to a #: increase in p> for

C>4COO>(a*) compared $ith a 7# increase in p> for

>Cl(a*)

(c) (i) 8hese marks are stand alone.

aintains an almostconstant p- / resists change(s) in p- (1

for smalladdition of -&or *-,ions (3B3 both ions needed) / forsmalladditions of acid or al$ali / for smalladditions of acid or

base (1

INO!Eany references to named buffer mitures !

"resists small change(s) in p>

O!

"p> does not change

(ii) citric acid 0

11


12/142

(iii) "irst mark:

(buffer contains) reservoir of -" and",

*C(buffer contains) large concentrations of D-" andD",

*Cbothequations:

-" ", & -& anda" a&& ",

$econd mark:

("ddition of al$ali/base)

-" & *-,. ",& -!**Cdescription/equations to show that -&reacts with *-,(to form -!*)

and more acid dissociates (to replace -&) (1

8hird mark:

("ddition of acid)

",& -&. -"*C", reacting with -&in any contet described in words (e3g3 by referenceto wea$ acid equilibrium) (1

"ourth mark:

the ratio of D",UD-" hardly changes / the ratio of D-"U D", hardlychanges*CD", nor D-" changes sinificantly (1 1

JUSTNaA Na'' A

and

>A >'' A

$ithout correct description

;ust >'0 remains constant

[15]

21. (a) *)(-)(4-

(4*))(-

!1

+!

ppp

pp3

(1

Brac$ets not required 0

[ ]

*)(-)(4-

(4*))(-

!1

+!

ppp

pp3

(b) (i) o effect (as3pdependent only on temperature) (10

12


13/142

(ii) (%ince3p7!

;

1

;

!1

+!

*)(-)(4-

(4*))(-

P

P

JJ

JJ

to maintain3pconstant mole fractions of numerator must

decrease *C mole fractions of denominatormust increase as

!;P overall)

"irst mark:

EIT>E!

mole fractions/partial pressures of numerator decreaseO!

mole fractions/partial pressures of denominator increase (1

$econd mark:

any mention of !;P *C !;

1

;

P

P

(1

ALLOWPforP;

E:

%f 4e 7hatelier =uoted, statements such as:

Equilibrium shifts to side of fewer moles (of gas molecules)/fewer(gas) molecules ma0 (1 !

(iii) Ceaction ta$es place on surfaceof the catalyst (1

"ctive sites/(catalyst) surface is saturated with reactant molecules/reactants (at the pressure of the reaction) (1

*;E: an answer such as333 depends on the availability of active sites oncatalyst surface scores (2 !

13


14/142

(c) 4* & -!* 4*! & -!

initial 1 1 3 3

e=>m 3.2 3.2 3. 3.

mol

frac

3.12 3.12 3.' 3.'

pp '. '. 11.2 11.2

V eqJm moles all correct (1

V mole fractions all correct (1

V partial pressures and answer 7 8 with no units(1

NOTE: 'rdmar$ not awarded if any units shown

NOTE%

!

!

F'3+

!'300

7 8 scores ('

14


15/142

15


16/142

*;E: ar$ each step 4W379E7; )44 5#R;%&< +

(d) (i) production (of hydrogen) forms 4*!*C

production (of hydrogen) forms a Preenhouse gas*C

production (of hydrogen) forms 4**C4*!is a Preenhouse gas

*C4* is a Preenhouse gas

"AA*I production (of hydrogen) uses/requires energy

ALLOW4* is toic/poisonous 0

methanero!uce! (0)

(ii) !5-4*+. 5!4*+& 4*!& -!*

ALLOWmultiples 0

16


17/142

(e) products removed*Cnot a closed system*C

balance between rate and yield

*Cbalance between time and yield*Crecycling of reactants*Cmore product in unit time (so process more economically viable)

LP*CE any comments relating to cost 0

references to atom economy

dangers of maintaining high pressures[12]

22. (a) "

0

(b) 4

0[2]

2'. B[1]

2+. O[1]

2. 4

[1]

2-. "[1]

17


18/142

2. 4[1]

2/. 4[1]

2. "[1]

'3. 4[1]

'1. (a) 4 0

(b) O 0

(c) B 0[3]

'2. (a) " 0

(b) O 0

(c) 4 0[3]

''. (a) methyl butanoate"ccept ethyl butaneoate 0

!eFect


19/142

(c) -ydrolysis 0

(d) WI4

ust cover advantages and disadvantages3 ust notbe contradictory

)d?antaes to manufacturers: (any two

V not dependent on weather seasons etc

V consistent taste /concentration/more consistent

V quality

V or alternative ideas

*isad?antaes to consumers : (any two

V some people put off by Knon2naturalJ food

V may not taste the same as natural product which may containother impurities

V unable to describe the product as organic

or alternative ideas 1

!eFect cost $ith no Fustification

(e) 5c 7 *(l)E(l)ED-4**4--4D

*-(l)E-4**-(l)ED4-4D

!+F+

+F+

(1"ccept eq subscripts

Moles at 7oncentration @

e=uilibrium mol dm'

butanoic acid7 131/== 7 939' 03alue of equilibrium constant increases (1 0

19


20/142

(b) WI4

Lf the equilibrium constant increases then more products will be formed (1"nd the position of equilibrium will move to the right (1 !

[3]

'. (a) g(s) & !-&(aq) g!&(aq) & -!(g)"ccept state symbols omitted 0

(b) (i) 6ositive because a gas is given off (1which is more disordered and so has more entropy (1 !

(ii) 6ositive because the reaction is eothermic (1

and 7 ,-/; (1 !

(iii) 6ositive because the reaction occurs / total entropy changeis the sum of the two positive values above3 0

(c) (i) %urface coated with magnesium oide (which would react toform water rather than hydrogen)3 0

(ii) WI4Lnitial number of moles of -4l 7 !9 0 /0999 7 939!

umber of moles of g 7 930 / !1 7 939910F (1number of moles of -4l which reacts is 9399=+1 (1

;herefore number of moles of -4l left 7 93900


21/142

(iii) Energy given out 7 1


22/142

'-. A57

"nswer must be given in a logical order addressing all the points using preciseterminology

V 4ollision fre=uency increases as particles moving more quic$ly (1

V ore collisions have sufficient energy to overcome activation energy /more molecules on collision have energy activation energy (1

V " greater proportion of collisions result in reaction (1

V 4ollision energy has greater effect (1

V -omogeneous all in same phase and heterogeneous in differentphases / gas and solid (1

V o need to separate products from catalyst (1 negati2e/re2erse reaction is endothermic

!eFect Fust "e*uili-rium shifts to the left

!eFect Fust "yield decreases

(iii) WI4

fewer (gaseous) molecules /particles/moles on the right (1

equilibrium shifts to the right increasing the yield (1

!eFect Fust "e*uili-rium shifts to the right

!eFect Fust "yield increases

!ndmar$ is dependent on the 0stand is not consequential3

LP*CE Ae 4hatelier eplanations

3B do not penalise omission of either Kequilibrium shiftsJor change of yield if already penalised in (ii) !

!eFect arguments -ased on 2olume

(c) Z> 7 Z>f(products) , Z>f(reactants)*r (,=01 !) , (,!=< !) (1

7 ,09'< ($ mol,0) (1LP*CE units

4orrect answer with no wor$ing (2

*mission of either or both of ! ma0 1. -ence,!1! with some wor$ing (1,0+1! with some wor$ing (1,'!= with some wor$ing (1

(&)09'< with some wor$ing (1 !

!eFect P>f2alues added scores Qero o2erall

[13]

26


27/142

++. (a) 1!

!

!

ON

NO

pp

p3 =

INO!E ?NIT1 >E!E 0

!eFect 0

(b) (i) !NOp

7 93= 0307 93== (atm)

and

!!ONp

7 93! 0307 93!! (atm) (1

3p7)!!39(

)==39( !

3p7 +3'! (1atm (1

1ECONK @A!3 I1 CR ON &A!TIAL &!E11?!E1

A1CALC?LATEK +

(ii) "irst mark:

1!ONJ

7 9309

!NOJ

7 9389 (1

!eFect

$econd mark:

3pconstant oruse of3p7 +3'! oruse of3pcalculated in (b)(i) (1

8hird mark:

>alue of 6;with some wor$ing e3g3

+3'! 7 ;

!;

6

)6(

1!

!

ON

NO

J

J

+3'! 7 0939

=039

6;6;7 931+' (atm) (1

@ar, CR on first and second ans$ers to (-)(ii)

Accept in range #S4 to #SS

T>I!K @A!3 NOT AHAILALE I 3pEJ&!E11ION

KOE1 NOT CONTAIN A p5TE!@ +

27


28/142

(c) (i) Lncreases / gets larger/ gets bigger/ goes up/greater 0

!eFect more

(ii) "irst mark:

Qraction/quotient/ 1!

!

!

ON

NO

p

p

/numerator has to increase(to equal new3p) (1

$econd mark (can only be awarded for an answer that refers

to the fraction@=uotient abo?e:

E%89ER

so shifts to R%


29/142

(iii) p- 7 ,log09D-&

#R

p- 7 ,log09D-+*&

#R

in words 0

Accept p> 8 lg 7/>'0

(iv) 3W7 D-&D*-,

'31= 09,017 D-&!(1

D-& 701091=3'

D-& 7 !3+1 09,F(mol dm,+)

p- 7


30/142

(iv) (at half2neutralised point so)

p3a7 13=

@ar, CR on (ii)

!eFect%ustp> 8 S#6 as already credited in (-)(ii)

*C

p- 7 p3a(1

5a7 antilog09(,13=)

5a7 03< 09,'(mol dm,+) (1

@ar, CR on p3a

Accept if p3a 8 S#9+ 3a 8 7#4 V 7:

!eFect ans$ers to other than 5 s#f#

Must be to two si fis

CO!!ECT AN1WE! WIT> O! WIT>O?T WO!3IN(2 !

!eFect 5#: V 79

scores (0)

(c) Bhenolphthalein:changes colour (*I;;E) in vertical part of the graph#R

changes colour within a stated range anywhere from F to 00 (1

!eFect if colour change "pin, to colourless

Methyl orane

changes colour at a low(er) p-#R

has already changed colour#R

changes colour before the vertical (section) (1

Allo$ range for methyl orange of 4 to U or colour change ta,es

place -elo$ p> 8

!eFect%ust


31/142

+-. (a) e3m3f3 of a half cell relative/compared to a (standard) hydrogen electrode*Cvoltage produced from a half cell Roined to a hydrogen electrode (1

Accept potential (difference) /2oltage for emf

Accept emf of a cell $ith standard hydrogen as the leftelectrode

Accept a description of the half cell e#g# a metal dipping into a

solution of its ions

!eFect 1>E

(solutions at) 0 mol dm,+concentration (gases at) 0 atm/099 $6a/09'6a/ 0 Bar pressure and stated temperature (1

all + conditions needed %;"O "A*E !

Accept 77 ,&a

Accept 596 3 or 5: CIf any other temperature is *uoted it must -e as an e.ample of a

stated temperature

!eFect


32/142

(c) (i) 1st mark(simultaneous) oidation and reduction of a (single) species/substance/ reactant/compound/chemical

!eFect o.idation and reduction occur at the same time

#r the oidation state/number is both increased anddecreased of a (single) species/ substance/ reactant/compound/chemical

!eFect o.idation states are M

#r a (single) species/ substance/ reactant/compound/chemical both loses and gains electrons (1

2nd mark

Qor a given type of atom within an ion/ molecule#r Lllustrated by a suitable eample in which theindividual atom is identified (1 !

(ii) !-!*!. !-!* & *!(1

!eFect 5>'on -oth sides of e*uation

Ecell7 (&) 0398 (>) (1

!eFect greater than any other stated num-er

Ecellis positive/greater than 9 so the reaction is feasible (1

+rdmar$ must be cq on sign of Ecell +

(iii) activation energy of the reaction may be high

*Creaction too slow to be observed 0

!eFect Fust "Not enough energy to o2ercome the acti2ation

energy

!eFect conditions are nonDstandard

!eFect Fust ",inetically sta-le[9]

+. (a) (i) ;he activation energy for the reaction is highor to ensure that more molecules haveE #Ea3 0

Accept E Ea

!eFect to o2ercome Eaalone

!eFect reactants ,inetically sta-le

reactants thermodynamically sta-le

32


33/142

(ii) protonates the alcohol (1

!eFect Cl />r

Accept neutralises acid

(v) Cemoves water 0

Accept a-sor-s $ater

Accept dries the product

(vi) Electric heating mantle or sand bath or oil bath (1

Accept $ater -ath

!eFect heat under reflu.

!eFect no na,ed flame

!eFect fume cup-oard

because the alcohol/reaction miture/bromobutane is

flammable orbecause the heating is uniform and lessli$ely to crac$ the flas$ (1;his mar$ is conditional on the first being scored3 !

!eFect


34/142

(b) WI4

E%89ER

Lntermediate (ion) in %0 is planar (1

Accept intermediate car-ocation is a planar molecule

intermediate molecule alone loses this mar,

equal attac$ (by hydroide ions) from either side (1produces a racemic miture (1

!eFect attac, -y -romide ions

&ote: %tatement that the %! mechanism is consistent withthe information cannot score any mar$s3

#R

%! involves attac$ from one side (1

so configuration of the product would be inverted (1leading to retention of optical activity so must be $&1 (1

Accept forms one optical isomer only

%tatement that the reaction is %0 alone scores Hero3 +

(c) (i) *range . green 0

(ii) 4r !*F!,& 6O

Accept e*uation ha2ing nonDcancelled >'ions

!eFect e*uation ha2ing nonDcancelled electrons

(iii) ;he broad pea$/absorption/trough around +199 cm,0due to ,*- (1

Accept 454 4::

!eFect -road transmission

has disappeared in the product to be replaced by 47* at 0F99 cm,0(1

Accept 7U6 7:

Lf no reference to both groups responsible for the pea$s then ma (1

*C

Lf no reference to both wavenumbers responsible for thepea$s then ma (1 !

34


35/142

(d) (i) "ddition of barium ions pulls equilibrium to r3h3s3 (1

increases D-& and so lower p-/the p- falls (1 stand2alone mar$ !

!eFect


36/142

(b) Z%]surroundings7 ;

-

*C

!8=

0!+=99

(1

7 , 10' mol,05,0(1 !

Accept #S7: ,; mol7

37

Accept S7:#S ; mol7

37

Accept final ans$er $ith no $or,ing (&)

Allo$ "F for ";

!eFect full calculator display eg S7:#S4U5S7U

!eFect more than 5 dp e#g# S7:#S4U

(c) (i) Z1total7 ,10' & !0< 7 ,088

or ,0883= or ,!99) ( mol,05,0)LP*CE 1thsignificant figure 0

Accept #799 ,; mol7

37

ALLOW TE from(a)(ii) and (-)

(ii) reactants predominate / equilibrium lies well to the left*CEquilibrium completely to the left 0

ALLOW TE from (c)(i)

(d) (i) '

!+

&Cl

CL&Cl

pp

pp3

=

(1

LP*CE state symbols or lac$ of them unless (s) or (l)

Xnits atm (1 !Accept capital "&

Accept use of ( )

If e.pression the $rong $ay up allo$ second mar, if units

gi2en as atm7

!eFect use of 0

36


37/142

(ii)

%ubstance oles atstart

oles atequilibrium

6eq/atm

64l'(g)3.23

(1 3.2,

3.1,

C +.'2D 2.2

64l+(g) 3.3

3.2,

3.3,

C +.'2

D 3./-+

4l!(g) 3.3 3./-+

;otal number of moles at equilibrium 3.2

"ll three(1 "ll three(1

"llow consequential mar$ing across columns +If moles at e*m are gi2en as #5: for &Cl4(g) and for Cl5(g)

then Sth

column should -e 4#5S+ #:S and #:S

and gets 5 (out of 4)

(iii) ( )'8!3!(

=


38/142

+. (a) (i) 3a7E4*D

E-4*ED-D

!

+

+

(1

mol dm,+(1

Lf -!* is included as denominator then allow only the !nd

mar$ if no units suggested !

(ii) p3a 7 , log3a / , lg3a / , log093a 0

Accept 3a8 7p3a

(b) " solution which does not change its p- value (significantly) (1

@ay -e sho$n using an e*uation

Ihen some/small amount of acid or al$ali is added (1 !

(c) "cting as a base because it is acceptinga proton (to form -!4*+/4*!& -!*) 0

(d) (i) Before race F31 7


39/142

(iii) -ypothesis L would result in an increase in

D4*! / D-4*+, / D4*!& -4*+

,*C-ypothesis LL would produce greater acidity without

additional D4*! / D-4*

+

, / D4*!& -4*

+

, (1

;he table shows a fall in D4*! / D-4*+, / D4*!& -4*+

,and therefore -ypothesis LL must be favoured3 (1 !

[11]

3. (a) /!goes from 9 to ,+ 7 reduction (1-/-!goes from 9 to (&)0 7 oidation (1 !

If "the o.idation num-er of N goes do$n hence reduced and the

o.idation num-er of > goes up and hence o.idised (ma ')If all O#N# correct -ut fails to state $hich is o.idation and

$hich is reduction scores 7#

If all O#N# correct -ut -oth reactions misclassified+ scores Qero#

Any ans$er not referring to nitrogen or hydrogen scores Qero#

(b) (i) 4alculation of bonds bro$en 1


40/142


41/142

1. (a) (i) ;o slow down the reaction/to stop the reaction*C to quench the reaction*C to freeHe the (position of) equilibrium OWTTE (1

so that the (equilibrium) concentrations/amounts do not change (1 !

Accept to stop e*uili-rium shifting to the left

(ii) "irst mark:

EDED)()( !! ggI> =

*C

Xse of ('39 09,1)!(1

If >I0 not s*uared+ first mar, only#

$econd mark:

90839

)0993'(ED

!1!

)(

=g>I

*C

93908 7!

(g)

!1

E-LD

)0993'(

*C

D-L(g) 7

90839

)0993'( !1

(1

8hird mark:

D-L(g) 7 +3< 09,+(mol dm,+) (1

4orrect answer scores + mar$s3Lgnore state symbols3Lgnore units unless wrong3Lgnore s3f3 +

If first mar, not a$arded+ total (0)

(b) (i) !!

!

I>

>Ip

pp

p3

=

Lgnore position of any ( 0

[ ] scores (0)

41


42/142

(ii) Each step of this calculation must -e loo,ed at#

0stmar$ is for calculating equilibrium moles_!7 93!`!7 93!_` 7 03< (1

@ar, conse*uentially

!ndmar$ is for dividing these by ! (to get mole fractions)

03993!

!39! ==>.

03993!

!39!

==I.

=3993!

I.

(1


+rdmar$ is for multiplying by 030 (to get partial pressures)

03093!

!396

!=>

7 9300 (atm)

0093!

!396

!=I

7 9300 (atm)

0093!

I

7 93== (atm) (1


1thmar$ is for substituting into their epression and calculating3p

)0039()0039(

)==39( !

=p3

7


43/142

(iii) %ame number of moles on each side*C(;otal) pressure cancels*C(6ressure) units cancel

(ay be shown by crossing out etc3 in b(ii)) 0Accept 4O'/ hydrogen / >

'ions

!eFect Fust "contains >4

O'M#

(b) (i) ED

EEDD

!+

+!+

COO>C>C>

O>COOC>C>3a

+

=0

Accept >'0 instead of >4O

'0

!eFect any e.pression containing >5O0

43


44/142

(ii) (D-& 7) +3'0 not s*uared+ only 7

st

mar, a2aila-le

D4-+4-!4**- 7'

!

09+930

E-D

+

*r

D4-+4-!4**- 7'

!1

09+930

)094C>5COO

8 >' (ie no s*uare -rac,ets)

$econd assumption mark:

Lonisation of the (wea$) acid is negligible*r ,D-& where is initial concentration of 4-+4-!4**-

*r D-&??D-" (1 '

Accept "*er#slight ionisation M

"the initial >A0 8 e*uili-rium >A0

!eFect any mention of nonDstandard conditions or


45/142

(ii) Ior$ing X%; be chec$ed"irst mark:

D-& 7 5aDbase

acidD

(1

Accept 3a8acidD

saltD-D +

$econd mark:

4orrect Dacid 7 9399!' and Dsalt 7 9399+F' (1

8hird mark:

4alculation of p- correct consequential on Dacid and Dsalt used3

D>& 7 03+9 09,' 99+F'39

99!'39

7 =3


46/142

'. (i) Aower temperature as reaction is e0othermic/gives out heat /Z> is ,ve (1-igher/raise pressure as reaction moves towards fewer aseous molecules (1 !

Accept Mas re2erse reaction is endothermic

Accept M a$ay from more gaseous molecules

!eFect Mmore gaseousro!ucts

(ii) Aowering temperature decreases reaction rate (1

Lncreasing pressure increases reaction rate (1

Accept increasing pressure increases num-er of collisions

4onsequential on either/both parts of (i) !

Chec, they are consistent $ith (i)

(iii) Energy of reactants above products KhillJ in between (1Aower KhillJ for catalysed reaction form same start to same finish (1ar$ independently

E n e r g yC e a c t a n t s

4 a t a l y s e d

6 r o d u c t s

C e a c t i o n p a t h

X n c a t a l y s e d

!

Accept la-elled acti2ation energies

Accept dou-le hump accepta-le[6]

+. (a) (i) !!

!

p

)(5

ON

NO

pp

p

=

"llow answer with brac$ets and/or omittedLgnore (g) and eq 0

Accept !!

!

p5ON

NO

pp

p

=

!eFect anything in 0

(ii) %ame number of moles on each side of the equation *C

;he (partial pressure) units all cancel out (in the epression for 5p) 0

46


47/142

(b) (i) (p*)!7 93=F 93!+ '39 09,+0(1

7 039 09,+0

p*7 S(039 09,+0)

7 +3! 09,0


48/142

(iii) (Z> is positive so) ;

-

7 Z%surroundingswill be negative

o mar$ for negative alone 0

Accept negati2e+ since for an endothermic reaction energy is

ta,en from the surroundings causing a decrease in disorder /

reduction in entropy

(iv) ("s ; increases) Z%surroundingsbecomes greater/less negative/more positive so Z%total(also) becomes greater/lessnegative/more positive/increases 0

Accept P1surroundings-ecomes "smaller+ if *ualified+ e#g#

-ecomes closer to Qero

(d) Equilibrium might not have been reached (in the very short time thegases are present in the engine)

Lgnore references to the fact that the system is not closed 0

Accept other gases are present in the air (apart from N5and

O5)

Accept temperature inside engine may -e less than 7:3

Accept actual (total) pressure may -e less than that assumed[12]

48


49/142

. D4 of S#: (&)

!eFect :#7S or :

!eFect 7 or 4 sig# fig#[3]

-. (i) WI4

%tand alone mar$s

Aower yield / less hydrogen produced (1LP*CE any reference to rate

ore (gaseous) molecules on rhs / fewer (gaseous)molecules on lhs (1 !

!eFect e*uili-rium mo2e left / re2erse reaction fa2oured+ if no

reference to yield

(ii) WI4

-igher yield / more hydrogen produced (1, if this isonly eplained in general terms of increasing rate of thereaction do not award the mar$

(Qorward) reaction is endothermic / absorbs heat (1 !

If for$ard reaction is e.othermic (0 out of &)

49


50/142

(iii) o effect (1 0[5]

. (a)

"

B

0 1

0 !

0 9

=

o l u m e 9 3 0 - ( a q ) a d d e d / c m ++

0

Oo not worry about general shape of the curve the scoring points are:

V %tarting p- 0 and finishing p- between 8 and 00 (1

V >ertical at !' cm+(1

V >ertical range: at least three p- units in the range + to =e3g3 p- range + to < *C + to F *C + to = *C 1 to F

*C 1 to = *C ' to = (1(do not need to start/finish on whole numbers)

Accept p> range 4 to :

V iddle of vertical p- range between 1 and < (1 1

(b) Bromocresol greenLndicator(s) 4W on graph Dchec$ table on question paper 0

Accept more than one indicator for e.tended 2ertical regions

50


51/142

(c) p- change around equivalence point too small*C p- changes over too big a volume (1

Accept too small a 2ertical (region)

O! no 2ertical (region)

O! no point of infle.ion

O! no sudden change in p>O! no straight section

for a sharp colour change of indicator (1

Accept no sharp/clear/precise end point

O! 2ery small range o2er $hich indicator changes colour

!eFect no suita-le indicator

O! No "easy colour change

DLf say ammonia is a strong base or ethanoic acid is astrong acid or both (3 out of 2 !

[7]

/. (a)

- 4

*

* 4

-

-

4 -

-

- 0

(b) ester 0

(c) (i) oles: 4!-'*-: +3F' (1

oles: -4**4!-': !3'9 and moles -!* : !3'9 (1 for both !

(ii) *--D-4**-D4

*-D--4**4D

'!

!'!=c30

!eFect o-2iously round -rac,ets ( )

51


52/142

(iii) 1='39F'3+

1='39'939

1='39'93!

1='39'93!

=c3

(1ust have clearly divided moles of each component by

931=' for 0

st

mar$ e3g3D-4**4!-' 7 D-!* 7 '30< (mol dm,+)

and D-4**- 7 039+ (mol dm,+)

and D4!-'*- 7 F3F+ (mol dm,+)

7 +3++ (1 stand alone mark

LP*CE sig3figs3 !

Accept 4#E:#:

(5#:)3

5

c

=8 4#44 only scores (&) if it is stated

that H cancels either here or in (i2)

If >5O0 omitted in (ii)+ then ans$er

3c8 #US mol7

dm4

(&) -ut this $ill gi2e

3c8 7#44 mol7

dm4$ith H omitted from calculation (')

!eFect 7st

mar, if S6: used as H in e.pression

(iv) o (as) equal numbers of moles on both sides*C volumes cancel

*C mol dm,+cancel*C units cancel*C crossing out units to show they cancel 0

Accept "e*ual po$ers/moles on -oth sides

O! "po$ers cancel

@ar, CR on 3ce.pression in (ii)

!eFectconcentrations cancel

(d) (i) (as reaction) endothermic (1

Accept e.othermic in -ac,$ard direction (or $ords to thateffect)

5cdecreases (1

If state e.othermic in for$ard direction+ ' mar" onl# (out of -)

for CR "increase in 3c

numerator in quotient (has to) decrease*C denominator in quotient (has to) increase*C fraction (has to) decrease (1

yield of -4**4!-'decreases (1 1

52


53/142

(ii) no effect as catalysts do not affect (the value of) 5*Cno effect as catalysts do not affect the position of equilibrium*Cno effect as catalysts do not affect the yield

*Co effect as catalysts increase the rate of the forward andbac$ward reactions equally/to the same etent*Cno effect as catalysts only increase the rate*Cno effect as catalysts only alter the rate

no effect can be stated or impliedLP*CE any references to activation energy 0

!eFect Fust "catalysts increase rate[13]

. (a) (i) usesE]values to findEreaction7 (&) 03'F (>) (1

!eFect 7#:

n & !*+,& 1-&n!&& !*!& !-!* (1 !

Accept e*uation $ith e*uili-rium sign

!eFection e*uation $ith Yn on the right

(ii) Ereactionfor the production of hydrogen is (&) 93F< (>) (1

smaller than reaction in (i) so is less li$ely (1

*C

*+,being the oidised form of a redo couple with a more

positive E]than E]-&/T -!(1

is a stronger oidising agent than -&(1 !

53


54/142

(iii) heaaquacopper(LL) (1

* - !

* - !

4 u * - !* - !- ! *

- ! *

! &

* C

* - !

* - !

* - !

* - !- ! *

- ! *

(1Both mar$s stand aloneDLP*CE charge !DLP*CE how -!* ligand is bonded to central cation

Accept he.a*uacopper(II)

!eFect formula

(iv) liand echange/replacement/substitution (1

D4u(-!*)) (so not feasible) Dvalue is required3 0

Accept Cu5'

-eing the o.idised form of the redo. couple $ith

the more negati2e E[+ $ill not o.idise I

(ii) 4uL is a solid (so conditions are not standard) (1

Equilibrium is pulled over/moves to favour the r3h3s3 (1 !

!eFect Fust 4)50'

!eFect Cu(N>4)U0'

!eFect any 5' comple.

54


55/142

(iv) (atmospheric) oygen (1

oidises 4u&to 4u!&(1 !

!eFect air for o.ygen

(c) (i) starch (1blue2blac$/blue/blac$ to colourless (1 !

!eFect clear for colourless

(ii) (Lf added too early) insoluble comple/blac$ solid formed ma$ingtitre too low

*C (Lf added too early) insoluble comple/blac$ solid formedremoves iodine from solution

*C (Lf added too early) insoluble comple/blac$ solid formedcauses inaccurate titre3

*C (Lf added too early) insoluble comple/blac$ solid formed notall the iodine is titrated3 0

(iii) "mount thiosulphate 7 9390


56/142

(c) 4orrect answer with some wor$ing and correct units scores full mar$s3*therwise steps in calculation must ma$e it reasonably clear to eaminerwhat is being calculated (WI4)3

(initial amount) L,7 93099 mol dm,+ 939'9 dm+7 ' 09,+mol (1

"mount "g&7 93099 mol dm,+ 939+0 dm+7 +30 09,+mol (1

equilibrium amount L,7 +30 09,+mol (1

L,reacted 7 (' , +30) 09,+mol 7 038 09,+mol (1Lf this subtraction is not carried out then the net mar$ (for calculatingamount of sulphate) can not be awarded3;hus amount of sulphate 7 T 038 09,+(7 83' 09,1mol) (1

conc iodide 7+

+

dm9'39

mol0903+

(7 939

"O conc sulphate 7+

+

dm9'39mol098'39

(7 93908 mol dm,+) (1

;he mar$ is for the process of dividing by 939' dm+

3c7 93908/939


57/142

(iii) D-+*& 7 09,'mol dm,+(1

"ssumption ioniHation of -1&(negligibly) small (1

"ssumption D-+ 7 D-+*& (1

Accept N>S'0 8 N>SCl0 or N>SCl totally ioniQed

thus D-14l 7 (0 09,')!/ '3

7 930F= mol dm,+(1"nswer to ! or more %3Q3 1

(iv) WI4

methyl red (1

indicator constant or p3Lnmust be near the endpoint p-

*C indicator constant or p3Lnmust be near ' (1!ndmar$ conditional on correct indicator !

Accept p3Inin the steep part of the graph or it is a $ea, -aseD

strong acid titration

(b) 4,& -!* -4 & *-,

LP*CE state symbols 0

Accept "Z instead of " "

(c) (i) nucleophilic addition 0

57


58/142

(ii)

( : ) 4

4 * 4 4

* ( : )

(1 for both arrows (1 for intermediate

( 1

4 4

* ( : ) - 4

4

* -

4 & ( : ) 4

*C for second step

4

* ( : )

4

-

4

* -

4

( 1 +

ish hoo, arro$s (penalise once)

V Lgnore the groups attached to the carbonyl carbon throughout

V ;he intermediate is not consequential on their first step

V ;he minus of the cyanide ion can be on either the 4 or the

V ;he arrow can start from the minus of ,4 in step 0 (but notfrom the minus of 4,) and can start from the minus of *,in step !

V ;he arrow from the bond must not go past the * atom

V Aone pairs not essential

V %ingle step addition of -4 or initial attac$ by -&/-4 scores Hero

V "utoionisation of 47* can only score the last two mar$s ie ma !

(iii) WI4

if too acidic too small a concentration of cyanide ions (1Accept not enough / too little CN

if too al$aline too little -4 to donate the proton in the last step*C -&ion concentration too low (1 !

58


59/142

(d) (i) rate 7 ,D4-+4-!4-!4l D4,

ust be an equationust be D *; ( )Lgnore upper case 5 0

Accept Cl0 / 7Dchloropropane0/chloropropane0

Accept cyanide ion0/cyanide0

!eFect 3CN0

(ii)

4 u r l y a r r o w ( 1

4 u r l y a r r o w ( 1 ; r a n s i t i o n s t a t e ( 1

-

4- 4 l

4 - 4

, ! '

- -

4 4 l 4

4 -! '

-

4 4 - & 4 l

4 -! '

,

,

V ust have partial bonds in transition state

V 4 and 4l must be on opposite sides of central 4 in thetransition state

V "ccept negative charge on of cyanide ion +@echanism -ased on 1N7 scores

!eFect fish hoo, arro$s (penalise once)

!eFect arro$ from N of CN[19]

-2. (i) higher pressure / temperature will increase rate of reaction

*Chigher pressure will increase production of methanol (as lessmoles of gas on the C-%) 0

Accept higher pressure faster reaction

Accept higher temperature faster reaction

Accept higher pressure greater yield

!eFect no catalyst used so cheaper

59


60/142

(ii) "ny three from:

lower temperatureincreases yield / because reaction eothermic (1

lower temperature costs less (less energy used) (1

Can gain 5 mar,s if -oth ideas of temperature and pressure puttogether in same ad2antage

lower pressure costs less (pipes thinner/less energy neededto pressurise plant) (1

catalyst speeds up reaction (1/allows a lower temperature to be used +

Accept catalyst allo$s a lo$er pressure to -e used

!eFect lo$er temp/pressure easier to achie2e[4]

-'. (a) (i) D< 0==3F & 1 !093F , D1 08!3+ & ' !9' (1

&0=93= mol,05,0(1

Accept '767 ; mol7

37

!eFect internal TE

,0 for missing & sign/missing or incorrect units but penalise onlyonce in part (a)DLP*CE sig fig !

(ii) yes as molecules of as are being changed to 13 molecules ofas (therefore increase in disorder) 0

Accept TE from (i)

Not Fust 9 molecules going to 7 molecules

(iii) ,89'3< 0999 /00!+ (1

& =9


61/142

(v) "ll products/reaction goes to completion because Z%totY !99

mol,05,0/Z%totis ?ery largeDeeds to be consistent with (iv) 0

(vi) catalysed pathway should have lower Eathan uncatalysed pathwayand the pea$ of the curve should be above the energy level of thereactants (1

Energy of products should be lower than energy of reactants (1 !

(b) (i) !!

!

!

pOpNO

pNO3p

=

0

Accept !!

!!

pONOp

NOp

!eFect 0

(ii) mole fraction *!7 '

8'31

or 9388 (1

mole fraction * 7 '

9!'39

or 9399'

*C

mole fraction *!7 '

9!'39

or 9399' (1

5p7++

!!

)0'30()99'39(

)'30()8839(

7 '!!F!99 / '3! 09


62/142

(iv) 5 premains unchanged as pressure does not affect it / onlytemperature affects 5p(1

partial pressure of *! increases as eqm moves to side offewest (gas) molecules/C-% (1

or6artial pressure of *! increases as pp 7 mole fraction totalpressure !

Accept Fustification in terms of entropy[17]

-+. (a) (i) -E4l4*4-D

E-ED4l4*4-D

!!

!!+

=a30

Accept >4O'0 in place of >'0

allo$ one set of s* -rac,ets to -e missing

(ii) D-&!7 03+ 09,+ 93990 (1

7 03+ 09,5CO4(a*)

Accept >CO5> for the acid

Accept >CO5Na or >COONa

'for salt

(c) (i) one acid: -4**-4onRugate base: -4**,1 mark for both

Accept correct acids and conFugate -ases in either order

ACCE&T

>CO5> and >CO5

O!*

- 4* -

*

- 4* ,

other acid: -+*&

4onRugate base: -!*1 mark for both !

!eFect >'for >4O

'

(ii) (5 a) 7-4**-ED

E*-ED-4**D ++

Accept >'0 instead of >4O

'0

ust use square brac$ets 0

>CO50 and >CO5>0

66


67/142

(iii) D-&!7 5a D-4**-*C

5a7-4**-D

-D !+

O!

D-&!7 03 2alue conse*uential on 0 >'0+ pro2ided p> ]

!eFect p> 8 5#49 (is a rounding error) so no third mar,

"lternative method

p5a7 +3=9 (1

p- 7acidElogD

!

0p5

!

0a

(1p- 7 0389 , (,93'9)

p- 7 !319 (1 +!eFect p> 8 5#49 (is a rounding error) so no third mar,

67


68/142

(d) (i) D-& 7 5aDsaltE

DacidE

O!

D-& 7 03


69/142

(ii) "ddition of -& ions:>COO

' >

'Z >COO>(1

Accept if descri-ed in terms of >A >'' A

shifting to left

"ddition of *-

,

ions:>COO> ' O>

>COO

' >5O(1

Lf the ionisation of sodium methanoate shown withthen ma0 (1 out of ! for above equations

Addition of O> ions%

>'' O>

Z >5O must befollo$ed -y more dissociation of

>COO> (to restore >'0)

Accept "molecular e*uations or e*uations descri-ed in $ords

or notation in2ol2ing >A+ >'and A

#

(buffer solution has) high concentrations*r a large reservoir of both>COO> and>COO,

relative to added>'/ O>(1(hence virtually no change in D-&) +

Accept Fust "large reser2oir of -oth >COO> and >COO

[16]

-. (a) %


70/142

(iii) "ll three total pressure (1i3e3

p%*! 7!0

1or993!'309

9930

7 93089 (atm)

p*! 7!0

!or993!'309

'9939

7 9398'! (atm)

p%*+ 7F

0!!0

+< oror993!'309

9938

7 03F0 (atm)

@ar, conse*uential on (a)(ii) 0

(iv) )98'!39()08939()F030(

!

!

=p3

3p7 ='0 (1atm,0(1

@ar, conse*uential on (a)(iii) and (a)(i2) !

Accept ans$er $ith units and no $or,ing (5)

Accept "correct ans$ers -et$een 6S: and 6:: as this co2ers

rounding up etc

!eFect $rong units e#g# mol7

dm4

(b) (i) (3p) decreases 0

(ii) (3pdecreases so)

!eFect any Le Chatelier argument (this pre2ents access to 7st

mar,)

fraction/quotient !!!

+!

pO1Op

1Op

has to decrease (to equal new $p) (1so shifts to left hand side (1 this mar$ onlyavailable if (b)(i) answer was $pdecreases3

!eFect shifts to right+ e/en if ans$er to (-)(i) $as ,pincreases

(as +%*p

decreases whereas !%*p

and !*p

increase) !

(c) (i) o effect/none/Hero (effect) 0

70


71/142

(ii) LncreasesO!

more %*+/more sulphur trioideO!

increases amount of %*+/sulphur trioide 0

(d) (i) o effect/none/Hero (effect) 0

(ii) o effect/none/Hero (effect) 0[13]

-/. (a) -& 0

Accept >4O'

(b) -4**-/-4*!- (1-*+(1

,0 for each etra incorrect answer !

Accept C and E[3]

-. (a) (i) p- 7 +3' (1

log09D-& 7 ,+3'

D-& 7 +30< 09,1(mol dm,+) (1

!3'(1 09,1(mol dm,+) based on p- 7 +3< (! mar$s) !

Accept T#E# from $rong p> pro2iding ]

Accept 4#5 V 7S

(mol dm4

)

4 V 7S

(mol dm4

) allo$ed if e2idence of rounding -eing

applied

(ii) 5 a7-E4*4-4-4-D

E4*4-4-4-ED-D

!!!+

!!!+

+

(1 0

Accept 2ersion $ith >4O'0

Accept molecular formulae

AcceptE*-4D

E*-4ED-D

!=1

!F1

+

71


72/142

(iii) 5a 7 4**-E4-4-D4-E-D

!!+

!+

(1

7 994C>5C>5CO5

'N>S'

!eFect any amide product

(ii) "mmonium butanoate (1(Ecess) butanoic acid (1no ;E from (b)(i) !

Accept ammonium ions and -utanoate ions (')

!eFect -utanoate ions alone

!eFect formulae

(iii) " buffer (miture) (1;here is a relatively small rise @chane in p9 (asaqueous ammonia is added) *I;;E (1ar$ independently !

!eFect sharp neutralisation point/no change in p>

(iv) ;here is no large increase in p- / vertical shape to thegraph (at the end2point) *I;;E 0

Accept no sudden change in p>

!eFect no indicator has the re*uired p> range

72


73/142

(v) EL;-EC

End2point 7 +9 cm+(1D-+ 7 (09/+9) 9399


74/142

(iii) add chlorine(1which drives equilibrium to the left(1

O!

increase the (total) pressure(1because there are fewer (gas) molecules on left hand side(1

O!

add 64l+(1Ihich drives equilibrium to the left(1 !

[8]

1. (a) (i) 2 lg (939') 7 03+(9) 0

INO!E sig figs from this point on in this *uestion

(ii) D*- 7 0 09,01/ 939' 7 ! 09,0+(mol dm,+) 0

O! 2ia pO>

Correct ans$er $ith no $or,ing (')

(b) (i) 3a7 D-!6*1D-+*

&/D-+6*1

NOTusing -&instead of -+*& 0

(ii) D-+*& 7 09,03!9

7 939


75/142

(ii) presence of -&from the first dissociation $eeps equilibrium to left/suppresses ionisation 0

(d) Bromocresol green(1

p5in/range/colour change (of indicator) lies in vertical section*CQor alternative indicators p5in/range/colour change (of indicator) lieoutside vertical section(1 !

[12]

2. (a) (i) E%89ER

E7 (&) 930' (>) *C E(n*1,

/n!&) more positive or

greater than E

(4l!/ 4l,) accept reverse argument(1

(so) n*1,reacts with 4l,*C 4l,ions form 4l!

*C 5n*1reacts with -4l(1O!

!n*1,& 0)(1 !

(ii) stated colour change of colourless to (pale) pin$ *; purple *C

stays (pale) pin$*C pin$ to colourless*C first ecess of (coloured) manganate((>LL))

INO!Eself2indicatingINO!Ereferences to n!& 0

(b) (i) (ultiply iron half2equation by five to) cancel out electrons*C balance electrons 0

75


76/142

(ii) oles n*17 0999

093!99!9939

7 9399919! mol n*1(1

oles Qe

!&

per !'39 cm

+

7 ' 9399919!7 9399!90 mol Qe!&(1

oles Qe!&per !99 cm+7 9399!90 !'

!99

mol Qe!&

7 9390)

4orrect answer alone(1 0

(ii)

theseofany

+

+

(1

(1

(1

(1

standardnotarebattery)car(in theconditionsthe

dmmol0notE6bD

dmmol0notED-

edprecipitat6b%*

+,aq)(

!

+,aq)(

1

temperature non2standard alone or not 0 atm pressurealone does not score 0

[11]

'. (a) (i) Qe!*+& +4* !Qe & +4*!(1

>7 (+ ,+81) 2 (+ ,009) , (,=!!)7 ,+9 ($ mol,0) (2

@ultiply -y 4 t$ice(1Correct ans$er $ith sign(1

ALLOW conse*uential calculation if $rong stoichiometry

If O5gi2en as product 1 ma0on conse*uential calculation +

76


77/142

(ii) (i) is more li$ely because the rate of a reaction between a solidand a gas will be faster than that between two solids

ALLOW

(i) is more li$ely because it is eothermic (and (ii) is endothermic)O!

products in (i) are more thermodynamically stable relative 0to reactants than in (ii)

Conse*uential on (a)(i)

(b) (i) 3p71

!

1!

*p-

p-

(1"p=s are essentialNOD

71

1

!30


78/142

(e) (i) add (aqueous) sodium hydroide / ammonia (1ALLOW *-,(aq)red/brown/foy red/red2brown/rust ppt/solid(1

O!

add (aqueous) potassium heacyanoferrate(LL)/heacyanoferrate(LL)

ions(1(6russian) blueppt@solid (1 ALLOW result for near miss spellingof reagent

O!

add (aqueous) potassium thiocyanate(1blood red (solution) (1NOTppt !

(ii) Qe+&polarises the (*- bond in water) ligands(1

DQe(-!*)


79/142

(ii) 099 , 09


80/142

(iii) 4'-09 03F (1 +39

F30

7 '3

,! !

(ii) -igh yield favoured by low temperature (1-igh rate favoured by high temperature (1

%o temperature used is a compromise (1, conditional on first t$o mar,s

ACCE&T correct in2erse argument +

80


81/142

(iii) ;oo costly for etra yieldO!6osition of equilibrium is well to right under these conditionsO!4orrosion problems at high pressureO!*nly need elevated pressure in practice to push gases through systemO!4apital cost high

O!aintenance cost highO!-igh energy costO!%ulphur dioide liquefies3

NOTtoo costly $ithout e.planationNOTtoo dangerous 0

(c) (i) Z>7 !Z>f(%*+) ,! Z-f(%*!) 7 (,+8' !) , (, !8F !) (1

7 ,08< ($ mol,0) (1 INO!E units

,08< ($ mol,0) $ith some $or,ing (2

No conse*uential mar, other than failing to multiply -y t$o to get,8= $ mol,0ma0 (1Any positi2e ans$er (3 !

WI4 (ii) Z>fis definedas formation from elementsO!Z>fof an element is definedas 9 (in its standard state)O!allelements are given the value Hero

KLt is an elementJ on its o$n (3 0

(d) (i) >!*' O! >!9'NOTnameNOT>!*'3If name and formula gi2en+ ignore name# 0

81


82/142

(ii)


4 a t a l y s e d

E u t h a l p y l e v e l s


4 a t a l y s e d

E u t h a l p y l e v e l s

( 0 )

( 0 )

( 0 )

( 0 )

( 0 )

( 0 )

" A A * I

( E n t h a l p y /h e a t / e n e r g y )

( E n t h a l p y /h e a t / e n e r g y )

6 r o d u c t s / 6 / % * +

C e a c t a n t s / C/ % * & *! !

C e a c t a n t s / C/ % * & *! !

6 r o d u c t s / 6 / % * +

ALLOWendothermic intermediatesALLOWsingle hump for catalysed pathway: (energy)If the diagram sho$s P> endothermic+ then can score the first t$o mar,s3

If yDa.is la-el is $rong 4rd

mar, can not -e a$arded

Catalysed and uncatalysed la-els missing scores 4rd

mar, only

If t$o diagrams dra$n+ full credit can -e gi2en if the catalysed

Eais clearly less than the uncatalysed#If Z> and Eaconfused+ thenma0 2 +

WI4 (iii) 4hanges mechanism to one of lowerEa

O!to a different route with lowerEa (1NOTAowersEa alone3

Ceactants (chemically) adsorb on catalyst surfaceO!(at given ;) more collisions haveEYEaso more successful collisions (1 !

(e) "orms (a difficult to condense mist @ fo @ smoke @ too ?iolent @too e0othermic

NOTetremely reactive 0[18]

82


83/142

. (a) starts at !3! (1

vertical section at 19cm+of sodium hydroide (1vertical section centred between p- =28 and between ! to + squares high (1

shape to include initial Rump and finish between p- 7 0! , 0+ (1

Lf curve drawn bac$ to front only !ndand +rdmar$s available 1

(b) (i) maintainsnearly constant p- / resists change in p- (1on adding small amountsof acid or al$ali (1 !

(ii)[ ]

ED

ED-salt

acid3a=+

O! p- 7 p5a,lg

[ ]DsaltE

acid

(1

D-& 7 03F= 09,1 0!'39

!'39

(1

D-& 7 +3'< 09,1(mol dm,+) +

p- 7 +31(') (1INO!E no# of decimal places -ut penalise p> 8 4

(iii) acid partially ionised and salt fully ionisedO!equations (1

-" & *-,. ", & -!* (1

ALLOW-

&

& *-

,

. -!* followed by more dissociation of -"",& -& . -" (1

D-" andD", are large (relative to -&and *-,added) / large reserves of

undissociated acid andsalt (and so the values of D-" and D", do notchange significantly) (1

*;E: Lf no equations given for effect of adding *-,and -& correcteplanation can score (1out of these two mar$s3 1

[13]

/. (a) ;he emf of a half2cell measured relative to the standard hydrogen electrode (1

all solutions at 0 mol dm,+concentration and gases at 0 atm pressure / 090 $6aand at a stated temperature / !8=5 (1 1tandalone mar,

ALLOWpressure of 099 $6a !

(b) Lntroducing another metal wire would set up its own p3d3 / canonly measure a potential difference / need source and sin$ for

electrons / voltmeter requires two connections 0

83


84/142

(c) (i) !Qe(s)& *!(g)& !-!*(l) !Qe!&(aq) & 1*-,(aq) or multiples

O!

!Qe(s)& *!(g)& !-!*(l) !Qe(*-)!(s)

%pecies (1balancing (1

Oo not allow species mar$ if electrons still in equation but allowbalancing mar$ if 1e on both sides !

(ii) E]

react7 (&) 93=1 (>) (1Preater than Hero therefore feasible (1 !

WI4 (iii) n oidises preferentially to Qe / inc acts as sacrificial (anode) (1Lf %n used (and damaged) Qe oidises preferentially (1Oisallow "o.idises more readily

E]

n!&/ n more negative than for QeO!

E]

n / n!&more positive than for QeO!

E

cellfor n being oidised by *!is more positive than for Qebeing oidised by *!O!

similar E]arguments related to preferential oidation with %n (1 +disallo$ "higher or "-igger for more negati2e or more positi2e

[10]

. (a) (i) Qorms ionswhich have partially filled d2orbitalsO!

Qorms ions which have a partially filled d2subshell 0

(ii) %candiurn / %c andinc / n 0

(b) (i) Qe!&D"r +dLL) gains 'e,/ change in oidation no3 ' (1

n(ll) / n!& (1 NOT standalone mar, 1

(e) (i) >*+,& !-&/ !-+*

&>*!&& -!* / +-!* 0

(ii) o because oidation no3 of > is &' in >*!&/ *idation no3 of >

unchanged (at &') 0(iii) Qirst green colour : >*!

&and>*!& (1

%econd green colour : >+&/ D>(-!*)iolet colour : >!&/ D>(-!*)


86/142

(ii) no3 moles!

+!*% used 7 0!3' 93 0 / 0999 7 03 !' 09,+ (1

no3 moles L!7 03!' 09,+/ ! 7

(iii) mass 4l!7 93

WI4 (d) *!oidises 5L / iodide to l!3 or balanced equation (1ll!reacts with starch / paper to give blue / blac$ (1 !

[14]

/1. (i)

- 4 4 4

- - -

- - 0

(ii)

- 4 4 4

- - -

- -

x

x x

x x

x

ALLOW all dots or crosses

ALLOW TE for a -utene/pentene in (a)(i)

INO!E circle 0[2]

/2. (a) (i) egative with some sensible eplanation eg fewer moles of product (1

+ moles of gases going to ! moles of gases (1 !@?1T mention gases or no changes in state

86


87/142


88/142

(c) (i) ust be a quantity that can be measuredEg

;he pressure could be measured (1as it will decrease as the reaction proceeds because there are onlytwo/fewer moles on the right compared to three on the left (1

O! colour (1as the nitrogen(L>) oide is brown whereas the other gasesare colourless (1

O! total volume (1which will decrease by one third/because there are fewer moles (1

ALLOWacidity because *!acidic andothers not (1 ma0

NOTdilatometryNOTtemperature !

(ii) D* second order (1

because when conc of * is doubled the rate goes up four times (1

D*! first order (1 +

Then (iii)+ (i2) and (2) must follo$ consistently from (ii)

(iii) ALLOW TE from (ii) e#g#

rate 7 $D*!D*! rate 7 $D*D*! 0

(iv) third / + second / ! 0

(v) =999 (1 dm


89/142

(b) (i) 3p7!

!!

(p(*4l))

p(*))p(4l

allo$ $ithout -rac,ets+ penalise D 0

(ii) !*4l !* & 4l!

%tart 0 9 9 ,93!! &93!! &9300eq moles 93F= 93!! 9300 (1total moles of gas 0300mole fractions above values U0300 (1

93F9!F 9308=! 9398809partial pressure / atm above values '399 (1

+3'0 93880 9318'

3p7!

!

atm)'03+(

atm)(93880atm18'39

(1

7 939+8'/ 939+81 atm (1range of ans$ers #S6 / #S7 #49 / #495 NOT #SACCE&T 5 1#

Correct ans$er plus some recognisa-le $or,ing(

@ar,s are for processes

E*uili-rium moles

Ki2iding -y total moles

@ultiplying -y total pressure

1u-stituting equilibrium 2alues into e.pression for 3& '

Calculating the 2alue of 36$ith correct conse*uential unit#

(iii) "s the reaction is endothermic ,stand alone(1

the value of36will increase (as the temperature is increased) 2 (1

conse*uential on 7st

ans$er (if e.othermic (3 then 36decreases(1)or effect on 36mar,+ must ha2e addressed $hether reaction isendothermic or e.othermic !

(iv) 6ecause (as the value of36goes up) the value ofp4l! (p*)

!/ (p*4l)!(the quotient) must also go up (1and so the position of equilibrium moves to the right ,stand alone(1

ut mar, conse*uentially on change in 5 in (iii)If "position of e*uili-rium mo2es to right so 5pincreases(ma0 1 !INO!E references to Le Chatelier=s &rinciple

[12]

89


90/142

/+. (a) 4-+4**- labelled as base and lin$ed to 4-+4**-!&labelled

(conRugate) acid (1

-!%*1labelled acid and lin$ed to -%*1,labelled (conRugate) base (1

If acids and -ases correct -ut not clearly or correctly lin,ed 1 (out of 2

;ust lin, -ut no identification of acids and -ases (3 !

(b) (i) (p-) more than F / =28 (1Lndicator: phenolphthalein "AA*I thymolphthalein *C thymol blue(mar, conse*uentially on p>)(1 !

@ar, conse*uentially on p> -ut if p> do not allo$ either methyl

orange or phenolphthalein

WI4k(ii) "s *-,/ base removes -&ions / -neutis per mole of -!* produced / (1

-&& *-,7 -!*the equilibrium shifts to the right (1and so all the ethanoic acid reacts (not Rust 0 of it) (1O!

Endothermic (*-) bond brea$ing (1is compensated for (1

by eothermic hydration of ions (1O!

- for 4-+4**- & -!* 4-+4**,& -+*

&7 &!$ mol,0/ almost Hero /very small (1

-neutD4-+4**- 7 &! & -neutD-4l (1the same (for both acids) (1O!

-neutis per mole of -!* produced (1(heat) energy required for full dissociation (of wea$ acid) (1so -neutslightly less eothermic (for wea$ acid) (1 +

(iii) D-&!73aD4-+4**- 7 03F1 09,' 93019 7 !311 09,>(1ACCE&T !3=9/!3= (answers to 0 or ! dp)

;he assumptions are two from:D-& 7 D4-+4**

, , this mar, can -e earned from $or,ing /

negligible D-& from ionisation of water (1

D4-+4**- 7 93019 , D-& 93019 (mol dm,+) / ionisation of acid

negligible (1solution at !'4 (1 ma0 2 1

90


91/142

(iv) 03F1 09,'7 ED

EDED

acid

salt>+

(1

D-& 7 03F1 09,' 939F9 7 03!! 09,'(193099

p- 7 1380 / 138 / 138!NOT :Ma0 2 if #7S / #5 is used(1 +[14]

/. (a) (i) Qe D"r+d


92/142

(ii) The mar, is for the shape

ALLOW -ond to > of >5O (e.cept on left side if O>5 is gi2en)INO!E charge unless incorrect 0

(iii) DQe(-!*)


93/142

(b) (i) Emf of cell / potential difference of cell containing Qe!&and Qe (1and standard hydrogen electrode / half cell NOTK%-EJO!hydrogen electrode and 0 mol dm,+-&and 0 atm -!(1

0 mol dm,+ Qe!&

INO!E temperature +

WI4k(ii) Emf of hydrogen electrode is Hero ,stated or implied (e3g3 ifcalculate Ecell7 &9311(>)) (1

Qe & !-&Qe!&& -!(1 e*uation stand alone6otential for the reaction is positive so reaction is feasible (1O!

-&and (T)-!has a more &ve electrode potential than Qe!&and Qe (1

-&will oidise Qe / -&is an oidising agent / Qe is a reducingagent for -&/ other correct redo statement (1

Qe & !-&Qe!&& -!(1 stand alone +

(iii) -ighEaso slow reaction / reactants are $inetically stableINO!E any mention of nonDstandard conditions 0

(c) !Qe+&& !L,!Qe!&& L!or words E97 (F 3.2'> (1

%o L,would reduce Qe+&/ Qe+&would oidise L,/ E9positive so reactionA C (1

O! reverse argument (2O!

Qe+&and Qe!&has a more positive electrode potential than L!and L,(1

L,will reduce Qe+&/ Qe+&will oidise L,(1 ![15]

/-. (a) (i) %tep 0hydrogen bromide / -Br / concentrated hydrobromic acid / 5Br &concentrated -!%*1(1

%tep !sodium / potassium hydroide / a*- / 5*- (1then any acid O!its formula O! -&(1

%tep +(potassium) (di)chromate((>L)) and sulphuric acid / acidifiedO! their formulae / ;ollensJ / QehlingJs / BenedictJs / acidified(potassium) manganate(>LL) (1 1

93


94/142

(ii)

(1

ot enough energy / heat to brea$ (and cause rotation) the (/ double)bond(1 !

(b) (i) 4-+4-(*-)4-(*-)4**,

O! structural formula dra$n#

ALLOW acid 0

(ii) 4-+4(*-)(4)4-!4**-

O! structural formula dra$n# 0

(c) (i)

(ii) ;he acid is partially ionisedO! equation - (&-!*) -

&(-+*&) & ,(1

WI4

;he salt is totally ionised O!equation a a&& ,(1

Ihen *-,ions are added they react with the lare reservoir of - (1molecules

*-,& - -!* & ,(or words) thus removing the added *-,ions (1

Alternati2e 4rd

and Sth

mar,s%

*-,reacts with -&from ionisation of acid (14ausing further ionisation of lare reservoir of - (1 1

94


95/142

(ii) 3a7

[ ] [ ][ ]acidwea$

salt- +

or D-& 7

[ ][ ]salt

acidwea$5a

or3a7

[ ][ ][ ]-

- ,+

(1

D-& 7 09,p-7 09,+3=97 03'= 09,1(mol dm,+) (1

Dsalt 73a Dwea$ acid D-& 7 !3

93199 , 93+!9 7 939=9 0309 , 93


96/142

(b) "mount of ethan20 !2diol 7 09'1 /

"mount of ethene 7 !=

'


97/142

//. (a) (i)

(1

cycle with state symbols or as energy level diagram3 (1labels (in sym-ols+ $ords or num-ers)(1>soln7 ,>lat& >hyd4a

!&& ! >hyd*-,*C values

>lat7 ,0


98/142

/. (a) (i) &+0+31 1 08F3< !838 (1"bsence of 1 (3

7 ,'9


99/142

(iii) Lncreasing the pressure/ concentration of 4* would force thereaction to the C-% with the smallest number of gaseous molecules(1

NOTpressure$ithrate

Ceduce the temperature so that the reaction goes in the eothermicdirection / increase the temperature to increase rate (1

Oo not allow equilibrium to be reached by passing the 4* over thenic$el/recovering the product formed (1

Xse a catalyst to increase rate / increase the surface area of the nic$elto increase number of collisions (1 +

(c) ;he reaction can be reversed by increasing the temperature (1

as Z1]surroundingswill become less positive/more negative as the temperatureis increased (and Z%systemwill remain almost unchanged) so Z% totalbecomesnegative for the forward reaction (1 !

[16]

3. (a) (i) rate forward 7 rate bac$ (1no change in concentration/partial pressure/amount(1 !

(ii) () increases(1 0

(iii) one(1 0

(b) Lf temperature too low rate too slow/high temperature gives fast rate(1,but if too high yield too small/high yield needs low temperature(1therefore a compromise temperature (of 1'9 4)(1and catalyst for quic$ rate (at temperature 1'9 4)/catalyst not effectiveif temperature below 199 4(1 1

[8]

1. (i) Iea$ acid is dissociated to a small etent/slightly dissociated/ionised/few molecules dissociate

ALLOWpartial dissociationNOTKnot fully dissociatedJ3 0

99


100/142

(ii) 5a 7 4**-E-D4

E4**-ED4D-

81

,81

+

O! D-+*& for D-& 0

(iii) 5a 7 D-+*&!/ Dacid O!D-+*

& 7 S 5a Dacid(1

D-+*&

7 03!+ 09,+

(1, dependent on 7st

mar,p- 7 !380/!38!(1ACCE&T!38 0 or ! d3p3Correct ans$er $ith $or,ing('Correct ans$er $ith no $or,ing(1

ALLOW TE only if p> -elo$ +

(iv) starting p- !38ALLOW starting in 5ndor 4rd-o.es a-o2e p> 5(1consequential on (iii)

p- range vertical ma < to 0! min F,09(1Equivalence point at !'cm+(1

Peneral shape of curve andfinish at p- between 0!,0+(1and end in 7stthree -o.es a-o2e 75+ e.tending to S: cm4

If dra$n $rong $ay round & maie e*ui2alence point(')and

2ertical drop (')mar,s can -e a$arded 1

(v) ;hymol blue(1, Conse*uential on (i2)(4ompletely) changes colour within vertical portion/the wor$ingrange of the indicator is within the vertical portion / p5indG 0 invertical position / p5indin centre of vertical position(1 !

[11]

2. (a) (i) 5 c7*-E-)4**-ED44-(-D4-

*EED--)4**44-(-D4-

'!!+

!'!!+

INO!E minor slip in formulae 0

(ii) Bonds bro$en: *- and 4*Bonds made: 4* and *-(1

otes that there is no change (and therefore Z- is Hero)(1O!

Bonds bro$en & (1


101/142

(b) (i)

- 4 4 4

--

--

&

- -*

*,

K o n o t a c c e p t ' 2 e c h a r g e o n c o 2 a l e n t l y - o n d e d > i n

N > - u t O 3 i f d a t i 2 e c o 2 a l e n t - o n d t o >& &

+

* C

*

4

*

,

ALLOW4-+4-(-+&)4**,/ 4-+4-(-+

&)4*!,-rac,ets can -e

omitted 0

(ii) "ttraction between (ionic) charges on differentions/Hwitterions (isstrong) 0

(iii)

- 4 4 4 * * & - - 4 4 4 * * -

- 4 4 4 * * & * - - 4 4 4 * * & - *

-

-

-

-

+

+

+

+

+

!

+

+

+

!

+

+ +

+

!

&

&

&

&

&

&,

, ,,

-

-

-

-

( - 4 4 - ( - ) 4 * * - ) - 4 4 - ( - ) 4 * * -

A C C E & T 2 a r i a t i o n s s t a r t i n g $ i t h - 4 4 4 * * --

-

@?1T -e -alanced e*uations

Can use NaO> or >Cl etc !

(c) (i) on,superimposable on its mirror imageO!has no plane of symmetry / it has an asymmetric carbon atom*; 1 different groups on a 4 atom on its o$n 0

(ii) *ne diagram correct and +O(1@irror image(1, can -e a$arded if 7stmar, not gi2en -ecause of a nearlycorrect structure eg ester !

(iii) Cotation of the plane of (plane),polarised light in opposite directions 0[13]

101


102/142

'. &enalise unitsonly once in this *uestion

(a) (!08!3+),D0803< & (0+93< +) (1D 08=3=/088 mol,05 ,0 (1 !

(b) !8=

/!38!,,

!8=

/0999!38!,,

,- / ; (1

D & +98(31) mol,05,0/ & 93+98(1) $ mol,05,0 (1 !

(c) (i) ,08=3= & +98 7 & 009 mol,05,0(+ %Q)O!

08=3= & +9831 7 & 000 mol,05,0(+ %Q)DOo not penalise missing & sign if penalised already in (b)

NOT1%Q3 6enatise %Q only once on paper 0

(ii) @es as %totalis positive / total entropy chane 0

(d) (i) -igher ; ma$es %surroundingsdecrease (so %totalis less positive) 0

(ii) 4ost (of energy) to provide compression/ cost of equipmentto withstand high 6/ maintenance costs3

NOTsafety considerations alone 0

(iii) Oifferent phase/state (to the reactants) 0[9]

+. (a) (i) p- 7 , log(09)D-+*& (1

O! D-&instead of D-+*& applied throughout 0

(ii) D-+*& greater than 0 (mol dm ,+) 0

(b) (i) 3a# 7D-"E

ED"E*D- ,++

(1

D-+*& 7 0301 09,+mol dm ,+(1p- 7 !38(1) (1 +

(ii) %tart at the same p- as in (i) (1

Praph showing vertical at !' cm+(1vertical section +,' units in length with midpoint around p- = (1general shape correct including buffer Hone and final p- not Y 0+ (1 1

(iii) p- 7 p5a 0++++++++++++++++++++++++++++++++++++

102


103/142

[10]

103


104/142


105/142

. (a) (i) 4!-


106/142

(b) (i) ;emperature

Qaster at 1994 (1even though yield is lower (16ressure-igher pressure improves yield of methanol (1-igher pressure increases rate (1Ma0imum ' +

(ii) ot in same phase as reactants3 "AA*Istateinstead ofphase 0

(iii) 3p7p(4-+*-)/p(4*)p(-!)! 0

(iv) 6artial pressure of methanol 7 !99 , '' , !9 7 0!' atm (13p7 (0!')/''!9

!

7 '3


107/142

(ii) D-& 7 D*!, or D-&!8 3a D-*! (1

D-& 7 (3a 930!) 7 9399F'0 mol dm,+(1

p- 7 , log D-& 7 !30!/!30 (1ALLOW any correct con2ersion of >

'l into p> pro2ided the

ans$er is less than +

(iii) oles a*!7 03+=/) (1

and Qe!&to Qe by n (E

cell7 &93+!>)(1

;hey have positive Eso are feasible (1NOTwill happen

*C"AA*I n!&/n is more negative than both Qe+&/Qe!&and Qe!&/Qe (1so Hinc is a stronger reducing agent (1so Hinc reducing both is feasible (1 +

(ii) Ceduction of Qe!&has high activation energy / $inetically stable 0

(b) (i) n *1,& 'Qe!&& =-&n!&& 'Qe+&& 1-!*

%pecies (1Balance (1"ny state symbols ignored3 !

(ii) purple colour of n*1,lost (1

end point when yellow / colourless solution (1

becomes (permanently) pin$ (1 +

107


108/142

(c) "mount n*1,in 0sttitration 7 9390=! dm+ 939!99 mol dm,+

7 +3


109/142

109


110/142


111/142

(b) (i) Lt will move to the right (1

Ihich is the eothermic direction (1 !

5nd mar, conditional upon first statement

(ii) ;he rate of reaction would be too slow if cooled (1

yield too small / too little reactants converted

O! converse arguments (1 !

23Te*uili-rium yield

(c) (i)

- -

4 4 4 4- -

- - 0

(ii) o as both the end carbons have two - atoms 0

(iii)

- - - -

4 4 4 4- -

* - * - * - * -

&enalise CD>O once

*r 4-!(*-)4-(*-)4-(*-)4-!*- (1for adding two *- groups acrossone double bond and (1for adding it across both34onsequential on structure in (c)(i) !

7 mar, per dou-le -ond ma &[11]

13'. (a) (i) 6airs up 4-+4-!4**- and 4-+4-!4**,

and -!*/-+*&(1 correct identification of which is acid andwhich base (1 !

(ii) 3a7 D4-+4-!4**, D-+*

& / D4-+4-!4**- (1 0

>'0 is accepta-le#

(iii) D-& 7 (5aD-")Tor 5aD-" (17 (03 + 09,' 9309) T

7 0301 09,+ mol dm,+(1p- 7 !38 or !381 i3e3 to 0 or ! d3p3 (1 +4onsequential on the value of D-& provided the p- resulting is

between 9 and F3

111


112/142

(iv) D-&D*-, 7 09,01 (1 D 0301 09,+D*-,

;hus D*-, 709,01 09,+(1D =3FF (=3=) 090!mol dm,+(1units needed (! or + sf)Conse*uential on the ans$er to (iii) for >

'0

"llow =3F0 09,0!

if solved using p- & p*- and p- 7 !381 F38 09,0!if solved using p- & p*- and p- 7 !383 +

(b) 4-+4-!4**,& -!* 4-+4-!4**- & *- (1

-ydroide ions ma$e the solution al$aline (1or propanoateion deprotonates the water

or 4-+4-!4**a & -!* 4-+4-!4**- & a*- (1Eplanation then must comment that acid is wea$/not fullyionised !

(c) (i) %olution that maintains almost constant p- (1

for small addition of acid or al$ali (1 !

(ii) p- 7 p3a & lg Dsalt/Dacid (1 7 138 & Lg (939')/(939!') (1for dividing by ! 7 '308 or '3! (1. +

Lf the -enderson equation is wrong but concs are divided by !then 0/+ ma3

*r[ ] )0(

DsaltE

5aDacidE- =+

)0(939'9

9!'390903+9 2' =

p- 7 '308 or '3! (1

If the concns are t$ice $hat they should -e+ ie# candidate does

not spot the 2olume increase+ then ma. (5)# The p> is still :#5+

so care is needed#

[16]

112


113/142

13+. (a) (i) 6 !13< / +0 (1 93F81 / 93F81 7 0 EQ is 6Q'(1Q F'31 /08 +38F / 93F81 7 '

@rof EQ 7 0!< (1;herefore Q 7 EQ 7 6Q'(1 1

There must be some use of the data of 126 g mol1

ORMass of phosphorus in I mole = 126 246!100 = 31 (1)

Mass of fluorine in 1 mole = 126 754!100 = 95 (1)Moles of phosphorus in 1 mole "ompoun# = 31!31 = 1

Mole of fluorine in 1 mole "ompoun# = 95!19 = 5 (1)M$ = %$5(1)

(ii)

Q Q

Q

Q6 6Q Q

Q

Q

Q Q

0 ! 9

8 9

* C

(1

note% there must -e an attempt at a 4DK dra$ing (i#e# one $edge

and one dotted line)

"ngles drawn on diagram of 89 (1and 0!9 (1 +

(iii)

Q Q

QQ

QQ6 6

( 1

Q Q

QQ

Q Q

8 9 * C

( , ) ( , )

note% again it must -e 4DK (again $edges and dotted lines)

ame stated as octahedral (1 +"ngle mar$ed / stated as 89 (1

(b) -Q has intermolecular hydroenbonding (but others do not) (1Because Q atom is very small / other halogen atoms / chlorine etc3 radii are toolarge (1-ydrogen bonding is stroner than LQ/vdI/dipole2dipole/induced dipole2dipole/dispersion forces and so more enery required (to boil) (1 +

Ko not gi2e any mar,s if the candidate ans$ers in terms of

strength of co2alent -onds#

Ko not gi2e all 4 mar,s unless the candidate has e.pressed

their ideas clearly#

113


114/142

(c) 3a7

+++

*-or-allow-QD

QD-D+(1

D-& 7 092!391(17 939980!9 mol dm2+

D-& 7 DQ2 or3a7 D-&!/ D-Q

7(1

90'939

)9980!939(or)9980!9390'939(

)9980!939( !!=

'

7 '389 0921(0) mol dm2+(1or 7 '3'' (or '3'1) 0921

the unit mar, can -e gi2en in the e.pression for 3#[18]

13. (a) 3c7[ ][ ]

(1!

!1

1!!

*-4-

E-DE4*D

Starting amounts:

(1

==

==

mol93+molg0=/g'1*-

mol

'2* = 30 ( 20 = 20 mol (1)

&*2= 00+ 20 = 0500mol (1)

'2= 20 mol ,-i.en/

Equilibrium concentrations:

ao.e .alues 4 #m3

(1) ,mar "onseuenl/

[&'4]= 003125 mol #m3

['2*] = 0500 mol #m3

[&*2] = 0125 mol #m3

['2] = 050 mol #m3

!

1

!

eq!eq1

1

eq!eq!

c'99399+0!'39

'9390!'39

E*-DE4-D

E-DE4*D5

==

7 039 (or 0 or 0399) (1mol!dm27 (2+81) , D(2F


115/142

(c) " catalyst (of nic$el) is used because the reaction even at F'94 is too slow /to speed up the reaction (1

8hen any si0 of the following eight points:a temperature of F'94 is used: as the reaction is endothermic (1 a high temperature increases the value of the equilibrium constant (1 and so increases the equilibrium yield (1 a high temperature also favours a fast rate (1 but a temperature Y F'9 would be too epensive / cause engineering

problems (18emperature could score up to but ma0 - for 8 and B combined.

If their calculation in (-) gi2es an e.othermic ans$er+ mar, conse*uentially

e.othermic (7)+ decreases 3p (7)+ decreases yield (7) -ut faster rate(7)+ so : is

compromise of fast rate and lo$er yield (7)0

" pressure of +9 atm is used even though the reaction goes from + to ' gas moles / more gas moles of

right of equation (1

causing a decrease in equilibrium yield (1

but a moderately high pressure is needed to push the gases through the Fplant (1

Ignore any reference to rate

Bressure could score up to ' but ma0 - for 8 and B combined.

Ko not gi2e all mar,s unless the candidate has e.pressed their ideas clearly

[18]

13-. (a) (i) ;wo reactants form one product 0

(ii) $ubstitution reactions occur under these conditions 0

(iii) ;he electrons of the double / bond polarise the Br , Br molecule (1

and Br&is the electrophile (1

O! sho$ r&

r,attac,ing in the correct orientation !

(b) (i)

4 4 4

4 4

4

44

B r B r

B r

B r--

-

- -

-

-

-

-

--

-

( 1 ( 1 !

(ii) o rotation about a 4 74 double bondO!only single bonds can rotate 0

115


116/142

(c) (i)

- -

-

-

---

--

-4

4

44

44

0

(ii) Aow temperature because eothermic reaction (1-igh pressure because fewer molecules of product than ofreactants gases are being converted into liquids (1 !

[10]

13. (a) p- 7Lg D-&(aq)

*C D-&(aq) 7 09,p-/ 09,83


117/142

(c) (i) p- 7 +(39) &enalise if more than 5 1 0

(ii) "mount of 4a(*-)!7 0999098830099

'

7 0388 C 09,


118/142

(b) (i) !* & *!!*!(1or !*1 0

(ii) 1*!& !-!* & *!1-*+(2(1species(1balance3 !

Ans$er could -e in terms of a reactions that gi2e >NO5and >NO4

as the first stage#i#e# 5NO5' >5O >NO5' >NO4

(5>NO5' O55>NO4)

or 4NO5' >5O 5>NO4' NO

(c) (i)

Q r a c t i o no fm o l e c u l e s

E c a t

E u n c a t

E n e r g y

a

a

"is labels(1

0 %tarts at or near origin (not on y or ais) s$ewed distributionthat is reasonably asymptotic to the.2ais(1

(ii) Eafor the uncatalysed reaction shown well to the right of thepea$ andEafor catalysed reaction to the left of this still to theright of the pea$(1

%ome comment concerning the areas under the curve to right ofEalines or labelled shading(1

! Preater number of collisions (or particles) have energy greaterthan the activation energy / enough energy to react(1

+ ;herefore greater number of successful collisions(13 1[12]

13. (a) (i) p- 7 log09D-& / p- 7 ,lg D-&(1 0

(ii) 5 I7 D-& D*-

or 5I7 D-+

&* D*-(1 0

(b) fully ionised / fully dissociated / almost completely ionised(1 0

118


119/142

(c) (i) 93F9 (or 93


120/142

(ii) D-& 7 5I/ D*- 7 03!' 09,01(1

p- 7 0+38 or 0+389(1 !

(d) (i) 5 a7D-"E

EED"D- ,+

(1 0

allow D-+&*

(ii) D-& 7 (5aD-")(17 93991F1(1p- 7 !3+! / !3++(1 +

(e) D-&

7ED"

D-"E5,

a

(1D-& 7 ('3

p- 7 13''(1 +*r

p- 7 p5a& logD-"E

ED",

7 log09('3enderson e*uation ma. 7

[13]

113. (a) (i) 5 c7 D%*+!/ D%*!

!D*!(1 0

(ii) +9

!39


121/142


122/142

112. (a) (i) Qorward and reverse reactions occur at the same rate (1so there is no change in the proportions of reactants and products (1 !

(ii) 6roportion of -L epected to become smaller (1because reaction will respond to temperature increase by shifting in theendothermic direction (1 !

(iii) o change epected because catalysts affect only the rateatwhich equilibrium is attained3 0

(b)

E n e r g y

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

! - l ( g )

( r e a c t a n t s )

- ( g ) & l ( g )

( p r o d u c t s )

E( c a t a l y s e d )

E( u n c a t a l y s e d )

a

a

! !

6roducts at higher energy level than reactants (1

Aine going up from reactants to pea$ (corresponding to transition state)then down to products (1

%econd line with lower pea$ representing the catalysed reaction (1"ctivation energies of uncatalysed and catalysed reactions correctly mar$ed (1 1

[9]

11'. (a) (i) Pases have much higher entropies than solids as there are many moreways of arranging the entities / less ordered / more random(ness)O! re2erse argument(1

n4*+has more atoms/is more comple than n* (1 !

(ii) %]system7 (&1+3


123/142

(b))s printed

%]surroundings7 ;, >

*C 7 !8=)09'31


124/142

11+. (a) (i) Kynamic%reaction occurring in both directions / rate of forward reactionand reverse reactions equal(1

E*uili-rium%

constant concentrations / no change in macroscopic properties(1 !

(ii) all substances in same phase / are all in the gaseous state(1 0

(b) (i) -igher yield of ammonia / (equilibrium position) moves to3 r3h3s(1Qewer product molecules(1 !

(ii) Aower yield of ammonia / (equilibrium position) moves to 03h3s3(1since this absorbs heat/ shift in endothermic direction / thereaction is eothermic(1 !

[7]

11. (a) (i) fraction of the total pressure generated by a gas oror

pressure gas would generate if it alone occupied thevolumeor6total mol fraction(1 0

(ii) *)p(-)p(4-)p(-p(4*)

5!1

+!

p

=

(1 not D 0

(iii) Lncrease in total pressure will result in less productmolecules in the equilibrium miture / equilibriummoves to left(1

because more molecules on product side of the equilibriumthan on left(1 !

(b) (i) o c

equilibria ans

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