1.	(a)	(i)	The energy the molecules must have to react / start the reaction	1
(ii)	larger	1
 
(b)	(i)	T1 skewed, no intercept of y axis , must be asymptotic to x axis. (1) 
T2 peak lower than T1 and to the right of T1  (1)  not consequential 
on shape.
(ii)	Some comment re greater area under graph – could be shown on 
graph  (1)  leading to more successful collision  (1)	5
 
(c)	Alternative route / mechanism  (1)
With lower activation energy  (1)
Reaction only takes place at surface of catalyst (1) and (this has large surface area) which increases chance of collision with gas molecules/ more active sites  (1)	4
[11]

2.	(a)		Diagram at T1 approximately correct shape which starts near origin and does not intersect the vertical axis or the horizontal axis (1) At higher T2 – flatter (1) and mode to right (1)
	3
 
(b)	Indication of activation energy on diagram to the right of both peaks (1)
Explanation of number past Ea point related to probability of reaction (1)
Higher T gives more molecules > Ea (1)
more effective / successful  collisions (1)	4
[7]

3.	(a)	(i)	carbon dioxide / gas evolved (1)
escapes from flask / lost (1)	2

(ii)	reaction (is fast at first then) slows down / gives off less CO2 per
minute (1)
when line is horizontal the reaction has finished /
after 6 or 7 minutes the reaction has finished /
when 1 g of CO2 lost the reaction has finished (1)	2
 
(b)	Experiment 2	steeper than 1 and same mass loss (1)
Experiment 3	less steep than 1 and same mass loss /
	reaction incomplete (1)
Experiment 4	steeper than 1 and horizontal at twice
	mass loss (1)	3
 
(c)	(i)	50.0 cm3 of 0.1 mol dm–3 HCl  = 50 × 1/1000 mols
	 = 5 × 10–2(1)
5 × 10–2 mol of HCl react with  (1) mol of CaCO3
= 2.5 × 10–2 × 100 g
= 2.5 g (1) units must be shown
Consequential step by step		3
 
(ii)	Suggested mass at least twice mass calculated in (c)(i)
e.g. 5 g (1) twice as much needed for experiment 4 (1)
If mass is larger than answer to(c)(i) and a reference to an
excess being needed score 1 mark
Consequential on previous answer.	2
[12]

4.	(a)	(i)	any two from
concentration
pressure
surface area / particle size (2 × 1)	2
 
(ii)	Pressure / concentration:
Increase of pressure/ concentration increases rate (1)
The particles are closer together therefore more
collisions / more collisions per unit volume per unit of time (1)
Allow more –’frequent’ collision
or
Surface area:
Increase in surface area increase the rate (1)
More collisions on surface of solid / more surface
available for collisions (1)	2

(b)	(i)	Similar curve with peak further to the right (1)
and lower maximum (1)	2
Max 1 mark if second line crosses the first more than
once or crosses axis
 
(ii)	Vertical line placed to the right of both of the peaks (1)	1
 
(iii)	(At higher temperature average kinetic) energy of molecules
is greater (1)
More molecules / collisions have energy greater than
/ equal to the activation energy (1)
Therefore more collisions are effective / result in reactions (1)	3
[10]

5.	(a)	(i)	Forward and reverse reactions occur at the same rate (1)
so there is no change in the proportions of reactants and products (1)	2
(ii)	Proportion of HI expected to become smaller (1)
because reaction will respond to temperature increase by shifting in the endothermic direction (1)	2
(iii)	No change expected because catalysts affect only the rate at
which equilibrium is attained.	1
 
(b)	

	Products at higher energy level than reactants (1)
	Line going up from reactants to peak (corresponding to transition state),
then down to products (1)
	Second line with lower peak representing the catalysed reaction (1)
Activation energies of uncatalysed and catalysed reactions correctly marked (1)	4
[9]

6.	(a)	(i)	correct shape:
starting at/ near origin, not crossing axes, not symmetrical (1)

	labels:
energy AND number/ fraction of molecules (1)	2
 
(ii)	Ea for the uncatalysed reaction shown well to the right of the peak
and Ea for catalysed reaction to the left of this, still to the right of
the peak (1)
Some comment concerning the areas under the curve to the right of the
Ea lines or labelled shading (1)
Greater number of collisions (or particles) have energy greater than
the activation energy/ have enough energy to react (1)
Therefore greater number of successful/ effective collisions (1)	4
 
(b)	The explanation must refer to molecules or particles:
	increase temperature (1)
molecules have more energy (1)
greater proportion of collisions successful / more effective collisions per
unit time / more frequent effective collisions (1)
	OR
	increase pressure/ concentration (1)
more molecules per unit volume or molecules closer together (1)
more frequent collisions / more collisions per unit time (1)	3
[9]

7.	(a)	C4H10O + Na ® C4H9O(–)Na(+) + ½ H2
entities (1)
balancing, ignoring charges in organic product (1)	2

(b)	(i)	Cr3+	1
(ii)	Heat and round-bottom (suitable i.e. not a beaker) flask (1)
condenser above (1)
water jacket and water direction
ALLOW arrows for water direction (1)
–1 poor diagram e.g. flask and condenser integrated
–1 sealed apparatus	3
 
(iii)	
 (1)
Butanone / butan-2-one (1)	2
(iv)	CH3CHOHCH2CH3
ALLOW TE from (iii) for butanal / butanoic acid	1
[9]

8.	(a)	(i)	Methanol is the biggest/ most complex molecule / greatest MR /most
atoms/most electrons	1
(ii)	DSsystem = 239.7 – 197.6 – 2(130.6)
 = –219.1/ –219 J mol–lK–1
Method (1)
answer + units (1)	2
(iii)	yes as 3 molecules ® 1 OR yes as (2) gases ® a liquid	1
(iv)	DSsurr = –DH/T (stated or used) (1)
= –(–129/ 298) = +0.433 kJ mol–1 K–1 / +433 J mol–1 K–1/+ 432.9 (1)
–1 for wrong units/ no units / more than 4 SF
–1 for wrong sign/ no sign	2
(v)	DStotal = –219.1 + 433 = +213.9 / +213.8 J mol–1 K–1/ +214 J mol–1 K–1/
+0.214 kJ mol –1K–1 (1)
Positive so possible (1)	2

(b)	(i)	Temperature
	Faster at 400°C (1)
even though yield is lower (1)
Pressure
Higher pressure improves yield of methanol (1)
Higher pressure increases rate (1)
Maximum 3	3
(ii)	Not in same phase as reactants. ALLOW state instead of phase	1
(iii)	Kp = p(CH3OH)/p(CO)×p(H2)2	1
(iv)	Partial pressure of methanol = 200 – 55 – 20 = 125 atm (1)
Kp = (125)/55×202
= 5.68 × 10–3 / 5.7 × 10–3 atm–2 (1)	2
 
(c)	(i)	Number of molecules / fraction of molecules with energy ³ EA /number
of molecules which have enough energy to react.	1
(ii)	Vertical line / mark on axis to show value to the left of line EA	1
[17]

9.	(a)	(i)	

	Starts at zero and approaching x-axis (1)
Maximum greater and at lower energy(1) – T2 needs only to be just
higher than T1
T2 curve must go below T1 curve approaching the x-axis	2

(ii)	As the temperature increases the energy of the particles increases (1)
	Use the diagram shading areas
OR more particles to the right hand side of EA line (1)
	and so more (successful) collisions/particles have energy greater /
equal or greater than the activation energy (1)
NOT “equal” on its own
NOT mention of “frequency of collisions” on its own	3
 
(iii)	A catalyst provides an alternative route with a lower activation energy/
which requires less energy (1)
	so more collisions / particles have energy greater than the activation
energy (1)	2
 
(b)	(i)	e.g.

	Measure the volume of gas given off in a given time / count bubbles /
obscuring cross using limewater (1)
	and then repeat over a range of temperatures (1)
	No diagram max 3
	If method shown cannot possibly work max 1 ie waterbath or
sensible range of temperatures BUT NOT different temperatures
	Penalty
–1 for poor diagram
	4
 
(ii)	Positive
	1 mol goes to 4 moles/particles (so more disorder) /increase in number
of moles/particles (1)
	products include a gas (and so more disorder) (1)
	NOT 1 mole of compound/element goes to 4 moles of
compound/element
	If “negative” 0 (out of 2)	2
 
(iii)	Positive with some explanation e.g. ∆Ssurroundings = – ∆H/T OR
because reaction is exothermic (1)
	∆H is therefore negative and so ∆Ssurroundings must be positive (1)
If negative given in (ii) allow TE here	2
[15]

10.	(a)	Fine powder because it has larger surface area (1)
	so more collisions per unit time OR greater collision frequency (between
the peroxide and the catalyst) (1)
OR ‘more active sites’
OR ‘more likely for collisions to occur’
NOT ‘more successful collisions’.
NOT ‘more collisions’ on its own	2
 
(b)	(i)	Axes labels (1)
ie y-axis = Number/”N” /fraction of molecules
	x-axis = (kinetic) energy/E      NOT potential energy
	Start at or going towards origin, asymmetric, asymptotic to
x-axis, T1 line correct shape (1)
	T2 line peak lower (1) and to the right (1)
T2 line must only cross T1, line once, otherwise max (1)
	4
 
(ii)	Ea shown well to the right of both peaks (1)
	larger area for T2 shown on diagram and related to number
of collisions/molecules with E ≥ Ea (1) - need to refer to shading
	Greater proportion of successful collisions
OR more of the collisions are successful (1)
ACCEPT more successful collisions per unit time
NOT ‘more successful collisions’ alone	3

(iii)	Ea (cat) at a lower energy than Ea (1) - check diagram, it is enough to
draw it on the diagram
	Greater proportion of molecules have energy greater than the new
activation energy OR relates areas to frequency of successful
collisions (1)	2
[11]

11.	(a)

(i)	Axes labelled (1)
Y: number/fraction of molecules/particles (with energy E) and
X: (kinetic) energy
	Correct shape (1)
starting at origin, and asymptotic to x-axis and not symmetrical
	2
 
(ii)	line TH with peak to the right of temp T and peak lower than temp T
 because crosses twice	1
 
(iii)	vertical line well to the right of both peaks	1

(b)	(i)	higher temp gives molecules higher (average kinetic) energy (1)
	so increase in frequency of collisions (1)
Accept more collisions per unit time
Reject more collisions
	area (under curve) to right of Ea greater at TH (1)
	more collisions have a greater energy ≥ Ea
OR a greater proportion of collisions have energy ≥ Ea
OR
more of the collisions are successful
OR a greater proportion of the collisions result in reaction /are
successful (1)	4
Accept molecules/particles for collisions
Reject “more successful collisions”
“increase in frequency of successful collisions”
 
(ii)	Energy of collisions	1
[9]

12.	(a)	(i)	2,2,4-trimethylpentane
Ignore punctuation (Commas and hyphens may be interchanged)	1
Accept 2,4,4 - trimethylpentane
Reject pentan for pentane
2-dimethyl-4
methylpentane
2,2-dimethyl-4-methyl
pentane
2-methyl-4,4-dimethyl
pentane
2,4-trimethylpentane
 
(ii)	C4H9	1
Accept C8H18 → C4H9
 
(iii)	C2H4	1
Reject CH2CH2

(iv)	Positive because energy is required to break (C–C) bonds
(and not completely replaced (from new bonds made))
OR Positive because cracking requires (continuous) supply of
heat so must be endothermic	1
Accept two C–C bonds are broken and one C=C made
Reject positive because it only occurs at high temperature
 
(v)	C8H18 + 17/2 O2 → 8CO + 9H2O
	OR 2C8H18 + 17 O2 → 16CO + 18H2O
	OR C8H18 + 9/2 O2 → 8C + 9H2O (or doubled)
	Oxygen on left and correct formulae of products (1)
balancing (1)
Second mark depends on first and a sensible hydrocarbon
formula must be used.	2
Accept balanced equations including CO and/or C with CO2
17/2 can be written 8.5 or 8½
Allow balanced equations based on C8H18 with a smaller alkane in the products for 1 mark eg
C8H18 + O2 → CO + C7H16 +H2O (1)
 
(b)	(i)	Increase in pressure: No effect as number of
moles/molecules (of gas) doesn’t change during reaction (1)
	Increase in temperature: more NO as forward reaction
endothermic OWTTE (1)
	One mark for two correct predictions with incorrect explanations	2
Reject increase in temperature moves equilibrium to the right
 
(ii)	Rate increases as converter gets hotter (as reaction is
exothermic)	1
 
(iii)	N2 / nitrogen is (major) part of air/ N2 unreactive/ not
poisonous/ not a greenhouse gas / not acidic	1
Accept correct harmful properties of other 3 gases
 
(iv)	Line from level of reactants to maximum labelled EA (1)
	Curve of similar shape above existing curve, starting and
finishing at same levels, with maximum above original maximum (1)	2
[12]

13.	(a)	N/N2 goes from 0 to –3 = reduction (1)
H/H2 goes from 0 to (+)1 = oxidation (1)	2
If “the oxidation number of N goes down hence reduced and the oxidation number of H goes up and hence oxidised” (max 1)
If all O.N. correct but fails to state which is oxidation and which is reduction scores 1.
If all O.N. correct but both reactions misclassified, scores zero.
Any answer not referring to nitrogen or hydrogen scores zero.
 
(b)	(i)	Calculation of bonds broken 463 × 3 + 944/ (= 2252) (1)
Calculation of bonds made 388×6/ (= 2328) (1)
∆H = –76 (kJ mol–1) (1)
mark consequential on numerical values calculated above	3
Correct answer with some working scores 3 marks
Correct answer alone scores 2 marks
 
(ii)	Average / mean bond enthalpy used for N–H bond / ammonia	1
Reject just “average bond enthalpies used”
 
(iii)	Thermodynamic:
energy level of products lower than that of reactants
OR
energy released in bond formation > energy used to break bonds (1)
Accept ∆H negative / reaction exothermic
	kinetic:
high activation energy (1)
	because strong N≡N (1)
[confusion between thermodynamic and kinetic loses first 2 marks].	3
Accept because N≡N is 944/ total bond breaking energy is high/2252(kJ mol–1)

(c)	(i)	QWC
One way
temperature increase therefore molecules have greater (average
kinetic) energy (1)
Accept moving faster
	more molecules/collisions have E ≥ Eact (1)
	Therefore a greater proportion of/ more of the collisions are
successful (1)
Ignore greater frequency of collision
Accept E > Eact particles for molecules
greater frequency of successful collisions/ more successful conditions per unit time
Reject just “more successful collisions”
	Another way
addition of (iron) catalyst (1)
Accept platinum catalyst
Reject incorrect catalyst
	provides alternative route of lower activation energy (1)
	EITHER:
A greater proportion of /more of the molecules/collisions have E ≥ Ecat/
a greater proportion of collisions are successful
Reject just “more successful collisions”
	OR provides (active) sites (where reactant molecules can
bond / be adsorbed) (1)
	Ignore any answers referring to pressure or concentration.
Do not penalise just “more collisions are successful” more
than once	6
 
(ii)	QWC
Decrease temperature (1)
because (forward) reaction exothermic (1)
increase pressure (1)
because more moles (of gas) on left (1)	4
Accept low temperature ∆H is negative
Answer based on endothermic reaction scores 0
Accept high pressure
Accept molecules for moles
[19]

14.	(a)	QWC
enthalpy/heat/energy change when 1 mole (of a substance) (1)
Accept “evolved” instead of “change”
Accept “sulphur” or “element” or “species” instead of “substance”
Reject heat/energy required
Reject “compound” instead of “substance”
	is completely burned in oxygen /
burned in excess oxygen (1)
Reject reacts completely with oxygen
Any mention of specific products or specific amounts of products, other than SO2, negates 2nd mark
	(all species) at 1 atm/100 kPa/105Pa/1 Bar and “a specified temperature” (1)	3
Accept ….298 K/ 25 °C /101 kPa
Or
“…..a specified temperature e.g. any value”
Reject just “273 K”
Reject any mention of concentration negates third mark
 
(b)	(i)	QWC
	Temperature
	More molecules/collisions/ particles have
E ≥ Eact /sufficient energy to react (1)
Accept E > Eact
“energy barrier” instead of “Eact/activation energy”
Reject more atoms….
	∴ a greater proportion of collisions are successful
Or
More of the collisions are successful (1)
Accept collisions more likely to be successful
Accept greater chance of successful…
Accept more successful collisions per second
Reject just “more successful collisions”
Reject “..fruitful collisions”
	IGNORE greater frequency of collision
	2nd mark dependent on 1st mark
UNLESS 1st mark is not awarded through use of “atoms”

	Catalyst
	EITHER:
provides alternative route of lower activation energy (1)
Accept “energy barrier” instead of “Eact/activation energy”
	more molecules have E > Ecat / a greater proportion of collisions
are successful (1)
Accept collisions more likely to be successful
Accept greater chance of successful…
Accept more successful collisions per second
Reject just “more successful collisions”
N.B. Penalise “more collisions are successful” only once
Reject “..fruitful collisions”
	2nd mark dependent on mention of lowered activation energy
Do not penalise use of “atoms” again
	OR:
provides (active) sites (1)
	where reactant molecules can bond/be adsorbed (1)	4
Reject where reaction can take place
 
(ii)	QWC
	reaction exothermic (1)
	equilibrium shifts to the left decreasing the yield (1)
2nd mark is dependent on the 1st and is not consequential.
	IGNORE Le Chatelier explanations	2
Accept ∆H negative/reverse reaction is endothermic
Reject just “equilibrium shifts to the left”
Reject just “yield decreases”
 
(iii)	QWC
	fewer (gaseous) molecules /particles/moles on the right (1)
	equilibrium shifts to the right increasing the yield (1)
Reject just “equilibrium shifts to the right”
Reject just “yield increases”
	2nd mark is dependent on the 1st and is not consequential.
	IGNORE Le Chatelier explanations
	N.B do not penalise omission of either ‘equilibrium shifts’
or change of yield if already penalised in (ii)	2
Reject arguments based on volume
 
(c)	∆H = ∆Hf (products) – ∆Hf
(reactants)
Or (–814 × 2) – (–286 × 2) (1)
	= –1056 (kJ mol–1) (1)
IGNORE units
	Correct answer with no working (2)
	Omission of either or both of ×2 max 1. Hence
–242 with some working (1)
–1342 with some working (1)
–528 with some working (1)
	(+)1056 with some working (1)	2
Reject ∆Hf values added scores zero overall
[13]

15.	(a)	(i)	Make halogenoalkanes miscible with silver nitrate/AgNO3 solution
OR to dissolve halogenoalkanes/acts as solvent (1)	1
 
(ii)	Feature of water molecule:
The oxygen atom has a lone pair of electrons (1)
	Either an SN2 mechanism
Arrow from O of water towards C atom (1)
and arrow from C–I s bond to I atom (1)
transition state with no charge (1)
Ignore final loss of H+ and formation of I–
	Or an SN1mechanism
Arrow from C–I s bond to I (1)
intermediate with + charge and I– ion (1)
arrow from O of water to C+ of intermediate (1)
Ignore final loss of H+	4
 
(iii)	C	1
 
(iv)	Silver((I)) chloride (1)
Ignore capitals	1
 
(v)	Precipitate dissolves/disappears/clears (1)	1
Reject precipitate changes colour

(vi)	QWC
	Must be given in a logical sequence
	C–I bond is weakest (and break more easily) (1)
Because the iodine atom is the largest / greatest bond length (1)
So lowest activation energy (1)
	Or reverse argument: e.g. C–Cl bond strongest	3
Reject Cl is more electronegative than I
OR
Cl forms a carbocation more readily than C–I
 
(b)	QWC
	Any two from three:
100 % atom economy (1)
higher cost of halogenoalkanes/halogenoalkanes are made from alcohols (1)
alkenes readily available from oil (1)	2
 
(c)	(i)	suck back (1)	1
 
(ii)	remove delivery tube from water/add Bunsen valve (1)	1
[15]