1.	B
[1]

2.	A
[1]

3.	B
[1]

4.	D
[1]

5.	(i)	increase in concentration of product per unit time / decrease
in concentration of reactant per unit time;	1
Accept change instead of increase/decrease and mass/amount/
volume instead of concentration.
 
(ii)	frequency of collisions;
kinetic energy/speed of reactant particles;
collision geometry/orientation;	3
[4]

6.	

correctly labelled axes showing number of particles/frequency against
(kinetic) energy;
correctly shaped graph for T (curve must not touch or cross x axes);
 curve to the right of T and with a peak lower than T;
increasing the temperature increases the (kinetic) energy of the
particles / more particles will possess the necessary activation energy;
there will be more collisions per unit time / the frequency of collisions
increases / there are more successful collisions;	5
[5]

7.	D
[1]

8.	C
[1]

9.	C
[1]

10.	(a)	[I2] does not affect rate / OWTTE;
neither correct/both partially correct with explanation as to how;	2
 
(b)	more particles/molecules have sufficient energy to overcome
activation energy / OWTTE;
more frequent collisions;	2
 
(c)	(i)

axes correctly labelled x = energy/velocity/speed, y = number/% of
molecules/particles/probability;
graph showing correct curve for Maxwell-Boltzmann distribution;
If two curves are drawn, first and second mark can still be scored, but not
third.
Curve(s) must begin at origin and not go up at high energy.
	two activation energies shown with Ecat shown lower;
Award the mark for the final point if shown on an enthalpy
level diagram.	3
 
(ii)	catalyst provides an alternative pathway of lower energy / OWTTE;
Accept catalyst lowers activation energy (of reaction).	1
[8]

11.	C
[1]

12.	D
[1]

13.	(i)	rate = increase in  = slope of graph;
initially/to begin with steeper slope / fastest rate / volume of gas/CO2
produced faster/quickly as concentration of HCl highest / OWTTE;
as reaction progresses/with time, less steep slope / volume of gas
production slows / rate decreases due to less frequent collisions
as concentration (of HCl) decreases / OWTTE;
curve flattens/becomes horizontal when HCl used up/consumed
(as there are no more H+ ions to collide with the CaCO3 particles);
Each mark requires explanation.	3 max

(ii)

less steep curve;
same maximum volume at later time;
half/lower H+ /acid concentration less frequent collisions/slower rate;
same amount of HCl, same volume CO2 produced;	4
 
(iii)	mass loss/of CO2 / mass of flask + content;

OR

OR

Do not penalize for missing x-axis label or for missing units on y-axis.
Accept if line meets time axis.	2
 
(iv)	minimum energy (of colliding particles) for a reaction to occur / OWTTE;
lower Ea / greater surface area/contact between CaCO3 and HCl / higher HCl
concentration / (sufficient) particles/molecules have activation energy;	2
[11]

14.	A
[1]

15.	A
[1]

16.	(i)	exothermic;
	Accept either of the following for the second mark.
increasing temperature favours endothermic/reverse reaction;
as yield decreases with increasing temperature;	2 max
 
(ii)	yield increases / equilibrium moves to the right / more ammonia;
increase in pressure favours the reaction which has fewer
moles of gaseous products;	2
 
(iii)	(rate increases because) increase in frequency (of collisions);
increase in energy (of collisions);
more colliding molecules with E ≥ Ea;	2 max
[6]

17.	D
[1]

18.	D
[1]

19.	C
[1]

20.	C
[1]

21.	(a)	(minimum) energy needed for a reaction to occur / (minimum) energy
difference between reactants and transition state;	1
 
(b)	particles must collide;
appropriate collision geometry/orientation;
E ≥ Ea;	2 max
 
(c)	Diagram showing:
correct labelling of axes (enthalpy/H/(potential) energy for y-axis and
time/progress/course of reaction/reaction coordinate for x-axis) and
H (products) line shown below H (reactants) line;
correct labelling of the two curves, catalysed and uncatalysed;
correct position of Ea shown with lines for a catalysed and uncatalysed
reaction;
the correct label ∆H /change in enthalpy;
Do not penalize if reactants and products are not labelled.

	If an endothermic reaction is shown, award [2 max] if all other parts are
shown correctly.	3 max
[6]

22.	(i)	decrease in concentration/mass/amount/volume of reactant with time /
increase in concentration/mass/amount/volume of product with time /
change in concentration/mass/amount/volume of reactant/product with time;	1
 
(ii)	MgCO3(s) + 2HCl(aq) → MgCl2(aq) + CO2(g) + H2O(l);
Ignore state symbols.	1

(iii)

Plot starts at the origin and levels off.
No mark awarded if axes are not labelled.	1
 
(iv)	new curve reaches same height as original curve;
new curve less steep than original curve;
volume of gas produced is the same because the same amount of
acid is used;
reaction is slower because concentration is decreased;	4
[7]

23.	B
[1]

24.	A
[1]

25.	

labelled axes (including appropriate units);
correctly drawn curve;
correctly drawn tangent;
	rate equal to slope/gradient of tangent (at given time) / rate =  at time t;
[3 max] for straight line graph or graph showing product formation.	4
[4]

26.	(a)	(i)	increases rate of reaction;
molecules (of H2O2) collide more frequently / more collisions
per unit time;
No ECF here.	2
 
(ii)	no effect / (solution) remains unchanged;
solid NaI is not reacting / aqueous solution of NaI is reacting / surface
area of NaI is not relevant in preparing the solution / OWTTE;	2
 
(b)	kinetic energy/speed of reacting molecules increases;
frequency of collisions increases per unit time;
greater proportion of molecules have energy greater than
activation energy/Ea;
Accept more energetic collisions.	3 max
[7]

27.	B
[1]

28.	A
[1]