Ch. 6 Kinetics SL Paper 1
1.
Name:______________________
Curve X on the graph below shows the volume of oxygen formed during the catalytic
decomposition of a 1.0 mol dm–3 solution of hydrogen peroxide.
2H2O2(aq) → O2(g) + 2H2O(l)
Which change would produce the curve Y?
2.
A.
Adding water
B.
Adding some 0.1 mol dm–3 hydrogen peroxide solution
C.
Using a different catalyst
D.
Lowering the temperature
Sodium carbonate and hydrochloric acid react according to the equation below.
Na2CO3(s) + 2HCl(aq) → CO2(g) + 2NaCl(aq) + H2O(l)
Which conditions will produce the fastest initial rate with 2.0 g of powdered sodium
carbonate?
3.
A.
100 cm3 of 1.0 mol dm–3 hydrochloric acid at 323 K
B.
50 cm3 of 2.0 mol dm–3 hydrochloric acid at 323 K
C.
100 cm3 of 1.0 mol dm–3 hydrochloric acid at 348 K
D.
50 cm3 of 2.0 mol dm–3 hydrochloric acid at 348 K
Under which conditions will the reaction between 1.0 g calcium carbonate and excess
hydrochloric acid be the fastest? Assume that all reactions are carried out at the same
temperature.
A.
One large piece of calcium carbonate and 2 mol dm–3 hydrochloric acid
B.
One large piece of calcium carbonate and 1 mol dm–3 hydrochloric acid
C.
Powdered calcium carbonate and 2 mol dm–3 hydrochloric acid
D.
Powdered calcium carbonate and 1 mol dm–3 hydrochloric acid
SA Topic 6: Kinetics SL
4.
Powdered manganese(IV) oxide, MnO2(s), increases the rate of the decomposition reaction
of hydrogen peroxide, H2O2(aq). Which statements about MnO2 are correct?
I.
The rate is independent of the particle size of MnO2.
II.
MnO2 provides an alternative reaction pathway for the decomposition with a
lower activation energy.
III.
All the MnO2 is present after the decomposition of the hydrogen peroxide is
complete.
5.
6.
7.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which unit could be used for the rate of a chemical reaction?
A.
mol
B.
mol dm–3
C.
mol dm–3 s–1
D.
dm3
Which of the following can increase the rate of a chemical reaction?
I.
Increasing the temperature
II.
Adding a catalyst
III.
Increasing the concentration of reactants
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
What is the best definition of rate of reaction?
A.
The time it takes to use up all the reactants
B.
The rate at which all the reactants are used up
C.
The time it takes for one of the reactants to be used up
D.
The increase in concentration of a product per unit time
SA Topic 6: Kinetics SL
8.
Which statement is correct given the enthalpy level diagram below?
A.
The reaction is endothermic and the products are more thermodynamically stable than
the reactants.
B.
The reaction is exothermic and the products are more thermodynamically stable than
the reactants.
C.
The reaction is endothermic and the reactants are more thermodynamically stable than
the products.
D.
The reaction is exothermic and the reactants are more thermodynamically stable than
the products.
(Total 1 mark)
9.
Excess magnesium, was added to a beaker of aqueous hydrochloric acid. A graph of the
mass of the beaker and contents was plotted against time (line 1).
Mass
1
2
Time
What change in the experiment could give line 2?
A.
The same mass of magnesium in smaller pieces
B.
The same volume of a more concentrated solution of hydrochloric acid
C.
A lower temperature
D.
A more accurate instrument to measure the time
(Total 1 mark)
SA Topic 6: Kinetics SL
10.
Consider the reaction between magnesium and hydrochloric acid. Which factors will affect
the reaction rate?
11.
I.
The collision frequency of the reactant particles
II.
The number of reactant particles with E ≥ Ea
III.
The number of reactant particles that collide with the appropriate geometry
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
A student wished to follow the rate of the reaction between hydrochloric acid and calcium
carbonate. Which of the following methods would NOT work?
12.
A.
Measuring the volume of carbon dioxide gas evolved over time.
B.
Measuring the change in the mass of the contents of the flask over time
C.
Measuring the change in color of the contents of the flask over time.
D.
Measuring the change in the pH of contents of the flask over time.
Which quantities in the enthalpy level diagram are altered by the use of a catalyst?
Enthalpy
I
II
III
Time
13.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which is a correct statement about the rate of a chemical reaction?
A.
It can only be determined experimentally.
B.
It can be deduced from the chemical equation of the reaction.
C.
It can be predicted from the sign and the value of the enthalpy change, H, for the reaction.
D.
It only depends on the nature of the reactants not on their concentration.
SA Topic 6: Kinetics SL
14.
A piece of zinc was added to aqueous nitric acid and the volume of hydrogen gas produced
was measured every minute. The results are plotted on the graph below. A
Which graph would you expect if the same mass of powdered zinc was added to nitric acid
with the same concentration?
15. The table below shows the concentrations of reactants and products during the reaction:
X + 2Y  2Z
At the start
After 10 seconds
[X] moldm-3
4
2
[Y] moldm-3
3
2
[Z] moldm-3
0
2
The rate a reaction can be referenced to any reactant or product. Which is the correct statement
about the rate of the reaction?
A.
Rate = 0.2 mol dm-3s-1 with reference to X
B.
Rate = 1.0 mol dm-3s-1 with reference to Y
C.
Rate = -0.2 mol dm-3s-1 with reference to Y
D.
Rate = 0.2 mol dm-3s-1 with reference to Z
End of Multiple Choice
/
SA Topic 6: Kinetics SL
Paper 2: SL Kinetics
1.
Name:____________________
Alex and Hannah were asked to investigate the kinetics involved in the iodination of propanone.
They were given the following equation by their teacher.

H ( aq )
CH3COCH3(aq) + I2(aq) 

 CH2ICOCH3(aq) + HI(aq)
Alex’s hypothesis was that the rate will be affected by changing the concentrations of the
propanone and the iodine, as the reaction can happen without a catalyst. Hannah’s hypothesis
was that as the catalyst is involved in the reaction, the concentrations of the propanone,
iodine and the hydrogen ions will all affect the rate.
They carried out several experiments varying the concentration of one of the reactants or the
catalyst whilst keeping other concentrations and conditions the same. Their results are shown
graphically below.
(a)
Discuss whether either Alex’s or Hannah’s hypothesis is correct.
[I2] does not affect rate / OWTTE;
neither correct/both partially correct with explanation as to how;
..................................................................................................................................................................
..................................................................................................................................................................
(b)
(2)
Explain why the reaction rate will increase with increasing temperature.
more particles/molecules have sufficient energy to overcome
activation energy / OWTTE;
more frequent collisions;
..................................................................................................................................................................
(2)
SA Topic 6: Kinetics SL
(c)
(i)
This reaction uses a catalyst. Sketch and annotate the Maxwell-Boltzmann
energy distribution curve for a reaction with and without a catalyst on labelled
axes below.
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)
(3)
(ii)
Describe how a catalyst works.
catalyst provides an alternative pathway of lower energy / OWTTE;
Accept catalyst lowers activation energy (of reaction). (1)
2.
The graph below shows how the volume of carbon dioxide formed varies with time when a
hydrochloric acid solution is added to excess calcium carbonate in a flask.
(i)
Explain the shape of the curve.
rate = increase in
volume
= slope of graph;
time
initially/to begin with steeper slope / fastest rate / volume of gas/CO2
SA Topic 6: Kinetics SL
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.
(ii)
3)
The graph below is the same as the one on the previous page. Sketch the curve you
would obtain if double the volume of hydrochloric acid solution of half the
concentration as in the example above is used instead, with all other variables kept
constant from the original. Explain why the shape of the curve is different.
(iii)
(iv) 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;
(v)
(vi) Outline one other way in which the rate of this reaction can be studied in a school
laboratory. Sketch a graph to illustrate how the selected variable would change with
time. (iii)
(4)
SA Topic 6: Kinetics SL
.............. mass loss/of CO2 / mass of flask + content......................................................................................
..................................................................................................................................................................
............................................................................................................................................................(2)
(vii)
Define the term activation energy and state one reason why the reaction between calcium
carbonate and hydrochloric acid takes place at a reasonably fast rate at room temperature.
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)
3.
Sketch an enthalpy level diagram to describe the effect of a catalyst on an exothermic
reaction.
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.
SA Topic 6: Kinetics SL
If an endothermic reaction is shown, award [2 max] if all other parts are
shown correctly.
4.
3 max
Chemists, like all scientists, use models to help explain what they observe. Discuss collision
theory as a useful model to explain what is observed during chemical reactions when
variables are manipulated and increase the rates of reactions. Use at least one specific
example.
A good model will allow scientists to predict and to explain what is observed
experimentally. Additionally, a good model will be simple, yet widely applicable. The
collision theory is a good model as it can be used to effectively predict results and explain
what is seen in the lab. For example, we see that when temperature increases, rates of
reaction increase. Collision theory says that particles must collide and collide with
adequate energy to overcome energy of activation. Since an increase in temperature
increases the overall KE of all of the particles, we would predict more frequent collisions,
but more importantly, more particles with enough energy to overcome activation energy,
as a result rates of reactions will increase. Or, take increasing concentrations of the
reactants, would lead to more frequent collisions, and increased rate, again useful model.
On the other hand, while collision theory predicts particles must collide in a specific
orientation, it is difficult to test only this aspect of the model and this aspect lies in theory
only.
..................................................................................................................................................................
..................................................................................................................................................................
[3]