Uddingston Grammar School
CfE Higher Chemistry
Unit 1: Chemical Changes and Structure
Sub-Topic A: Controlling the Rate
Homework 1: Rate
1. Two identical samples of zinc were added to an excess of two solutions of
sulphuric acid, concentrations 2 moll-1 and 1 moll-1 respectively.
Which of the following would have been the same for the two samples?
A.
B.
C.
D.
The total mass lost
The total time for the reaction
The initial rate of the reaction
The average rate of evolution of gas
2. Which of the following graphs could represent the change in the rate of a
reaction between magnesium ribbon and hydrochloric acid.
3. Which of the following graphs of rate of reaction against temperature would
apply to the neutralisation of dilute hydrochloric acid with zinc?
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4. Graph X was obtained when 1 g of calcium carbonate powder reacted with
excess dilute hydrochloric acid at 20 °C.
Which curve would best represent the reaction of 0·5 g lump calcium carbonate with
excess of the same dilute hydrochloric acid?
5.
Excess zinc was added to 100 cm3 of hydrochloric acid, concentration 1 mol l–1.
Graph I refers to this reaction.
Graph II could be for
A
excess zinc reacting with 100 cm3 of hydrochloric acid, concentration
2 mol l–1
B
excess zinc reacting with 100 cm3 of sulphuric acid, concentration
1 mol l–1
C
excess zinc reacting with 100 cm3 of ethanoic acid, concentration
1 mol l–1
D
excess magnesium reacting with 100 cm3 of hydrochloric acid,
concentration 1 mol l–1
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6. A small increase in temperature results in a large increase in rate of reaction.
The main reason for this is that
A
more collisions are taking place
B
the enthalpy change is lowered
C
the activation energy is lowered
D
many more particles have energy greater than the activation
energy
7. For any chemical, its temperature is a measure of
A
B
C
D
the average kinetic energy of the particles that react
the average kinetic energy of all the particles
the activation energy
the minimum kinetic energy required before reaction occurs
8. The graph below shows the variation of concentration of a reactant with time as
a reaction proceeds.
concentration/ mol/l
0.20
0.15
0.10
0.05
0.00
0
10
20
30
40
50
time/s
What is the average rate during the first 10s?
A
0.0100 mol l-1s-1
B
0.0036 mol l-1s-1
C
0.0075 mol l-1s-1
D
0.0090 mol l-1s-1
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9. The graph shows how the rate of a reaction varies with the concentration of one
of the reactants.
What was the reaction time, in seconds, when the concentration of the reactant was
1.00 mol l–1?
A
0.2
B
0.5
C
2.5
D
5.0
10. In which of the following will both changes result in an increase in the rate of a
chemical reaction?
A
A decrease in activation energy and an increase in the frequency
of collisions.
B
An increase in activation energy and a decrease in particle size.
C
An increase in temperature and an increase in the particle size.
D
An increase in concentration and a decrease in the surface area of
the reactant particles.
11. In a reaction involving gases, an increase in temperature results in
A
an increase in activation energy
B
an increase in the enthalpy change
C
a decrease in the activation energy
D
more molecules per second forming an activated complex.
12.
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Which line in the table is correct for curves Q and R in the above graph?
A
B
C
D
Curve Q
1 mol of O2 at 50oC
1 mol of O2 at 100oC
2 mol of O2 at 50oC
2 mol of O2 at 100oC
Curve R
2 mol of O2 at 100oC
2 mol of O2 at 100oC
1 mol of O2 at 100oC
1 mol of O2 at 100oC
13.
When copper carbonate is reacted with excess acid, carbon dioxide is produced. The
curves shown above were obtained under different conditions. The change from P to Q
could be brought about by
A
B
C
D
increasing the concentration of the acid
decreasing the mass of copper carbonate
decreasing the particle size of the copper carbonate
adding a catalyst
14.
In area X
A
molecules always form an activated complex
B
no molecules have the energy to form an activated complex
C
collisions between molecules are always successful in forming products
D
all molecules have the energy to form an activated complex
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15 .
Which line in the table is correct for a reaction as the temperature decreases from
T2 to T1?
Activation energy (EA)
Number of successful collisions
A
Remains the same
Increases
B
Decreases
Decreases
C
Decreases
Increases
D
Remains the same
Decreases
16. A student investigated the effect of changing temperature on the rate of chemical
reaction. The results from the investigation are shown in the graph below.
(a) Use the graph to determine the temperature rise required to double the rate of
reaction.
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(b) Collision theory can be used to explain reaction rates. Collision theory states that
for two molecules to react, they must first collide with one another.
State two
conditions necessary for the collisions to result in the formation of products.
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17. The rate of carbon dioxide production was measured in three laboratory
experiments carried out at the same temperature and using excess calcium
carbonate.
Experiment
Acid
40cm3 of 0.10 mol l-1 sulphuric
A
acid
40cm3 of 0.10 mol l-1 sulphuric
B
C
acid
40cm3 of 0.10 mol l-1 hydrochloric
acid
Calcium carbonate
1g lumps
1g powder
1g lumps
The curve obtained for Experiment A is shown.
total volumee of gas
collected/ml
120
100
80
60
40
20
0
0
20
40
60
time/s
a. Use the graph to calculate the average reaction rate in ml s-1 , between 10
and 20s.
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b.
Make a rough copy of the graph in your jotter. Draw curves on the graph to
show the results that could be obtained for experiments B and C. Label
each curve clearly.
2
c.
Draw a labelled diagram of the assembled apparatus which could be used
to carry out this experiment.
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18. In experiments with four different gases, a syringe was held vertically as
shown with the weight of the syringe piston applying a downward pressure on the
gas. The times taken for 60 cm3 of helium, methane, carbon dioxide and butane
to escape through the pinhole were measured and the graph shows the results
plotted against relative formula mass.
(a) Calculate the average rate of escape from the syringe of 60 cm3 of methane, in
cm3s-1.
1
(b) Name a hydrocarbon gas which would take 56 s to escape.
1
(c) The error in a measurement decreases as the actual size of the measurement
increases. Suggest one way of reducing the error in each of the time measurements.
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19. The effect of temperature changes on reaction rate can be studied using the
reaction between an organic acid solution and acidified potassium permanganate
solution.
5(COOH)2(aq) + 6H+(aq) + 2MnO4-(aq)
2Mn2+(aq) + 10CO2(g) + 8H2O(l)
The apparatus required is shown in the diagram.
(a) Describe how the reaction time can be measured.
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(b) The headings for a set of results are shown below.
Temperature / oC
Reaction time / s
Reaction rate /
Copy and complete the headings by entering the correct unit in the third
column.
1
(c) State two factors that should be kept the same in these experiments.
2
(d) Suggest why is it difficult to measure an accurate value for the reaction
time when the reaction is carried out at room temperature?
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Total : 30 Marks
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