Q3.
A student investigated the rate of reaction between calcium carbonate (marble chips) and
hydrochloric acid.
The student used the apparatus shown in Figure 1.
The student:
• recorded the volume of gas collected every 5 seconds
• repeated the experiment using hydrochloric acid at different temperatures.
The equation for the reaction is:
CaCO3(s) + 2 HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)
(a) The student plotted results for the hydrochloric acid at 20 °C and 40 °C on a graph.
Figure 2 shows the student’s graph.
Use information from Figure 2 to answer these questions.
Page 1
(i) State one conclusion the student could make about the effect of temperature
on the rate of the reaction.
...............................................................................................................
...............................................................................................................
(1)
(ii) Give one reason why the student could make this conclusion.
...............................................................................................................
...............................................................................................................
(1)
(iii) For the hydrochloric acid at 60 °C the student had collected 30 cm3 after 15
seconds.
Calculate the average rate of reaction from 0 to 15 seconds.
...............................................................................................................
...............................................................................................................
Rate of reaction = ........................................ cm3 per second
(1)
(b) The student then investigated how the surface area of marble chips affected the rate
of reaction.
(i) Which two variables should the student keep constant?
Tick ( ) two boxes.
Amount of water in the trough
Concentration of acid
Mass of marble chips
Size of marble chips
Volume of measuring cylinder
(2)
Page 2
(ii) Explain, in terms of particles and collisions, the effect that increasing the
surface area of the marble chips has on the rate of reaction.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(c) Calcium carbonate is a catalyst for the industrial production of biodiesel.
Give one reason why using a catalyst reduces costs.
........................................................................................................................
........................................................................................................................
(1)
(Total 8 marks)
Q4.A student investigated the reaction between magnesium and hydrochloric acid.
The equation for the reaction is:
Mg(s) 2 HCl(aq) MgCl2(aq)
H2(g)
magnesiu + hydrochloric magnesiu +
hydrogen
m acid m chloride
(a) Give two observations the student could make during the reaction.
1 ......................................................................................................................
........................................................................................................................
Page 3
2 ......................................................................................................................
........................................................................................................................
(2)
(b) In this question you will be assessed on using good English, organising information
clearly and using specialist terms where appropriate.
The student investigated how the rate of this reaction changed when the
concentration of hydrochloric acid was changed.
Write a plan the student could use.
In your plan you should:
• describe how you would carry out the investigation and make it a fair test
• describe the measurements you would make.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(6)
(Total 8 marks)
Q5. Hydrogen peroxide slowly decomposes into water and oxygen.
Page 4
hydrogen peroxide → water + oxygen
The reaction can be speeded up by adding manganese dioxide.
(a) (i) What do we call a substance that speeds up a chemical reaction without being
changed itself?
...........................................................................................................................
(1)
(ii) Give two other ways of increasing the rate of this reaction.
1 ........................................................................................................................
2 ........................................................................................................................
(2)
(b) The diagram shows how the rate of this reaction can be measured.
As the hydrogen peroxide decomposes, the mass of the flask and its contents
decreases.
Why does this decrease in mass take place?
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 4 marks)
Q6. The apparatus shown in the diagram was used to investigate the rate of reaction of
excess marble chips with dilute hydrochloric acid, HCl. Marble is calcium carbonate,
formula CaCO . The salt formed is calcium chloride, CaCl .
3 2
Page 5
(a) Write a balanced equation for the reaction.
....................................................................................................................................
....................................................................................................................................
(2)
The following results were obtained from the experiment.
Time in Reading on balance
minutes in g
0.5 269.6
1.0 269.3
2.0 269.0
3.0 268.8
5.0 268.7
9.0 268.6
(b) (i) Plot the results and draw a graph on the axes below.
Page 6
(3)
(ii) Continue the graph you have drawn to show the expected reading after11
minutes.
(1)
(iii) On the axes above, sketch a graph of the result which would be obtained if in
a similar experiment the same mass of powdered marble was used instead of
marble chips.
(2)
(Total 8 marks)
Q7. Magnesium reacts with dilute sulphuric acid.
magnesium + sulphuric acid → magnesium sulphate + hydrogen
A student measured the volume of hydrogen given off every 10 seconds. The results are
shown on the graph.
Page 7
(a) The average rate of hydrogen production in the first 10 seconds is
(60 cm ÷ 10 s) = 6 cm /s.
3 3
(i) Calculate the average rate of production of hydrogen between 30 seconds and
50 seconds. Show clearly how you work out your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Rate ............................... cm /s 3
(3)
(ii) Explain, as fully as you can, why the average rate between 30 and 50 seconds
is different from the rate between 0 and 10 seconds.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Page 8
(2)
(b) In industry, enzymes are used in both batch processes and continuous processes.
Give one reason why continuous processes are usually more profitable than batch
processes.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
Page 9
