Coordinated Science II
Rates of Reaction
Name:
Date:
1. The apparatus below was used to measure the volume of gas produced when zinc reacted with
hydrochloric acid.
A student measured the volume of gas produced
during the first minute of the reaction. The student
repeated the experiment altering one condition at a
time. What effect would each of the following have on
the volume of gas produced during the first minute of
the reaction. [3]
a. Decreasing the concentration of acid
b. Increasing the temperature
c. Using finely divided zinc instead of lumps of zinc
2. A small piece of marble, CaCO3, was added to 5.0 cm3 of hydrochloric acid, concentration 1.0mol /dm3,
at 25°C. The time taken for the reaction to stop was measured. The experiment was repeated using
5.0 cm3 of different solutions of acids. The acid was in excess in all of the experiments.
Typical results are given in the table.
(a)
(i) Explain why it is important that the pieces of marble are the same size and the same shape. [2]
(ii) How would you know when the reaction had stopped? [1]
(b) The equation for the reaction in experiment 1 is: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
Complete the following ionic equation. [1]
CaCO3(s) + 2H+(aq) → ............ + ............ + ............
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(c)
Coordinated Science II
Rates of Reaction
(i) Explain why the reaction in experiment 1 is faster than the reaction in experiment 2. [1]
(ii) The acids used for experiment 1 and experiment 3 have the same concentration. Explain why
experiment 3 is slower than experiment 1. [2]
(iii) Explain in terms of collisions between reacting particles why experiment 4 is slower than
experiment 1. [3]
3. In two separate experiments, two metals A and B were reacted with an excess of dilute hydrochloric
acid. The volume of hydrogen was measured every 10 seconds. These graphs show the results:
(a) Which metal, A or B, reacts faster with hydrochloric acid? Give your evidence.
(b) Sketch and label the curves that will be obtained for metal B if:
. i more concentrated acid is used (name it curve X)
. ii the reaction is carried out at a lower temperature (name it curve Y)
4. Zinc and iodine solution react to synthesize zinc iodide.
(a) Write a balanced equation for the reaction, given that Zinc has a charge of +2.
(b) The rate of reaction can be followed by measuring the mass of zinc metal at regular intervals, until
all the iodine has been used up.
(i) What will happen to the mass of the zinc, as the reaction proceeds?
(ii)The reaction rate slows down with time. Why?
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Coordinated Science II
Rates of Reaction
(c) How will the reaction rate change if the temperature of the iodine solution is increased by 10 °C?
Explain your answer using the idea of collisions between particles.
5. Hydrochloric acid reacts with marble chips (calcium carbonate).
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
A 50 cm3 sample of dilute hydrochloric acid was added to a large quantity of marble chips in an
evaporating dish, which was placed on the pan of the balance. The mass of the dish and its contents was
recorded every 30 seconds. The results are shown in the graph below.
(a)
(i) Draw a smooth curve through the points on the grid.
(ii) Which result appears to be incorrect? Why have you selected this result?
(b) Use the graph to answer the following questions.
(i) How long did the reaction last? [1]
(ii) What mass of carbon dioxide was produced? [1]
(c) Sketch on the grid the curve you would expect if 50 cm3 of more concentrated hydrochloric acid had
been used in the experiment. [2]
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Coordinated Science II
Rates of Reaction
6. Hydrogen peroxide decomposes slowly at room temperature to form water and oxygen. The reaction
is catalyzed by manganese(IV) oxide.
2H2O2→ 2H2O + O2
A student used the apparatus shown below to study how changing the concentration of hydrogen
peroxide affects the speed of this reaction.
(a) Apart from the volume of hydrogen peroxide, state two things that the student must keep the same in
each experiment.
1. .......................................................................................................................................
2. ................................................................................................................................. [2]
(b) The student measured the volume of oxygen produced using three different concentrations of
hydrogen peroxide. The results are shown on the graph below
(i) Describe how the speed of the reaction varies with the concentration of hydrogen peroxide. [1]
(ii) Explain why the final volume of oxygen given off is less for graph B than for graph A. [1]
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Coordinated Science II
Rates of Reaction
(iii) From the graph, determine
 the time taken for the reaction to be completed when 3 g / dm3 hydrogen peroxide (line A) was
used. [1]

the volume of oxygen produced by 2 g / dm3 hydrogen peroxide (line B) in the first 15 seconds. [1]
(c) The student then tested various compounds to see how well they catalyzed the reaction.
He used the same concentration of hydrogen peroxide in each experiment.
The table shows the time taken to produce 20 cm3 of oxygen using each compound as a catalyst.
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