EXERCISE 1: RATE OF REACTION

1. An experiment was carried out to study the effect of heat on the rate of the reaction between sodium thiosulphate solution and hydrochloric acid. The time taken for the formation of a fixed quantity of sulphur was recorded. The results of the experiment were recorded as shown in Table below.

 (a) What was the colour of sulphur formed? [1 mark]

(b) What is meant by the rate of reaction in this experiment? [1 mark]

(c) Write an equation for the reaction which occured in this experiment. [1 mark]

(d) (i) Complete Table above by writing the values of 1/time. [1 mark]

(ii) Draw a graph of   against temperature on a graph paper. [3 marks]

(iii)The rate of reaction is directly proportional to 1/time. Based on your graph, what inference can be drawn concerning the rate of reaction and temperature? [2 marks]

(e) State the variable which is fixed in the above experiment.[1 mark]

(f) State another factor besides temperature which can influence the rate of reaction in this experiment. [1 mark]

2. Diagram below shows two sets of apparatus set up in an experiment to study one of the factors affecting the rate of reaction between sodium thiosulphate and dilute sulphuric acid.

 (a) Write a balanced chemical equation for the reaction in this experiment. [2 marks](b) What is the measurement that needs to be recorded for both sets of apparatus to determine the rates of

reaction? [1 mark](c) (i) By using the data given in the diagram, compare the rates of reaction in set A and set B. Explain your

answer based on the factor affecting the rate of reaction. [2 marks](ii) Explain the answer in (c) (i) with reference to the collision theory.

[3 marks](d) State another factor that can increase the rate of reaction in the above experiment. [1 mark]

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3. Two experiments are carried out as follows to investigate the rate of reaction between marble and dilute nitric acid.

(a) Draw the set up apparatus for Experiment I. [2 marks]

(b) (i) State how the mass of the conical flask and its contents changes with time in Experiment I [1 mark](ii) Give one reason for your answer in (b)(i). [1 mark]

(c) What is the function of copper(II) sulphate? [1 mark]

(d) Suggest two ways of making the reaction in Experiment I faster. [2 marks](e) Experiment III is carried out by replacing 2 g of marble powder in Experiment I with 2 g of marble chips.

Sketch the curves of volume of gas against time for Experiments I, II and III. Label the curves as I, II and III.

[3 marks]

4. The table below shows two experiments carried out to investigate the decomposition of hydrogen peroxide..

TABLE  The volume of gas produced is measured at 30-second intervals until no reaction is observed..(a) Write a balanced chemical equation to represent the reaction in Experiment I. [1 mark](b) Sketch graphs of volume of the gas produced in Experiment I and Experiment II against time. [2 marks]

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(c) i. Based on (b), compare the rate of reaction in the two experiments. [1 mark]ii. Give a reason for your answer. [1 mark]

(d) Predict the following changes in Experiment II if the mass of copper(II) sulphate is increased to 10 g. Give reasons for your answer.

i. The rate of reaction. [2 marks]ii. The volume of gas. [2 marks]

(e) Name one substance which performs the same function as copper(II) sulphate in hydrogenation.[1 mark]

5. Five sets of experiment are conducted to study the eff ect of temperature on the rate of reaction. 50 cm3 of 0.2 mol dm–3sodium thiosulphate at 35°C are poured into a conical flask. The conical flask is then placed on a sheet of white paper with an “X” mark on it as shown in the diagram below.

DIAGRAM 10 cm3 of 0.2 mol dm–3 hydrochloric acid are added to the sodium thiosulphate solution and a stopwatch is started immediately. Th e mixture in the conical flask is swirled. The stopwatch is stopped as soon as the “X” mark is no longer visible.The experiment is repeated by changing only the temperature, as shown in the table below.

TABLE (a) Why does “X” mark disappear slowly aft er the hydrochloric acid is added to the sodium thiosulphate

solution in the conical flask?  [1 mark](b) Calculate the values of 1/time in the table above. [1 mark]

(c) Draw a graph of temperature against 1/time. [3 marks]

(d) Write an ionic equation for this reaction. [2 marks](e) Based on the graph drawn in (d), determine the time taken in set 4. [2 marks]  Based on the graph drawn in (d), state the relationship between the temperature and the rate of reaction

[1 mark]  Suggest one other method to increase the rate of reaction. [1 mark]

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6. Diagram shows two experiments which are conducted to investigate one of the factors that influences the rate of a reaction.Experiment I

Time taken for all the zinc to dissolve = 30 secondsReaction temperature = 35°C

Experiment IIEksperimen II

Diagram/Rajah

Time taken for all the zinc to dissolve = 12 secondsReaction temperature = 35°C

(a) Write a balanced chemical equation for the reaction. [ 2 marks](b) What is the factor that influences the rate of the reaction? [ 1 mark](c) What is the quantity which should be recorded in the two experiments to determine the rate of the

reaction? [ 1 mark](d) State two fixed variables in these two experiments. [2 marks](e) (i) Compare the rate of reaction in experiment I with that in experiment II.

Explain your answer based on the factor which affects the rate of reaction. [ 2 marks](ii) Explain your answer in (e)(i) with reference to the collision theory. [ 3 marks]

7. The diagram below shows the apparatus set up to measure the average rate of reaction between 2 g of granulated calcium carbonate and 25 cm3 of 1.0 mol dm–3 hydrochloric acid.

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DIAGRAM  

The gas evolved is measured at 30-second intervals. The results collected are shown in the table below.

TABLE (a) i. Write a chemical equation for this reaction. [1 mark]

ii. Name the gas evolved in this reaction. [1 mark]iii. Give a test to identify the gas collected. [1 mark]

(b) Plot a graph of the volume of gas against time. [3 marks]

(c) Based on the graph in (b), calculatei. the average overall rate of reaction.

ii. the average rate of reaction for the fi rst 90 seconds.

iii. the rate of reaction at 90 seconds.

[6 marks](d) Compare the rate of reaction at 60 seconds and that at 90 seconds. Give one reason for your answer.

[2 marks]

8. (a) Diagram below shows two experiments conducted to investigate a factor that influences the rate of a chemical reaction.

Diagram/Rajah

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 (i) What is the factor that infl uences the rate of the chemical reaction that is studied in the experiments?

[1 mark]

(ii) What is the role of CuSO4 in experiment II? [1 mark](iii)State two fixed variables in the two experiments. [2 marks]

(b) Two experiments were carried out to determine the rate of production of oxygen gas during the decomposition of hydrogen peroxide. In experiment I, 30 cm3 of 0.10 mol dm–3 hydrogen peroxide were used. The results obtained from experiment I are given in the graph shown below.

Diagram/Rajah

 (i) Sketch another graph on the same axes to show the results of the experiment II that will obtain if 15

cm3 of 0.15 mol dm–3 hydrogen peroxide were used. [1 mark](ii) Based on graph above, which experiment has a higher rate of reaction and give a reason for your

answer. [2 marks](iii)Why are the two curves not at the same level at the end of the experiment? [1 mark](iv)State two methods that can be used to increase the rate of decomposition of hydrogen peroxide.

[2 marks]

9. The diagram below shows the apparatus set up for the experiments carried out to study a factor that affects the rate of reaction. The experiment was carried out three times at diff erent temperatures and the results were recorded as shown in the table below.

  

ExperimentEksperimen

Temperature/°CSuhu/°C

Time taken for all themagnesium to dissolve/sMasa yang diambil untuk semuamagnesium melarut/s

Volume of gas collected/cm3

Isipadu gas terkumpul/cm3

I 30 50 1200

II 40 20 1200

III 50 15 1200

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TABLE

 (a) Write an ionic equation for the reaction between magnesium and hydrochloric acid. [2 marks](b) i. Name the gas produced in the above experiment. [1 mark]

ii. Calculate the mass of magnesium used in the experiment.[Relative atomic mass: Mg,24; Volume of 1 mole of gas at room temperature = 24 dm3] [2 marks]

(c) Calculate the average rate of reaction in cm3s-1 for...i. experiment I

ii. experiment II

iii. experiment III

[3 marks](d) Compare the rates of reaction of experiments I, II and III. Explain your answer by using the collision

theory. [2 marks]

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