10.rate Of Reaction F5
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RATE OF REACTION/F5/HST RATE OF REACTION 1. Concept Map Average rate of reaction
Rate of reaction at a given time
Observable changes in chemical reaction
Rate of reaction
Factors affecting rate of reaction
Collision Theory to explain factors affecting rate of reaction
2. Rate of reaction (a) Rate of reaction is the …………………at which reactants react to form products in a chemical reaction. (b) Not all chemical reactions have the same rate of reaction, some reactions occur ……………… with rate of reaction that is …………….., and some reactions occur ……………… with rate of reaction that is ……………... (c) Examples of fast chemical reaction: Type of reaction
Example of chemical equation for the reaction
Neutralisation Double decomposition reaction Acid with active metals
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RATE OF REACTION/F5/HST Combustion of magnesium
(d) Examples of slow chemical reaction. Corrosion of iron Photosynthesis Reaction of hydrochloric acid with sodium thiosulphate solution. (e) Time taken for a fast chemical reaction is ……………and the time taken for slow chemical reaction of ……………. Hence the rate of reaction is …………………… to time taken for the reaction. Rate of reaction α ……………….. (f) The rate of reaction can be determined by measuring the time taken for an observable chemical change to occur. Rate of reaction = Observable chemical change Time taken (g) The observable chemical changes in a chemical reaction are (i) ……………………………………………………………………………. (ii) …………………………………………………………………………… (iii) …………………………………………………………………………. (iv) ………………………………………………………………………… (v) ………………………………………………………………………….. (h) Rate of reaction can be defined as the rate of change of volume of gas produced per unit time. Rate of reaction = Change in volume of gas produced Time taken =
……………… cm3 s-1
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RATE OF REACTION/F5/HST (i) Example: If 50.0 cm3 of hydrogen gas is collected in 20 seconds during a chemical reaction between magnesium and dilute hydrochloric acid . What is the rate of reaction? Rate of reaction =
cm3 s-1
=
(ii) Example: If 5.0 gram of magnesium ribbon reacts completely with dilute hydrochloric acid in 25s, what is the rate of reaction? Rate of reaction =
g s-1.
=
3. To determine the rate of reaction from graph. (a) For a chemical reaction, if the concentration of reactants or mass of reactant is plotted against the time, sketch the graph produced:
Mass of reactant /g
Concentration of reactant / mol dm-3
Time/s
Time/s
(b) For a chemical reaction, if the concentration of products or the volume of gas released is plotted against time, sketch the graph is produced.
Volume of gas/cm3 Vmax
Concentration of product / mol dm-3
Time/s
Time/s
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RATE OF REACTION/F5/HST (c) If the concentration of reactant is plotted against 1/time, sketch the graph produced. Concentration of reactant / mol dm-3
1/time , s-1 (d) In a chemical reaction involving release of a gas, it is easier to determine the rate of reaction by measuring the ……………………………….. at a certain time interval. (f) There are 2 methods to determine the rate of reaction, namely (i) average rate or overall rate of reaction Average rate of reaction = Total volume of gas released Time taken = V cm3 s-1 or cm3 min-1 t (ii) rate of reaction at a given time. To determine the rate of reaction at a given time t1 s on the graph at point M, the following steps are taken. - Draw a tangent at the point M on the graph. - Draw a right angle triangle using the tangent as hypotenuse. - Determine the gradient of the tangent. - Rate of reaction at t1 s = y/x cm3 s-1 Example: Rate of reaction at t1 =
Volume of gas/cm3
Rate of reaction at t2 =
M
Rate of reaction at t3 = t1
t2
t3 4
Time/s HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST Example: To determine the rate of reaction between zinc and dilute hydrochloric acid. Aim of experiment: To investigate………….. Apparatus:
Material:
Procedure: (diagram)
(i)
(ii)
(iii)
(iv)
(v)
(vi) (vii)
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RATE OF REACTION/F5/HST Result: Time/minute
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Burette 49.00 36.00 25.00 17.00 11.00 8.00 6.00 5.00 4.00 4.00 4.00 3 reading/cm Volume of 0.00 13.00 24.00 32.00 38.00 41.00 43.00 44.00 45.00 45.00 45.00 gas collected/cm3 Discussion: 1. Plot a graph of volume of gas collected against time of reaction. 2. From the graph, calculate the (i) overall average rate of reaction.
(ii) rate of the reaction in the first 3 minutes.
(iii) rate of reaction in the second minute
(iv) rate of reaction at (a) 1 minute
(b) 2 minute
(c) 3 minute
3. Compare the rate of reaction obtained in 2(iv). Explain your answer.
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4. Write a balance chemical equation of the reaction between zinc and hydrochloric acid.
5.What is the name of the gas released and suggest a test for the gas.
Conclusion:
4. Factors affecting rate of reaction Name the factors that affect the rate of reaction.. (A) (B) (C) (D) (E) (A) Effect of total surface area of reactant on the rate of reaction. (a) The smaller the size of particle of solid reactant the larger the surface area of reactant exposed, hence the higher is the rate of reaction. Give 3 examples for the above statement. (i) Cube sugar dissolves slower than that of fine sugar of the same mass in same amount of water. (ii) Minced meat cooks faster that solid piece of meat of the same mass. (iii) Powdered zinc reacts faster than granulated zinc of the same mass with hydrochloric acid of the same volume and concentration.
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RATE OF REACTION/F5/HST (b) Experiment to investigate the effect of total surface area of calcium carbonate on the rate of reaction Problem statement:
Hypothesis:
Variables: (i) manipulate variable: (ii) responding variable: (iii) fixed variable:
Materials: Apparatus: Procedure:
(i)
(ii)
(iii)
(iv)
(v)
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RATE OF REACTION/F5/HST (vi)
(vii) (viii)
Results: (i) Experiment I using large marble chips: Time/ minute 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 49.50 45.20 42.0 39.00 36.50 34.00 31.80 29.50 27.80 26.20 24.50 23.50 Burette reading/cm3 Volume of gas collected/cm3
(ii) Experiment II using crushed marble chips: Time/ minute 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Burette 49.00 39.00 33.00 28.50 25.00 21.50 19.00 16.70 14.70 13.00 11.50 10.00 reading/cm3 Volume of gas collected/cm3 1. Plot the graph of total volume of gas collected against time taken for the reaction for experiment I and II on the same axes.
2. Based on the graph , calculate (a) the overall rate of rate of reaction for the first 5 minutes of the reaction between hydrochloric acid and (i) large marble chips:
(ii) crushed marble chips
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(b) The rate of reaction at 2.5 minute for (i) large marble chips:
(ii) crushed marble chips:
3. Based on your answers in 2(a) and 2(b) , how does the rate of reaction differ?
4. What is the factor that causes the difference in rate of reaction?
5. Write a balanced chemical equation for the reaction between calcium carbonate and hydrochloric acid.
6. Explain why does the rate of reaction decreases with increase of time.
7. If both reactions are allowed to react until completion, is the total volume of gas collected the same? Explain your answer.
8. If the marble chips used in the experiment is in excess, what is the maximum total volume of gas collected? [ 1 mole of gas at room temperature occupies a volume of 24dm3]
Conclusion:
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RATE OF REACTION/F5/HST 5. The effect of concentration of reactant on the rate of reaction. (a)When concentration of reactant increases, the rate of reaction increases. Give one example for the above statement.
(b) Experiment to investigate the effect of concentration of sodium thiosulphate with hydrochloric acid on the rate of reaction Problem statement: Hypothesis: Variables: (i) manipulated variable: (ii) responding variable: (iii) fixed variable: Procedure: (diagram)
(i)
(ii)
(iii)
(iv)
(v)
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RATE OF REACTION/F5/HST (vi)
(vii) Results: Experiment
1
2
3
4
5
Volume of 0.2moldm-3 sodium thiosulphate solution, V1 cm3 Volume of distilled water added/cm3 Volume of 1.0mol hydrochloric acid added/cm3 Total volume of reactant /cm3
45
40
35
30
25
0.0
5.0
10.0
15.0
20.0
5.0
5.0
5.0
5.0
5.0
50.0
50.0
50.0
50.0
50.0
16
20
27
41
83
Concentration of sodium thiosulphate solution used/moldm-3 Time taken/s 1/time , s-1
1. Plot the graph of concentration of sodium thiosulphate solution used against time taken for the reaction. 2. Plot the graph of concentration of thiosuphate solution used against 1/time. 3. What does the value of 1/time represents?
4. Based on your graph, state the relationship between (i) the concentration of sodium thiosulphate and the time taken for the reaction.
(ii) the rate of reaction and the concentration of sodium thiosulphate solution.
5. What is colour of the precipitate formed and name the precipitate.
6. What is the time taken for the mark ‘X” to disappear if the concentration of sodium thiosulphate solution used is 0.10 mol dm-3?
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RATE OF REACTION/F5/HST 7. Write a balanced chemical equation for the reaction in this experiment.
8. Write an ionic equation for the reaction in this experiment.
9. If dilute sulphuric acid of the same concentration is used to replace hydrochloric acid in this experiment, predict the rate of reaction and explain your answer.
Conclusion:
6. The effect of temperature on rate of reaction. (a) Increase in temperature of reaction, increases the rate of reaction. Give two examples for the above statement. (i) (ii)
(b) Experiment to investigate the effect of temperate on the rate of reaction between thiosulphate solution and dilute hydrochloric acid. Problem statement: Hypothesis: Variables: (i) manipulate variable: (ii) responding variable: (iii) fixed variable:
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RATE OF REACTION/F5/HST Procedure: (diagram)
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
Results: Experiment
1
2
3
4
5
Temperature/oC
30
35
40
45
50
Time taken/s
55
48
42
37
33
1/time, s-1
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RATE OF REACTION/F5/HST
1. Plot the graph of (i) temperature against time and (ii) temperature against 1/time. 2. Based on your graph, what is the relationship between rate of reaction with temperature.
3. Write a balance chemical equation for the reaction of this experiment.
4. why is the volume of sodium thiosulphate solution and hydrochloric acid fixed for each experiment? 5. What is the time taken for the mark ‘X’ to disappear when the temperature is 60oC?
Conclusion:
7. Effect of catalyst on the rate of reaction. (a) A catalyst is a substance which added to a chemical reaction can ………. the rate of reaction and itself remains ………………………………. at the end of the reaction. (b) A catalyst does not ………………………………….. in a chemical reaction. It only ……………………….. the rate of reaction if it is a positive catalyst, and …………………………the rate of reaction if it is a negative catalyst.
(c) Example: When copper(II) sulphate solution is added into a reaction between zinc and hydrochloric acid, the rate of reaction increases but the final quantity of hydrogen produced is the same the reaction of zinc with hydrochloric acid without copper(II) sulphate solution. Sketch the graphs of volume of hydrogen gas against time for comparison of reaction of zinc and hydrochloric acid with catalyst and without catalyst .
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RATE OF REACTION/F5/HST
Volume of hydrogen released/cm3
Time/s (d) Experiment to investigate the effect of catalyst on the rate of reaction for decomposition of hydrogen peroxide solution. Problem statement: Hypothesis: Variables: (i) manipulated variable: (ii) responding variable: (iii) fixed variable: Apparatus: Materials:
Procedure:
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RATE OF REACTION/F5/HST (i)
(ii)
(iii)
(iv)
(v)
Observation: Test tube A
Observation
B
Discussion: 1. What is the effect of manganese(IV) oxide on the decomposition of hydrogen peroxide solution?
2. What is the function of manganese(IV) oxide in this experiment?
3. Write a balanced chemical equation for the reaction in this experiment.
4. Will the mass of manganese(IV) oxide change at the end of the reaction in test tube B?
Conclusion:
(e) Experiment to investigate the effect of the amount of catalyst on the rate of reaction for decomposition of hydrogen peroxide solution. Problem statement:
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RATE OF REACTION/F5/HST
Hypothesis: Variables: (i) manipulated variable: (ii) responding variable: (iii) fixed variable: Apparatus: Materials: Procedure:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
18
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RATE OF REACTION/F5/HST
Results: (a) Experiment 1, using 0.2g of manganese(IV) oxide Time/s
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Burette reading/cm3 Volume of gas cm3
49.70
48.70
47.10
45.70
44.20
43.20
42.00
41.10
40.20
39.50
39.00
38.40
38.00
(b) Experiment II, using 0.6g of manganese(IV) oxide Time/s
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Burette reading/cm3 Volume of gas cm3
49.00
43.60
40.50
38.00
36.00
34.50
33.00
31.70
30.50
29.70
29.00
28.20
28.00
1. Plot the graph of total volume of gas against time for experiment I and experiment II on the same axes. 2. Based on your graph, calculate the rate of reaction at 120 seconds for each of the reaction . (i) Experiment I:
(ii) Experiment II:
3. How did the rates of reaction in experiment I and II differ?
4. Which experiment shows the higher rate of decomposition of hydrogen peroxide?
5. If both experiments are allowed to proceed until completion, is the total volume of gas collected in both experiments the same? Explain your answer.
Conclusion:
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RATE OF REACTION/F5/HST (f) Application of catalyst in industry. Most catalysts are transition elements or compounds of transition elements. Catalyst is specific in its action and only a small amount is required in a chemical reaction. Industrial process Haber Process
Product produced
Equation
Catalyst
Contact Process Ostwald Process Hydrogenation of vegetable oil Cracking of petroleum (g) Other examples: Table shows the reacting conditions for the following experiments. For the following experiments , sketch graph of (i) volume of gas against time Experiment 1 Experiment 2
5cm3 “5 volume of H2O2” + 45cm3 water + MnO2 3cm3 “5 volume of H2O2” + 47cm3 water + MnO2
Volume of oxygen/cm3
Time/s
(ii) volume of gas against time Experiment 1 Experiment 2
5cm3 “5 volume of H2O2” + 45cm3 water at 40oC 5cm3 “5 volume of H2O2” + 45cm3 water at room temperature
Volume of oxygen/cm3
20
Time/s HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST
(iii) Volume of hydrogen against time Experiment 1 Experiment 2 Experiment 3
4 g of excess zinc powder + 100 cm3 of sulphuric acid 0.5 mol dm-3 + 5cm3 copper(II) sulphate solution at room temperature 4 g of excess zinc powder + 100 cm3 of sulphuric acid 0.5 mol dm-3 room temperature 4 g of excess zinc powder + 50 cm3 of sulphuric acid 0.5 mol dm-3 at room temperature
8. Collision Theory (a) For a chemical reaction to occur, the particles of the reactants must collide with each other. However, not all collisions result in a chemical reaction to form products. (b) According to collision theory, only those collisions which (i) with ……………………….. orientation and (ii) posses ………………………amount of energy called activation energy , Ea will result in chemical reaction. (c) Collisions of particles of reactants that result in chemical reaction is known as …………………………. (d) Activation energy , Ea, is defined as the minimum amount of energy of collision that is required for particles of reactant to react or to produce effective collision. (i) Exothermic reaction
(ii) Endothermic reaction
Energy
Energy
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RATE OF REACTION/F5/HST
(e) Using Collision Theory to explain the factors affecting the rate of reaction. 1. The effect of increase in total surface area of reactant.
Using solid reactant that is smaller in size. When size of solid reactant is smaller, the total surface area increases The frequency of collision of particles of reactant increases The frequency of effective collision increases The rate of reaction increases.
2. The effect of increase in concentration of reactant. Increasing the concentration of reactant will increase the number of particles of reactant per unit volume. The frequency of collision of particles of reactant increases. The frequency of effective collision increases. The rate of reaction increases. 3. The effect of increase in temperature of reaction o By increasing the temperature of the reactant o Increased in temperature, increases the kinetic energy of the reactant particles. o The frequency of colliding particles possesses energy higher than the activation energy increases. o The frequency of effective collision increases o The rate of reaction increases. 4. The effect of catalyst on the rate of reaction.
Addition of a positive catalyst to a chemical reaction provides an alternative path of reaction that requires a lower activation energy. The frequency of effective collision increases The rate of reaction increases. Energy profile diagrams to show the effect of catalyst on rate of reaction. Energy
Energy
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9. The effect of pressure on rate of reaction. (i) The effect of pressure only affects the rate of chemical reaction when the reactants are in the gaseous state. Eg: N2(g) +
3H2(g)
2NH3(g)
(ii) Increased in pressure by increasing the concentration of gas or by reducing the volume of the vessel, o the number of particles per unit volume increases. o The frequency of collision among the reactant particles increases o The frequency of effective collision increases o Hence the rate of reaction increases.
Reinforce exercise; N03/P1 18.
Which of the following can be used to determine the rate of the reaction? I Release of gas per unit time. II Change of colour intensity per unit time. III Formation of precipitate per unit time. IV Increase in the mass of reactant per unit time. A. I and II B. III and IV C. I, II and III D. II, III and IV
35.
An equation of a reaction is as follows 2Fe2+ Green
+
2Fe3+ + Brown
Cl2
2Cl
In the reaction represented by the equation above, it was found that the change of colour from green to brown was faster when the reactant mixture was heated. This was due to the… I. decrease in the activation energy. II. increase in the frequency of effective collision . III. increase in the kinetic energy of ferrum(II) ions and chlorine molecules. IV. increase in the frequency of collision between ferrum(II) ions and chlorine molecules. A. I and II only B. II and III only C. I, III and IV only D. II, III and IV only
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RATE OF REACTION/F5/HST 44.
Table 4 shows the total volume of gas collected at regular intervals in a reaction. Time / s Volume of gas/ cm3
0 0
30 2.0
60 3.7
90 5.2
120 6.4
150 7.3
180 8.6
210 8.6
What is the average rate of reaction in the second minute ? A. B. C. D. 48.
0.040 0.045 0.053 0.062
cm3s-1 cm3s-1 cm3s-1 cm3s-1
The equation below represents the decomposition of hydrogen peroxide solution. 2H2O2(aq)
2H2O(l)
+ O2(g)
Which of the following are produced when 1 mole of hydrogen peroxide is decomposed completely ? [1 mole of gas occupies 24 dm3 at room condition; Avogadro’s constant : 6 X 1023 mol-1] I II III IV A B C D
2 moles of water 12 dm3 of oxygen gas 3 X 1023 of oxygen molecules 1.2 X 1024 of water molecules I and III only I and IV only II and III only II and IV only
N03/2B 1. The rate of reaction is affected by several factors. One o the factors is the size of particles. One kilogramme of meat, cut into big pieces, takes a longer time to cook compared to one kilogram of meat cut into smaller pieces. (a) Explain the above statement based on the size of the particles. [2 marks] (b) A student carried out three experiments to investigate the effects of the factors influencing the rate of reaction. Table 1 shows the results of the experiments.
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(i) Write the chemical equation for the reaction between magnesium and hydrochloric acid. Calculate the maximum volume of hydrogen gas produced. [ Relative atomic mass: mg,24; molar mass volume: 24 dm3 mol-1 at room condition] [4 marks] (ii) Sketch the graphs for the volume of hydrogen gas against time for Experiment I, II and III on the same axes. [3 marks] (iii) Calculate the average rate of reaction for Experriment I, II and III in cm3 s-1. [3 marks] (iv) Compare the rates of reaction between Experiment I and Experiment II, and between Experiment II and Experiment III. With reference to collision theory, explain why there are differences in the rates of reaction in the experiments. [8 marks] N03/P3/1 An experiment was conducted to find out the effects of temperature on the rate of reaction. 50cm3 of sodium thiosulphate solution 0.05 mol dm-3 at 30oC was put into a 250cm3 conical flask. Then the conical flask was placed on an ‘X’ sign on a piece of white paper. 10cm3 of hydrochloric acid 1.0 mol dm-3 was added to the sodium thiosulphate solution and shaken. At the same time, the stop watch was started. The stop watch was stopped as soon as the ‘X’ sign was no longer visible.
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RATE OF REACTION/F5/HST The same steps of the experiment were repeated for sodium thiosulphate solution which was heated to 35oC, 40oC, 45oC and 50oC. Figure 1 shows the readings of the stop watch for each of the reaction at different temperatures.
(a) Record the time for each reaction in the spaces provided in Figure 1. (b) Construct a table and record temperature, time and 1/time for this experiment.
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RATE OF REACTION/F5/HST (c) (i) Draw a graph of temperature against 1/time on the graph paper. (ii) Based on the graph in c(i) , state the relationship between the rate of reaction and temperature.
(d) Predict the time taken as soon as the sign ‘X’ to be not longer visible if this experiment is repeated at 55oC.
(e)(i) State the variables involved in this experiment. Manipulated variable: Responding variable: Constant variable: (ii) State how you would manipulate one variable while keeping the other variables constant. (f) State the hypothesis for this experiment.
(g) From the above experiment, the student found a relationship between temperature and rate of reaction. The same situation can be applied in our daily lives, for example, keeping food that is easily spoiled in the refrigerator. Using your knowledge of chemistry, state the relationship between temperature and the rate at which food turns bad.
N04/P1 33
An experiment is carried out to study the rate of reaction between marble and hydrochloric acid to produce carbon dioxide gas. Experiment Substances I Excess marble and 50.0 cm3 of 2 mol dm-3 hydrochloric acid II
Excess marble and 100.0cm3 of 1 mol dm-3 hydrochloric acid
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RATE OF REACTION/F5/HST A Volume of CO2/cm3
C Volume of CO2/cm3
I II
I II
Time/s B Volume of CO2/cm3
Time/s D Volume of CO2/cm3
II
I II
I
Time/s
Time/s 45
The reaction between hydrochloric acid and zinc produces hydrogen gas. The reaction is complete in 50 seconds and the maximum volume of gas produced is 25 cm3. What is the average rate of the reaction? A. 0.5 cm3 s-1 B. 1.0 cm3 s-1
C. 2.0 cm3 s-1 D. 4.0 cm3 s-1
N05/P1 12
The diagram shows the energy profile of a reaction. Ea is the activation energy for this reaction. Energy Ea Reactant
Ea’ Products Reaction path
What will change the activation energy from Ea to Ea’? A. Temperature C. Concentration B. Catalyst D. Total surface area
28
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RATE OF REACTION/F5/HST 13
Which of the following explains the meaning of effective collision? A. B. C. D.
45
The collision where its energy is less than the activation energy. The collision that has a low energy The collision which takes place before a reaction The collision that causes a reaction
The diagram shows the set up of the apparatus for an experiment to determine the rate of reaction between sodium thiosulphate and sulphuric acid.
Which of the following combination of conditions take the shortest time for the mark ‘X’ to diappear from sight? Sulphuric acid Sodium thiosulphate Temperature o 3 3 Volume/cm Concentration/ Volume/cm Concentration/ / C mol dm-3 mol dm-3 A 10 1.0 50 0.5 30 B 10 1.0 50 0.5 40 C 10 0.5 50 0.5 30 D 20 0.5 40 0.5 40 46
In an experiment, the decomposition of 25cm3 of 0.1 mol dm-3 hydrogen peroxide solution produces oxygen gas. Volume of oxygen gas/cm3
P Q Time/s
If the experiment is repeated using another solution, which solution will produce curve Q? A. 25 cm3 of 0.15 mol dm-3 hydrogen peroxide B. 20 cm3 of 0.15 mol dm-3 hydrogen peroxide C. 15 cm3 of 0.15 mol dm-3 hydrogen peroxide D. 10 cm3 of 0.25 mol dm-3 hydrogen peroxide
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RATE OF REACTION/F5/HST N05/P2/7 (a) Food stored in a refrigerator last longer than food stored in a kitchen cabinet. Explain why. [4 marks] (b) A group of pupils carried out three experiments to investigate the factors affecting the rate of a reaction. Table 7 shows information about the reactants and the temperature used in each experiment. Experiment I II III
Reactants Excess calcium carbonate chips and 30 cm3 of 0.5 mod dm-3 hydrochloric acid Excess calcium carbonate chips and 30 cm3 of 0.5 mod dm-3 hydrochloric acid Excess calcium carbonate powder and 30 cm3 of 0.5 mod dm-3 hydrochloric acid
Temperature /oC 30 40 40
Table 7. Graph 7 shows the results of these experiments.
(i) Calculate the average rate of reaction for experiment I.
[2 marks]
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RATE OF REACTION/F5/HST (ii) Based on Table 7 and graph 7, compare the rate of reaction between: • Experiment I and Experiment II • Experiment II and Experiment III In each case explain the difference in rate of reaction with reference to the collision theory. [ 10 marks] (iii) The chemical equation below shows the reaction between calcium carbonate and hydrochloric acid. CaCO3 + 2HCl CaCl2 + CO2 + H2O Given that the relative atomic mass of C=12, O=16, Ca=40 and the molar volume of any gas is 24 cm3 mol-1 at room temperature and pressure. Calculate the maximum volume of carbon dioxide gas produced in Experiment II. [4 marks] N06/P1 30
The following statements are related to the collision theory of a reaction. I. The total surface area of the reactant particles increases. II. The kinetic energy of the reactant particles increases. III. The frequency of the collision between the reactant particles increases. IV. The number of the reactant particles per unit volume increases. Which of the following combinations is true about the effect of the rise in temperature on the reactant particles? A I and II only C III and IV only B II and III only D I and IV only
43
If you want to cook 100 potatoes within a short time, which is the most suitable method? A Boil the potatoes in a pan B Boil the potatoes in a pressure cooker C Steam the potatoes in a steamer D Fry the potatoes in a wok
44
Which of the following reactants produces the highest rate of reaction with zinc powder? A 25 cm3 of sulphuric acid 0.1 mol dm-3. B 25 cm3 of ethanoic acid 0.1 mol dm-3. C 25 cm3 of nitric acid 0.1 mol dm-3. D 25 cm3 of hydrochloric acid 0.1 mol dm-3.
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RATE OF REACTION/F5/HST N06/P2/6 Diagram 6 shows two experiments to investigate one factor that influences the rate of a reaction.
(a) What is the factor that influences the rate of reaction in both experiments? [1 mark] (b) The reaction in the experiment is represented by the following equation: CaCO3(s) + 2HCl(aq)
CaCl2(aq) + CO2(g) + H2O(l)
(i) Among the products stated in the equation, which is the most suitable to be chosen to determine the rate of reaction? [1 mark]
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST (ii) State one reason for choosing the product in 6(b)(i) [1 mark]
(c) State two controlled variables in both experiments. 1. 2. [2 marks] (d) The results for both experiments are represented by graph 6. Quantity of product
Key: Experiment I Experiment II Time
x Based on Graph 6:
(i) Experiment II has a higher rate of reaction. How does the graph show this? [1 mark] (ii) What has happened to the reactants at time x? [1 mark]
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HST/RATE OF REACTION/SMKPB
Rate of reaction at a given time
Observable changes in chemical reaction
Rate of reaction
Factors affecting rate of reaction
Collision Theory to explain factors affecting rate of reaction
2. Rate of reaction (a) Rate of reaction is the …………………at which reactants react to form products in a chemical reaction. (b) Not all chemical reactions have the same rate of reaction, some reactions occur ……………… with rate of reaction that is …………….., and some reactions occur ……………… with rate of reaction that is ……………... (c) Examples of fast chemical reaction: Type of reaction
Example of chemical equation for the reaction
Neutralisation Double decomposition reaction Acid with active metals
1
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RATE OF REACTION/F5/HST Combustion of magnesium
(d) Examples of slow chemical reaction. Corrosion of iron Photosynthesis Reaction of hydrochloric acid with sodium thiosulphate solution. (e) Time taken for a fast chemical reaction is ……………and the time taken for slow chemical reaction of ……………. Hence the rate of reaction is …………………… to time taken for the reaction. Rate of reaction α ……………….. (f) The rate of reaction can be determined by measuring the time taken for an observable chemical change to occur. Rate of reaction = Observable chemical change Time taken (g) The observable chemical changes in a chemical reaction are (i) ……………………………………………………………………………. (ii) …………………………………………………………………………… (iii) …………………………………………………………………………. (iv) ………………………………………………………………………… (v) ………………………………………………………………………….. (h) Rate of reaction can be defined as the rate of change of volume of gas produced per unit time. Rate of reaction = Change in volume of gas produced Time taken =
……………… cm3 s-1
2
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RATE OF REACTION/F5/HST (i) Example: If 50.0 cm3 of hydrogen gas is collected in 20 seconds during a chemical reaction between magnesium and dilute hydrochloric acid . What is the rate of reaction? Rate of reaction =
cm3 s-1
=
(ii) Example: If 5.0 gram of magnesium ribbon reacts completely with dilute hydrochloric acid in 25s, what is the rate of reaction? Rate of reaction =
g s-1.
=
3. To determine the rate of reaction from graph. (a) For a chemical reaction, if the concentration of reactants or mass of reactant is plotted against the time, sketch the graph produced:
Mass of reactant /g
Concentration of reactant / mol dm-3
Time/s
Time/s
(b) For a chemical reaction, if the concentration of products or the volume of gas released is plotted against time, sketch the graph is produced.
Volume of gas/cm3 Vmax
Concentration of product / mol dm-3
Time/s
Time/s
3
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RATE OF REACTION/F5/HST (c) If the concentration of reactant is plotted against 1/time, sketch the graph produced. Concentration of reactant / mol dm-3
1/time , s-1 (d) In a chemical reaction involving release of a gas, it is easier to determine the rate of reaction by measuring the ……………………………….. at a certain time interval. (f) There are 2 methods to determine the rate of reaction, namely (i) average rate or overall rate of reaction Average rate of reaction = Total volume of gas released Time taken = V cm3 s-1 or cm3 min-1 t (ii) rate of reaction at a given time. To determine the rate of reaction at a given time t1 s on the graph at point M, the following steps are taken. - Draw a tangent at the point M on the graph. - Draw a right angle triangle using the tangent as hypotenuse. - Determine the gradient of the tangent. - Rate of reaction at t1 s = y/x cm3 s-1 Example: Rate of reaction at t1 =
Volume of gas/cm3
Rate of reaction at t2 =
M
Rate of reaction at t3 = t1
t2
t3 4
Time/s HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST Example: To determine the rate of reaction between zinc and dilute hydrochloric acid. Aim of experiment: To investigate………….. Apparatus:
Material:
Procedure: (diagram)
(i)
(ii)
(iii)
(iv)
(v)
(vi) (vii)
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RATE OF REACTION/F5/HST Result: Time/minute
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Burette 49.00 36.00 25.00 17.00 11.00 8.00 6.00 5.00 4.00 4.00 4.00 3 reading/cm Volume of 0.00 13.00 24.00 32.00 38.00 41.00 43.00 44.00 45.00 45.00 45.00 gas collected/cm3 Discussion: 1. Plot a graph of volume of gas collected against time of reaction. 2. From the graph, calculate the (i) overall average rate of reaction.
(ii) rate of the reaction in the first 3 minutes.
(iii) rate of reaction in the second minute
(iv) rate of reaction at (a) 1 minute
(b) 2 minute
(c) 3 minute
3. Compare the rate of reaction obtained in 2(iv). Explain your answer.
6
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RATE OF REACTION/F5/HST
4. Write a balance chemical equation of the reaction between zinc and hydrochloric acid.
5.What is the name of the gas released and suggest a test for the gas.
Conclusion:
4. Factors affecting rate of reaction Name the factors that affect the rate of reaction.. (A) (B) (C) (D) (E) (A) Effect of total surface area of reactant on the rate of reaction. (a) The smaller the size of particle of solid reactant the larger the surface area of reactant exposed, hence the higher is the rate of reaction. Give 3 examples for the above statement. (i) Cube sugar dissolves slower than that of fine sugar of the same mass in same amount of water. (ii) Minced meat cooks faster that solid piece of meat of the same mass. (iii) Powdered zinc reacts faster than granulated zinc of the same mass with hydrochloric acid of the same volume and concentration.
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RATE OF REACTION/F5/HST (b) Experiment to investigate the effect of total surface area of calcium carbonate on the rate of reaction Problem statement:
Hypothesis:
Variables: (i) manipulate variable: (ii) responding variable: (iii) fixed variable:
Materials: Apparatus: Procedure:
(i)
(ii)
(iii)
(iv)
(v)
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RATE OF REACTION/F5/HST (vi)
(vii) (viii)
Results: (i) Experiment I using large marble chips: Time/ minute 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 49.50 45.20 42.0 39.00 36.50 34.00 31.80 29.50 27.80 26.20 24.50 23.50 Burette reading/cm3 Volume of gas collected/cm3
(ii) Experiment II using crushed marble chips: Time/ minute 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Burette 49.00 39.00 33.00 28.50 25.00 21.50 19.00 16.70 14.70 13.00 11.50 10.00 reading/cm3 Volume of gas collected/cm3 1. Plot the graph of total volume of gas collected against time taken for the reaction for experiment I and II on the same axes.
2. Based on the graph , calculate (a) the overall rate of rate of reaction for the first 5 minutes of the reaction between hydrochloric acid and (i) large marble chips:
(ii) crushed marble chips
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RATE OF REACTION/F5/HST
(b) The rate of reaction at 2.5 minute for (i) large marble chips:
(ii) crushed marble chips:
3. Based on your answers in 2(a) and 2(b) , how does the rate of reaction differ?
4. What is the factor that causes the difference in rate of reaction?
5. Write a balanced chemical equation for the reaction between calcium carbonate and hydrochloric acid.
6. Explain why does the rate of reaction decreases with increase of time.
7. If both reactions are allowed to react until completion, is the total volume of gas collected the same? Explain your answer.
8. If the marble chips used in the experiment is in excess, what is the maximum total volume of gas collected? [ 1 mole of gas at room temperature occupies a volume of 24dm3]
Conclusion:
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RATE OF REACTION/F5/HST 5. The effect of concentration of reactant on the rate of reaction. (a)When concentration of reactant increases, the rate of reaction increases. Give one example for the above statement.
(b) Experiment to investigate the effect of concentration of sodium thiosulphate with hydrochloric acid on the rate of reaction Problem statement: Hypothesis: Variables: (i) manipulated variable: (ii) responding variable: (iii) fixed variable: Procedure: (diagram)
(i)
(ii)
(iii)
(iv)
(v)
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RATE OF REACTION/F5/HST (vi)
(vii) Results: Experiment
1
2
3
4
5
Volume of 0.2moldm-3 sodium thiosulphate solution, V1 cm3 Volume of distilled water added/cm3 Volume of 1.0mol hydrochloric acid added/cm3 Total volume of reactant /cm3
45
40
35
30
25
0.0
5.0
10.0
15.0
20.0
5.0
5.0
5.0
5.0
5.0
50.0
50.0
50.0
50.0
50.0
16
20
27
41
83
Concentration of sodium thiosulphate solution used/moldm-3 Time taken/s 1/time , s-1
1. Plot the graph of concentration of sodium thiosulphate solution used against time taken for the reaction. 2. Plot the graph of concentration of thiosuphate solution used against 1/time. 3. What does the value of 1/time represents?
4. Based on your graph, state the relationship between (i) the concentration of sodium thiosulphate and the time taken for the reaction.
(ii) the rate of reaction and the concentration of sodium thiosulphate solution.
5. What is colour of the precipitate formed and name the precipitate.
6. What is the time taken for the mark ‘X” to disappear if the concentration of sodium thiosulphate solution used is 0.10 mol dm-3?
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RATE OF REACTION/F5/HST 7. Write a balanced chemical equation for the reaction in this experiment.
8. Write an ionic equation for the reaction in this experiment.
9. If dilute sulphuric acid of the same concentration is used to replace hydrochloric acid in this experiment, predict the rate of reaction and explain your answer.
Conclusion:
6. The effect of temperature on rate of reaction. (a) Increase in temperature of reaction, increases the rate of reaction. Give two examples for the above statement. (i) (ii)
(b) Experiment to investigate the effect of temperate on the rate of reaction between thiosulphate solution and dilute hydrochloric acid. Problem statement: Hypothesis: Variables: (i) manipulate variable: (ii) responding variable: (iii) fixed variable:
13
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RATE OF REACTION/F5/HST Procedure: (diagram)
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
Results: Experiment
1
2
3
4
5
Temperature/oC
30
35
40
45
50
Time taken/s
55
48
42
37
33
1/time, s-1
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RATE OF REACTION/F5/HST
1. Plot the graph of (i) temperature against time and (ii) temperature against 1/time. 2. Based on your graph, what is the relationship between rate of reaction with temperature.
3. Write a balance chemical equation for the reaction of this experiment.
4. why is the volume of sodium thiosulphate solution and hydrochloric acid fixed for each experiment? 5. What is the time taken for the mark ‘X’ to disappear when the temperature is 60oC?
Conclusion:
7. Effect of catalyst on the rate of reaction. (a) A catalyst is a substance which added to a chemical reaction can ………. the rate of reaction and itself remains ………………………………. at the end of the reaction. (b) A catalyst does not ………………………………….. in a chemical reaction. It only ……………………….. the rate of reaction if it is a positive catalyst, and …………………………the rate of reaction if it is a negative catalyst.
(c) Example: When copper(II) sulphate solution is added into a reaction between zinc and hydrochloric acid, the rate of reaction increases but the final quantity of hydrogen produced is the same the reaction of zinc with hydrochloric acid without copper(II) sulphate solution. Sketch the graphs of volume of hydrogen gas against time for comparison of reaction of zinc and hydrochloric acid with catalyst and without catalyst .
15
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RATE OF REACTION/F5/HST
Volume of hydrogen released/cm3
Time/s (d) Experiment to investigate the effect of catalyst on the rate of reaction for decomposition of hydrogen peroxide solution. Problem statement: Hypothesis: Variables: (i) manipulated variable: (ii) responding variable: (iii) fixed variable: Apparatus: Materials:
Procedure:
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST (i)
(ii)
(iii)
(iv)
(v)
Observation: Test tube A
Observation
B
Discussion: 1. What is the effect of manganese(IV) oxide on the decomposition of hydrogen peroxide solution?
2. What is the function of manganese(IV) oxide in this experiment?
3. Write a balanced chemical equation for the reaction in this experiment.
4. Will the mass of manganese(IV) oxide change at the end of the reaction in test tube B?
Conclusion:
(e) Experiment to investigate the effect of the amount of catalyst on the rate of reaction for decomposition of hydrogen peroxide solution. Problem statement:
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RATE OF REACTION/F5/HST
Hypothesis: Variables: (i) manipulated variable: (ii) responding variable: (iii) fixed variable: Apparatus: Materials: Procedure:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
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RATE OF REACTION/F5/HST
Results: (a) Experiment 1, using 0.2g of manganese(IV) oxide Time/s
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Burette reading/cm3 Volume of gas cm3
49.70
48.70
47.10
45.70
44.20
43.20
42.00
41.10
40.20
39.50
39.00
38.40
38.00
(b) Experiment II, using 0.6g of manganese(IV) oxide Time/s
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Burette reading/cm3 Volume of gas cm3
49.00
43.60
40.50
38.00
36.00
34.50
33.00
31.70
30.50
29.70
29.00
28.20
28.00
1. Plot the graph of total volume of gas against time for experiment I and experiment II on the same axes. 2. Based on your graph, calculate the rate of reaction at 120 seconds for each of the reaction . (i) Experiment I:
(ii) Experiment II:
3. How did the rates of reaction in experiment I and II differ?
4. Which experiment shows the higher rate of decomposition of hydrogen peroxide?
5. If both experiments are allowed to proceed until completion, is the total volume of gas collected in both experiments the same? Explain your answer.
Conclusion:
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RATE OF REACTION/F5/HST (f) Application of catalyst in industry. Most catalysts are transition elements or compounds of transition elements. Catalyst is specific in its action and only a small amount is required in a chemical reaction. Industrial process Haber Process
Product produced
Equation
Catalyst
Contact Process Ostwald Process Hydrogenation of vegetable oil Cracking of petroleum (g) Other examples: Table shows the reacting conditions for the following experiments. For the following experiments , sketch graph of (i) volume of gas against time Experiment 1 Experiment 2
5cm3 “5 volume of H2O2” + 45cm3 water + MnO2 3cm3 “5 volume of H2O2” + 47cm3 water + MnO2
Volume of oxygen/cm3
Time/s
(ii) volume of gas against time Experiment 1 Experiment 2
5cm3 “5 volume of H2O2” + 45cm3 water at 40oC 5cm3 “5 volume of H2O2” + 45cm3 water at room temperature
Volume of oxygen/cm3
20
Time/s HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST
(iii) Volume of hydrogen against time Experiment 1 Experiment 2 Experiment 3
4 g of excess zinc powder + 100 cm3 of sulphuric acid 0.5 mol dm-3 + 5cm3 copper(II) sulphate solution at room temperature 4 g of excess zinc powder + 100 cm3 of sulphuric acid 0.5 mol dm-3 room temperature 4 g of excess zinc powder + 50 cm3 of sulphuric acid 0.5 mol dm-3 at room temperature
8. Collision Theory (a) For a chemical reaction to occur, the particles of the reactants must collide with each other. However, not all collisions result in a chemical reaction to form products. (b) According to collision theory, only those collisions which (i) with ……………………….. orientation and (ii) posses ………………………amount of energy called activation energy , Ea will result in chemical reaction. (c) Collisions of particles of reactants that result in chemical reaction is known as …………………………. (d) Activation energy , Ea, is defined as the minimum amount of energy of collision that is required for particles of reactant to react or to produce effective collision. (i) Exothermic reaction
(ii) Endothermic reaction
Energy
Energy
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RATE OF REACTION/F5/HST
(e) Using Collision Theory to explain the factors affecting the rate of reaction. 1. The effect of increase in total surface area of reactant.
Using solid reactant that is smaller in size. When size of solid reactant is smaller, the total surface area increases The frequency of collision of particles of reactant increases The frequency of effective collision increases The rate of reaction increases.
2. The effect of increase in concentration of reactant. Increasing the concentration of reactant will increase the number of particles of reactant per unit volume. The frequency of collision of particles of reactant increases. The frequency of effective collision increases. The rate of reaction increases. 3. The effect of increase in temperature of reaction o By increasing the temperature of the reactant o Increased in temperature, increases the kinetic energy of the reactant particles. o The frequency of colliding particles possesses energy higher than the activation energy increases. o The frequency of effective collision increases o The rate of reaction increases. 4. The effect of catalyst on the rate of reaction.
Addition of a positive catalyst to a chemical reaction provides an alternative path of reaction that requires a lower activation energy. The frequency of effective collision increases The rate of reaction increases. Energy profile diagrams to show the effect of catalyst on rate of reaction. Energy
Energy
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RATE OF REACTION/F5/HST
9. The effect of pressure on rate of reaction. (i) The effect of pressure only affects the rate of chemical reaction when the reactants are in the gaseous state. Eg: N2(g) +
3H2(g)
2NH3(g)
(ii) Increased in pressure by increasing the concentration of gas or by reducing the volume of the vessel, o the number of particles per unit volume increases. o The frequency of collision among the reactant particles increases o The frequency of effective collision increases o Hence the rate of reaction increases.
Reinforce exercise; N03/P1 18.
Which of the following can be used to determine the rate of the reaction? I Release of gas per unit time. II Change of colour intensity per unit time. III Formation of precipitate per unit time. IV Increase in the mass of reactant per unit time. A. I and II B. III and IV C. I, II and III D. II, III and IV
35.
An equation of a reaction is as follows 2Fe2+ Green
+
2Fe3+ + Brown
Cl2
2Cl
In the reaction represented by the equation above, it was found that the change of colour from green to brown was faster when the reactant mixture was heated. This was due to the… I. decrease in the activation energy. II. increase in the frequency of effective collision . III. increase in the kinetic energy of ferrum(II) ions and chlorine molecules. IV. increase in the frequency of collision between ferrum(II) ions and chlorine molecules. A. I and II only B. II and III only C. I, III and IV only D. II, III and IV only
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RATE OF REACTION/F5/HST 44.
Table 4 shows the total volume of gas collected at regular intervals in a reaction. Time / s Volume of gas/ cm3
0 0
30 2.0
60 3.7
90 5.2
120 6.4
150 7.3
180 8.6
210 8.6
What is the average rate of reaction in the second minute ? A. B. C. D. 48.
0.040 0.045 0.053 0.062
cm3s-1 cm3s-1 cm3s-1 cm3s-1
The equation below represents the decomposition of hydrogen peroxide solution. 2H2O2(aq)
2H2O(l)
+ O2(g)
Which of the following are produced when 1 mole of hydrogen peroxide is decomposed completely ? [1 mole of gas occupies 24 dm3 at room condition; Avogadro’s constant : 6 X 1023 mol-1] I II III IV A B C D
2 moles of water 12 dm3 of oxygen gas 3 X 1023 of oxygen molecules 1.2 X 1024 of water molecules I and III only I and IV only II and III only II and IV only
N03/2B 1. The rate of reaction is affected by several factors. One o the factors is the size of particles. One kilogramme of meat, cut into big pieces, takes a longer time to cook compared to one kilogram of meat cut into smaller pieces. (a) Explain the above statement based on the size of the particles. [2 marks] (b) A student carried out three experiments to investigate the effects of the factors influencing the rate of reaction. Table 1 shows the results of the experiments.
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST
(i) Write the chemical equation for the reaction between magnesium and hydrochloric acid. Calculate the maximum volume of hydrogen gas produced. [ Relative atomic mass: mg,24; molar mass volume: 24 dm3 mol-1 at room condition] [4 marks] (ii) Sketch the graphs for the volume of hydrogen gas against time for Experiment I, II and III on the same axes. [3 marks] (iii) Calculate the average rate of reaction for Experriment I, II and III in cm3 s-1. [3 marks] (iv) Compare the rates of reaction between Experiment I and Experiment II, and between Experiment II and Experiment III. With reference to collision theory, explain why there are differences in the rates of reaction in the experiments. [8 marks] N03/P3/1 An experiment was conducted to find out the effects of temperature on the rate of reaction. 50cm3 of sodium thiosulphate solution 0.05 mol dm-3 at 30oC was put into a 250cm3 conical flask. Then the conical flask was placed on an ‘X’ sign on a piece of white paper. 10cm3 of hydrochloric acid 1.0 mol dm-3 was added to the sodium thiosulphate solution and shaken. At the same time, the stop watch was started. The stop watch was stopped as soon as the ‘X’ sign was no longer visible.
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST The same steps of the experiment were repeated for sodium thiosulphate solution which was heated to 35oC, 40oC, 45oC and 50oC. Figure 1 shows the readings of the stop watch for each of the reaction at different temperatures.
(a) Record the time for each reaction in the spaces provided in Figure 1. (b) Construct a table and record temperature, time and 1/time for this experiment.
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST (c) (i) Draw a graph of temperature against 1/time on the graph paper. (ii) Based on the graph in c(i) , state the relationship between the rate of reaction and temperature.
(d) Predict the time taken as soon as the sign ‘X’ to be not longer visible if this experiment is repeated at 55oC.
(e)(i) State the variables involved in this experiment. Manipulated variable: Responding variable: Constant variable: (ii) State how you would manipulate one variable while keeping the other variables constant. (f) State the hypothesis for this experiment.
(g) From the above experiment, the student found a relationship between temperature and rate of reaction. The same situation can be applied in our daily lives, for example, keeping food that is easily spoiled in the refrigerator. Using your knowledge of chemistry, state the relationship between temperature and the rate at which food turns bad.
N04/P1 33
An experiment is carried out to study the rate of reaction between marble and hydrochloric acid to produce carbon dioxide gas. Experiment Substances I Excess marble and 50.0 cm3 of 2 mol dm-3 hydrochloric acid II
Excess marble and 100.0cm3 of 1 mol dm-3 hydrochloric acid
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RATE OF REACTION/F5/HST A Volume of CO2/cm3
C Volume of CO2/cm3
I II
I II
Time/s B Volume of CO2/cm3
Time/s D Volume of CO2/cm3
II
I II
I
Time/s
Time/s 45
The reaction between hydrochloric acid and zinc produces hydrogen gas. The reaction is complete in 50 seconds and the maximum volume of gas produced is 25 cm3. What is the average rate of the reaction? A. 0.5 cm3 s-1 B. 1.0 cm3 s-1
C. 2.0 cm3 s-1 D. 4.0 cm3 s-1
N05/P1 12
The diagram shows the energy profile of a reaction. Ea is the activation energy for this reaction. Energy Ea Reactant
Ea’ Products Reaction path
What will change the activation energy from Ea to Ea’? A. Temperature C. Concentration B. Catalyst D. Total surface area
28
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RATE OF REACTION/F5/HST 13
Which of the following explains the meaning of effective collision? A. B. C. D.
45
The collision where its energy is less than the activation energy. The collision that has a low energy The collision which takes place before a reaction The collision that causes a reaction
The diagram shows the set up of the apparatus for an experiment to determine the rate of reaction between sodium thiosulphate and sulphuric acid.
Which of the following combination of conditions take the shortest time for the mark ‘X’ to diappear from sight? Sulphuric acid Sodium thiosulphate Temperature o 3 3 Volume/cm Concentration/ Volume/cm Concentration/ / C mol dm-3 mol dm-3 A 10 1.0 50 0.5 30 B 10 1.0 50 0.5 40 C 10 0.5 50 0.5 30 D 20 0.5 40 0.5 40 46
In an experiment, the decomposition of 25cm3 of 0.1 mol dm-3 hydrogen peroxide solution produces oxygen gas. Volume of oxygen gas/cm3
P Q Time/s
If the experiment is repeated using another solution, which solution will produce curve Q? A. 25 cm3 of 0.15 mol dm-3 hydrogen peroxide B. 20 cm3 of 0.15 mol dm-3 hydrogen peroxide C. 15 cm3 of 0.15 mol dm-3 hydrogen peroxide D. 10 cm3 of 0.25 mol dm-3 hydrogen peroxide
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST N05/P2/7 (a) Food stored in a refrigerator last longer than food stored in a kitchen cabinet. Explain why. [4 marks] (b) A group of pupils carried out three experiments to investigate the factors affecting the rate of a reaction. Table 7 shows information about the reactants and the temperature used in each experiment. Experiment I II III
Reactants Excess calcium carbonate chips and 30 cm3 of 0.5 mod dm-3 hydrochloric acid Excess calcium carbonate chips and 30 cm3 of 0.5 mod dm-3 hydrochloric acid Excess calcium carbonate powder and 30 cm3 of 0.5 mod dm-3 hydrochloric acid
Temperature /oC 30 40 40
Table 7. Graph 7 shows the results of these experiments.
(i) Calculate the average rate of reaction for experiment I.
[2 marks]
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RATE OF REACTION/F5/HST (ii) Based on Table 7 and graph 7, compare the rate of reaction between: • Experiment I and Experiment II • Experiment II and Experiment III In each case explain the difference in rate of reaction with reference to the collision theory. [ 10 marks] (iii) The chemical equation below shows the reaction between calcium carbonate and hydrochloric acid. CaCO3 + 2HCl CaCl2 + CO2 + H2O Given that the relative atomic mass of C=12, O=16, Ca=40 and the molar volume of any gas is 24 cm3 mol-1 at room temperature and pressure. Calculate the maximum volume of carbon dioxide gas produced in Experiment II. [4 marks] N06/P1 30
The following statements are related to the collision theory of a reaction. I. The total surface area of the reactant particles increases. II. The kinetic energy of the reactant particles increases. III. The frequency of the collision between the reactant particles increases. IV. The number of the reactant particles per unit volume increases. Which of the following combinations is true about the effect of the rise in temperature on the reactant particles? A I and II only C III and IV only B II and III only D I and IV only
43
If you want to cook 100 potatoes within a short time, which is the most suitable method? A Boil the potatoes in a pan B Boil the potatoes in a pressure cooker C Steam the potatoes in a steamer D Fry the potatoes in a wok
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Which of the following reactants produces the highest rate of reaction with zinc powder? A 25 cm3 of sulphuric acid 0.1 mol dm-3. B 25 cm3 of ethanoic acid 0.1 mol dm-3. C 25 cm3 of nitric acid 0.1 mol dm-3. D 25 cm3 of hydrochloric acid 0.1 mol dm-3.
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST N06/P2/6 Diagram 6 shows two experiments to investigate one factor that influences the rate of a reaction.
(a) What is the factor that influences the rate of reaction in both experiments? [1 mark] (b) The reaction in the experiment is represented by the following equation: CaCO3(s) + 2HCl(aq)
CaCl2(aq) + CO2(g) + H2O(l)
(i) Among the products stated in the equation, which is the most suitable to be chosen to determine the rate of reaction? [1 mark]
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HST/RATE OF REACTION/SMKPB
RATE OF REACTION/F5/HST (ii) State one reason for choosing the product in 6(b)(i) [1 mark]
(c) State two controlled variables in both experiments. 1. 2. [2 marks] (d) The results for both experiments are represented by graph 6. Quantity of product
Key: Experiment I Experiment II Time
x Based on Graph 6:
(i) Experiment II has a higher rate of reaction. How does the graph show this? [1 mark] (ii) What has happened to the reactants at time x? [1 mark]
33
HST/RATE OF REACTION/SMKPB
