Rate of Reaction (AQA GCSE Chemistry: Combined Science)

Exam Questions

2 hours19 questions
1a1 mark

A student investigated how the rate of reaction is affected by concentration in the reaction between calcium carbonate and hydrochloric acid.

The method they used is shown below.

  1. Pour 25 cm3 of hydrochloric acid into a conical flask
  2. Add 5.0 g of calcium carbonate powder to the conical flask
  3. Attach a gas syringe to the conical flask
  4. Measure the volume of gas produced every 30 seconds for 150 seconds
  5. Repeat steps 1 to 4 two more times
  6. Repeat steps 1 to 5 with a higher concentration of hydrochloric acid

What piece of equipment would be most suitable to measure the volume of hydrochloric acid?

Tick (✓) one box.

Beaker  
Measuring cylinder  
Conical flask  
Test tube  
1b3 marks

Draw lines from each variable to identify two control variables and one dependent variable in this investigation.

rates-variables

1c1 mark

Table 1 shows the results collected in the investigation for a low concentration of hydrochloric acid.

Table 1

Volume of gas collected in cm3
Time in seconds Test 1 Test 2 Test 3 Mean
0 0 0 0 0
30 49 47 48 48
60 78 39 80 79
90 93 91 92 92
120 98 97 98 98
150 100 100 100 100


One result was anomalous.

Identify which result by stating the time in seconds and the test where this occurred.

Time in seconds: _______________________________

Test: __________________________________

1d3 marks

Plot the results from Table 1 onto Figure 1.

Use the mean volume of gas collected in cm3.

Draw a line of best fit.

Figure 1

aqa-gcse-6-1e-tq-1d-rate-graph-caco3--hcl-blank

1e1 mark

The student repeated the experiment for a higher concentration of hydrochloric acid.

What would happen to the rate of reaction?

Tick (✓) one box.

Remain the same  
Become quicker  
Become slower  

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2a
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2 marks

A student added 1.0 g of magnesium powder to 25 cm3 of hydrochloric acid and monitored the volume of gas collected over time to investigate the rate of reaction.

The results obtained are shown in Figure 1.

Figure 1

aqa-gcse-6-1e-tq2a-rate-graph-magnesium-hcl

Calculate the mean rate of reaction between 0 and 40 seconds.

Use Figure 1 and the equation below.

mean space rate space equals space fraction numerator mean space volume space of space gas space collected over denominator time space taken space to space collect end fraction


Mean rate of reaction =                                                                cm3 / s

2b3 marks

Complete the sentences using Figure 1.

Circle one answer from each box.

  The reaction was quickest between

0 to 20 seconds.

40 to 60 seconds.

80 to 100 seconds.

  The reaction stopped after

40 seconds.

80 seconds.

100 seconds.

  The total amount of gas collected was

92 cm3.

94 cm3.

96 cm3.

2c1 mark

The student repeated the experiment but used 1.0 g of magnesium ribbon instead of magnesium powder and plotted their results.

How does this graph differ from the graph in Figure 1 between 0 and 40 seconds?

Tick (✓) one box.

There is no difference  
Gradient of the curve with magnesium ribbon is steeper  
Gradient of the curve with magnesium ribbon is less steep  
2d1 mark

What would happen to the total volume of gas collected?

Tick (✓) one box.

Remains the same  
Increases  
Decreases  

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3a2 marks

The rate of reaction can be affected by the concentration of reactants in solution and the temperature at which the reaction is carried out.

Give two more factors that affect the rate of chemical reaction. 

3b2 marks

Complete the following sentences using words from the box below.

increases decreases remains the same

As the concentration of a reactant increases, the rate of reaction ____________________.

As the temperature of the reaction ____________________, the rate of the reaction decreases.

3c1 mark

A student reacted calcium carbonate with hydrochloric acid.

Name the gas produced by this reaction. 

3d3 marks

Figure 1 shows how the volume of gas produced changed during the reaction in part (c).

On the same axes, sketch a curve to show how the volume of gas produced would change over time if a higher concentration of gas is used.

The hydrochloric acid is in excess.

Figure 1

aqa-gcse-6-1e-tq3d-graph-of-hcl-and-caco3

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4a2 marks

A student investigated the effect of temperature on the rate of reaction.

Figure 1 shows the equipment they used.

Figure 1

c3oYktGM_disappearing-cross-experiment

The student added dilute hydrochloric acid to the sodium thiosulfate solution.

A cloudy solution was produced.

The student timed how long it took for the cross to disappear.

This was repeated at different temperatures.

Complete the balanced symbol equation for the reaction.

Na2S2O3 (aq) + ___ HCl (aq) → ___ NaCl (aq) + H2O (l) + SO2 (g) + S (s)

4b1 mark

The reaction mixture turned cloudy.

What is produced in the reaction that caused the mixture to turn cloudy?

Use the equation in part (a). 

4c
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3 marks

At 30 oC, 0.46 g of sulfur was produced in 58 seconds.

Use the equation below to calculate the mean rate for reaction at 30 oC.

Mean space rate space of space reaction space equals space fraction numerator mass space of space sulfur space produced over denominator time space taken end fraction

Give your answer to 2 significant figures.

Mean rate of reaction: ____________________ g / s

4d3 marks

The student found that as the temperature of hydrochloric acid increased, the time taken for the cross to disappear decreased.

Complete the sentences using words from the box below.

increases more slower
faster less decreases

The rate of reaction ____________________ as the temperature increases.

This is because the particles are moving ____________________ and the particles collide with ____________________  energy.

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5a1 mark

Hydrogen peroxide decomposes slowly into water and oxygen.

Complete the word equation for this reaction. 

____________________   →   ____________________   +   ____________________

5b2 marks

The reaction in part (a) can be sped up by a catalyst.

Complete the sentence below.

A catalyst provides an alternative ____________________ that has a lower ____________________ energy.

5c3 marks

The reaction profile for the uncatalysed decomposition of hydrogen peroxide is shown in Figure 1.

Figure 1

aqa-gcse-6-1e-tq5c-catalysed-reaction-profile

Draw one line from each label to what the label represents on the reaction profile.

reaction-profile-catalyst-labels

5d1 mark

Circle the correct words to complete the sentence.

  By the end of the reaction, the mass of the catalyst is

lower.

higher.

the same.

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1a1 mark

This question is based on the chemistry of methanol, CH3OH.

Digestive processes in the body break down methanol.

What is the catalyst in this process?

Tick one box.

Nucleotide  
Ester  
Enzyme  
Amino acid  
1b3 marks

Methanol is produced industrially by reacting carbon monoxide with hydrogen.

The equation for the reaction is:

CO (g) + 2H2 (g) ⇌ CH3OH (g)

The reaction is carried out at a pressure of 100 atmospheres. 

This pressure gives a higher yield and a faster rate of reaction.

Explain why the rate of reaction is faster at higher pressures.

1c4 marks

A catalyst is used in the reaction. 

Explain how a catalyst increases the rate of a reaction.

1d2 marks

Name two factors other than concentration and the use of a catalyst that can speed up the rate of a reaction.

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2
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1 mark

The rate of a reaction was monitored by recording the volume of gas produced every 5 seconds.

TIUbhf1t_q1

What is the mean rate of reaction in the first 10 seconds of the reaction, in cm3/s?

  • 2.9

  • 3.0

  • 3.5

  • 2.5

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3
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1 mark

Hydrogen peroxide, H2O2, quickly decomposes to produce water and oxygen when a catalyst is added to the solution:

2H2O2 (aq) → 2H2O (l)  + O2 (g)

The volume of gas produced was measured and is shown in the graph below:

TIUbhf1t_q1

Which statement is not true for this reaction?

  • The reaction finishes after 30 seconds

  • The mean rate of reaction in the first 5 seconds is 2.5 cm3/s

  • The final volume of gas produced is 60 cm3

  • The concentration of the hydrogen peroxide decreases during the reaction

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4a1 mark

A student was investigating the rate of reaction between dilute hydrochloric acid and an excess of calcium carbonate. 

calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide

They measured the volume of gas every minute and drew a graph of their data shown in Figure 1. 

Figure 1

aqa-gcse-6-1m-tq4a-rates-graph-carbon-dioxide-against-time

What is the limiting reagent in this reaction?

4b1 mark

After how many minutes did the reaction finish?

 

4c3 marks

Use the graph to explain what happens to the rate of reaction from 0 - 8 minutes.

4d2 marks

The student carried out the experiment at a higher temperature, but kept all other variables the same.

Draw a line on the curve you would expect to see for this set of results. 

4e2 marks

Another student investigated the effect of increasing the concentration of hydrochloric acid on the rate of reaction.

Explain why increasing concentration increases the rate of reaction.

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5
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1 mark

Magnesium metal reacts with an excess of hydrochloric acid solution to form magnesium chloride and hydrogen:

Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

Which of the following will not increase the rate of this reaction?

  • Increase the temperature of the acid

  • Increase the surface area to volume ratio of the pieces of magnesium

  • Increase the concentration of the hydrochloric acid

  • Increase the volume of hydrochloric acid solution used

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61 mark

Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, water and carbon dioxide:

CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g)

Which statement is not true if the temperature of the reaction decreases?

  • The frequency of the collisions between particles decreases

  • The collisions are less energetic

  • The activation energy increases

  • There are fewer particles with the minimum energy to react

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71 mark

Catalysts are often used in chemical reactions.

Which letter represents two correct features of catalysts?

  Feature 1 Feature 2
A Lower activation energy for the reaction More products made in total
B Alternative pathway for the reaction is provided Not used up over the course of the reaction
C Makes industrial processes cheaper Metal catalysts are cheap to buy
D Reduce the overall energy change of the reaction Can be present in biological systems as enzymes

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    8a1 mark

    This question is about the rate of reaction between sodium thiosulfate solution and dilute hydrochloric acid:

    Na2S2O3 (aq) + 2HCl (aq)   2NaCl (aq) + S (s) + SO2 (g) + H2O (l)

    The reaction between these two substances produces a precipitate which makes the mixture turn cloudy. 

    A student timed how long it took until the cross could no longer be seen through the precipitate, shown in Figure 1.

    They then calculated the rate of reaction. 

    Figure 1 

    c3oYktGM_disappearing-cross-experiment

    Name the product that made the mixture go cloudy. 
    8b2 marks

    The student investigated the effect of temperature on the rate of the reaction in part (a).

    Their results are plotted in Figure 2. 

    Figure 2

     aqa-gcse-6-1m-tq2b-effect-of-temperature-on-rate-on-rate-of-reaction-resultsDescribe the trends shown in Figure 2.

    8c2 marks

    Suggest two control variables for the investigation that would ensure valid results are obtained.

    8d3 marks
    The student then investigated the effect of changing the concentration of sodium thiosulfate solutioin on the rate of reaction. 

    They came to the following conclusion:

    'As the concentration of sodium thiosulfate solution doubles, so does the rate of reaction.'


    Explain why the student is correct. 

    Answer the question in terms of particles. 

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    9a2 marks

    This question is about the effect of temperature on rate of reacton.

    A student was investigating the effect of temperature on the the rate of reaction between calcium carbonate and hydrochloric acid. 

    CaCO3 (s) + 2HCl (aq) CaCl2 (aq) + H2O (l) + CO2 (g)

    They used the apparatus in Figure 1 to record the volume of gas collected every five seconds and repeated their experiment at different temperatures. 

    Figure 1

    aqa-gcse-6-1m-tq3a-measuring-the-volume-of-a-gas-rp

     

    Their results are shown in Figure 2. 

    aqa-gcse-6-1m-tq3a-graph-to-show-effect-of-temp-on-rate-of-reaction

    What conclusion could the student make about the effect of temperature on the rate of the reaction? 

    Suggest one reason for your answer. 

    9b2 marks

    Identify the following variables in this investigation:

          Independent: _________________________________________

          Dependent: __________________________________________

    9c
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    2 marks

    The student had collected 40 cm3 after 20 seconds for the hydrochloric acid at 60 °C.

    Calculate the average rate of reaction from 0-20 seconds.

    Give units for your answer. 

    9d2 marks

    The student then investigated the effect of the surface area of the calcium carbonate on the rate of reaction.

    Explain, in terms of particles and collisions, the effect of surface area on rate of reaction. 

    9e1 mark

    Calcium carbonate can be used as a catalyst for the industrial production of biodiesel.

    How does a catalyst increase the rate of reaction? 

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    1a2 marks

    A student used the reaction between calcium carbonate and dilute hydrochloric acid to investigate how temperature affects the rate of reaction. 

    The student used the method as shown below.

    1. Heat the hydrochloric acid to a temperature of 30 °C in a conical flask.
    2. Add powdered calcium carbonate to the conical flask.
    3. Measure the loss in mass of the reaction flask and contents every 20 seconds for 140 seconds.
    4. Repeat steps 1 - 3 with hydrochloric acid heated to a temperature of 50 °C

    Explain why there is a loss in mass of the contents of the conical flask.

    1b3 marks

    Table 1 shows results the student obtained for hydrochloric acid at 30 °C.

    Table 1

    Time in seconds Loss of mass in grams
    0 0.00
    20 0.27
    40 0.49
    60 0.68
    80 0.83
    100 0.92
    120 0.97
    140 0.99


    Plot the data from the table above on
    Figure 1 and draw a line of best fit.

    Figure 1

    6-1-1b-question-graph

    1c
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    4 marks

    Figure 2 shows the results that the student obtained for hydrochloric acid at a temperature of 50 °C

    Figure 2

    loss-in-mass-vs-time-tangent

    Use the graph to determine the rate of reaction at 50 °C when the loss of mass is 0.90 g.

    You should show your working clearly in Figure 2.

    Give your answer correct to 2 significant figures.

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    2a2 marks

    This question is about rates of reaction.

    Hydrogen peroxide, H2O2 decomposes in the following reaction:

    2H2O2   →   2H2O   +   O2 

    The catalyst for this reaction is manganese dioxide. 

    A student investigated the effect of manganese dioxide particle size on the rate of reaction using the following method: 

    1. Measure 30 cm3 of 9.0 g/dm3 hydrogen peroxide solution into a conical flask 
    2. Add a spatula of coarse manganese dioxide powder to the conical flask 
    3. Measure the volume of gas made every minute for ten minutes. 
    4. Repeat steps 1-3 with some fine manganese dioxide lumps.

    This method did not give the student valid results.

    Which two improvements would need to be made that would produce valid results?

    Tick () two boxes. 

     Use 0.2 g/dm3 hydrogen peroxide solution  
     Use a mass of 1.5 g manganese dioxide each time   
     Measure the volume of gas produced every 30 seconds   
     Measure the mass of the conical flask and its contents   
     Place the conical flask in a water bath at a constant temperature   
    2b2 marks

    Describe and give the result of a test that could be done to identify the gas made during the decomposition of hydrogen peroxide.

    2c
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    3 marks

    Another student followed a method that produced valid results. 

    The results are shown in Figure 1. 

    Figure 1

    surface-area-rate-of-reaction-graph-

    Calculate the mean rate of reaction, in cm3/s, between 1 and 3 minutes for coarse manganese lumps. 

    Give your answer to 2 significant figures. 

    Use data from the graph. 

    2d2 marks

    The student repeated the experiment with coarse lumps of manganese dioxide. 

    They used the same volume of hydrogen peroxide but used a concentration of 3.0 g/dm3.

    Sketch on the graph the curve you would expect to see. 

    Assume that the reaction is complete after 9 minutes. 

    2e2 marks

    Explain why the rate of reaction is different when manganese dioxide is used as coarse lumps rather than fine powder. 

    You should answer in terms of collision theory. 

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    3a2 marks

    A solution of sodium thiosulfate reacts with dilute hydrochloric acid producing a cloudy solution as the reaction progresses.

    The reaction equation is:

    Na2S2O3 (aq) + 2HCl (aq) ⟶ 2NaCl (aq) + SO2 (g) + H2O (l) + S (s)

    Explain why the solution turns cloudy.

    3b6 marks

    The rate of reaction is affected by the concentration of the sodium thiosulfate solution. 

    Plan an investigation to show this relationship.

    Your plan should allow the collection of valid results.

    3c4 marks

    Another student investigated the effect of increasing temperature of the sodium thiosulfate solution on the rate of reaction.

    State what the effect would be and explain this effect in terms of particles and collisions.

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    4a4 marks

    A student investigated the rate of reaction between hydrochloric acid and marble chips using the apparatus shown in Figure 3. 

    Figure 3

    hcl-and-marble-chip-rate-exp

    Table 2 below shows the student’s results.

    Table 2

    Time in s Volume of gas in dm3
    0 0.000
    30 0.032
    60 0.048
    90 0.054
    120 0.067
    150 0.072
    180 0.078
    210 0.081
    240 0.083
    270 0.083


    On Figure 4:

    • Plot the results from the investigation on the grid.
    • Draw a line of best fit on the grid.

    Figure 4hcl-and-marble-chip-rate-graph

    4b2 marks

    Sketch a line on the grid in Figure 4 to show the results you would expect if the experiment was repeated but instead using 20 g of marble chips of smaller size.

    4c4 marks

    Explain, in terms of particles, how and why the rate of reaction changes during the reaction.

    4d
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    4 marks

    A different student investigated the rate of reaction for the same reaction by measuring the change in mass.

    Figure 5 shows the graph plotted from the results obtained in this investigation.

    Figure 5

    hcl-and-marble-chip-rate-mass-change

    Use Figure 5 to calculate the mean rate of the reaction up to the time when the reaction has gone to completion. 

    Give your answer correct to three significant figures.

    Mean rate of reaction = ______________________ g / s

    4e
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    4 marks

    Use Figure 5 to determine the rate of reaction at 150 seconds.

    Show your working clearly on Figure 5, giving your answer in standard form.

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    5a3 marks

    A student investigated the effect of the size of calcium carbonate lumps, CaCO3, on the rate of reaction with hydrochloric acid, HCl, using the following method:

    1. Put 50 cm3 of hydrochloric acid into a conical flask 
    2. Add 12 g of large calcium carbonate lumps into the flask
    3. Attach the gas syringe
    4. Measure the volume of gas produced every 30 seconds for 180 seconds 
    5. Repeat steps 1 - 4 using 12 g of small calcium carbonate lumps.
    6. The number of moles of gas for each volume was calculated.

    The results for large calcium carbonate lumps are shown below.

    Table 1. 

    Time in seconds Number of moles of gas 
    0 0.000
    30 0.0012
    60 0.0022
    90 0.0030
    120 0.0034
    150 0.0037
    180 0.0038


    The student had already plotted the data for small calcium carbonate lumps.

    Plot the data for the large calcium carbonate lumps and draw a line of best fit.

    moles-of-gas-against-time-rates-graph

    5b
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    4 marks

    Determine the mean rate of reaction for small calcium carbonate lumps between 35 seconds and 90 seconds. 

    Give the unit. 

    Use the graph in part (a).

    5c2 marks

    What conclusion can be made about the rate of reaction of small calcium carbonate lumps compared to large calcium carbonate lumps?

    Give one reason for your answer. 

    5d
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    2 marks

    Complete and balance the equation for the reaction between calcium carbonate and hydrochloric acid.

    __________   +   __________     →     CaCl2   +   __________   +    __________

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