Controlling reactions: OCR GCSE Chemistry A questions

Every OCR GCSE Chemistry A exam question on C5.2 Controlling reactions, 2018–2025, with its mark scheme and examiner’s report.

All 115 questions on Controlling reactions, as a list

June 2025, Paper 2 Foundation, Q6 (1 mark): Magnesium reacts with excess hydrochloric acid. What would increase the rate of the reaction? A Use a larger volume of hydrochloric acid. B Use a smaller beaker
June 2025, Paper 2 Foundation, Q7 (1 mark): A student measures the volume of gas made during a reaction. The graph shows their results. 60 50 40 Volume of 30 gas (cm3) 20 10 0 0 5 10 15 20 25 30 35 40 Tim
June 2025, Paper 2 Foundation, Q22(a) (2 marks): The student has made a mistake setting up the delivery tube in their experiment. Describe the mistake and the problem this will cause. Mistake Problem [2]
June 2025, Paper 2 Foundation, Q22(b)(i) (4 marks): Calculate the mean rate of reaction between 0 seconds and 60 seconds. Use the graph and the equation: volume of gas mean rate of reaction = time Give the units
June 2025, Paper 2 Foundation, Q22(b)(ii) (2 marks): The student repeats the experiment. They use the same mass of zinc, but in smaller pieces. Draw a line on the graph to show the student’s results. [2]
June 2025, Paper 2 Foundation, Q22(c) (2 marks): The reaction is faster when more concentrated hydrochloric acid is used. Explain why. [2]
June 2025, Paper 2 Foundation, Q23(b)(ii) (2 marks): Explain how the catalyst speeds up the reaction. [2]
June 2025, Paper 3 Higher, Q22(b)(i) (3 marks): Plot the results on the graph. Volume of carbon dioxide (cm3) Time (s) [3]
June 2025, Paper 3 Higher, Q22(b)(ii) (1 mark): Draw a curve of best fit. [1]
June 2025, Paper 3 Higher, Q22(b)(iii) (1 mark): Use the graph to estimate the volume of carbon dioxide that has been made after 30 seconds. Volume of carbon dioxide after 30 seconds = cm3 [1]
June 2025, Paper 3 Higher, Q22(c) (2 marks): The student repeats the experiment with a different concentration of nitric acid. Table 22.2 shows the results of both experiments. Table 22.2 Volume of carbon
June 2025, Paper 3 Higher, Q22(d) (1 mark): The diagram shows the apparatus the student uses. Volume of carbon dioxide collected Nitric acid and Measuring cylinder calcium carbonate Suggest another piece
June 2025, Paper 4 Higher, Q16(a) (2 marks): The student has made a mistake setting up the delivery tube in their experiment. Describe the mistake and the problem this will cause. Mistake Problem [2]
June 2025, Paper 4 Higher, Q16(b)(i) (4 marks): Calculate the mean rate of reaction between 0 seconds and 60 seconds. Use the graph and the equation: volume of gas mean rate of reaction = time Give the units
June 2025, Paper 4 Higher, Q16(b)(ii) (2 marks): The student repeats the experiment. They use the same mass of zinc, but in smaller pieces. Draw a line on the graph to show the student’s results. [2]
June 2025, Paper 4 Higher, Q16(c) (2 marks): The reaction is faster when more concentrated hydrochloric acid is used. Explain why. [2]
June 2025, Paper 4 Higher, Q17(b)(ii) (2 marks): Explain how the catalyst speeds up the reaction. [2]
June 2024, Paper 1 Foundation, Q19(a)(iii) (2 marks): One of the products is a gas. The student wants to collect the gas formed. Complete the diagram to show how they can collect and measure the volume of gas. Coni
June 2024, Paper 1 Foundation, Q19(b)(i) (1 mark): Plot the results from the table on the graph. Six points have already been plotted. [1] 6.0 5.0 4.0 Volume of gas 3.0 collected (cm3) 2.0 1.0 0.0 0 1 2 3 4 5 6
June 2024, Paper 1 Foundation, Q19(b)(ii) (1 mark): Draw a curve of best fit. [1]
June 2024, Paper 1 Foundation, Q19(b)(iii) (1 mark): Use the graph to estimate the volume of gas that has been collected at 7.5 minutes. Volume of gas collected = cm3 [1]
June 2024, Paper 1 Foundation, Q22(a)(i) (2 marks): Calculate the surface area to volume ratio of tablet C. Surface area to volume ratio = [2]
June 2024, Paper 1 Foundation, Q22(a)(ii) (1 mark): Complete the sentence to describe the relationship between the surface area to volume ratio and the time taken to dissolve. As the surface area to volume ratio
June 2024, Paper 1 Foundation, Q22(a)(iii) (2 marks): The scientist thinks that tablet D will dissolve slowest in 20cm3 of water. Explain why the scientist is incorrect. [2]
June 2024, Paper 2 Foundation, Q3 (1 mark): Which change would decrease the rate of a chemical reaction? A Adding a catalyst B Increasing the concentration of the solution C Increasing the size of the sol
June 2024, Paper 2 Foundation, Q10 (1 mark): Two chemicals react together over time to make a cloudy precipitate. What is the best method for determining the rate of reaction? A Measure the loss in mass us
June 2024, Paper 2 Foundation, Q20(a) (1 mark): Which other piece of equipment could the student use to measure the volume of carbon dioxide gas collected? Tick (✓) one box. Balance Beaker Gas syringe Pipette
June 2024, Paper 2 Foundation, Q20(b)(i) (3 marks): Plot the results from the table on the graph. [3]
June 2024, Paper 2 Foundation, Q20(b)(ii) (1 mark): Draw a curve of best fit. [1] Volume of carbon dioxide gas collected (cm3) 0 30 60 90 120 150 180 210 240 270 300 Time (s)
June 2024, Paper 2 Foundation, Q20(b)(iii) (1 mark): State the time when the reaction stops. Time = s [1]
June 2024, Paper 2 Foundation, Q20(b)(iv) (1 mark): The student observes that there are still some marble chips in the conical flask when the reaction stops. Explain why the reaction stops. [1]
June 2024, Paper 2 Foundation, Q20(c) (6 marks): A student investigates the reaction between marble chips and dilute hydrochloric acid. The diagram shows their experiment. Measuring cylinder Bubbles of carbon
June 2024, Paper 3 Higher, Q16(a)(i) (2 marks): Calculate the surface area to volume ratio of tablet C. Surface area to volume ratio = [2]
June 2024, Paper 3 Higher, Q16(a)(ii) (1 mark): Complete the sentence to describe the relationship between the surface area to volume ratio and the time taken to dissolve. As the surface area to volume ratio
June 2024, Paper 3 Higher, Q16(a)(iii) (2 marks): The scientist thinks that tablet D will dissolve slowest in 20cm3 of water. Explain why the scientist is incorrect. [2]
June 2024, Paper 4 Higher, Q8 (1 mark): What is the average rate of this reaction, in cm3 / s, during the first 5 seconds? 8 20 15 Volume of gas 10 (cm3) 5 0 0 5 10 15 20 25 Time (s) 0.5 cm3 / s A B 2
June 2024, Paper 4 Higher, Q13 (1 mark): Which statement about activation energy is correct? A Activation energy is increased by the addition of a catalyst. B Activation energy is lowered when the temp
June 2024, Paper 4 Higher, Q22(a)(i) (1 mark): Suggest another piece of equipment that could be used to measure the volume of carbon dioxide gas. [1]
June 2024, Paper 4 Higher, Q22(b) (3 marks): The student plots their results on a graph. 80 70 60 50 Volume of carbon dioxide 40 gas (cm3) 30 20 10 0 0 30 60 90 120 150 180 210 240 270 Time (s) Use the gra
June 2024, Paper 4 Higher, Q22(c)(i) (1 mark): What happens to the final volume of carbon dioxide when a catalyst is added? [1]
June 2024, Paper 4 Higher, Q22(c)(ii) (1 mark): How does the mass of the catalyst change during the experiment? [1]
June 2024, Paper 4 Higher, Q22(d) (6 marks): A student investigates the reaction between marble chips and dilute hydrochloric acid. The diagram shows their experiment. Measuring cylinder Bubbles of carbon
June 2023, Paper 2 Foundation, Q3 (1 mark): Why do marble chips react faster with warm hydrochloric acid than with cold hydrochloric acid? A The warm hydrochloric acid acts as a catalyst. B The warm hydro
June 2023, Paper 2 Foundation, Q16(a) (2 marks): The teacher says that the reaction is faster with magnesium powder than with magnesium ribbon. Use the results to explain why the teacher is correct. [2]
June 2023, Paper 2 Foundation, Q16(b)(i) (1 mark): Describe how the rate of reaction changes when the concentration of the hydrochloric acid increases. [1]
June 2023, Paper 2 Foundation, Q16(b)(ii) (2 marks): Explain your answer to (i) using ideas about particles. [2]
June 2023, Paper 2 Foundation, Q16(c) (1 mark): The teacher used 0.1 g of magnesium. 0.1 g of magnesium reacts with hydrochloric acid to make 0.008 g of hydrogen gas. A student suggests that the rate of react
June 2023, Paper 2 Foundation, Q17(c)(ii) (2 marks): Transition metals can be used as catalysts. What is meant by a catalyst? [2]
June 2023, Paper 4 Higher, Q7 (1 mark): The graph shows the volume of hydrogen gas made in an experiment. 70 60 50 Volume of 40 hydrogen 30 (cm3) 20 10 0 0 10 20 30 40 50 Time (s) What is the rate of
June 2023, Paper 4 Higher, Q18(b) (1 mark): The teacher says, ‘The reaction is faster the more concentrated the hydrochloric acid’. Use the results to explain why the teacher is correct. [1]
June 2023, Paper 4 Higher, Q18(c)(i) (1 mark): Use the graph to deduce the time for magnesium powder to react if 1.3 mol / dm3 hydrochloric acid is used. Time = s [1]
June 2023, Paper 4 Higher, Q18(c)(ii) (2 marks): The teacher repeats the experiment with 0.1 g of magnesium ribbon. Draw a line on the graph to show the results you would expect the teacher to get. [2]
June 2022, Paper 2 Foundation, Q3 (1 mark): What is an enzyme? A A catalyst found in living organisms. B A man-made catalyst. C A non-biological catalyst. D A substance which makes a catalyst more efficie
June 2022, Paper 2 Foundation, Q9 (1 mark): The rate of the reaction between marble chips and dilute hydrochloric acid is increased by breaking the marble chips into smaller pieces. Why does this increase
June 2022, Paper 2 Foundation, Q15 (1 mark): Dilute hydrochloric acid reacts with marble chips. Beaker Dilute hydrochloric acid Marble chips Balance Which statement about the reaction is correct? A The rea
June 2022, Paper 2 Foundation, Q22(b) (2 marks): The decomposition of hydrogen peroxide is very slow at room temperature. The reaction can be speeded up by adding a catalyst. • A student investigates the decom
June 2022, Paper 2 Foundation, Q22(c) (2 marks): The student thinks catalyst B is the better catalyst. Explain why the student is correct. Use data from the graph. [2]
June 2022, Paper 2 Foundation, Q22(d) (1 mark): The volume of oxygen made in each experiment is 18 cm3. Explain why it is the same value. [1]
June 2022, Paper 2 Foundation, Q22(e) (1 mark): The student repeats the experiment with 1.0 g of catalyst A instead of 0.5 g. What is the volume of oxygen gas made at the end of the experiment? Volume of oxyg
June 2022, Paper 2 Foundation, Q22(f) (3 marks): The student thinks the decomposition of hydrogen peroxide will be faster at 30 °C than at room temperature. Describe an experiment the student could do, and its
June 2022, Paper 4 Higher, Q2 (1 mark): Dilute hydrochloric acid reacts with marble chips. Beaker Dilute hydrochloric acid Marble chips Balance Which statement about the reaction is correct? A The rea
June 2022, Paper 4 Higher, Q5 (1 mark): A student investigates the reaction between sodium thiosulfate solution and dilute hydrochloric acid. They want to find out how temperature changes the rate of
June 2022, Paper 4 Higher, Q9 (1 mark): A student reacts dilute hydrochloric acid with marble chips. Carbon dioxide gas is made. • The student repeats the experiment with different size marble chips.
June 2022, Paper 4 Higher, Q16(b) (2 marks): The decomposition of hydrogen peroxide is very slow at room temperature. The reaction can be speeded up by adding a catalyst. • A student investigates the decom
June 2022, Paper 4 Higher, Q16(c) (2 marks): The student thinks catalyst B is the better catalyst. Explain why the student is correct. Use data from the graph. [2]
June 2022, Paper 4 Higher, Q16(d) (1 mark): The volume of oxygen made in each experiment is 18 cm3. Explain why it is the same value. [1]
June 2022, Paper 4 Higher, Q16(e) (1 mark): The student repeats the experiment with 1.0 g of catalyst A instead of 0.5 g. What is the volume of oxygen gas made at the end of the experiment? Volume of oxyg
June 2022, Paper 4 Higher, Q16(f) (3 marks): The student thinks the decomposition of hydrogen peroxide will be faster at 30 °C than at room temperature. Describe an experiment the student could do, and its
June 2022, Paper 4 Higher, Q18(g)(i) (2 marks): Explain how the use of a catalyst in the catalytic converter increases this rate of reaction. [2]
November 2021, Paper 1 Foundation, Q16(c)(ii) (2 marks): Table 16.2 shows the student’s results. Time (s) Decrease in mass (g) 0 0.00 20 0.10 40 0.20 80 0.40 100 0.50 120 0.60 Table 16.2 Plot the results from Table 16
November 2021, Paper 1 Foundation, Q16(c)(iii) (1 mark): Use your graph to estimate the decrease in mass at 60 seconds. Decrease in mass = g [1]
November 2021, Paper 1 Foundation, Q16(d)(i) (1 mark): The student notices that one of the results is anomalous. Put a ring around the anomalous result in Table 16.3. [1]
November 2021, Paper 1 Foundation, Q16(d)(ii) (3 marks): Calculate the mean decrease in mass of the experiments in Table 16.3. You should not include the anomalous result. Give your answer to 2 significant figures. Me
November 2021, Paper 2 Foundation, Q19(a) (1 mark): Suggest a piece of apparatus that the student could use to measure the volume of carbon dioxide more accurately. [1]
November 2021, Paper 2 Foundation, Q19(c)(i) (1 mark): What is the time taken to make 23 cm3 of carbon dioxide? Time = s [1]
November 2021, Paper 2 Foundation, Q19(c)(ii) (2 marks): The student repeats the experiment. The only difference is they use larger marble chips. Draw a line on the graph to show the results of this experiment. [2]
November 2021, Paper 2 Foundation, Q19(e) (3 marks): Another student investigates the effect of changing the temperature of the dilute hydrochloric acid on the rate of the reaction. The table shows the student’s r
November 2021, Paper 4 Higher, Q2 (1 mark): Lumps of zinc react with dilute sulfuric acid. What change would decrease the rate of this reaction? A Further diluting the sulfuric acid with water. B Using a
November 2021, Paper 4 Higher, Q11 (1 mark): A student investigates the reaction between magnesium and dilute hydrochloric acid. Which graph shows the effect of the concentration of the dilute hydrochloric
November 2021, Paper 4 Higher, Q18(a) (1 mark): State how the student can improve their experiment to measure the volume of carbon dioxide more accurately. [1]
November 2021, Paper 4 Higher, Q18(b)(i) (2 marks): The student has drawn a tangent to the line on the graph at 60 seconds. Use the tangent to calculate the rate of reaction at 60 seconds. Rate of reaction = cm3
November 2021, Paper 4 Higher, Q18(b)(ii) (2 marks): The student repeats the experiment. The only difference is they use smaller marble chips. Draw a line on the graph to show the results of this experiment. [2]
November 2021, Paper 4 Higher, Q18(d) (6 marks): A student investigates the rate of reaction between large marble chips and dilute hydrochloric acid. The student measures the volume of carbon dioxide gas given
November 2020, Paper 2 Foundation, Q11 (1 mark): A student investigates the reaction between zinc and dilute sulfuric acid. He measures the time taken to collect 50 cm3 of hydrogen gas. This time is 65 seconds
November 2020, Paper 2 Foundation, Q14 (1 mark): A student investigates the decomposition of hydrogen peroxide. 2H2O2(aq) 2H2O(l) + O2(g) 0.2 g of oxygen gas is produced in the reaction. The student uses 0.5 g
November 2020, Paper 2 Foundation, Q18(a) (4 marks): Another student also investigates the rate of reaction between dilute hydrochloric acid and magnesium carbonate. Fig. 18.2 shows diagrams of some of the apparat
November 2020, Paper 2 Foundation, Q18(b)(i) (3 marks): Plot a graph of the results on the grid. Draw a line of best fit. 140 120 100 Reaction time 80 (s) 60 40 20 0 0 10 20 30 40 50 60 Temperature (°C) [3]
November 2020, Paper 2 Foundation, Q18(b)(ii) (1 mark): What is the reaction time at 25 °C? Reaction time = s [1]
November 2020, Paper 2 Foundation, Q18(b)(iii) (1 mark): What happens to the rate of reaction as the temperature increases? [1]
November 2020, Paper 2 Foundation, Q18(b)(iv) (2 marks): Explain your answer to (b)(iii). Include ideas about collisions between particles in your answer. [2]
November 2020, Paper 4 Higher, Q1 (1 mark): A student investigates the decomposition of hydrogen peroxide. 2H2O2(aq) 2H2O(l) + O2(g) 0.2 g of oxygen gas is produced in the reaction. The student uses 0.5 g
November 2020, Paper 4 Higher, Q6 (1 mark): Enzymes are a type of catalyst. Which of the following catalysts is an example of an enzyme? A Amylase – a catalyst found in human saliva. B Iron – a catalyst u
November 2020, Paper 4 Higher, Q15 (1 mark): The rate of reaction of marble chips with dilute hydrochloric acid depends on the surface area of the marble chips. Which surface area of the marble chips gives
November 2020, Paper 4 Higher, Q19(a) (5 marks): Another student also investigates the rate of reaction between dilute hydrochloric acid and magnesium carbonate. He also wants to find out how the concentration
November 2020, Paper 4 Higher, Q19(b)(i) (4 marks): Plot a graph of the results on the grid. Draw a line of best fit. rate of reaction × 10–2 (s–1) Temperature (°C) [4]
November 2020, Paper 4 Higher, Q19(b)(ii) (1 mark): What happens to the rate of reaction as the temperature increases? [1]
November 2020, Paper 4 Higher, Q19(b)(iii) (3 marks): Explain your answer to (b)(ii). Use ideas about collisions between particles in your answer. [3]
June 2019, Paper 2 Foundation, Q4 (1 mark): The rate of a reaction can be changed by adding a catalyst to the reaction mixture. Which line of the table shows how the rate of reaction and the mass of the c
June 2019, Paper 2 Foundation, Q21(b) (6 marks): A student investigates the reaction between magnesium and dilute hydrochloric acid, HCl. The student adds magnesium ribbon to hydrochloric acid in a beaker, as
June 2019, Paper 2 Foundation, Q21(c) (3 marks): The student repeats experiment 1. This time he uses acid at a lower temperature. Explain, using the reacting particle model, what happens to the rate of reactio
June 2019, Paper 2 Foundation, Q21(d) (2 marks): During chemical reactions, reactants are used up and the rate of reaction decreases. Explain, in terms of particles, why the rate of reaction decreases. [2]
June 2019, Paper 4 Higher, Q8 (1 mark): A catalyst can be used to increase the rate of a reaction. Which graph shows the mass of the catalyst as the reaction takes place? Mass of catalyst A 00 Time Ma
June 2019, Paper 4 Higher, Q18(b)(i) (1 mark): What happens to the rate of the reaction when the temperature is increased? [1]
June 2019, Paper 4 Higher, Q19(b) (6 marks): A student investigates the reaction between magnesium and dilute hydrochloric acid, HCl. The student adds magnesium ribbon to hydrochloric acid in a beaker, as
June 2019, Paper 4 Higher, Q19(c) (3 marks): The student repeats experiment 1. This time he uses acid at a higher temperature. Explain, using the reacting particle model, what happens to the rate of reacti
June 2019, Paper 4 Higher, Q19(d) (3 marks): Another student investigates the reaction between marble chips and hydrochloric acid. She times how long it takes for all the marble chips to react. Look at her
June 2018, Paper 2 Foundation, Q7 (1 mark): Which statement about catalysts is correct? A A catalyst decreases the activation energy of a reaction. B A catalyst increases the activation energy of a reacti
June 2018, Paper 2 Foundation, Q18(b)(i) (1 mark): The graph shows the results for tablet X. What is the volume of gas made by the end of the experiment? Answer = cm3 [1] 80 70 60 50 tablet X Volume of gas 40 (c
June 2018, Paper 2 Foundation, Q18(b)(ii) (2 marks): Plot the results for tablet Y on the grid. Draw a line of best fit. [2]
June 2018, Paper 2 Foundation, Q18(c) (4 marks): The rate of reaction between calcium carbonate and hydrochloric acid can be increased by: • Using a more concentrated solution of hydrochloric acid • Increasing
June 2018, Paper 4 Higher, Q18(b)(i) (1 mark): Look at the line for experiment B on the graph. When is the rate of reaction greatest? Choose your answer from the list. 0 – 30 seconds 30 – 60 seconds 60 – 90
June 2018, Paper 4 Higher, Q18(b)(ii) (3 marks): Look at the line for experiment C. Calculate the rate of reaction during the first 45 seconds. Give your answer to 2 significant figures. Answer = cm3 / s [3]
June 2018, Paper 4 Higher, Q18(c) (4 marks): The rate of reaction between marble and hydrochloric acid can be decreased by: • Using a more dilute solution of hydrochloric acid • Cooling the acid. Explain h
June 2018, Paper 4 Higher, Q18(d)(i) (1 mark): The reaction profile for the reaction with a catalyst. [1]
June 2018, Paper 4 Higher, Q18(d)(ii) (1 mark): Label the activation energy for the reaction with a catalyst. [1]

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