Monitoring chemical reactions: OCR GCSE Chemistry A questions

Every OCR GCSE Chemistry A exam question on C5.1 Monitoring chemical reactions, 2018–2025, with its mark scheme and examiner’s report.

All 107 questions on Monitoring chemical reactions, as a list

June 2025, Paper 2 Foundation, Q13 (1 mark): The theoretical yield of a product in a reaction is 100 g. The actual yield is 60 g. What is the percentage yield? A 40% B 60% C 67% D 167% Your answer [1]
June 2025, Paper 2 Foundation, Q17(b)(ii) (3 marks): Calculate the atom economy for the reaction. Use the equation: Ar of Mo atom economy = Ar of Mo + Mr of 3H2O × 100 Relative atomic mass (Ar): H = 1.0 O = 16.0 M
June 2025, Paper 2 Foundation, Q20(a)(i) (1 mark): hydroxide solution? Tick (✓) one box. Beaker Dropping pipette Measuring cylinder Volumetric pipette [1]
June 2025, Paper 2 Foundation, Q20(a)(ii) (1 mark): State a suitable indicator for the student to use in the titration. [1]
June 2025, Paper 2 Foundation, Q20(a)(iii) (1 mark): Suggest an improvement to the student’s method. [1]
June 2025, Paper 2 Foundation, Q20(b) (1 mark): The reading at the start of the rough titration is 0.0 cm3. At the end of the rough titration the student reads the volume of dilute sulfuric acid added from th
June 2025, Paper 2 Foundation, Q20(c) (2 marks): After the rough titration the student repeats the experiment four more times. The table shows their results. Titration number 1 2 3 4 Volume of dilute sulfuric
June 2025, Paper 4 Higher, Q5 (1 mark): The theoretical yield of a product in a reaction is 71 g. The actual yield is 60 g. What is the percentage yield? A 15.5% B 18.3% C 84.5% D 118.3% Your answer [
June 2025, Paper 4 Higher, Q7 (1 mark): Which equation shows the relationship between: • the mass of a solute • the volume of a solution • the concentration of the solution? mass of solute = concentra
June 2025, Paper 4 Higher, Q9 (1 mark): Nitrogen reacts with hydrogen to make ammonia. N2(g) + 3H2(g) 2NH3(g) What is the volume of ammonia made from 366 cm3 of hydrogen? 183 cm3 A 244 cm3 B 549 cm3 C
June 2025, Paper 4 Higher, Q20(a)(i) (1 mark): sodium hydroxide solution. [1]
June 2025, Paper 4 Higher, Q20(a)(ii) (1 mark): State a suitable indicator for the student to use in the titration. [1]
June 2025, Paper 4 Higher, Q20(a)(iii) (1 mark): Suggest an improvement to the student’s method. [1]
June 2025, Paper 4 Higher, Q20(b) (1 mark): The reading at the start of the rough titration is 0.0 cm3. At the end of the rough titration the student reads the volume of dilute sulfuric acid added from th
June 2025, Paper 4 Higher, Q20(c) (2 marks): After the rough titration the student repeats the experiment five more times. The table shows their results. Titration number 1 2 3 4 5 Volume of dilute sulfuri
June 2025, Paper 4 Higher, Q20(d) (4 marks): The equation for the reaction in the student’s titration is H2SO4 + 2NaOH Na2SO4 + 2H2O They used 25.0 cm3 of 0.40 mol / dm3 sodium hydroxide solution and 24.50
June 2025, Paper 4 Higher, Q23(c) (2 marks): A household gas central heating boiler produces 42 460 g of carbon dioxide in a week. Calculate the volume of carbon dioxide, in dm3, produced at room temperatu
June 2024, Paper 1 Foundation, Q19(b)(iv) (1 mark): The student collects 5.1 cm3 of gas. The student wants to collect more gas. How does the student change the experiment so that more gas is collected? Tick (3) o
June 2024, Paper 2 Foundation, Q13 (1 mark): Magnesium carbonate, MgCO3, decomposes to make magnesium oxide, MgO. Carbon dioxide is a waste product. MgCO3 MgO + CO2 Relative formula mass (Mr): MgO = 40.3 C
June 2024, Paper 2 Foundation, Q19(a) (1 mark): What is the name of the piece of equipment labelled X? [1]
June 2024, Paper 2 Foundation, Q19(b) (1 mark): The student places the conical flask on a white tile. Explain why. [1]
June 2024, Paper 2 Foundation, Q19(c) (1 mark): The student adds the alkali to the acid drop by drop near the endpoint of the titration. Explain why. [1]
June 2024, Paper 2 Foundation, Q22(c) (2 marks): A factory predicts they will make 800 tonnes of ammonia. They actually make 620 tonnes of ammonia. Calculate the percentage yield of ammonia. Percentage yield o
June 2024, Paper 2 Foundation, Q22(d) (1 mark): State why the reaction in the Haber process has an atom economy of 100%. Use the balanced symbol equation. [1]
June 2024, Paper 3 Higher, Q22(c)(ii) (4 marks): The student uses 0.2 mol of hydrochloric acid in the reaction. The hydrochloric acid is the limiting reagent. At the end of the reaction, 0.82 g of magnesium ca
June 2024, Paper 4 Higher, Q9 (1 mark): How is the mass of a solute, in g, related to the concentration of the solution, in g / dm3, and the 9 volume of the solution, in dm3? A mass = concentration ×
June 2024, Paper 4 Higher, Q14 (1 mark): What is the volume of 0.6 moles of nitrogen gas, N2, at room temperature and pressure? 14.4 dm3 A B 16.8 dm3 C 40.0 dm3 D 46.7 dm3 [1] Your answer
June 2024, Paper 4 Higher, Q17(c) (2 marks): A factory predicts they will make 800 tonnes of ammonia. They actually make 620 tonnes of ammonia. Calculate the percentage yield. Percentage yield of ammonia =
June 2024, Paper 4 Higher, Q17(d) (1 mark): State why the reaction in the Haber process has an atom economy of 100%. Use the balanced symbol equation. [1]
June 2024, Paper 4 Higher, Q21(a) (5 marks): Describe how the student uses the apparatus to do the titration. Include the name of a suitable indicator and state the colour change that would be seen. [5]
June 2024, Paper 4 Higher, Q21(b)(i) (1 mark): What is meant by concordant results? [1]
June 2024, Paper 4 Higher, Q21(b)(ii) (4 marks): In the titration the student: uses 25 cm3 of 0.12 mol / dm3 dilute hydrochloric acid in the conical flask • adds 0.4 mol / dm3 sodium hydroxide solution from th
June 2024, Paper 4 Higher, Q22(a)(ii) (1 mark): Explain how the student could tell that the dilute hydrochloric acid is the limiting reactant in this reaction. [1]
June 2023, Paper 2 Foundation, Q17(e)(ii) (3 marks): A student reacts 2.8 g of iron with dilute sulfuric acid. The student makes 5.4 g of iron sulfate. They predicted that they should have made 7.6 g of iron sulfa
June 2023, Paper 2 Foundation, Q19(a) (4 marks): The student writes their method. A Add a few drops of methyl orange indicator. B Fill the burette with dilute hydrochloric acid. Record the initial reading on t
June 2023, Paper 2 Foundation, Q19(b)(ii) (3 marks): Water is a waste product in this reaction. Calculate the atom economy for the reaction. Relative atomic mass (Ar): H = 1.0 O = 16.0 Na = 23.0 Cl = 35.5 Atom eco
June 2023, Paper 2 Foundation, Q22(d) (3 marks): Barium chloride solid is toxic if swallowed and harmful if inhaled. Barium chloride solutions with concentrations of 21 g / dm3 are suitable for experiments in
June 2023, Paper 4 Higher, Q16(d) (3 marks): Barium chloride solid is toxic if swallowed and harmful if inhaled. Barium chloride solutions with concentrations of 21 g / dm3 are suitable for experiments in
June 2023, Paper 4 Higher, Q18(d) (4 marks): 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. Calculate the volume occupied by 0.008 g
June 2023, Paper 4 Higher, Q21(c) (3 marks): A factory makes some methanol. They predict they will make 60 tonnes of methanol. The reaction has a percentage yield of 78%. Calculate the mass of methanol the
June 2023, Paper 4 Higher, Q23(a) (1 mark): At the end of the titration, the student reads the final volume reading from the top of the meniscus instead of from the bottom of the meniscus. How does the me
June 2023, Paper 4 Higher, Q23(b)(i) (1 mark): Calculate the average titre using the student’s concordant results. Average titre = cm3 [1]
June 2023, Paper 4 Higher, Q23(b)(ii) (5 marks): This is the equation for the reaction in this experiment. 2KOH + H2SO4 K2SO4 + 2H2O Calculate the concentration of sulfuric acid in g / dm3. Relative atomic mas
June 2022, Paper 2 Foundation, Q10 (1 mark): Copper carbonate, CuCO3, decomposes when heated. Copper oxide, CuO, is made. Carbon dioxide is a waste product. CuCO3 CuO + CO2 What is the atom economy of the
June 2022, Paper 2 Foundation, Q17(a) (4 marks): Calculate the theoretical yield of ammonium nitrate, NH4NO3. Give your answer to 3 significant figures. Relative atomic mass (Ar): H = 1.0 N = 14.0 O = 16.0. Th
June 2022, Paper 2 Foundation, Q17(b) (1 mark): The atom economy for the reaction between nitric acid and ammonia is 100%. HNO3 + NH3 NH4NO3 Use the balanced symbol equation to explain why the atom economy is
June 2022, Paper 2 Foundation, Q17(c) (3 marks): In another reaction, the student makes 4.0 g of ammonium sulfate. They predicted that they should have made 6.6 g. Calculate their percentage yield. Give your a
June 2022, Paper 3 Higher, Q9 (1 mark): One mole of hydrogen gas, H2, fills a volume of 24 dm3. 9 How much volume does 2.0 g of hydrogen gas fill? 12 dm3 A 24 dm3 B 36 dm3 C 48 dm3 D Your answer [1]
June 2022, Paper 3 Higher, Q21(a)(iii) (4 marks): The scientist reacts the 2.0 mol of phosphorus, P4, with 866.2 g of chlorine, Cl 2. Which is the limiting reactant? Explain your answer. Limiting reactant Expla
June 2022, Paper 4 Higher, Q14 (1 mark): The actual yield in a reaction is often less than the predicted yield. Why? A One reactant is in excess. B One reactant is the limiting reactant. C The reaction
June 2022, Paper 4 Higher, Q18(g)(ii) (4 marks): The equation shows the reaction that takes place in a catalytic converter. 2CO + 2NO N2 + 2CO2 During a car journey, 187 g of carbon dioxide is made by the cata
June 2022, Paper 4 Higher, Q19(a) (5 marks): The student makes 4.22 g of ammonium sulfate. The percentage yield is 80%. Calculate the mass of sulfuric acid the student used in the reaction. Give your answe
June 2022, Paper 4 Higher, Q21(c) (4 marks): A factory uses 200 tonnes of methane a day. The factory produces 68.4 tonnes of hydrogen per day as shown in the equation. CH4(g) + H2O(g) CO(g) + 3H2(g) Calcul
June 2022, Paper 4 Higher, Q22(a)(i) (1 mark): Calculate the volume of acid used in titration number 3. Write your answer in the table. [1]
June 2022, Paper 4 Higher, Q22(a)(iii) (1 mark): The student decides to only use the results from titration numbers 2 and 4. Explain why. [1]
June 2022, Paper 4 Higher, Q22(a)(iv) (5 marks): The equation for the reaction between dilute hydrochloric acid and sodium carbonate solution is shown. 2HCl + Na2CO3 2NaCl + H2O + CO2 Calculate the concentrati
November 2021, Paper 2 Foundation, Q4 (1 mark): Look at the diagram of a titration experiment. Apparatus X Dilute nitric acid Dilute sodium hydroxide solution What is the name of apparatus X? A Burette B Coni
November 2021, Paper 2 Foundation, Q13 (1 mark): Look at the results of a titration experiment. Titration 1 Titration 2 Titration 3 Titration 4 (rough) Volume of acid 26.00 25.20 25.50 25.60 used (cm3) What is
November 2021, Paper 2 Foundation, Q19(d) (3 marks): The student made 0.073 g of carbon dioxide in their experiment. They predicted that they should have made 0.088 g. Calculate the percentage yield. Give your ans
November 2021, Paper 2 Foundation, Q21(d) (2 marks): Ethanol, C2H5OH, can be dehydrated to make ethene, C2H4. C2H5OH C2H4 + H2O Calculate the atom economy for the production of ethene from ethanol. (The relative f
November 2021, Paper 3 Higher, Q22(a)(i) (1 mark): Explain what is meant by the term limiting reactant. [1]
November 2021, Paper 3 Higher, Q22(a)(ii) (1 mark): Explain what effect a limiting reactant has on a reaction. [1]
November 2021, Paper 4 Higher, Q5 (1 mark): A scientist predicts that they should make 96 tonnes of product in a reaction. They only actually make 81 tonnes of product. What is the percentage yield? A 15%
November 2021, Paper 4 Higher, Q7 (1 mark): The concentration of a solution of sodium hydroxide, NaOH, is 0.725 mol / dm3. 7 What is the concentration of this solution in g / dm3? (The relative atomic mas
November 2021, Paper 4 Higher, Q16(d) (2 marks): Ethanol, C2H5OH, can be dehydrated to make ethene, C2H4. C2H5OH C2H4 + H2O Calculate the atom economy for the production of ethene from ethanol. (The relative f
November 2021, Paper 4 Higher, Q18(c) (1 mark): The balanced equation for this reaction is: CaCO3 + 2HCl CaCl 2 + H2O + CO2 In their experiment the student reacted 0.5 mol of dilute hydrochloric acid, HCl, wi
November 2021, Paper 4 Higher, Q22(a)(i) (1 mark): What is the volume of hydrogen gas, in dm3, needed to react with 150 dm3 iodine at room temperature and pressure? Use the balanced symbol equation to help you.
November 2021, Paper 4 Higher, Q22(a)(ii) (1 mark): Calculate the volume of hydrogen iodide formed, in dm3, when 150 dm3 of iodine completely reacts with hydrogen at room temperature and pressure. Use the balance
November 2021, Paper 4 Higher, Q22(a)(iii) (4 marks): Calculate the mass, in kilograms, of 150 dm3 of iodine at room temperature and pressure. One mole of any gas occupies 24 dm3. Give your answer to 1 decimal plac
November 2020, Paper 2 Foundation, Q15 (1 mark): Hydrogen gas, H2, reacts with oxygen gas, O2, to make water, H2O. 2H2 + O2 2H2O What is the atom economy for this reaction? Mr : H2 = 2, O2 = 32, H2O = 18. A 50
November 2020, Paper 2 Foundation, Q20(b) (2 marks): Look at the student’s method for her experiment. Pipette Filler Burette Pipette Conical Flask Conical Flask Measure 25.0 cm3 of alkali solution into a conical f
November 2020, Paper 2 Foundation, Q20(c) (2 marks): The student repeats the experiment three times. Look at the student’s results. Titration number 1 2 3 Volume of acid (cm3) 25.75 23.60 23.70 Calculate the accur
November 2020, Paper 2 Foundation, Q24(c)(ii) (2 marks): A student makes some ammonium nitrate in the laboratory. He predicts that he should make 12.5 g of ammonium nitrate. His percentage yield is 80%. Calculate the
November 2020, Paper 4 Higher, Q2 (1 mark): Hydrogen gas, H2, reacts with oxygen gas, O2, to make water, H2O. 2H2 + O2 2H2O What is the atom economy for this reaction? Mr: H2 = 2, O2 = 32, H2O = 18 A 50%
November 2020, Paper 4 Higher, Q8 (1 mark): In the Haber process, nitrogen reacts with hydrogen to make ammonia. N2(g) + 3H2(g) 2NH3(g) What is the maximum volume of ammonia, NH3, that can be made from 15
November 2020, Paper 4 Higher, Q12 (1 mark): Which is the correct expression for calculating the concentration of a solution in g / dm3? Concentration = volume of solution in dm3 A mass of solute in g Conc
November 2020, Paper 4 Higher, Q17(c)(ii) (2 marks): A student makes some ammonium nitrate in the laboratory. He predicts that he should make 12.5 g of ammonium nitrate. His percentage yield is 80%. Calculate the
November 2020, Paper 4 Higher, Q21(a) (2 marks): Look at the student’s method for her experiment. Pipette Filler Burette Pipette Conical Flask Conical Flask • Measure 25.0 cm3 of 0.200 mol / dm3 potassium hydr
November 2020, Paper 4 Higher, Q21(b)(i) (2 marks): Calculate the accurate volume of the acid that reacts with the alkali. Accurate volume of acid = cm3 [2]
November 2020, Paper 4 Higher, Q21(b)(ii) (4 marks): Look at the equation for the reaction between sulfuric acid and potassium hydroxide. H2SO4 + 2KOH K2SO4 + 2H2O Use your answer from part (b)(i) to calculate the
November 2020, Paper 4 Higher, Q22(b)(i) (2 marks): Calculate the number of moles of hydrogen gas produced. One mole of any gas occupies 24 dm3 at room temperature and pressure. Moles of hydrogen gas = [2]
June 2019, Paper 2 Foundation, Q12 (1 mark): Which statement describes the atom economy of a reaction? A A measure of how many atoms in the reactants form the waste products. B A measure of how many atoms
June 2019, Paper 4 Higher, Q4 (1 mark): Which statement about atom economy is correct? A A reaction that has only one product has a higher atom economy than a reaction that has two products, one of th
June 2019, Paper 4 Higher, Q15 (1 mark): Which of the following is the expression used to calculate concentration in g / dm3? mass of solute in g A Concentration = volume of solution in dm3 mass of sol
June 2019, Paper 4 Higher, Q22(b)(i) (3 marks): 35.0 cm3 of 0.075 mol / dm3 hydrochloric acid, HCl, are added to 25.0 cm3 of 0.100 mol / dm3 sodium hydroxide solution, NaOH. Use the information to determine w
June 2019, Paper 4 Higher, Q22(b)(ii) (2 marks): To find the exact amount of dilute hydrochloric acid that reacts with 25.0 cm3 of the sodium hydroxide solution, the student does a titration. Look at the stude
June 2019, Paper 4 Higher, Q22(c) (4 marks): In another titration 25.0 cm3 of potassium hydroxide solution, KOH, are titrated with 0.200 mol / dm3 sulfuric acid, H2SO4. 2KOH + H2SO4 K2SO4 + 2H2O 24.80 cm3
June 2018, Paper 2 Foundation, Q17(a) (1 mark): Explain how you can tell from the student’s observation that the hydrochloric acid was in excess. [1]
June 2018, Paper 2 Foundation, Q17(b) (1 mark): Look at the equation for the reaction. Mg + 2HCl MgCl2 + H2 The student knows the reaction is complete when there is no magnesium left. Use the equation to expl
June 2018, Paper 2 Foundation, Q17(c) (3 marks): The student predicts she should make 9.5 g of magnesium chloride, MgCl2. She actually makes 7.9 g. Calculate the percentage yield. Give your answer to 3 signifi
June 2018, Paper 2 Foundation, Q17(d) (1 mark): Write down one reason, other than a mistake, why the student may have obtained a percentage yield of less than 100%. [1]
June 2018, Paper 2 Foundation, Q18(b)(iii) (1 mark): Tablet X contains less calcium carbonate than tablet Y. How do the results show this? [1]
June 2018, Paper 2 Foundation, Q21(a) (4 marks): The student wants to get a more accurate value for how much acid reacts with 25.0 cm3 of sodium hydroxide solution. Describe and explain how the student could i
June 2018, Paper 2 Foundation, Q21(b) (2 marks): Another student does a titration. She also uses dilute sulfuric acid, sodium hydroxide solution and an indicator solution. The table shows her results. Titratio
June 2018, Paper 2 Foundation, Q21(c) (3 marks): The equation for this reaction is H2SO4 + 2NaOH Na2SO4 + 2H2O Relative formula mass, Mr H2SO4 98 NaOH 40 Na2SO4 142 H2O 18 Water is a waste product in this reac
June 2018, Paper 3 Higher, Q22 (4 marks): Copper oxide can be reduced to copper by reaction with hydrogen. CuO + H2 Cu + H2O A reaction mixture contains 1.59 g of copper oxide and 0.20 g of hydrogen. 1.
June 2018, Paper 4 Higher, Q11 (1 mark): How much 0.2 mol / dm3 hydrochloric acid solution could you make from 100 cm3 of 1.0 mol / dm3 hydrochloric acid? 20 cm3 A 200 cm3 B 500 cm3 C 600 cm3 D Your an
June 2018, Paper 4 Higher, Q20(a) (4 marks): Describe and explain how the student could improve his experiment to get a more accurate value. [4]
June 2018, Paper 4 Higher, Q20(b) (1 mark): Student B does a titration. Burette Sodium hydroxide Datalogger Sulfuric acid pH probe Sodium hydroxide solution is slowly added to the beaker of dilute sulfuri
June 2018, Paper 4 Higher, Q20(c)(ii) (1 mark): What volume of alkali is needed to exactly neutralise the sulfuric acid? Answer = cm3 [1]
June 2018, Paper 4 Higher, Q20(d)(i) (1 mark): Student B decides to only use the results from titration numbers 2 and 4. Explain why. [1]
June 2018, Paper 4 Higher, Q20(d)(ii) (4 marks): Look at the equation for the reaction between hydrochloric acid, HCl, and sodium hydroxide, NaOH. HCl + NaOH → NaCl + H2O Calculate the concentration of hydroch
June 2018, Paper 4 Higher, Q21(a)(i) (1 mark): Calculate the volume of the water in dm3. Answer = dm3 [1]
June 2018, Paper 4 Higher, Q21(a)(ii) (1 mark): Use your answer to part (a)(i) to help you calculate the concentration of the zinc sulfate in g / dm3. Answer = g / dm3 [1]
June 2018, Paper 4 Higher, Q21(b)(ii) (2 marks): Use your answer to part (b)(i) to calculate the volume of hydrogen gas produced at room temperature and pressure. One mole of any gas occupies 24 dm3 at room te
June 2018, Paper 4 Higher, Q21(c)(i) (3 marks): Calculate the atom economy for the production of hydrogen from ammonia. Give your answer to 3 significant figures. Answer = % [3]
June 2018, Paper 4 Higher, Q21(c)(ii) (3 marks): Suggest other factors, apart from atom economy, that must be considered when deciding which reaction pathway to choose for the manufacture of hydrogen. [3]

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