Q1
ORIGINAL
The mass of a reaction flask falls from to during the first . Calculate the mean rate of mass loss.
[3 marks]
Total for this question: 3
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AQA GCSE Chemistry · Topic 4.6
The rate and extent of chemical change questions
Practice questions covering the rate and extent of chemical change from this specification. Every question below is the real AQA question as it is printed on the paper, with its mark scheme.
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6 questions on The rate and extent of chemical change, each with its mark scheme and worked method. Reveal the answer when you have had a go.
- Q2ORIGINALA student investigates how acid concentration affects the rate of gas production from marble chips. Describe how the student should collect suitable results while changing only the acid concentration.
[4 marks]
Total for this question: 4
- Q3ORIGINALExplain, using collision theory, why increasing the pressure of two reacting gases increases their reaction rate at constant temperature.
[3 marks]
Total for this question: 3
- Q4ORIGINALAn uncatalysed reaction has an activation energy of and an overall energy change of . A catalyst lowers the activation energy to . State the reduction in activation energy and the catalysed reaction's overall energy change.
[3 marks]
Total for this question: 3
- Q5ORIGINALThe reaction is reversible. State which substances react in the reverse reaction and which substances they form.
[2 marks]
Total for this question: 2
- Q6ORIGINALThe forward direction of a reversible reaction transfers to the surroundings. State the energy change for the reverse direction, including its sign.
[2 marks]
Total for this question: 2
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Printable question pack — 4.6 The rate and extent of chemical changeAll 113 questions across 11 specification points — 107 more than the 6 above — with the full mark scheme. Guest accessible · browser print.Real past-paper questions
36 questions shown as printed, 6 reference-only · newest series first
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AQA 8462 · June 2025 · Paper 2F · Q3 · 8 marks
8 marks
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[03.4] Around half of students correctly identified both materials. Many students completely reversed the responses. If 1 mark was awarded it was most likely for correctly identifying the reinforcement.
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Cement contains calcium oxide. Calcium oxide reacts with water to produce calcium hydroxide. The equation for the reaction is: calcium oxide + water ⇌ calcium hydroxide. The forward reaction is exothermic. Pre-stressed concrete contains concrete and steel wires.
AQA 8462 · June 2025 · Paper 2H · Q8 · 8 marks
8 marks
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[08.2] Three quarters of students described how catalysts provide an alternative pathway for the reaction. A description of a shorter pathway is not equivalent to an © 2025 AQA alternative pathway. Marking points 2 and 3 needed comparative statements between catalyst A and B. Some students just described in general how catalysts lower activation energy. This was not enough for these two marking points. Students needed to say the activation energy was lower using B. Saying catalyst B requires a lower activation energy was also not accepted, because a catalyst provides or allows a lower activation energy rather than requiring or needing one.
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Hydrogen peroxide decomposes: 2H<sub>2</sub>O<sub>2</sub>(aq) -> 2H<sub>2</sub>O(l) + O<sub>2</sub>(g). A student compared 1.00 g each of catalysts A and B with 50 cm<sup>3</sup> of 1.5 mol/dm<sup>3</sup> hydrogen peroxide by recording mass loss. The reaction profile shows catalyst B has lower activation energy than A.
AQA 8462 · June 2025 · Paper 2H · Q9 · 14 marks
14 marks
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[09.6] Around two-thirds of students gained at least one mark for this high demand interpretation question. The most common answer was for linking carbon dioxide to climate change. Many students did not gain this mark as there was a need to mention that the production of hydrogen causes this, if further detail was given. Mant talked about hydrogen producing carbon dioxide, which is incorrect and did not gain credit. The next most common response was for the idea that nitrogen was abundant in the atmosphere.
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Ammonia is made from nitrogen and hydrogen. Hydrogen is produced by CH<sub>4</sub>(g) + H<sub>2</sub>O(g) ⇌ CO(g) + 3H<sub>2</sub>(g); the forward reaction is endothermic. The Haber process uses nitrogen from air.
AQA 8462 · June 2024 · Paper 2F · Q5 · 11 marks
11 marks
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[05.7] Just over 60% of students correctly identified what would happen to the time taken for the cross to disappear for both of the changes made to the investigation with a further 10% of students correctly identifying the effect of just one change. The most common incorrect response was to reverse the order.
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A student timed how long a pencil cross took to disappear when 75 cm<sup>3</sup> sodium thiosulfate solution reacted with 15 cm<sup>3</sup> hydrochloric acid. The investigation was repeated at different sodium thiosulfate concentrations.
AQA 8462 · June 2024 · Paper 2F · Q9 · 6 marks
6 marks
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[09.4] Over 25% of students either correctly labelled the products and reactants or correctly drew an arrow, labelled the activation energy, and gained one mark. A further 10% of students gained two marks by doing both correctly. There were many variations of drawing and labelling the arrow for the activation energy. Some students mistakenly labelled the peak as being the activation energy or despite the dotted line drew the arrow too short or at an angle. Many students incorrectly identified the reactants and products from the equation or used nitrogen, hydrogen, and ammonia from the previous question. Other students were unsure where the reactants and products would be located on a reaction profile diagram.
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Figure 10 shows the Haber process: nitrogen gas and hydrogen gas enter a reactor containing a metal catalyst at 450 °C and 200 atmospheres; the reactor gases pass to a condenser; liquid ammonia leaves the condenser; Pipe P returns the remaining condenser gas to the reactor. Nitric acid is produced from ammonia and oxygen, with platinum as catalyst: ammonia + oxygen -> water + nitric acid.
AQA 8462 · June 2024 · Paper 2F · Q10 · 9 marks
9 marks
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[10.2] Over 65% of students were able to correctly identify the sentence that described the reversible reaction in the question.
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This question is about water. Figure 12 shows this flow: river -> ground water -> Process A (to produce potable water) -> potable water -> use in the home -> sewage -> Process B (to treat sewage). Inside Process B the sewage first meets a labelled metal grid, then separates into labelled effluent and sludge; the effluent returns to the river.
AQA 8462 · June 2024 · Paper 2H · Q2 · 6 marks
6 marks
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[02.2] This question was answered well by the majority of students, with roughly two-thirds of students gaining the mark.
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Figure 1 shows the Haber process: nitrogen gas and hydrogen gas enter a reactor containing a metal catalyst at 450 °C and 200 atmospheres; the reactor gases pass to a condenser; liquid ammonia leaves the condenser; Pipe P returns the remaining condenser gas to the reactor. Nitric acid is produced from ammonia and oxygen, with platinum as catalyst: ammonia + oxygen -> water + nitric acid.
AQA 8462 · June 2024 · Paper 2H · Q3 · 9 marks
9 marks
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[03.3] This standard demand item was generally answered quite well. A majority of students had a good overall understanding of the sequence of steps involved in potable water production and wastewater treatment and so scored highly on this item. Weaker responses tended to focus on wastewater treatment, for which the diagram in the stem provided more scaffolding. Most students recognised that ground water needed to be filtered initially. A few responses referred to screening before the use of filter beds, although only referring to screening in potable water production was considered insufficient. Sometimes the descriptions of things removed by filter beds did not make it clear that they were solid. The process of sterilisation was generally well described, although removal of microbes rather than their destruction was not creditworthy. Removal of solids using a metal grid was included by most students. Fewer students referred to this step as screening and again things removed by screening were not always clearly identified as solid. Organic matter in sewage is not removed by screening as this is treated subsequently. The final steps were less well addressed overall. Most students referred to sludge and effluent (again these featured in the diagram), but many failed to recognise that these were separated by sedimentation. Some responses confused the separation of sludge and effluent with their biological treatment afterwards. Some students recognised that sludge is treated anaerobically and effluent aerobically but did not refer to digestion or biological treatment or an equivalent description of microbial action. References to flocculation, desalination, fluoridation or pH adjustment were considered irrelevant and ignored in the marking of this item. Around a third of students gained a Level 3 mark, with roughly another third achieving Level 2.
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This question is about water. Figure 3 shows this flow: river -> ground water -> Process A (to produce potable water) -> potable water -> use in the home -> sewage -> Process B (to treat sewage). Inside Process B the sewage first meets a labelled metal grid, then separates into labelled effluent and sludge; the effluent returns to the river.
AQA 8462 · June 2024 · Paper 2H · Q7 · 8 marks
8 marks
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[07.2] This multiple-choice question was well answered with two-thirds of students gaining the mark.
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Sulfur dioxide and oxygen reach dynamic equilibrium: 2SO<sub>2</sub>(g) + O<sub>2</sub>(g) ⇌ 2SO<sub>3</sub>(g). The supplied yield graph shows that sulfur trioxide yield becomes smaller as temperature rises. Industry uses 450 °C, atmospheric pressure, 86% yield and a metal-oxide catalyst.
AQA 8462 · June 2024 · Paper 2H · Q9 · 5 marks
5 marks
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[09.3] Most students were able to construct a tangent at 45 s. The scale on the y-axis posed a problem for a significant number of the students. The calculation of the rate was well done, and most were able to convert their answer into standard form. A small number calculated the mean rate between 0 s and 45 s by drawing a single pair of construction lines which met the curve. Such students were only able to gain a mark for an answer correctly expressed in standard form. Just over half of the students scored five marks.
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A student reacted excess zinc with 50 cm<sup>3</sup> sulfuric acid and collected hydrogen in a 50 cm<sup>3</sup> measuring cylinder. The reaction is Zn + H<sub>2</sub>SO<sub>4</sub> -> ZnSO<sub>4</sub> + H<sub>2</sub>.
AQA 8462 · June 2023 · Paper 2F · Q1 · 6 marks
6 marks
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[01.1] Just over three quarters of students identified the correct planet, with the other distractors being roughly equally selected.
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This question is about oxygen. Scientists think there was little or no oxygen in the Earth's early atmosphere. Some scientists think that 1100 million years ago the atmosphere contained 16% oxygen and 4% carbon dioxide. Oxygen is produced when manganese dioxide is added to hydrogen peroxide solution: hydrogen peroxide -> water + oxygen.
AQA 8462 · June 2023 · Paper 2F · Q4 · 9 marks
9 marks
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[04.7] Over two thirds of students correctly identified the forward reaction as endothermic. Very few selected ‘combustion’.
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A student heated 2.00 g of calcium hydroxide to make calcium oxide and water vapour, cooling and weighing after each minute. Appearances: calcium hydroxide and calcium oxide are white powders; water vapour is a colourless gas. Mass of contents (g) after 0-6 minutes: 2.00, 1.76, 1.64, 1.56, 1.52, 1.51, 1.51. The reversible equation is calcium hydroxide ⇌ calcium oxide + water. Changing 4.00 g calcium hydroxide completely into 3.03 g calcium oxide takes in 5.90 kJ.
AQA 8462 · June 2023 · Paper 2F · Q8 · 10 marks
10 marks
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[08.4] Only 25% of students were able to give the correct test and result for hydrogen gas. Weaker responses failed to include the test and only described the result usually as a squeaky pop and gained no marks. Incorrect tests were less commonly seen but the most frequent incorrect test used was a glowing splint.
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A student investigated the rate of the reaction between zinc and sulfuric acid. Hydrogen is produced. The student added 50 cm<sup>3</sup> acid and 2.0 g zinc, quickly stoppered the flask, timed collection of 20 cm<sup>3</sup> gas and repeated. Rates (cm<sup>3</sup>/s) were 0.78, 0.81, 0.68 and 0.81.
AQA 8462 · June 2023 · Paper 2H · Q1 · 10 marks
10 marks
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[01.2] The vast majority of students used the main approach on the mark scheme. Around three- quarters of students scored all the marks. Of those who didn’t, the majority scored 4 marks by failing to discard the anomalous result in MP1. Weaker responses typically calculated the mean rate of 0.80 cm3/s but were able to take the process further and gained two marks.
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A student investigated the rate of the reaction between zinc and sulfuric acid. Hydrogen gas is produced during this reaction. This is the method used. 1. Add 50 cm<sup>3</sup> of sulfuric acid to a conical flask. 2. Add 2.0 g of zinc to the conical flask. 3. Quickly put a stopper in the conical flask and start a timer. 4. Measure the time taken to collect 20 cm<sup>3</sup> of gas. 5. Repeat steps 1 to 4 three more times.
AQA 8462 · June 2023 · Paper 2H · Q7 · 4 marks
4 marks
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[07.1] The effect of a catalyst on the rate of a reaction was generally well known. Most correct answers referred to the lowering of the activation energy. Many students also referred to the catalyst providing a different pathway for the reaction. References to changes in the number of collisions were insufficient as they did not answer the question. Over one-third of responses gained two marks, and around two-thirds of responses gained one mark.
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Manganese dioxide catalyses the decomposition of hydrogen peroxide solution. Oxygen and water are produced. A student investigated the rate of this reaction. This is the method used. 1. Add 50 cm<sup>3</sup> of 2.0 mol/dm<sup>3</sup> hydrogen peroxide solution to a conical flask. 2. Add 1.0 g of manganese dioxide to the conical flask. 3. Place the conical flask on a balance and start a timer. 4. Record the total mass lost from the conical flask every 20 seconds for 180 seconds.
AQA 8462 · June 2023 · Paper 2H · Q9 · 13 marks
13 marks
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[09.8] This question was not well done. Students appear not to understand what is happening at equilibrium and responses did not relate to the rate of reaction. Around one-quarter of students gained this mark.
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This question is about reversible reactions. When 4.68 g of hydrated copper sulfate changes into anhydrous copper sulfate: 2.99 g of anhydrous copper sulfate is produced, and 1.47 kJ of energy is taken in from the surroundings. The equation for the reversible reaction is: hydrated copper sulfate ⇌ anhydrous copper sulfate + water.
AQA 8462 · June 2022 · Paper 2F · Q6 · 7 marks
7 marks
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[06.5] Many deduced that one of the reactants was used up, with over 60% of the students gaining a mark. A sizeable number asserted that no light was reaching the sensor, even though the graph did not reach y = 0.
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A student added 10 cm<sup>3</sup> hydrochloric acid to 50 cm<sup>3</sup> sodium thiosulfate and recorded the percentage of light reaching a sensor every 20 s as sulfur clouded the mixture. Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> + 2HCl -> NaCl + H<sub>2</sub>O + SO<sub>2</sub> + S.
AQA 8462 · June 2022 · Paper 2F · Q9 · 8 marks
8 marks
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[09.5] Exothermic and chemical were common incorrect responses. Approximately one-third of the students scored this mark.
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Hydrated cobalt chloride is heated reversibly: hydrated cobalt chloride ⇌ anhydrous cobalt chloride + water. Starting with 2.0 g hydrate, test-tube-plus-contents masses at 0,30,60,90,120 s were 26.5,26.2,25.9,25.6,25.6 g. Heating 238 g hydrate takes in 88.1 kJ.
AQA 8462 · June 2022 · Paper 2H · Q2 · 8 marks
8 marks
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[02.1] The majority of students correctly determined the mass of the empty test tube as 24.5g.
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Hydrated cobalt chloride is heated reversibly: hydrated cobalt chloride ⇌ anhydrous cobalt chloride + water. Starting with 2.0 g hydrate, test-tube-plus-contents masses at 0,30,60,90,120 s were 26.5,26.2,25.9,25.6,25.6 g. Heating 238 g hydrate takes in 88.1 kJ.
AQA 8462 · June 2022 · Paper 2H · Q7 · 11 marks
11 marks
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[07.5] Most students extrapolated their line correctly and read off the value of the percentage at 500 atmospheres. About two-thirds of the students scored both marks.
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The Haber process is N<sub>2</sub>(g)+3H<sub>2</sub>(g) ⇌ 2NH<sub>3</sub>(g), forward exothermic. It uses 450 °C, 200 atm and an iron catalyst.
AQA 8462 · June 2022 · Paper 2H · Q8 · 4 marks
4 marks
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[08.4] Some students made an insufficient general statement about reactants being used up. However a larger number mentioned the acid being used up. Few used the term limiting reactant. Over a third of students gained this mark.
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Hydrochloric acid reacts with sodium thiosulfate: Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub>+2HCl -> 2NaCl+H<sub>2</sub>O+SO<sub>2</sub>+S. A student measures cloudiness with a light sensor. Sodium thiosulfate is in excess; the best-fit line is horizontal from 80-120 s because reaction stopped.
AQA 8462 · November 2021 · Paper 2F · Q4 · 8 marks
8 marks
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Hydrogen and iodine gases reversibly form colourless hydrogen iodide in a sealed container; the initial iodine mixture is purple.
AQA 8462 · November 2021 · Paper 2F · Q5 · 2 marks
2 marks
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A student reacts 2.0 g zinc powder with 40 cm3 sulfuric acid and collects hydrogen. The apparatus drawing shows the delivery tube ending below the acid surface. A higher acid concentration is later tested.
AQA 8462 · November 2021 · Paper 2H · Q9 · 4 marks
4 marks
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[09.2] Many students were able to say that the reaction had stopped but only a much smaller number could explain why.
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A student reacts zinc powder with 0.05 and 0.10 mol/dm3 sulfuric acid. The apparatus drawing shows the delivery tube ending in the acid.
AQA 8462 · November 2021 · Paper 2H · Q10 · 17 marks
17 marks
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[10.4] Fermentation was well known.
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Ethene is made from large crude-oil hydrocarbons. Ethene and steam reversibly form ethanol exothermically. A yeast process and bacterial butanol production from sugar are also considered. Ethanol energy content=1300 kJ/mol; car needs 1.95 kJ/m over 200 km.
AQA 8462 · November 2020 · Paper 2F · Q1 · 5 marks
5 marks
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Ammonia is made from nitrogen and hydrogen by a reversible catalysed reaction. NPK fertilisers contain nitrogen, phosphorus and potassium. Fertilisers A-D contain N/P/K percentages A 14/0/39, B 25/16/23, C 21/23/0, D 21/0/0.
AQA 8462 · November 2020 · Paper 2F · Q3 · 7 marks
7 marks
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Hydrochloric acid reacts with calcium carbonate lumps and produces carbon dioxide. A 2 mm-sided calcium carbonate cube is later divided into eight smaller cubes.
AQA 8462 · November 2020 · Paper 2H · Q7 · 11 marks
11 marks
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[07.3] This part was quite well answered. Most students stated that the mass decreases. Not all of the students who identified carbon dioxide as a product of the reaction went on to explain that it is the escape of this gas that causes the mass to decrease.
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Carboxylic acid data at 0.01 mol/dm3: methanoic pH 2.91; ethanoic CH3COOH pH 3.39; propanoic CH3CH2COOH pH 3.44. Ethanoic acid ionises reversibly.
AQA 8462 · November 2020 · Paper 2H · Q8 · 4 marks
4 marks
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[08.4] This item was quite well answered by many students. The most common error was to fail to multiply the area of one face by six.
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Calcium carbonate reacts with hydrochloric acid. Large-lump mole data at 0,30,60,90,120,150,180 s are 0,0.0011,0.0020,0.0028,0.0034,0.0038,0.0040. A small reference cube has side 0.5 cm; a larger cube has side 5 cm.
AQA 8462 · November 2020 · Paper 2H · Q10 · 10 marks
10 marks
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[10.2] The mark for describing the colour change was scored more often than the mark for the shift in the position of equilibrium that caused this colour change. The mark for the application of Le Chatelier's Principle was rarely scored by students.
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Fe3+(aq) yellow + SCN-(aq) colourless <-> FeSCN2+(aq) red. The equilibrium mixture is orange at room temperature.
AQA 8462 · June 2018 · Paper 2H · Q5 · 8 marks
8 marks
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[05.1] This question was generally well done. Most students could identify that the solution became cloudy because sulfur was produced and that it was a solid. A few students however were unfamiliar with the experiment and thought that a gas was produced, and that this was the cause. 42% of students achieved both marks.
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Hydrochloric acid reacts with sodium thiosulfate and produces a sulfur precipitate. A disappearing-cross experiment investigates concentration and rate.
AQA 8462 · June 2018 · Paper 2H · Q8 · 2 marks
2 marks
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[08.1] Most students recognised that a gas is given off by the reaction. Sometimes it was incorrectly identified as hydrogen. The ‘escape’ mark was less commonly awarded either because the students thought it was sufficient to state that a gas is given off or because they thought that the gas ‘evaporated’. 43% of students achieved full marks.
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A carbonate reacts with hydrochloric acid in a flask on a balance, producing carbon dioxide.
AQA 8462 · June 2018 · Paper 2H · Q9 · 12 marks
12 marks
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[09.7] The effect of a catalyst on the equilibrium yield of methanol was not well understood. It was widely thought that a catalyst increased the yield of methanol because the reaction was faster and would, therefore, produce more of the product. 24% of students answered correctly.
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Methanol forms by CO+2H2 <-> CH3OH at 250 degC and high pressure with a catalyst; the forward reaction is exothermic.
AQA 8462 · sample1 · Paper 1F · Q3 · 4 marks
4 marks
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Lithium carbonate decomposes on heating and carbon dioxide is collected over water.
AQA 8462 · sample1 · Paper 2H · Q9 · 6 marks
6 marks
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Marble chips react with hydrochloric acid. As the reaction proceeds, reactant concentration falls and surface area can decrease.
AQA 8462 · sample1 · Paper 2H · Q10 · 5 marks
5 marks
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Ethanol is made reversibly from ethene and steam; the forward reaction is exothermic and has fewer gas molecules on the product side.
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