Quantitative chemistry questions

Question and mark-scheme extracts © AQA. Reproduced for educational use; the original paper is linked on every question. Contact hello@oscarsongtutoring.co.uk for removal.

• AQA 8462 · June 2025 · Paper 1F · Q7 · 8 marks

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  [07.3] Four fifths of students scored both marks. A few inverted the expression provided.

  Text version

  This question is about mixtures. A mixture contains salt, which is soluble in water, and sand, which is insoluble in water.

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• AQA 8462 · June 2025 · Paper 1F · Q10 · 11 marks

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  [10.3] Whilst a third of students scored one mark, only about one in ten scored all three. Many could not recall the expression for percentage atom economy and therefore did not attempt to find the total Mr of the reactants. A significant minority added the two relative atomic masses provided to give 124 and then divided by 128. © 2025 AQA

  Text version

  This question is about metals and metal oxides. Tin is extracted by SnO₂ + C -> Sn + CO₂. Cadmium is extracted by CdO + C -> Cd + CO. Tungsten oxide reacts by WO₃ + 3H₂ -> W + 3H₂O.

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• AQA 8462 · June 2025 · Paper 1H · Q3 · 11 marks

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  [03.3] More than two thirds of students achieved full marks. Some did not calculate a total Mr but used the Mr of CdO instead; these answers were not creditworthy. Others added up all the Mr of reactants and products instead of just the reactants; these gained partial credit.

  Text version

  This question is about metals and metal oxides. Tin is extracted by SnO₂ + C -> Sn + CO₂. Cadmium is extracted by CdO + C -> Cd + CO. Tungsten oxide reacts by WO₃ + 3H₂ -> W + 3H₂O.

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• AQA 8462 · June 2025 · Paper 1H · Q8 · 12 marks

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  [08.3] The vast majority gave the correct reading. The most common error was 25.3 cm3.

  Text version

  This question is about alkalis and acids. A student planned to titrate 25.0 cm³ of known sulfuric acid against sodium hydroxide using universal indicator, a pipette, conical flask, white tile and burette, adding alkali while swirling until a colour change and repeating to consistency.

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• AQA 8462 · June 2025 · Paper 1H · Q9 · 11 marks

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  [09.2] Nearly a half of students gained full marks in this calculation and over three quarters could make some progress. This was a multi-step calculation, which is classed as an extended response question. As such, the working has to make sense chemically. Those students who managed to put the data together in such a way as to obtain an answer of 78.9%, but whose working made no sense chemically, were often limited to the mark for the correct number of significant figures. There were many excellent fully correct answers, and many students were able to make some progress by calculating the number of moles of iodine and / or zinc iodide. While most adopted the expected approach, calculating the expected mass of zinc iodide and finding the actual mass as a percentage of that value, two other valid approaches also gained credit. One of these was to find the moles of zinc iodide produced as a percentage of the expected moles. The other, far less commonly seen, was to find the mass of iodine actually reacted and take that as a percentage of the mass provided. Of those who adopted the approach of calculating the expected mass of zinc iodide, many surprisingly calculated the mass of zinc and added that to the mass of iodine, rather than simply multiplying the number of moles by the Mr of ZnI2, which was provided. Students had little difficulty in rounding correctly to 3 significant figures.

  Text version

  Zinc reacts with iodine to produce zinc iodide in ethanol. Ethanol is flammable and boils at 78 °C. Zinc is insoluble in ethanol; iodine and zinc iodide are soluble.

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• AQA 8462 · June 2025 · Paper 2F · Q8 · 11 marks

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  [08.1] Just over half of students gave the correct answer here. Many who did not gain the mark did not give the required comparative answer.

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  A student measured 10.0 cm³ sea-water samples A-D with a burette, evaporated the water in a pre-weighed basin, and measured dissolved-solid masses 0.35, 0.37, 0.33 and 0.34 g.

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• AQA 8462 · June 2025 · Paper 2F · Q9 · 6 marks

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  [09.6] A quarter of students named butane correctly. Propane was the most common incorrect answer.

  Text version

  This question is about hydrocarbon fuels. Crude oil is heated and its vapours enter a fractionating column, where fractions condense at different heights. Boiling ranges: petrol 40-110 °C, kerosene 180-260 °C, diesel 260-320 °C, heavy fuel oil 320-400 °C, petroleum gases below 30 °C.

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• AQA 8462 · June 2025 · Paper 2H · Q1 · 11 marks

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  [01.3] The idea of heating to constant mass was known by a quarter of students, who gained two marks. Nearly 3 in 5 students gained no marks, often suggesting heating for longer, looking at the basin to see if there was any water left, heating above 100°C or patting dry.

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  A student measured 10.0 cm³ sea-water samples A-D with a burette, evaporated the water in a pre-weighed basin, and measured dissolved-solid masses 0.35, 0.37, 0.33 and 0.34 g.

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• AQA 8462 · June 2025 · Paper 2H · Q2 · 6 marks

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  [02.1] Over 90% of students correctly identified fractional distillation.

  Text version

  This question is about hydrocarbon fuels. Crude oil is heated and vapours enter a fractionating column where fractions condense at different heights. Boiling ranges: petrol 40-110 °C, kerosene 180-260 °C, diesel 260-320 °C, heavy fuel oil 320-400 °C, petroleum gases below 30 °C.

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• AQA 8462 · June 2025 · Paper 2H · Q5 · 11 marks

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  [05.5] Around three quarters of students correctly identified propene. The most common incorrect response was butene. Very few students did not identify an alkene.

  Text version

  This question is about unsaturated hydrocarbons. Boiling points: C₂H₄ -104 °C, C₃H₆ -47 °C, C₄H₈ unknown, C₅H₁₀ 30 °C, C₆H₁₂ 63 °C.

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• AQA 8462 · June 2025 · Paper 2H · Q8 · 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.

  Text version

  Hydrogen peroxide decomposes: 2H₂O₂(aq) -> 2H₂O(l) + O₂(g). A student compared 1.00 g each of catalysts A and B with 50 cm³ of 1.5 mol/dm³ hydrogen peroxide by recording mass loss. The reaction profile shows catalyst B has lower activation energy than A.

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• AQA 8462 · June 2024 · Paper 1F · Q3 · 9 marks

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  [03.8] Students struggled with this standard demand question, with only a quarter gaining a mark. More than a half of students selected the second distractor, in which both parts of the statement are the opposite of the correct version. When temperature decreases, heat energy is being taken in from the surroundings and converted to chemical energy, so the reaction is endothermic. It is this reduction in heat energy that causes the temperature decrease. A misconception for many students is thinking that when heat energy is taken in from the surroundings it remains as heat energy in the system, causing the confusion with the direction of temperature change.

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  Zinc reacts with copper sulfate solution: zinc + copper sulfate -> zinc sulfate + copper. A student measured energy changes using 25 cm³ of copper sulfate solution in a polystyrene cup and different masses of zinc powder.

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• AQA 8462 · June 2024 · Paper 1F · Q6 · 10 marks

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  [06.1] Fewer than a half of students identified the reason why molten substances can be electrolysed. The incorrect distractor that electrons can move through the substance was almost as popular.

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  This question is about electrolysis and extracting metals. The reactivity sequence supplied is potassium, lithium, carbon, zinc, tin, gold, in decreasing reactivity.

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• AQA 8462 · June 2024 · Paper 1F · Q8 · 10 marks

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  [08.2] About a half of students gave a correct observation that would show that the reaction was no longer proceeding. Many did not realise that they were looking for signs of the reaction having stopped, and gave observations they would make while it was still ongoing.

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  A student produced a salt by reacting excess copper carbonate with 50 cm³ of sulfuric acid, filtering, warming the filtrate until crystals started to appear, then cooling to crystallise.

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• AQA 8462 · June 2024 · Paper 1H · Q1 · 10 marks

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  [01.5] The great majority of students were able to substitute the values and rearrange the expression to give the correct answer. Some students used their calculator incorrectly, using both the % button and also dividing by 100, giving an answer that was a factor of 100 too low. They seemed unfamiliar with the idea that the symbol ‘%’ means divided by 100. A minority of students tried to incorporate the 50 cm3 into their calculation.

  Text version

  A student produced a salt by reacting excess copper carbonate with 50 cm³ of sulfuric acid, filtering, warming the filtrate until crystals started to appear, then cooling to crystallise.

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• AQA 8462 · June 2024 · Paper 1H · Q4 · 8 marks

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  [04.2] This question discriminated well, with a quarter of students scoring 3 or 4 marks and the great majority scoring at least one mark. The question asked students to explain the results, but many simply described them. It was not sufficient just to describe the temperature increasing with the addition of more zinc; reference to the reaction being exothermic was also needed. The fact that the maximum temperature change occurred when 0.80 g of zinc was added was the mark scored most often, but many students were also able to explain this turning point in terms of no further reaction being possible because the zinc was now in excess. There were some excellent answers in terms of the zinc being the limiting reactant up to 0.8 g, after which the copper sulfate became the limiting reactant.

  Text version

  A student investigated the energy change when different masses of zinc powder reacted with 25 cm³ of copper sulfate solution in a polystyrene cup. A second student repeated the method four times using 0.50 g of zinc.

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• AQA 8462 · June 2024 · Paper 1H · Q6 · 11 marks

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  [06.1] Over three fifths of students scored all three marks. Most students could list the metals in order of decreasing reactivity, although some ignored the sign and ordered the metals in order of absolute magnitude of voltage. A few tried to remember the reactivity series, even though nickel and silver are not listed in the specification. The best answers justified the order not only in terms of the most reactive metal producing the most positive voltage, but also that the negative voltages were produced by elements less reactive than nickel.

  Text version

  Figure 6 shows a chemical cell with a nickel electrode and electrode A in 1.0 mol/dm³ sodium chloride, both connected to a voltmeter. Results for electrode A were: Cu -0.59 V; Mg 2.12 V; Ni 0.00 V; Ag -1.05 V; Zn 0.51 V.

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• AQA 8462 · June 2024 · Paper 1H · Q7 · 15 marks

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  [07.2] This question discriminated well, with over a half of students scoring 2 or 3 marks. There were many well-expressed, complete answers. Common errors often involved an attempt to describe some sort of stronger bonding (sometimes covalent or ionic) in the alloy. Some lost credit because of poor use of language; it is not ‘metals’ which are different sizes, but their atoms (or positive ions). A common error was to refer to different shapes of atoms. ‘Particles’ is also insufficient as it could refer to other types of particle than atoms. ‘Intermolecular forces’ were often referred to, although they are not present in either a pure metal or an alloy.

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  This question is about iron. The common oxides include Fe₂O₃ and Fe₃O₄.

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• AQA 8462 · June 2024 · Paper 1H · Q9 · 12 marks

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  [09.1] Over a half of students knew that a weak acid is one which is partially ionised, although many forgot to state that this was in aqueous solution. Some students incorrectly stated that an acid is ionising (ionises other species) rather than ionised (is itself ionised). Some incorrectly stated that it was H+ ions which are ionised or dissociated, rather than the acid molecules. The H+ ions are the result of the ionisation or dissociation.

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  This question is about acids and their reactions.

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• AQA 8462 · June 2024 · Paper 2H · Q5 · 12 marks

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  [05.4] Over one-third of students gained all three marks. However, some students appeared to believe that the other 80% of the air was hydrogen. Some tried to involve the relative atomic masses, even though these were not provided. A few unnecessarily converted the volume of hydrogen to moles and then the moles of oxygen to volume, not realising that the mole ratio is the volume ratio for gases. This did score full marks if correct.

  Text version

  For each 1 dm³ burned: hydrogen releases 11.9 kJ, 0.00 g CO₂, 0.75 g water vapour and 6.6x10^-4 g nitrogen oxides; natural gas releases 37.1 kJ, 1.83 g CO₂, 1.50 g water vapour and 4.9x10^-4 g nitrogen oxides.

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• AQA 8462 · June 2024 · Paper 2H · Q8 · 9 marks

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  [08.1] Around 60% of students correctly identified the C=C bond. For students who were not awarded the mark common mistakes were incorporating the 3 Hs and 1 O atom attached to the C=C group in their circle or also circling the C=O group. Others circled only the double bond and not the carbon atoms on either side.

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  Compound A contains both alkene and ester functional groups and has formula C₄H₆O₂. It is flammable and forms polymer B by joining many molecules.

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• AQA 8462 · June 2023 · Paper 1F · Q2 · 10 marks

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  [02.4] This was well answered, with the vast majority recognising a burette as the correct piece of equipment.

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  This question is about acids, alkalis and titration. A student titrated 25.0 cm³ sodium hydroxide solution with hydrochloric acid. Four acid volumes were 24.3, 24.5, 28.1 and 24.4 cm³.

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• AQA 8462 · June 2023 · Paper 1F · Q8 · 10 marks

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  [08.4] This question also discriminated well. Most students could substitute the values correctly into the given expression. However, some did not know how to evaluate that expression and some incorrectly rounded a value of 77.9% to 77% instead of 78%.

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  Iron oxide is displaced by carbon. Copper oxide reacts with hydrogen: CuO + H₂ -> Cu + H₂O. A student also tested metals A-D in each metal-sulfate solution. Results (columns A/B/C/D sulfate) were A: no/no/yes/no; B: yes/no/yes/no; C: no/no/no/no; D: yes/yes/yes/no.

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• AQA 8462 · June 2023 · Paper 1F · Q10 · 6 marks

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  [10.5] This was very poorly answered. Only a handful of students scored both marks, with just over one in ten scoring one. Students are unfamiliar with the idea of uncertainty as the range about the mean, as stated in the specification. There were some good descriptions of the highest value being 0.3 °C above the mean and the lowest being 0.3 °C below the mean, but very few used the word uncertainty.

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  A student dissolved different masses of ammonium nitrate in 200 cm³ water and recorded the lowest temperature. For 8.0 g, four repeat temperatures were 16.2, 16.6, 16.8 and 16.4 °C, with mean 16.5 ± 0.3 °C.

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• AQA 8462 · June 2023 · Paper 1H · Q2 · 6 marks

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  [02.4] Nearly four fifths of students answered correctly in terms of the decrease of temperature. It was not necessary to refer to energy transfer as that is not shown in the results; however, those who did so usually referred correctly to energy being taken in. Those who contradicted their answer by giving an incorrect reference to energy being given out did not score the point.

  Text version

  This question is about temperature changes. A student investigated the change in temperature of a solution when different masses of ammonium nitrate were dissolved in water. This is the method used. 1. Measure 200 cm³ of water into a polystyrene cup. 2. Measure the temperature of the water. 3. Add 4.0 g of ammonium nitrate to the water. 4. Stir the solution until all the ammonium nitrate has dissolved. 5. Measure the lowest temperature reached by the solution. 6. Repeat steps 1 to 5 with different masses of ammonium nitrate. Table 2 shows the results (mass of ammonium nitrate added in grams / lowest temperature of solution in °C): 4.0 / 18.2; 8.0 / 16.2; 12.0 / 15.2; 16.0 / 13.6; 20.0 / 12.4; 24.0 / 10.6.

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• AQA 8462 · June 2023 · Paper 1H · Q5 · 12 marks

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  [05.4] About three fifths of students knew that the OH– ion is responsible. When asked for a formula, an equation is not an appropriate response.

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  This question is about acids and alkalis.

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• AQA 8462 · June 2023 · Paper 1H · Q7 · 9 marks

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  [07.4] Nearly two thirds of students scored at least one mark, but just over half of these also scored the second mark. The easiest change to the apparatus is to change the test tubes to measuring cylinders or inverted burettes. Many students suggested gas syringes; this was allowed, although it would be difficult to set up the apparatus in such a way that this would work. However, a ‘gas cylinder’ is not a measuring device. One popular misconception is that gas would escape from the apparatus so a lid should be used. Most students realised that the reason was so that the gas volume could be measured rather than estimated, or that test tubes have no scale; any equivalent way of expressing this idea was allowed. Some students used imprecise language such as ‘so the gas could be measured’ without referring to volume or a scale.

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  This question is about electrolysis. Aluminium is manufactured by electrolysing a molten mixture of aluminium oxide (Al₂O₃) and cryolite (Na₃AlF₆).

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• AQA 8462 · June 2023 · Paper 1H · Q10 · 8 marks

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  [10.2] This question discriminated well. The great majority of students scored at least one mark, with nearly a half scoring five or six marks. The most common error was not converting 100 kilograms to grams in order to calculate the moles, or converting incorrectly. Another common error was to calculate a spurious volume of TiO2. Some converted the number of moles of chlorine to a mass first, before converting to a volume; whilst unnecessary, this did give the correct answer and gained full credit. Students who gained one or two marks usually calculated the relative formula mass of TiO2 and/or converted 100 kilograms to grams. A few seemed to be concerned by the large value of the answer and introduced a division by 1000 into what would have been a correct answer. Students sometimes tried more than one method and did not cross out the one they did not want to be marked. This led to confusion and contradictions, sometimes meaning that marks could not be awarded. Students should always cross out discarded methods; examiners will not make the choice for the student.

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  This question is about titanium dioxide (TiO₂).

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• AQA 8462 · June 2023 · Paper 2F · Q4 · 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.

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• AQA 8462 · June 2023 · Paper 2H · Q5 · 9 marks

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  [05.2] This calculation was well done by many students, with more than three-quarters of students scoring the mark. The commonest error was to incorrectly calculate the relative formula mass of the compound due to missing the fact that the compound contained two atoms of sulfur and not one. More than three-quarters of students scored the mark.

  Text version

  Copper is extracted from metal ores. Chalcopyrite is a metal ore containing a compound with the formula CuFeS₂.

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• AQA 8462 · June 2023 · Paper 2H · Q7 · 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 cm³ of 2.0 mol/dm³ 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.

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• AQA 8462 · June 2022 · Paper 1F · Q6 · 5 marks

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  [06.5] Just over half of the students could count the atoms in the figure and then write the formula correctly. Many failed to gain credit because the numbers were not subscripts but the same size as the letters, or even larger.

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  This question is about carbon and its compounds. Diamond has a giant covalent structure. Carbonic acid has formula H₂CO₃.

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• AQA 8462 · June 2022 · Paper 1F · Q8 · 8 marks

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  [08.4] This was well answered, with the great majority of students naming both correct products.

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  A student electrolyses sodium sulfate solution containing hydrogen, hydroxide, sodium and sulfate ions. Oxygen forms at the positive electrode. Molten electrolysis products include potassium iodide -> potassium + [blank], and zinc bromide -> [blank] + bromine. Titanium is produced by TiO₂ -> Ti + O₂.

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• AQA 8462 · June 2022 · Paper 1H · Q3 · 11 marks

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  [03.2] There were many excellent answers. However, a large number of students contradicted themselves by referring to ‘strong intermolecular forces’ as well as strong bonds. There are no intermolecular forces in diamond, let alone strong ones. Students sometimes referred to ‘more energy’ required to break the bonds. This did not gain credit as there was no idea of what the energy was being compared with.

  Text version

  This question is about different forms of carbon. Diamond is a form of carbon. C₇₀ is a carbon molecule. The Avogadro constant is 6.02x10²³ mol^-1.

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• AQA 8462 · June 2022 · Paper 1H · Q5 · 11 marks

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  [05.1] Nearly half of students described how a specific observation would differ. Vague comments about a more violent reaction, with no specific visual observation, did not gain credit.

  Text version

  Rubidium is below potassium in Group 1. Neon isotope data: mass 20 at 90.48%, mass 21 at 0.27%, mass 22 at 9.25%.

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• AQA 8462 · June 2022 · Paper 1H · Q7 · 14 marks

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  [07.1] This was well answered, with more than half of students scoring both marks. There was, however, some ambiguous use of the word ‘it’ such as ‘it shows that it is below carbon because it displaces it’. If it was not clear what ‘it’ referred to, credit was not given.

  Text version

  Silicon can be extracted by 2C+SiO₂ -> Si+2CO or by 2Mg+SiO₂ -> Si+2MgO. Si₂H₆ reacts: 2Si₂H₆(g)+7O₂(g) -> 4SiO₂(s)+6H₂O(g).

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• AQA 8462 · June 2022 · Paper 1H · Q8 · 14 marks

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  [08.2] Most students were able to explain that the first titration is anomalous and the mean of the other four titrations is used. Some correctly described this as taking the mean of the concordant results, or the mean of the results within 0.10 cm3. Incorrect answers included that the value used was the mean of all five results, or that it was the mode or median of the results.

  Text version

  A student titrated 25.00 cm³ hydrochloric acid with 0.100 mol/dm³ barium hydroxide. Volumes were 23.90, 23.45, 23.55, 23.55 and 23.45 cm³; the calculation used 23.50 cm³. Equations: 2HCl+Ba(OH)₂ -> BaCl₂+2H₂O; H₂SO₄+Ba(OH)₂ -> BaSO₄(s)+2H₂O.

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• AQA 8462 · June 2022 · Paper 2F · Q5 · 7 marks

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  [05.5] Around one-third of students obtained all three marks. Over 50% of students plotted the points correctly but did not obtain the line of best fit mark. Common mistakes when drawing the line of best fit were to draw a straight line, a series of dot-to-dot straight lines, a very thick line or multiple lines.

  Text version

  Ammonia is made in the Haber process from nitrogen and hydrogen. At pressures 50, 100, 150, 200, 250 and 300 atm, ammonia yields are 20, 33, 44, 52, 59 and 64%.

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• AQA 8462 · June 2022 · Paper 2F · Q6 · 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 cm³ hydrochloric acid to 50 cm³ sodium thiosulfate and recorded the percentage of light reaching a sensor every 20 s as sulfur clouded the mixture. Na₂S₂O₃ + 2HCl -> NaCl + H₂O + SO₂ + S.

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• AQA 8462 · June 2022 · Paper 2F · Q9 · 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.

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• 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.

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• AQA 8462 · June 2022 · Paper 2H · Q4 · 16 marks

  16 marks

  4

  
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  [04.1] The vast majority of students wrote detailed answers to this question and the full range of marks was awarded although relatively few answers were awarded full marks. About 1 in 10 students scored all four marks, while a quarter scored three. Students often neglected to state the crude oil must be heated to begin the separation process. Some students failed to score the second marking point in the mark scheme because their description of a temperature gradient was not in the context of gases rising through a fractionating column or fractionating tower. A handful of students illustrated this idea by referring to a labelled diagram. The idea of fractions collecting at different levels in the fractionating column was well understood but many described the collection of fractions without mentioning condensing and so could not access this mark. Some students incorrectly suggested that petroleum gases would condense at the top of the column. The idea that the separation of crude oil is based on differences in boiling points was an accessible mark but many failed to mention boiling points or simply quoted boiling point ranges from the table.

  Text version

  Crude-oil fractions include lubricating oil (300-350 °C), naphtha (90-200 °C) and petroleum gases (<25 °C). Kerosene molecules have 11-15 carbon atoms and heavy-fuel-oil molecules 20-40.

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• AQA 8462 · June 2022 · Paper 2H · Q7 · 11 marks

  11 marks

  7

  
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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.

  Text version

  The Haber process is N₂(g)+3H₂(g) ⇌ 2NH₃(g), forward exothermic. It uses 450 °C, 200 atm and an iron catalyst.

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• AQA 8462 · June 2022 · Paper 2H · Q8 · 4 marks

  4 marks

  8

  
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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.

  Text version

  Hydrochloric acid reacts with sodium thiosulfate: Na₂S₂O₃+2HCl -> 2NaCl+H₂O+SO₂+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.

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• AQA 8462 · November 2021 · Paper 1F · Q4 · 9 marks

  9 marks

  4

  
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  A student reacted cobalt, magnesium and zinc powders with 50 cm3 hydrochloric acid. Temperature increases (degC) were cobalt 6,7,5,9; magnesium 54,50,37,55; zinc 18,16,18,20. The anomalous magnesium result is 37.

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• AQA 8462 · November 2021 · Paper 1F · Q10 · 10 marks

  10 marks

  10

  
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  Element R is extracted by 3H₂+RO₃ -> R+3H₂O; the total M_r of reactants is 150. Tin is extracted by SnO₂+C -> Sn+CO₂. A_r: H=1, C=12, O=16, Sn=119. Three tungsten-extraction methods use carbon (low cost; W, CO2 and tungsten carbide), hydrogen (high cost; W and water vapour), or iron (low cost; W and iron oxide); other solids must be separated.

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• AQA 8462 · November 2021 · Paper 1H · Q3 · 10 marks

  10 marks

  3

  
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  [03.2] This was well answered. Credit was given to those who applied an incorrect response to question 03.1 correctly. Some students gave an answer which corresponded to their answer to question 03.1 used as atomic number rather than relative atomic mass.

  Text version

  Element R is extracted by 3H₂+RO₃ -> R+3H₂O; total reactant M_r=150. Tin extraction is SnO₂+C -> Sn+CO₂. A_r: H=1, C=12, O=16, Sn=119. Tungsten methods use carbon (low cost; W, CO2, tungsten carbide), hydrogen (high cost; W, water vapour), or iron (low cost; W, iron oxide).

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• AQA 8462 · November 2021 · Paper 1H · Q5 · 10 marks

  10 marks

  5

  
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  [05.5] Very few students knew that a water bath or an electric heater should be used, despite this being stated in the specification.

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  This question is about making salts, including magnesium sulfate crystals and iron(III) chloride.

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• AQA 8462 · November 2021 · Paper 1H · Q7 · 16 marks

  16 marks

  7

  
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  [07.2] Many students were unable to write the formula of bromine. Those who could, often scored at least one mark, although the half-equation was not always balanced.

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  This question compares electrolysis with chemical cells and investigates copper nitrate electrolysis. At 20 minutes, Figure 5 shows 0.12 g copper at 0.3 A and 0.24 g at 0.6 A.

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• AQA 8462 · November 2021 · Paper 1H · Q8 · 7 marks

  7 marks

  8

  
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  [08.4] A good number of students were successful with this calculation, although some failed to count all of the bonds correctly. Where students made a slip of this nature, or an arithmetic error, it was sometimes impossible to award marks for following through with the method, since there was often a jumble of numbers scattered over the page with no words to explain what was going on. ‘Bonds broken’ and ‘bonds made’ should be stated in calculations of this type. Many students did not use the value of 1034 kJ/mol provided.

  Text version

  2H₂S(g)+3O₂(g) -> 2H₂O(g)+2SO₂(g). Bond energies: H-S 364, O=O 498, O-H 464 kJ/mol; S=O is X. Energy released forming bonds is 1034 kJ/mol greater than energy needed to break bonds. The displayed equation contains four H-S and three O=O bonds broken, and four O-H and four S=O bonds formed.

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• AQA 8462 · November 2021 · Paper 1H · Q9 · 9 marks

  9 marks

  9

  
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  [09.4] As with other calculations, students often failed to explain what they were doing, which made it difficult for the examiners to award partial credit. Numbers were scattered around without helpful words such as ‘moles =’ or ‘mass =’. Although most students convert the volume of a solution to dm3 for a titration calculation, far fewer did in this calculation, so their calculated number of moles was 1000 times the correct value.

  Text version

  Hydrogen chloride is fully ionised; about 1% of ethanoic acid ionises. A titration uses 0.0480 mol/dm3 ethanedioic acid and 25.0 cm3 sodium hydroxide. Equation: H₂C₂O₄+2NaOH -> Na₂C₂O₄+2H₂O.

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• AQA 8462 · November 2021 · Paper 2F · Q6 · 8 marks

  8 marks

  6

  
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  Potash alum contains K+, Al3+ and sulfate ions. A solution concentration is 258 g/dm3.

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• AQA 8462 · November 2021 · Paper 2F · Q7 · 11 marks

  11 marks

  7

  
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  Ethene and steam reversibly produce ethanol. Actual yield is 380 kg from a 400 kg theoretical yield. Fermentation uses renewable sugar, low energy, slow rate and gives 15% ethanol; hydration uses crude oil, high energy, fast rate and gives 98% ethanol.

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• AQA 8462 · November 2021 · Paper 2H · Q6 · 6 marks

  6 marks

  6

  
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  [06.3] Only around a third of students gained at least one mark in this demanding question.

  Text version

  Cycloalkenes are ring hydrocarbons with one C=C bond. Cyclobutene C4H6, cyclopentene C5H8, cyclohexene C6H10. Chlorine adds to cyclohexene to form C6H10Cl2.

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• AQA 8462 · November 2021 · Paper 2H · Q10 · 17 marks

  17 marks

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  [10.4] Fermentation was well known.

  Text version

  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.

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• AQA 8462 · November 2020 · Paper 1F · Q10 · 10 marks

  10 marks

  10

  
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  Silver iodide forms by AgNO₃(aq)+NaI(aq)->AgI(s)+NaNO₃(aq). Before mixing, beakers A and B have masses 78.26 g and 78.50 g; after, 108.22 g and 48.54 g. M_r: AgNO3=170, NaI=150, AgI=235, NaNO3=85.

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• AQA 8462 · November 2020 · Paper 1H · Q3 · 10 marks

  10 marks

  3

  
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  [03.6] Most answered correctly in terms of profitability, or reduction of waste. There was some confusion between atom economy and percentage yield.

  Text version

  Silver iodide forms by AgNO₃(aq)+NaI(aq)->AgI(s)+NaNO₃(aq). Before mixing, beakers A and B have masses 78.26 g and 78.50 g; after, 108.22 g and 48.54 g. M_r: AgNO3=170, NaI=150, AgI=235, NaNO3=85.

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• AQA 8462 · November 2020 · Paper 1H · Q8 · 16 marks

  16 marks

  8

  
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  [08.4] Many students realised that the fume cupboard would prevent inhalation of the gas, which is toxic. However, some students regard a fume cupboard as insulation to prevent the escape of heat energy, or thought it was to trap and retain the gas.

  Text version

  Halogen data: fluorine mp -220, bp -188 degC; chlorine -101, -35; bromine -7, 59. Iron reacts with gaseous halogens. A tube has mass 51.56 g, with iron 56.04 g, and after chlorination 64.56 g.

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• AQA 8462 · November 2020 · Paper 2F · Q2 · 8 marks

  8 marks

  2

  
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  This question concerns atmospheric pollutants from fuels, diesel engines and high-temperature car engines.

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• 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.

  Text version

  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.

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• AQA 8462 · June 2019 · Paper 1F · Q5 · 6 marks

  6 marks

  5

  
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  [05.5] Just under a half of students correctly identified the independent variable.

  Text version

  Calcium carbonate reacts with hydrochloric acid: CaCO3(X)+2HCl(aq)->CaCl2(aq)+CO2(g)+H2O(l). Four mass decreases for 2 g carbonate are 0.84, 0.79, 0.86 and 0.47 g.

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• AQA 8462 · June 2019 · Paper 1F · Q6 · 11 marks

  11 marks

  6

  
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  [06.3] Approximately 70% of students calculated the relative formula mass correctly.

  Text version

  Tungsten forms by WO3+3H2->W+3H2O. Mr WO3=232, H2=2 and Ar W=184. Aluminium extraction data are also given.

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• AQA 8462 · June 2019 · Paper 1H · Q8 · 8 marks

  8 marks

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  [08.1] Only approximately a quarter of students scored this mark. They usually did so by identifying the need to ensure that the oxide of copper had completely reacted. Common responses seen that were not credited included: • to ensure complete reaction (unqualified) • to ensure reliable / valid / accurate results.

  Text version

  Copper oxide is reduced by hydrogen in heated tube A; water is captured in tube B. Tube A empty 105.72 g, with oxide 115.47 g, final 114.38 g. Tube B starts 120.93 g and ends 123.38 g.

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• AQA 8462 · June 2019 · Paper 1H · Q9 · 8 marks

  8 marks

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  [09.1] Almost a half of students scored 0 marks. The mark scheme required the use of comparatives. Common correct responses were: • Better insulator • Less heat loss Common responses seen that were not credited included: • good insulator • no heat loss.

  Text version

  Sulfuric acid is added to 25.0 cm3 KOH in a polystyrene cup. A later run uses 15.5 cm3 of 0.500 mol/dm3 H2SO4. Equation: 2KOH+H2SO4->K2SO4+2H2O.

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• AQA 8462 · June 2018 · Paper 1F · Q5 · 4 marks

  4 marks

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  [05.3] This was very well answered, with 83% of students achieving the mark.

  Text version

  Copper carbonate is heated to copper oxide and carbon dioxide. Table results include an anomalous trial and a mass X.

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• AQA 8462 · June 2018 · Paper 1F · Q9 · 11 marks

  11 marks

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  [09.3] Whilst 56% of students achieved at least one mark, 34% of these students achieved both. • Many students repeated information in the stem of the question. And some appeared to ignore it as they declared sodium to be a non-metal. • Many gave differences in the structure of the atoms instead of differences in properties of the substances. • Some effectively gave the same difference twice, for example writing that sodium is soft on one line and iron is hard on the other.

  Text version

  A particle diagram of iron pyrites shows an iron:sulfur atom ratio of 1:2; iron-56 has atomic number 26. Nickel is extracted by carbon; atom-economy reactants have total Mr 87 and useful product Mr 59.

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• AQA 8462 · June 2018 · Paper 1H · Q2 · 11 marks

  11 marks

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  [02.1] Because the question asked for the formula rather than the empirical formula, an answer of Fe9S18 was accepted. Even so, 51% of students could not count the atoms and produce a ratio of 1:2. A formula was required, not an equation which some students provided.

  Text version

  A particle diagram of iron pyrites shows an iron:sulfur atom ratio of 1:2; iron-56 has atomic number 26. Nickel is extracted by carbon; atom-economy reactants have total Mr 87 and useful product Mr 59.

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• AQA 8462 · June 2018 · Paper 1H · Q6 · 14 marks

  14 marks

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  [06.3] 58% of students did not achieve a mark for this question. The investigation was stated to be about the relationship between volume and time, but the diagram showed no means of measuring volume. The expected answer was to use inverted measuring cylinders so that volume (not ‘amount’) could be measured. Although it would pose practical difficulties, the idea of using gas syringes was also accepted (on the grounds that it could be made to work if they were attached to funnels placed over the electrodes). Many suggested changing the electrodes as graphite is not inert, suggesting a lack of understanding of the required practical. Some students suggested that the apparatus is upside down.

  Text version

  A student electrolyses zinc chloride using graphite. Hydrogen collection is steady at 0.45 cm3/min; chlorine initially collects more slowly, then at the same rate after about 8 min. At 20 min chlorine volume is 6.6 cm3. Gas molar volume=24 dm3.

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• AQA 8462 · June 2018 · Paper 1H · Q8 · 15 marks

  15 marks

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  [08.7] This difficult unstructured calculation tested a new area of the specification, and discriminated very well. 74% of students were able to achieve at least one mark, usually for calculating the Mr of TiCl4. 7% of students achieved all four marks, with 12% achieving at least three marks and there were some valiant efforts. Common errors were: • using 92 instead of 23 to calculate the number of moles of Na • omitting the unit conversion from kg to g for the mole calculations • using the 1:4 mole ratio incorrectly or not at all. Also, it is not appropriate to leave answers in the form of a fraction, even if this is the default on their calculator. Answers should always be converted to decimal form.

  Text version

  Titanium manufacture uses chlorine, titanium chloride, sodium and argon. Stage 2 reacts TiCl4 with 4Na. Ar Ti=48,Cl=35.5,Na=23; actual yield comparison uses theoretical 13.5 kg and 92.3%.

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• AQA 8462 · June 2018 · Paper 2H · Q7 · 12 marks

  12 marks

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  [07.5] This was generally well answered, although ‘2N’ was a common incorrect response. Students need to remember that gases such as nitrogen, hydrogen and oxygen normally exist as diatomic molecules. 61% of students achieved both the marks.

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  This question is about car-engine pollutants, catalytic converters and nitrogen dioxide decomposition.

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• 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.

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• 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.

  Text version

  Methanol forms by CO+2H2 <-> CH3OH at 250 degC and high pressure with a catalyst; the forward reaction is exothermic.

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• AQA 8462 · sample1 · Paper 1F · Q6 · 13 marks

  13 marks

  6

  
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  Copper carbonate reacts with sulfuric acid to form copper sulfate, carbon dioxide and water. Useful-product Mr=159.5 and total reactant Mr=221.5.

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• AQA 8462 · sample1 · Paper 1H · Q3 · 12 marks

  12 marks

  3

  
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  Potassium forms ionic K2S; sulfur also forms covalent H2S. Ar Al=27,S=32,O=16.

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• AQA 8462 · sample1 · Paper 1H · Q7 · 11 marks

  11 marks

  7

  
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  Sodium carbonate reacts with acid and CO2 volume plateaus at 95.0 cm3. Gas molar volume is 24000 cm3/mol.

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