Paper 62, worked through. Cambridge IGCSE Chemistry, May/June 2026: worked solutions

Forty marks in an hour. This paper tests what you would do at the bench: naming apparatus, reading scales, plotting a graph, the tests for ions, and planning a method. The notes for qualitative analysis are printed at the back, so the colours of precipitates and the gas tests can be looked up. Use them.

1. 1(a)Naming two pieces of apparatus used in a distillation.[2]
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   1. A is the sloping tube with an outer jacket, where the vapour turns back into liquid: a condenser.
   2. B is the open container that the liquid drips into: a beaker.

   AnswerA: condenser. B: beaker.

   Give the plain name. "Cooling tube", "delivery tube" and "water jacket" are not accepted for the condenser.

   Revise this: Separating mixtures
2. 1(b)(i)Showing where the heat should go.[1]
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   1. The flask of alkanes sits in a beaker of water: a water bath. The heat is applied to the water, and the water heats the flask.
   2. Draw the arrow pointing up at the bottom of the left-hand beaker, the one holding the water.

   AnswerAn arrow under the left-hand beaker (the water bath).

   Not under the collecting beaker on the right, and not on the condenser. The arrow must be where the heater would stand.

   Revise this: Separating mixtures
3. 1(b)(ii)Why a Bunsen burner is the wrong heater here.[1]
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   1. A Bunsen burner has a naked flame. The alkanes are flammable, as the question's first line says, and their vapour could catch fire.

   AnswerThe alkanes are flammable.

   The first sentence of the question hands you the answer. "It would be too hot" is ignored.

   Revise this: Separating mixtures
4. 1(c)Marking where the cooling water goes into the condenser.[1]
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   1. Cooling water always enters a condenser at its lower end and leaves at the top, so that the jacket fills completely and stays full of cold water.
   2. The condenser slopes down towards the collecting beaker, so the lower end is the one near the beaker. Write W by the inlet there.

   AnswerW at the lower inlet of the condenser, at the end nearer the collecting beaker.

   In at the bottom, out at the top. Fed in at the top, the water would run straight through and leave the jacket half empty.

   Revise this: Separating mixtures
5. 1(d)Which alkane distils over first.[1]
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   1. Fractional distillation separates liquids by boiling point. As the mixture warms up, the liquid with the lowest boiling point boils first.
   2. Pentane boils at 36 °C, lower than hexane (69 °C) or undecane (196 °C).

   AnswerPentane, because it has the lowest boiling point.

   One mark for the pair, so the reason must be there. The table is not in order of boiling point: check the numbers, not the order of the rows.

   Revise this: Separating mixtures
6. 1(e)What stays behind in the flask, and why.[2]
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   1. The flask is heated by a water bath, and water boils at 100 °C. The mixture cannot get hotter than that.
   2. Pentane (36 °C) and hexane (69 °C) boil below 100 °C, so both distil over.
   3. Undecane boils at 196 °C, which the water bath can never reach, so it stays in the flask.

   AnswerUndecane. Its boiling point is above 100 °C, the highest temperature the water bath can reach.

   "It has the highest boiling point" is not enough: you must link it to the water. The second mark is given only if the first is right.

   Revise this: Separating mixtures
7. 2(a)Completing a results table from the method and from five measuring-cylinder diagrams.[3]
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   1. Volume of acid: the method says every experiment repeats Experiment 1, so it is 10.0 cm³ each time.
   2. Volume of water: 100, 90, 80, 70 and 60 cm³, from the instructions for each experiment.
   3. Volume of gas: read each diagram. The cylinder is upside down, so the numbers get bigger going down the page, and each small division is 1 cm³. The readings are 10, 16, 27, 46 and 82 cm³.

   AnswerAcid: 10.0 in every row. Water: 100, 90, 80, 70, 60. Gas: 10, 16, 27, 46, 82.

   One of the three marks is for consistent recording: the acid to one decimal place every time (10.0, as in the first row), and the water and the gas as whole numbers. An upside-down scale is read the same way as any other, but check which way the numbers run.

   Revise this: Measuring and apparatus
8. 2(b)Choosing a scale, plotting five points and drawing a line of best fit.[4]
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   1. Scale: the largest value is 82, so let the y-axis run from 0 to 100 with equal steps. The points should use more than half of the grid.
   2. Plot (100, 10), (90, 16), (80, 27), (70, 46) and (60, 82), each with a small neat cross.
   3. The points do not lie on a straight line: they fall steeply at first and then level off. Draw one smooth curve through them.

   AnswerA linear y-axis from 0 to 100; five points plotted correctly; one smooth curve through them, falling from left to right.

   A line of best fit is not always straight. Never join the points dot to dot with a ruler, and draw one clean line, not a sketchy one. Check the x-axis before plotting: it starts at 60, not 0.

   Revise this: Measuring and apparatus
9. 2(c)(i)Working out a mean rate of reaction, with its units.[2]
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   1. Mean rate = volume of gas collected ÷ time taken.
   2. In Experiment 3 the volume is 27 cm³ and the time is 75 s: 27 ÷ 75 = 0.36.
   3. The units follow the sum: cm³ divided by s gives cm³/s.

   Answer0.36 cm³/s

   The unit has a mark of its own. Build it from the two things you divided: volume over time.

   Revise this: Rates of reaction
10. 2(c)(ii)Which experiment was fastest.[1]
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    1. Every experiment ran for the same 75 s, so the one that collected the most gas has the highest mean rate.
    2. Experiment 5 collected 82 cm³, the most.

    AnswerExperiment 5.

    It also makes sense chemically. Experiment 5 had the least water added, so its acid was the most concentrated, and a higher concentration gives a faster reaction.

    Revise this: Rates of reaction
11. 2(d)Using the graph to predict a volume at a value that was not tested.[3]
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    1. Find 77 on the x-axis and rule a line straight up to your curve.
    2. From that point rule a line across to the y-axis and read the value.
    3. On a correctly drawn curve this is just over 30 cm³, between the readings for 80 cm³ of water (27) and 70 cm³ (46). Write the unit.

    AnswerAbout 32 cm³, read from your own curve.

    Three marks: the construction lines drawn on the graph, the value read correctly from your line, and the unit. "Show your working on the figure" means the lines must be there.

    Revise this: Measuring and apparatus
12. 2(e)(i)Why the smaller measuring cylinder is the better choice.[1]
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    1. A 10 cm³ cylinder is narrow, and its scale has smaller divisions than a 50 cm³ one. A volume of 10.0 cm³ can be read more precisely.

    AnswerIt is more accurate.

    Choose the smallest piece of apparatus that will hold the volume: the scale divisions are finer.

    Revise this: Measuring and apparatus
13. 2(e)(ii)An advantage of a volumetric pipette over a measuring cylinder.[1]
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    1. A volumetric pipette is made to deliver one fixed volume, and it does so more accurately than a measuring cylinder can.

    AnswerIt is more accurate.

    In order of accuracy: beaker, measuring cylinder, then burette and pipette. Speed and ease of use are not credited.

    Revise this: Measuring and apparatus
14. 2(f)(i)The effect of losing some gas before the stopper goes back.[1]
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    1. Gas that escapes never reaches the measuring cylinder, so the volume recorded is smaller than the volume actually made.

    AnswerThe volume of gas collected is smaller.

    The question asks about the volume collected. Talk of the rate changing is rejected: the reaction is no faster or slower, you just fail to catch some of the gas.

    Revise this: Rates of reaction
15. 2(f)(ii)In which experiment the most gas would be lost, and why.[2]
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    1. The gas escapes in the moment between adding the solid and replacing the stopper.
    2. The faster the reaction, the more gas is made in that moment. Experiment 5 is the fastest, because its acid is the most concentrated.

    AnswerExperiment 5, because its reaction is the fastest, so the most gas is produced before the stopper is replaced.

    The reason has to be about speed. "It makes the most gas" does not explain why more is lost in those first seconds.

    Revise this: Rates of reaction
16. 2(g)Sketching the line for a repeat with twice as much acid.[1]
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    1. With 20.0 cm³ of acid in place of 10.0 cm³, and the same volumes of water, the acid is more concentrated every time. The reaction is faster, so more gas is collected in 75 s in every experiment.
    2. Draw a second line that is above your first one all the way along, and does not touch it.

    AnswerA line above the original at every point.

    A sketch needs the right position, not exact points. The mark is lost if the two lines meet anywhere.

    Revise this: Rates of reaction
17. 3(a)What it means when a heated solid gives off a vapour that condenses on the tube.[1]
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    1. The condensation is water. It was driven out of the solid by heating, so the solid contained water of crystallisation.

    AnswerSolid C is hydrated (it contains water).

    "Hydrated" is the word to learn. "Water forms" on its own only repeats the observation and is ignored.

    Revise this: Tests for ions and gases
18. 3(b)Naming three ions from a flame test and two precipitate tests.[3]
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    1. Test 1: a lilac flame shows potassium ions, K⁺.
    2. Test 3: with aqueous sodium hydroxide, a green precipitate that dissolves in excess to give a green solution shows chromium(III) ions, Cr³⁺.
    3. Test 4: dilute nitric acid and then aqueous barium nitrate give a white precipitate, which shows sulfate ions, SO₄²⁻.

    AnswerPotassium ions, chromium(III) ions and sulfate ions.

    Iron(II) also gives a green precipitate with sodium hydroxide, but that one does not dissolve in excess. "Soluble in excess" is the detail that says chromium(III). Any extra wrong ion loses a mark.

    Revise this: Tests for ions and gases
19. 3(c)What you see when aqueous sodium hydroxide is added to an ammonium salt.[1]
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    1. Sodium hydroxide gives a precipitate with many metal ions, but ammonium bromide contains no metal ion. Nothing visible happens while the mixture is cold.

    AnswerNo change (no precipitate forms).

    "Record the expected observations" means what you would see. "Ammonia is made" is a conclusion, and no gas comes off until the mixture is warmed.

    Revise this: Tests for ions and gases
20. 3(d)The observation when the mixture is warmed and the gas is tested.[1]
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    1. Warming an ammonium compound with sodium hydroxide gives off ammonia.
    2. Ammonia is the alkaline gas: it turns damp red litmus paper blue.

    AnswerDamp red litmus paper turns blue.

    Give the test and its result, with the colours in the right order: red to blue.

    Revise this: Tests for ions and gases
21. 3(e)The result of the silver nitrate test on a bromide.[1]
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    1. Dilute nitric acid followed by aqueous silver nitrate is the test for halide ions. The colour of the precipitate tells you which one.
    2. Chloride gives white, bromide gives cream and iodide gives yellow.

    AnswerA cream precipitate.

    Write "precipitate", not "solution" or "colour". White, cream, yellow: in the same order as the halogens go down the group.

    Revise this: Tests for ions and gases
22. 4Planning how to get tin metal from a lump of its ore.[6]
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    1. Crush the lump to a powder, using a pestle and mortar. A powder has a larger surface area, so it reacts faster.
    2. Mix the powder with powdered carbon. Tin is below carbon in the reactivity series, so carbon can take the oxygen from tin(IV) oxide.
    3. Put the mixture in a crucible and heat it strongly.
    4. The tin(IV) oxide is reduced: tin(IV) oxide + carbon → tin + carbon dioxide. Tin metal is left in the crucible.

    AnswerCrush the ore with a pestle and mortar. Mix it with carbon, put the mixture in a crucible and heat it strongly. The carbon reduces the tin(IV) oxide, leaving tin.

    Six marks for six points: crush, how you crush, add a reducing agent, name it, heat, name the container, and say what the reaction is (seven are on offer). A second route also scores: dissolve the crushed ore in a named dilute acid, then add a more reactive metal such as zinc or iron to displace the tin. Starting from tin itself scores nothing.

    Revise this: Extracting metals

These explanations are Papermunch’s own, written to teach the method. The answers have been checked against the exam board’s mark scheme, which has the final say: open it above. The question paper and mark scheme belong toCambridge University Press & Assessment: each question shown here is drawn from the paper itself as you read, and is not kept on this site.