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Chemistry · Oct / Nov 2021 · Paper 61 · Question 2

0620

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The question as text

A student investigated the rate of reaction between small lumps of calcium carbonate and dilute hydrochloric acid. The experiment was done at two different temperatures using the apparatus shown in the diagram. All other conditions were kept the same. dilute hydrochloric acid calcium carbonate gas syringe Experiment 1 ● Using a 50 cm3 measuring cylinder, 25 cm3 of dilute hydrochloric acid was poured into a boiling tube. ● The temperature of the dilute hydrochloric acid was measured using a thermometer. ● 10 g of lumps of calcium carbonate were added to the boiling tube, the bung replaced and the stop‑watch started. ● The volume of gas collected in the gas syringe was measured every 50 seconds for 250 seconds. Experiment 2 ● Using a 50 cm3 measuring cylinder, 25 cm3 of dilute hydrochloric acid was poured into a boiling tube. ● The dilute hydrochloric acid in the boiling tube was warmed using a Bunsen burner. ● The temperature of the dilute hydrochloric acid was measured using a thermometer. ● 10 g of lumps of calcium carbonate were added to the boiling tube, the bung replaced and the st ● The volume of gas collected in the gas syringe was measured every 50 seconds for 250 seconds.

Read automatically from the paper; the printed page above is exact.

Show the answer and mark scheme

  • 2(a)[2]

    mark syringe diagrams only.

    0, 12, 20, 27, 32, 36

  • 2(b)[2]

    thermometer diagrams

    Experiment 1: 23 and Experiment 2: 44

    syringe diagrams

    0, 25, 35, 40,40,40

  • 2(c)[5]

    all 12 points plotted correctly

    smooth curve for Experiment 1

    smooth curve for Experiment 2, must level off

    lines labelled either with Experiment 1/2, (a)/(b) or temperature

  • 2(d)[2]

    correct indication/construction shown on graph

    correct reading for their indication/construction

  • 2(e)[1]

    gas volume constant / stays at 40 cm3

  • 2(f)[2]

    40

    same amount of reactants/acid as Experiment 2

  • 2(g)[2]

    more data / more points

    can plot a better graph / see trend more clearly

  • 2(h)[2]

    any two from

    insulate the tube / use a waterbath
    use a pipette/burette in place of the measuring cylinder
    use a divided flask / description of this

    max 2

  • 2(i)[1]

    description of how the acid would be cooled, such as place acid in fridge or freezer / stand tube in ice bath

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