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Biology · May / June 2026 · Paper 62 · Question 1

0610

As printed in the paper

The question as text

A student estimated the concentration of vitamin C in a drink by comparing it to solutions with known vitamin C concentrations. The concentration of vitamin C in a sample can be estimated by testing it with iodine solution. The test is done by adding drops of iodine solution to the sample until the colour remains blue-black. The greater the volume of iodine solution added, the higher the concentration of vitamin C in the sample.

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

Show the answer and mark scheme

  • 1(a)(i)[1]

    0.2 ;

  • 1(a)(ii)[3]

    table drawn with minimum of two columns and a header line ;

    suitable headings with units for:

    (final) percentage / % , concentration (of vitamin C)

    and volume (of iodine solution) , remaining OR used / cm3 ;

    three correct percentage concentrations and three correct volumes recorded that match the header ;

  • 1(a)(iii)[1]

    V1 3.6 (cm3)

    and

    V2 2(.0) (cm3)

    and

    V3 0.4 (cm3)

    volume of iodine (solution), remaining / added / used (in the syringe) ;

  • 1(a)(iv)[1]

    The answer is a drawing: see the picture of this mark scheme row.

  • 1(a)(v)[1]

    starch is present / iodine (solution) turns blue-black with starch / starch gives positive result with iodine (solution) / AW ;

  • 1(a)(vi)[1]

    greater volume required / AW ;

  • 1(a)(vii)[1]

    drops vary in, volume / size / cm3

    or

    miscounting / AW ;

  • 1(b)(i)[1]

    2.8 (cm3) ;

  • 1(b)(ii)[1]

    any value greater than 0.4 (%) and less than 0.6 (%) ;

  • 1(b)(iii)[1]

    at least one more concentration between 0.4% and 0.6% / use smaller intervals of concentration / AW ;

  • 1(b)(iv)[2]

    (use) Benedict’s test / solution ;

    heat ;

  • 1(b)(v)[1]

    DCPIP ;

  • 1(c)(i)[4]

    axes labelled with units ;

    suitable linear scale and data occupies at least half the grid in both directions ;

    five points plotted accurately ± half a small square ;

    suitable line drawn ;

  • 1(c)(ii)[2]

    (vitamin C) concentration / vitamin C / it , increases (as drying time increases) and then, levels off / plateaus / AW ;

    (vitamin C) concentration / vitamin C / it , increases because , water is being lost / water content reduces

    OR

    (vitamin C) concentration / vitamin C / it , levels off as , no more water can be lost / has lost the maximum amount of water it can / all water is lost / (fruit) is (completely) dry / AW ;

  • 1(c)(iii)[2]

    intercept indicated on the graph at 10 hours ;

    answer consistent with the intercept at 10 hours ± half a small square on the candidate’s graph ;

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