An experiment was carried out to determine the concentration of citric acid in lemon juice using a titration. Three students used the following procedure. Procedure Step 1 Add $$\(24.0 \mathrm{~g}\)$$ of lemon juice to a $$\(250 \mathrm{~cm}^{3}\)$$ volumetric flask. Step 2 Make up the volume of the lemon juice to $$\(250 \mathrm{~cm}^{3}\)$$ using deionised water and mix thoroughly. Step 3 Pipette $$\(25.0 \mathrm{~cm}^{3}\)$$ of the diluted lemon juice into a conical flask and add a few drops of phenolphthalein indicator. Step 4 Titrate the diluted lemon juice with standardised sodium hydroxide of concentration $$\(0.103 \mathrm{~mol} \mathrm{dm}^{-3}\)$$. Student $$\(\mathbf{A}\)$$ obtained the results shown. Suggest a possible reason why the value obtained in (c) is valid, even though lemon juice also contains some ascorbic acid and malic acid. (1) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................

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