The structure of vitamin C is shown in Fig. 5.1. [Figure 5.1]

1. (a)Deduce the empirical formula of vitamin C.[1]
2. (b)(i)The mass of vitamin C present in 150.0 g of lemon is found in an experiment. stage 1 All the vitamin C in 150.0g of lemon is extracted and dissolved in water to make 100.0 cm³ of solution L. stage 2 A 25.0 cm³ sample of solution L is titrated with 5.00 × 10–3 mol dm-3 I2(aq). [Figure 5.2: vitamin C + I2 → M + 2I- + 2H+] Exactly 36.65 cm³ of I2(aq) reacts with the 25.0cm³ sample of solution L. [Mr: vitamin C, 176] Calculate the amount, in mol, of I2(aq) added in the titration.[1]
3. (b)(ii)Use your answer to (b)(i) to calculate the percentage by mass of vitamin C present in 150.0 g of lemon. (If you were unable to calculate a value for the amount of I2(aq) in (b)(i), use the value 7.65 x 10-4 mol. This is not the correct value.)[2]
4. (b)(iii)The progress of the reaction of vitamin C with I2(aq) to produce M is monitored using infrared spectroscopy. Table 5.1 indicates the presence of some absorptions in the infrared spectrum of vitamin C. Complete Table 5.1 to predict which of these absorptions, if any, are present in the infrared spectrum of M. Table 5.1 absorption/cm-1 | present in spectrum of vitamin C | present in spectrum of M 1500-1680 | ✓ | 2850-2950 | ✓ | 3200-3650 | ✓ | Table 5.2 bond functional groups containing the bond | characteristic infrared absorption range (in wavenumbers)/cm-1 C-O hydroxy, ester | 1040–1300 C=C aromatic compound, alkene | 1500–1680 C=O amide | 1640–1690 carbonyl, carboxyl | 1670–1740 ester | 1710–1750 C≡N nitrile | 2200–2250 C-H alkane | 2850–2950 N-H amine, amide | 3300–3500 O-H carboxyl | 2500–3000 hydroxy | 3200–3650[1]

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