Patients suffering from iron deficiency are often prescribed tablets containing hydrated iron(II) sulphate, FeSO4.7H2O.
[Molar mass FeSO4.7H2O = 278 g mol–1 )
Some tablets, of total mass 6.00 g, were dissolved in distilled water and made up to 200 cm3 in a volumetric flask. 25.0 cm3 portions of this solution were titrated against a 0.0200 mol dm–3 solution of acidified potassium manganate(VII). The mean titre was 20.10 cm3.
The Fe(II) is oxidized to Fe(III) during the titration
- What is the mean number of moles of potassium manganate(VII) used in the titration
- MnO4 – is reduced to Mn2+ in the titration. Find the mole ratio of MnO4 – : Fe2+ in this titration, either by combining two half-equations or using changes in oxidation no.
- Hence find the moles of Fe2+ in each 25.0 cm3 portion used
- Hence find the moles of Fe2+ in the 200 cm3 portion solution in the volumetric flask
- Hence find the mass of FeSO4.7H2O in the 200 cm3 solution in the volumetric flask
- Calculate the percentage of hydrated iron(II) sulphate in the tablets.
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