The label on a bottle of a preservative solution lists the mass of sulfur dioxide, SO2\text{SO}_2SO2, in mg, in a typical serving of 200 cm3200\text{ cm}^3200 cm3.
A student carries out an investigation to check the sulfur dioxide content in the solution.
Sulfur dioxide is oxidised by iodine according to the following equation:
SO2(aq)+I2(aq)+2H2O(l)→SO42−(aq)+2I−(aq)+4H+(aq) \text{SO}_2(\text{aq}) + \text{I}_2(\text{aq}) + 2\text{H}_2\text{O}(\text{l}) \rightarrow \text{SO}_4^{2-}(\text{aq}) + 2\text{I}^-(\text{aq}) + 4\text{H}^+(\text{aq}) SO2(aq)+I2(aq)+2H2O(l)→SO42−(aq)+2I−(aq)+4H+(aq)The student dilutes a 200 cm3200\text{ cm}^3200 cm3 serving of the preservative solution with water to 250.0 cm3250.0\text{ cm}^3250.0 cm3 in a volumetric flask.
The student then titrates a 25.0 cm325.0\text{ cm}^325.0 cm3 volume of this diluted solution with a 1.50×10−3 mol dm−31.50 \times 10^{-3}\text{ mol dm}^{-3}1.50×10−3 mol dm−3 iodine solution, I2(aq)\text{I}_2(\text{aq})I2(aq).
The mean titre of I2(aq)\text{I}_2(\text{aq})I2(aq) is 18.40 cm318.40\text{ cm}^318.40 cm3.
Determine the mass, in mg, of sulfur dioxide in the 200 cm3200\text{ cm}^3200 cm3 serving of the preservative solution. Give your answer to 3 significant figures.
199 exam-style questions on OCR A A Level Chemistry Atoms and reactions, covering Atomic structure and isotopes, Compounds, formulae and equations, Amount of substance, Acids, and Redox. Each one has a worked solution and a mark scheme showing where the marks go.