Question 1
Paper 2Medium8 marksA quality-control test estimates the hydrogen peroxide concentration in a solution labelled 10.0 g dm⁻³. A 10.00 cm³ sample is completely decomposed according to the equation:
2 H₂O₂(aq) → 2 H₂O(l) + O₂(g)
The oxygen produced has a volume of 36.0 cm³. A 25.0 cm³ sample of nitrogen at the same temperature and pressure contains 1.00 × 10⁻³ mol of nitrogen. Assume both gases behave ideally and that no oxygen is lost. Use M(H₂O₂) = 34.0 g mol⁻¹.
Determine the amount, in mol, of oxygen produced.
Calculate the molar concentration, [H₂O₂], in the original solution, in mol dm⁻³.
Calculate the mass concentration of hydrogen peroxide in the original solution, in g dm⁻³.
Using the labelled concentration as the reference, calculate the percentage by which your result in (c) differs from the label, and state whether the measured value is higher or lower.