A student investigates the decomposition of a hydrogen peroxide solution:
2H2O2(aq)→2H2O(l)+O2(g) 2\text{H}_2\text{O}_2(\text{aq}) \rightarrow 2\text{H}_2\text{O}(\text{l}) + \text{O}_2(\text{g}) 2H2O2(aq)→2H2O(l)+O2(g)The student adds 40.00 cm340.00\text{ cm}^340.00 cm3 of H2O2(aq)\text{H}_2\text{O}_2(\text{aq})H2O2(aq) to a conical flask, adds a small amount of manganese(IV) oxide catalyst, and quickly connects the flask to a gas syringe.
The student allows the reaction to proceed until no more gas is evolved. The final volume of O2\text{O}_2O2 in the syringe is 75 cm375\text{ cm}^375 cm3, measured at room temperature and pressure (RTP).
Calculate the initial concentration of the H2O2(aq)\text{H}_2\text{O}_2(\text{aq})H2O2(aq) solution. Give your answer to two significant figures. (Assume the molar gas volume at RTP is 24.0 dm3 mol−124.0\text{ dm}^3\text{ mol}^{-1}24.0 dm3 mol−1.)
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.