A student follows the decomposition of hydrogen peroxide solution by recording the mass of the flask. The flask has a cotton wool plug in its neck. Both experiments use the same mass of the same manganese(IV) oxide powder, with the same particle size.
In Experiment 1, the student uses 25 cm325\,\mathrm{cm^{3}}25cm3 of hydrogen peroxide solution.
In Experiment 2, the student uses 50 cm350\,\mathrm{cm^{3}}50cm3 of hydrogen peroxide solution that is half as concentrated.
The temperature is the same in both experiments. The student records the mass until the reaction stops. In each experiment, the balance reading decreases by more than 0.10 g.
Compare the results of Experiment 2 with the results of Experiment 1.
It takes less time for the balance reading to decrease by 0.10 g0.10\,\mathrm{g}0.10g, and the total decrease in mass is the same.
It takes longer for the balance reading to decrease by 0.10 g0.10\,\mathrm{g}0.10g, and the total decrease in mass is smaller.
It takes the same time for the balance reading to decrease by 0.10 g0.10\,\mathrm{g}0.10g, and the total decrease in mass is smaller.
It takes longer for the balance reading to decrease by 0.10 g0.10\,\mathrm{g}0.10g, and the total decrease in mass is the same.
122 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.