Hydrogen peroxide solution breaks down slowly into water and oxygen.
2H2O2(aq)→2H2O(l)+O2(g)\mathrm{2H_{2}O_{2}(aq)} \rightarrow \mathrm{2H_{2}O(l)} + \mathrm{O_{2}(g)}2H2O2(aq)→2H2O(l)+O2(g)
A student tests some oxides of transition metals to see how well they catalyse this reaction. She adds 0.50 g of each oxide to 25 cm3\mathrm{cm^{3}}cm3 of hydrogen peroxide solution and measures the volume of oxygen given off in the first 60 seconds.
| Substance added | Volume of oxygen in 60 s / cm3\mathrm{cm^{3}}cm3 |
|---|---|
| nothing | 2 |
| copper(II) oxide | 18 |
| iron(III) oxide | 9 |
| manganese(IV) oxide | 84 |
Name a piece of apparatus the student could use to measure the volume of oxygen.
Give two variables the student must keep the same to make this a fair test.
Use the results to answer these questions.
Identify the most effective catalyst.
Calculate the mean rate of oxygen production when manganese(IV) oxide is added. Use the equation: mean rate=volume of oxygentime\displaystyle \text{mean rate} = \frac{\text{volume of oxygen}}{\text{time}}mean rate=timevolume of oxygen. Give the unit.
Devise an experiment to show that manganese(IV) oxide speeds up the reaction and is not used up.
42 exam-style questions on Edexcel GCSE Chemistry 6.1 Transition metals, alloys and corrosion, covering 6.1.1 Properties of transition metals, 6.1.2 Corrosion and its prevention, and 6.1.3 Alloys and the uses of metals. Each one has a worked solution and a mark scheme showing where the marks go.