A student reacts excess granulated zinc with 25.0 cm3\mathrm{cm^{3}}cm3 of dilute sulfuric acid and collects the hydrogen in a gas syringe.
Zn(s)+H2SO4(aq)→ZnSO4(aq)+H2(g)\mathrm{Zn(s)} + \mathrm{H_{2}SO_{4}(aq)} \rightarrow \mathrm{ZnSO_{4}(aq)} + \mathrm{H_{2}(g)}Zn(s)+H2SO4(aq)→ZnSO4(aq)+H2(g)
The table shows the student's results.
| Time in s | 0 | 20 | 40 | 60 | 80 | 100 | 120 | 140 |
|---|---|---|---|---|---|---|---|---|
| Volume of hydrogen in cm3\mathrm{cm^{3}}cm3 | 0 | 30 | 54 | 72 | 84 | 92 | 96 | 96 |
Calculate the mean rate of reaction between 20 s and 60 s.
Describe how the rate of reaction at exactly 40 s could be found from a graph of these results.
Calculate the concentration of the sulfuric acid, in mol dm−3\mathrm{mol\,dm^{-3}}moldm−3. One mole of any gas occupies 24 000 cm3\mathrm{cm^{3}}cm3 at room temperature and pressure.
The student repeats the experiment using the same mass of zinc powder instead of granulated zinc. All other conditions are the same. Describe and explain how the results would be different.
The student says: "The reaction stopped at 120 s because all the zinc had been used up." Explain why the student is wrong.
54 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.