A student investigates the effect of acid concentration on the rate of reaction between magnesium and hydrochloric acid. She uses the same length of magnesium ribbon each time and measures the time taken to collect 48 cm3\mathrm{cm^{3}}cm3 of hydrogen gas.
The table shows her results.
| Concentration of acid in mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 | Time to collect 48 cm3\mathrm{cm^{3}}cm3 of hydrogen in s |
|---|---|
| 0.5 | 80 |
| 1.0 | 40 |
| 1.5 | 27 |
| 2.0 | 20 |
Calculate the mean rate of reaction, in cm3 s−1\mathrm{cm^{3}\,s^{-1}}cm3s−1, for the 2.0 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 acid.
Convert your answer to (a) into a rate in mol s−1\mathrm{mol\,s^{-1}}mols−1. One mole of any gas occupies 24 000 cm3\mathrm{cm^{3}}cm3 at room temperature and pressure.
Describe the relationship between the concentration of the acid and the rate of reaction. Use data from the table to support your answer.
Explain, using collision theory, why increasing the concentration of the acid increases the rate.
Ethanoic acid is a weak acid. Explain why 2.0 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 ethanoic acid reacts more slowly with magnesium than 2.0 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 hydrochloric acid.
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.