A student compares hydrochloric acid and ethanoic acid by reacting each acid with marble chips (calcium carbonate). The student uses 25.0 cm3\mathrm{cm^{3}}cm3 of 0.200 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 acid and an excess of marble chips of the same size each time. The carbon dioxide is collected in a gas syringe.
CaCO3(s)+2HCl(aq)→CaCl2(aq)+H2O(l)+CO2(g)\mathrm{CaCO_{3}(s)} + 2\mathrm{HCl(aq)} \rightarrow \mathrm{CaCl_{2}(aq)} + \mathrm{H_{2}O(l)} + \mathrm{CO_{2}(g)}CaCO3(s)+2HCl(aq)→CaCl2(aq)+H2O(l)+CO2(g)
The table shows the results.
| Time / s | Volume of CO2\mathrm{CO_{2}}CO2 with hydrochloric acid / cm3\mathrm{cm^{3}}cm3 | Volume of CO2\mathrm{CO_{2}}CO2 with ethanoic acid / cm3\mathrm{cm^{3}}cm3 |
|---|---|---|
| 0 | 0 | 0 |
| 20 | 30 | 6 |
| 40 | 46 | 12 |
| 60 | 54 | 17 |
| 80 | 58 | 22 |
| 100 | 60 | 26 |
| 120 | 60 | 30 |
Calculate the maximum volume of carbon dioxide that can be produced from 25.0 cm3\mathrm{cm^{3}}cm3 of 0.200 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 hydrochloric acid. One mole of any gas occupies 24 000 cm3\mathrm{cm^{3}}cm3 at room temperature and pressure.
Calculate the mean rate of reaction for hydrochloric acid in the first 20 s. Give the unit.
The student leaves the ethanoic acid experiment for several hours. Predict the final volume of carbon dioxide collected. Justify your prediction.
Explain the differences between the results for the two acids.
44 exam-style questions on Edexcel GCSE Chemistry 4.1 Acids, covering 4.1.1 Acids, alkalis and the pH scale, 4.1.2 Hydrogen ion concentration and pH, 4.1.3 Dilute and concentrated, weak and strong acids, 4.1.4 Bases, alkalis and the reactions of acids, 4.1.5 Chemical tests for hydrogen and carbon dioxide, 4.1.6 Neutralisation as a reaction of acids with bases, 4.1.7 Preparing soluble salts, and 4.1.8 Solubility rules and preparing insoluble salts. Each one has a worked solution and a mark scheme showing where the marks go.