Sodium thiosulfate reacts with dilute hydrochloric acid to form a precipitate of sulfur.
Na2S2O3(aq)+2HCl(aq)→2NaCl(aq)+SO2(g)+S(s)+H2O(l)\mathrm{Na_{2}S_{2}O_{3}(aq)} + \mathrm{2HCl(aq)} \rightarrow \mathrm{2NaCl(aq)} + \mathrm{SO_{2}(g)} + \mathrm{S(s)} + \mathrm{H_{2}O(l)}Na2S2O3(aq)+2HCl(aq)→2NaCl(aq)+SO2(g)+S(s)+H2O(l)
A student measures the time for the sulfur to hide a cross under the flask at different temperatures. All other conditions are kept the same.
| Temperature in °C | 20 | 30 | 40 | 50 |
|---|---|---|---|---|
| Time for cross to disappear in s | 120 | 60 | 31 | 15 |
Determine how many times faster the reaction is at 50 °C than at 20 °C.
A 10 °C rise in temperature increases the average speed of the particles by only about 2%. A student says: "Heating the mixture speeds up the reaction only because the particles collide more often." Evaluate this statement. Use collision theory and the data in your answer.
Sulfur dioxide is a toxic gas. Give one precaution the student should take.
In each experiment, the student uses 10.0 cm3\mathrm{cm^{3}}cm3 of 0.40 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 sodium thiosulfate solution with excess acid. Calculate the mass of sulfur formed. Relative atomic mass: S = 32. Give your answer to two significant figures.
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.