When ammonium chloride is heated, it breaks down into ammonia and hydrogen chloride.
NH4Cl(s)⇌NH3(g)+HCl(g)\mathrm{NH_{4}Cl(s)} \rightleftharpoons \mathrm{NH_{3}(g)} + \mathrm{HCl(g)}NH4Cl(s)⇌NH3(g)+HCl(g)
A student heats some ammonium chloride at the bottom of an open test tube. After a few minutes a white solid appears near the cool top of the tube.
Explain why a white solid forms near the top of the test tube.
In another experiment, a different reversible reaction takes place in a sealed container. The table shows the concentration of the product at different times.
| Time / min | Concentration of product / g dm−3\mathrm{g\,dm^{-3}}gdm−3 |
|---|---|
| 0 | 0.0 |
| 2 | 3.2 |
| 4 | 5.6 |
| 6 | 6.8 |
| 8 | 7.2 |
| 10 | 7.2 |
| 12 | 7.2 |
Give the time at which equilibrium was first reached.
Describe how the rate of the forward reaction changes between 0 and 8 minutes.
After 8 minutes the forward and backward reactions are both still happening. Explain why the concentration of the product stays the same.
Explain why this equilibrium can only be reached because the container is sealed.
45 exam-style questions on Edexcel GCSE Chemistry 5.2 Reversible reactions and equilibria, covering 5.2.1 Reversible reactions and dynamic equilibrium, 5.2.2 The Haber process, and 5.2.3 Changing the position of a dynamic equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.