A student heats a small amount of solid ammonium chloride at the bottom of a test tube. The solid breaks down into two gases. At the cooler top of the tube a white solid forms again.
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)
State what is meant by a reversible reaction.
Explain why a white solid forms at the top of the test tube.
In the Haber process, nitrogen and hydrogen react in a closed system and reach a dynamic equilibrium.
Describe two features of a dynamic equilibrium.
State why a dynamic equilibrium can only be reached in a closed system.
The table shows the percentage of ammonia in the equilibrium mixture at a pressure of 200 atm and different temperatures.
| Temperature / °C | Percentage of ammonia / % |
|---|---|
| 300 | 63 |
| 400 | 36 |
| 500 | 18 |
| 600 | 8 |
Describe the effect of increasing the temperature on the percentage of ammonia in the equilibrium mixture.
Use the table in (d) to estimate the percentage of ammonia in the equilibrium mixture at 450 °C and 200 atm.
43 exam-style questions on Edexcel GCSE Chemistry 6.3 Dynamic equilibria, covering 6.3.1 The Haber process as a reversible reaction, 6.3.2 Conditions and rate in industrial equilibria, and 6.3.3 Fertilisers and the preparation of ammonium sulfate. Each one has a worked solution and a mark scheme showing where the marks go.