Ammonia and carbon dioxide react to form solid ammonium carbamate.
2NH3(g)+CO2(g)⇌NH2COONH4(s) \mathrm{2NH_{3}(g) + CO_{2}(g) \rightleftharpoons NH_{2}COONH_{4}(s)} 2NH3(g)+CO2(g)⇌NH2COONH4(s)The same starting amounts of ammonia and carbon dioxide are used in each experiment. The table shows the percentage yield of ammonium carbamate when equilibrium is reached.
| Temperature (°C) | Pressure (atm) | Percentage yield at equilibrium (%) |
|---|---|---|
| 80 | 10 | 62 |
| 80 | 40 | 84 |
| 140 | 10 | 28 |
| 140 | 40 | 55 |
Explain what the results show about the energy change of the forward reaction.
Explain why increasing the pressure at a fixed temperature changes the percentage yield of ammonium carbamate.
A catalyst is used at 140 °C and 10 atm.
State the percentage yield when equilibrium is reached.
Extra carbon dioxide is added to an equilibrium mixture. The temperature and pressure are kept constant.
Predict what happens to the amount of ammonia when a new equilibrium is reached. Explain your answer.
124 exam-style questions on OCR GCSE Chemistry 5.3 Equilibria, covering 5.3.1 Reversible reactions and dynamic equilibrium and 5.3.2 Changing the position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.