GCSE Chemistry · Edexcel 1CH0 · Topic 4C
Reversible reactions and equilibria
Key points
- A reversible reaction can go both ways, shown by ⇌, e.g. heating ammonium chloride ⇌ ammonia + hydrogen chloride.
- In a closed system, a reversible reaction reaches dynamic equilibrium: the forward and backward reactions happen at the same rate, so the amounts of reactants and products stay constant.
- The Haber process makes ammonia: N₂ + 3H₂ ⇌ 2NH₃. Conditions: about 450 °C, about 200 atmospheres and an iron catalyst.
- Nitrogen comes from the air; hydrogen comes from natural gas.
- Higher tier: Le Chatelier: changing conditions shifts the position of equilibrium to oppose the change. Raising pressure favours the side with fewer gas molecules; raising temperature favours the endothermic direction.
- A catalyst speeds up both reactions equally, so it does not change the position of equilibrium.
Topic notesPremium
Many reactions only go one way, but some can be reversed. These notes cover reversible reactions, dynamic equilibrium, the Haber process and (Higher tier) how changing conditions shifts the position of equilibrium.
Unlock the full notes with Premium
Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.
Practise this topicPremium
Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Reversible reactions and equilibria.