This topic summary covers Knowledge Organiser: Reversible Reactions within Reversible Reactions for GCSE Chemistry. Revise Reversible Reactions in Rates of Reaction for GCSE Chemistry with 20 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 12 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Reversible Reactions
Key Terms
- Reversible reaction — uses ⇌ symbol
- Forward reaction — left to right
- Backward reaction — right to left
- Closed system — nothing enters or leaves
Energy Rule
- Forward exo = Backward endo
- Forward endo = Backward exo
- Energy values are equal in magnitude
Copper Sulfate Test
- Blue (hydrated) ⇌ White (anhydrous)
- Heating → endothermic → white
- Add water → exothermic → blue
- Detects water presence
Common Errors
- Using → not ⇌ in reversible equations
- Saying forward AND backward are exothermic
- Thinking products reach 100%
Key Equations
- CuSO₄·5H₂O ⇌ CuSO₄ + 5H₂O (copper sulfate dehydration)
- If forward reaction is exothermic (−x kJ), reverse is endothermic (+x kJ)
- NH₄Cl ⇌ NH₃ + HCl (thermal decomposition — reversible on cooling)
Practice questions for Reversible Reactions
What does the symbol ⇌ mean when used in a chemical equation?
Explain the relationship between the energy changes in the forward and reverse reactions of a reversible reaction.
Quick recall flashcards
What symbol shows a reaction is reversible?
⇌ (double arrow)
What is a reversible reaction?
A reaction where products can react together to reform the original reactants