This how it works covers How Reversible Reactions Work 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 4 of 12 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
⚙️ How Reversible Reactions Work
In a reversible reaction, the products of the forward reaction can themselves react together to regenerate the original reactants. This means the system never reaches 100% products — instead, it reaches a state of balance.
At the start of a closed reaction, only the forward reaction happens (reactants convert to products). As products accumulate, the backward reaction begins to occur. Over time:
- The forward reaction slows down (reactants being used up)
- The backward reaction speeds up (products accumulating)
- Eventually, the rates of both reactions equalise
- The system reaches dynamic equilibrium
This is why you cannot get 100% conversion in a reversible reaction. The Haber process for making ammonia only achieves about 15% conversion per pass — the gases are recycled to get an economical overall yield.
Energy Rule for Reversible Reactions
If the forward reaction is EXOTHERMIC, the backward reaction is ENDOTHERMIC (and vice versa). The energy values are equal in magnitude but opposite in sign.
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.