Specification Point 3.17:
Know that some reactions are reversible and this is indicated by the symbol ⇌ in equations

Reversible Reactions

Reversible reactions: A reaction that can occur in both directions (the products can react to produce the original reactants again).

Chemical equations for reversible reactions:

When writing chemical equations for reversible reactions, two arrows are used, each with just half an arrowhead – the top one point right, and the bottom one pointing left:

Dehydration of Hydrated Copper (II) Sulfate:

Hydrous Copper (II) Sulfate     ⇌   Anhydrous Copper (II) Sulfate     +     Water

Thermal Decomposition of Ammonium Chloride:

 Ammonium Chloride     ⇌     Ammonia     +     Hydrogen Chloride

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.