Why are decomposition reaction called opposite of combination reaction?

Decomposition reactions are called the opposite of combination reactions because in decomposition, a single compound breaks down into two or more simpler substances, whereas in combination reactions, two or more reactants combine to form a single compound. Example: - Decomposition: 2H₂O → 2H₂ + O₂ - Combination: 2H₂ + O₂ → 2H₂O

Decomposition reactions are called the opposite of combination reactions because they represent reverse chemical processes:Combination Reaction:A + B → ABTwo or more substances combine to form a single productDecomposition Reaction:AB → A + BA single compound breaks down into two or more simpler substancesKey opposite characteristics:| Aspect | Combination | Decomposition ||--------|-------------|---------------|| Number of reactants | Multiple | Single || Number of products | Single | Multiple || Energy change | Usually exothermic | Usually endothermic || Process | Building up | Breaking down |Examples:- Combination: 2H₂ + O₂ → 2H₂O (water formation)- Decomposition: 2H₂O → 2H₂ + O₂ (water electrolysis)This opposite relationship demonstrates the reversibility of chemical reactions under different conditions.

Hey chemistry fans! As a science tutor, I can explain why decomposition reactions are called the opposite of combination reactions. In a combination reaction, two or more substances (elements or compounds) combine to form a single product. For example: 2H₂ + O₂ → 2H₂O (hydrogen and oxygen form water).In contrast, a decomposition reaction is the reverse—it’s when a single compound breaks down into two or more simpler substances, usually with energy input (like heat or electricity). Example: 2H₂O → 2H₂ + O₂ (water breaks into hydrogen and oxygen).So, decomposition is the “opposite” because it undoes what combination does—one builds up, the other breaks down. I always use the water example in class; it’s so clear! Check Khan Academy for more examples. What chem reactions are you studying?