When two or more compounds combine to form one compound, this type of reaction is called a combination reaction.
Example: When carbon is burnt in the air, it gives carbon dioxide.
C + O2 → CO2
When a reactant dissociates to give two or more products, this type of reaction is called decomposition reaction. This reaction is the opposite of a combination reaction.
Example: Decomposition of water by electrolysis.
2H2O(l) → 2H2(g) + O2(g)
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