why are decomposition reactions called the opposite of combination reactions write equation for this reaction

Dear student,
Those reactions in which two or more substances combine to form a single substance , are called addition or combination reactions. For example : C(s) + O2(g) → CO2 (g) 2 SO2(g) + O2 (g) →2SO3​ (g)
Those reactions in which a compound splits up into two or more simpler substances are known as decomposition reactions. The decomposition reactions are carried out by applying heat, light or electricity.
For example : CaCO3(s) →heat CaO(s) + CO2(g)
2 Pb(NO3)2 →heat2 PbO (s) + 4 NO2(g) + O2(g)
Thus as seen from above examples in addition reactions two or more substances add up to give a single product. Whereas decomposition is exactly opposite to this where a single substance splits into two or more products. Thus because of the opposite nature of the two reactions addition reactions are called opposite of decomposition reactions.

Regards

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