under which two conditions do decomposition reaction normally take place?

Decomposition reactions are those chemical reactions which takes place when a single compound breaks into two or more simpler substances under suitable conditions .

Example:-

CaCO₃(s) CaO (s) + CO₂ (g)

Suitable condition for decomposition are :-

a) Most decomposition reactions are endothermic so they require some source of energy like heat, light or electricity.

b) Stability of the product so formed is usually higher than the reactant .