Solution:
Concept- A decomposition type of reaction is the one in which one reactant is decomposed (broken down) into two or more than two products.In a decomposition reaction, the bonds present between a compound break and new bonds are formed leading to new smaller compounds.
Breaking of a bond needs an input of energy, while forming bonds releases energy. Since a decomposition reaction involves breaking the bonds of a large molecule to form two or more smaller molecules, more bonds are broken than formed, meaning the reaction will need a net amount of energy, making it endothermic.
Thus, it can be concluded that most of the decomposition reactions are endothermic.
Hence, the correct option is (2).
