Reaction of quick lime (CaO) with water to produce slaked lime (Ca(OH)

Reaction of quick lime (CaO) with water to produce slaked lime (Ca(OH)₂) is an example of

Displacement reaction.
Endothermic reaction.
Decomposition reaction.
Exothermic reaction.
This question was previously asked in
UPSC NDA-1 – 2021
The reaction between quick lime (calcium oxide, CaO) and water (H₂O) to form slaked lime (calcium hydroxide, Ca(OH)₂) is represented by the equation: CaO(s) + H₂O(l) → Ca(OH)₂(s). This reaction is well-known for releasing a significant amount of heat, making it a highly exothermic process.
Exothermic reactions are chemical reactions that release energy, typically in the form of heat or light. Endothermic reactions absorb energy. Displacement reactions involve one element displacing another from a compound. Decomposition reactions involve a single compound breaking down into simpler substances. The reaction of quick lime with water fits the definition of an exothermic reaction due to the large heat release, also sometimes classified as a combination reaction.
This reaction is used in the industrial production of slaked lime, which has various applications, including in mortar and plaster, water treatment, and agriculture. The heat released during the reaction is often sufficient to boil the water.