UPSC NDA I 2021 General Ability Solved Paper

The correct answer is Exothermic reaction.
Key Points
- The formation of slaked lime (calcium hydroxide) Ca(OH)2 when water is added to lime (CaO) is exothermic.
∘CaO(s)+H2O(l)→Ca(OH)2(s) (Evolution of heat)
- This reaction occurs when water is added to dry portland cement to make concrete, and the evolution of energy as heat is evident because the mixture becomes warm.
- A chemical reaction in which heat energy is released is known as an exothermic reaction.