Question

Give the chemical reaction when a few pieces of slaked lime are added to a beaker half-filled with water. Will it be an endothermic or exothermic reaction?

Answer 1

Calcium hydroxide [Ca(OH)₂] is formed by the combination of calcium oxide and water with the generation of a large amount of heat.

\[\ce{\underset{Calcium oxide}{CaO} + \underset{Water}{H2O} -> \underset{Calcium hydroxide}{Ca(OH)2} + Heat}\]

Since large amount of heat is evolved it is an exothermic reaction.