When calcium oxide (CaO), commonly known as quicklime, reacts with water (H₂O), it undergoes a vigorous exothermic reaction to produce calcium hydroxide {Ca(OH)₂}. The chemical equation for this reaction is:
CaO(s) + H₂O(l) → Ca(OH)₂(aq)
In this process, calcium oxide combines with water to form calcium hydroxide, which is a white, sparingly soluble solid. The reaction is highly exothermic, and it is often used in various applications, including the preparation of slaked lime for construction, water treatment, and as a reactant in chemical processes.