This is a chemical equation showing the conversion of calcium oxide (CaO) to calcium chloride (CaCl2) through a series of reactions involving calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3). The equation can be written as:

CaO + Ca(OH)2 + 2CaCO3 → 2CaCl2 + 3CO2 + H2O

In this reaction, calcium oxide reacts with calcium hydroxide and calcium carbonate to form calcium chloride, carbon dioxide, and water.