Calcium hydroxide (Ca(OH)2) is produced when calcium oxide (CaO) reacts with water (H2O). Calcium chloride (CaCl2) is produced when calcium carbonate (CaCO3) reacts with hydrochloric acid (HCl). Calcium carbonate is formed when calcium ions (Ca2+) react with carbonate ions (CO32-).

Overall, the reaction can be represented as:

CaO + H2O → Ca(OH)2

CaCO3 + 2HCl → CaCl2 + CO2 + H2O

Therefore, in the overall reaction, calcium oxide (CaO) reacts with water to form calcium hydroxide (Ca(OH)2), and calcium carbonate (CaCO3) reacts with hydrochloric acid (HCl) to form calcium chloride (CaCl2), carbon dioxide (CO2), and water (H2O).