CaO+Hce

Assuming you meant CaO + H2O:

• Balanced equation (solid reagents): CaO(s) + H2O(l) → Ca(OH)2(s)
  (In water it can form Ca2+(aq) + 2 OH−(aq) as the solution: CaO(s) + H2O(l) → Ca2+(aq) + 2 OH−(aq).)

• Nature: Highly exothermic reaction.

• Enthalpy change (approximate): ΔH° ≈ -65 kJ per mole of CaO reacted.

• Notes:

  • Ca(OH)2 is only sparingly soluble; the reaction is often observed as a heat-producing slurry.
  • Limewater (Ca(OH)2 in water) is used to test for CO2: CO2 reacts with Ca(OH)2 to form CaCO3 precipitate.

If you actually meant CaO + HCl (instead of H2O), the products would be CaCl2 + H2O, also exothermic. Let me know which one you intended.