CaO + 2 HCl → CaCl₂ + H₂O

This is an acid-base reaction (neutralization): CaO is a base, HCl is an acid.

Reactants:

• CaO – Calcium oxide
  • Other names: Quicklime , Burnt lime , Unslaked lime ... show morePebble lime , Calcia , Caustic lime , Calx , Calcium monoxide , Limestone , Burned lime , Lime , Quick lime show less
  • Appearance: White to pale yellow/brown powder ; White hygroscopic crystalline powder ; White or gray, odorless lumps or granular powder.
• HCl – Chlorane , Hydrogen chloride
  • Other names: Hydrochloric acid , M , Uriatic acid ... show moreHydronium chloride , Chlorhydric Acid , Hydrochloric acid gas , HCl , Anhydrous hydrogen chloride , Hydrochloric acid, anhydrous , Aqueous hydrogen chloride , [Note: Often used in an aqueous solution.] show less
  • Appearance: Colorless, transparent liquid, fumes in air if concentrated ; Colorless gas ; Colourless compressed liquefied gas with pungent odour ; Colorless to slightly yellow gas with a pungent, irritating odor. [Note: Shipped as a liquefied compressed gas.]

Products:

• CaCl₂ – Calcium chloride
  • Other names: Calcium(II) chloride , Calcium dichloride , E509 ... show moreCalcium chloride (anhydrous) , Calcium chloride anhydrous , CaCl2 , Calcium chloride, anhydrous , Calcium Chloride , Calcium(2+) chloride show less
  • Appearance: White powder, hygroscopic ; Odourless hygroscopic colourless or white crystals
• H₂O – Water, oxidane
  • Other names: Water (H2O) , Hydrogen hydroxide (HH or HOH) , Hydrogen oxide ... show moreDihydrogen monoxide (DHMO) (systematic name) , Hydrogen monoxide , Dihydrogen oxide , Hydric acid , Hydrohydroxic acid , Hydroxic acid , Hydrol , Μ-oxido dihydrogen , Κ1-hydroxyl hydrogen(0) show less
  • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas