This is an acid-base reaction (neutralization): CaCO3 is a base, HCl is an acid.
Reactants:
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CaCO3 – Calcium carbonate
Other names: Calcite; aragonite; chalk; Lime (material); Limestone; marble; oyster; pearl;, Calcium salt of carbonic acid, Children's Mylanta Upset Stomach Relief
Appearance: Fine white powder; chalky taste ; White powder or pellets
HCl – Chlorane, Hydrogen chloride
Other names: Hydrochloric acid, M, Uriatic acid
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
Appearance: White powder, hygroscopic ; Odourless hygroscopic colourless or white crystals
H2O – Water, oxidane
Other names: Water (H2O), Hydrogen hydroxide (HH or HOH), Hydrogen oxide
Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas
CO2
Names: Carbon dioxide, {{plainlist|, CO2
Appearance: Colorless gas ; Odourless colourless compressed liquefied gas ; Colorless, odorless gas. [Note: Shipped as a liquefied compressed gas. Solid form is utilized as dry ice.]