How do acids react with carbonates?
Acids react with carbonates to form carbon dioxide gas.
Carbonates such as calcium carbonate, CaCO₃, are ionic compounds.
For example, CaCO₃ consists of Ca²⁺ ions and CO₃²⁻ ions.
The carbonate ions are basic. They react with the H⁺ ions from an acid such as HCl to form carbonic acid.
2H⁺ + CO₃²⁻ → H₂CO₃
The carbonic acid is unstable and decomposes into CO₂ and water.
H₂CO₃ → H₂O + CO₂
The overall equation (3) is the sum of equations (1) and (2)
(1) CaCO₃ + 2HCl → CaCl₂ + H₂CO₃
(2) H₂CO₃ → H₂O + CO₂
(3) CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂